Immunity: Protection Against Disease
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Questions and Answers

What is a primary characteristic of innate immunity?

  • It has a specific response to antigens.
  • It is present from birth. (correct)
  • It involves memory of past infections.
  • It requires prior exposure to pathogens.

    • Which function is NOT associated with the immune system?

  • Mounting a specific response against non-self antigens.
  • Creating new pathogens. (correct)
  • Recognition of self from non-self antigens.
  • Memory of previously recognized non-self antigens.

    • What distinguishes adaptive immunity from innate immunity?

  • Adaptive immunity does not trigger responses.
  • Adaptive immunity is not present at birth. (correct)
  • Adaptive immunity has immediate protection.
  • Adaptive immunity lacks specificity.

    • Which type of immunity involves the transfer of antibodies from mother to child?

    <p>Passive immunity.</p> Signup and view all the answers

    How does innate immunity primarily function?

    <p>By providing immediate defense without prior exposure.</p> Signup and view all the answers

    What is the primary function of epithelial barriers in innate immunity?

    <p>To act as mechanical barriers against microbes</p> Signup and view all the answers

    Which cells are primarily responsible for humoral immunity?

    <p>B lymphocytes</p> Signup and view all the answers

    Which characteristic is true about the memory aspect of the immune response?

    <p>It is exclusive to adaptive immunity.</p> Signup and view all the answers

    What role does the adaptive immune response play after the innate immune response?

    <p>It provides a specific and sustained response.</p> Signup and view all the answers

    Which component of the immune system is responsible for defense against intracellular microbes?

    <p>Cell-mediated immunity</p> Signup and view all the answers

    Which of the following best describes the nature of adaptive immunity?

    <p>Slow to develop but powerful and specific</p> Signup and view all the answers

    What can cause diseases of the immune system?

    <p>Failure or derangement of the immune system function.</p> Signup and view all the answers

    In which organ do T cells primarily develop?

    <p>Thymus</p> Signup and view all the answers

    What role do regulatory T lymphocytes play in the immune response?

    <p>Suppress the immune response</p> Signup and view all the answers

    Which of the following is NOT a primary lymphoid organ?

    <p>Spleen</p> Signup and view all the answers

    What is the primary function of natural killer (NK) cells?

    <p>To destroy infected or tumor cells</p> Signup and view all the answers

    What is the primary function of B lymphocytes?

    <p>To produce antibodies</p> Signup and view all the answers

    How do Natural Killer (NK) cells recognize abnormal cells?

    <p>Through antibody-dependent cellular cytotoxicity and perforin-granzymes system</p> Signup and view all the answers

    Which antibodies are first produced by plasma cells upon activation?

    <p>IgM</p> Signup and view all the answers

    What markers are commonly used to identify Natural Killer (NK) cells?

    <p>CD16 and CD56</p> Signup and view all the answers

    What percentage of human peripheral lymphoid cells do NK cells comprise?

    <p>5% to 15%</p> Signup and view all the answers

    How do inhibitory receptors on NK cells function?

    <p>They interact with MHC class I molecules to prevent killing of normal cells</p> Signup and view all the answers

    What type of cells do B lymphocytes develop into after stimulation?

    <p>Plasma cells</p> Signup and view all the answers

    Which surface molecules do NK cells use to recognize targets?

    <p>CD16 and CD56</p> Signup and view all the answers

    What is the primary role of opsonins in the immune response?

    <p>Enhancing the phagocytosis of pathogens</p> Signup and view all the answers

    Which cytokines primarily mediate inflammation and anti-viral defense?

    <p>TNF, IL-1, and IL-12</p> Signup and view all the answers

    Which of the following is NOT a function of macrophages?

    <p>Production of antibodies</p> Signup and view all the answers

    Which class of cytokines is primarily responsible for the stimulation of hematopoiesis?

    <p>Colony-Stimulating Factors</p> Signup and view all the answers

    Which statement about monocytes is true?

    <p>Monocytes can differentiate into macrophages once activated</p> Signup and view all the answers

    What is the relationship between cytokines and immune cells?

    <p>Cytokines mediate communication between various immune cells</p> Signup and view all the answers

    What role does the Major Histocompatibility Complex (MHC) play in the immune system?

    <p>Presenting antigen fragments to T cells</p> Signup and view all the answers

    Which type of cellular communication do cytokines facilitate in the immune system?

    <p>Soluble signals between cells</p> Signup and view all the answers

    Which of the following statements about MHC class I molecules is correct?

    <p>They are encoded by the HLA-A, HLA-B, and HLA-C loci.</p> Signup and view all the answers

    What is the primary function of MHC class II molecules?

    <p>Presenting antigens to CD4+ T lymphocytes.</p> Signup and view all the answers

    HLA-B27 is most strongly associated with which of the following conditions?

    <p>Ankylosing spondylitis.</p> Signup and view all the answers

    What distinguishes MHC class II molecules from MHC class I molecules?

    <p>Class II molecules are recognized by CD4+ T cells.</p> Signup and view all the answers

    Which of the following is NOT a function associated with MHC molecules?

    <p>Directly killing cancer cells.</p> Signup and view all the answers

    The genes encoding MHC molecules are located on which chromosome in humans?

    <p>Chromosome 6.</p> Signup and view all the answers

    Which type of MHC molecule is primarily expressed on professional antigen-presenting cells?

    <p>MHC class II.</p> Signup and view all the answers

    Which of the following is a function of MHC class III molecules?

    <p>Encoding components of the complement system.</p> Signup and view all the answers

    Mature B cells constitute 20% to 30% of the circulating peripheral lymphocyte population.

    <p>False</p> Signup and view all the answers

    The primary antibody produced by plasma cells is IgA.

    <p>False</p> Signup and view all the answers

    Natural Killer (NK) cells are classified as phagocytic lymphocytes.

    <p>False</p> Signup and view all the answers

    NK cells recognize abnormal cells primarily through a perforin-granzymes system.

    <p>True</p> Signup and view all the answers

    B cells can function as antigen presenting cells without prior activation.

    <p>True</p> Signup and view all the answers

    NK cells bear the markers CD16 and CD56, which are used to identify T lymphocytes.

    <p>False</p> Signup and view all the answers

    B-cell receptors (BCR) are composed of IgE and IgD on the surface of B cells.

    <p>False</p> Signup and view all the answers

    Natural Killer cells comprise about 10% to 20% of human peripheral lymphoid cells.

    <p>False</p> Signup and view all the answers

    Epithelial barriers serve as mechanical barriers to protect against the entry of microbes.

    <p>True</p> Signup and view all the answers

    Humoral immunity is primarily responsible for defending against intracellular microbes.

    <p>False</p> Signup and view all the answers

    CD8+ T cells are also known as helper T cells and play a role in suppressing the immune response.

    <p>False</p> Signup and view all the answers

    Primary lymphoid organs, such as the thymus and bone marrow, are essential for the maturation of T cells and B cells.

    <p>True</p> Signup and view all the answers

    The adaptive immune response provides short-lasting immunity after exposure to an antigen.

    <p>False</p> Signup and view all the answers

    Natural killer (NK) cells are primarily responsible for the humoral immune response.

    <p>False</p> Signup and view all the answers

    Both B and T lymphocytes have highly specific receptors for a wide variety of substances known as antigens.

    <p>True</p> Signup and view all the answers

    Regulatory T lymphocytes express CD4 molecules and assist in enhancing the immune response.

    <p>False</p> Signup and view all the answers

    Circulating monocytes make up approximately 10% of peripheral leukocytes.

    <p>False</p> Signup and view all the answers

    Opsonization is the process by which pathogens are directly destroyed by immune cells without any prior coating.

    <p>False</p> Signup and view all the answers

    Cytokines of Adaptive Immunity are primarily secreted by macrophages and dendritic cells.

    <p>False</p> Signup and view all the answers

    Major histocompatibility complex (MHC) molecules are membrane-bound proteins encoded by MHC genes.

    <p>True</p> Signup and view all the answers

    Cytokines can stimulate hematopoiesis, increasing leukocyte numbers during immune responses.

    <p>True</p> Signup and view all the answers

    Acute phase reactants include cytokines like IL-4 and IL-17.

    <p>False</p> Signup and view all the answers

    Macrophages are the only cells capable of secreting acute phase reactants.

    <p>False</p> Signup and view all the answers

    Innate immunity provides immediate protection but lacks specificity.

    <p>True</p> Signup and view all the answers

    Opsonins are produced exclusively by phagocytic cells.

    <p>False</p> Signup and view all the answers

    The adaptive immune system develops memory cells upon first exposure to an antigen.

    <p>True</p> Signup and view all the answers

    Passive immunity can only be acquired through artificial means.

    <p>False</p> Signup and view all the answers

    Antibody formation is a major function of innate immunity.

    <p>False</p> Signup and view all the answers

    Memory is a characteristic feature of innate immunity.

    <p>False</p> Signup and view all the answers

    Adaptive immunity can be categorized into active and passive types.

    <p>True</p> Signup and view all the answers

    A primary characteristic of innate immunity is its ability to recognize self from non-self antigens.

    <p>False</p> Signup and view all the answers

    HLA class I molecules are expressed on all nucleated cells and platelets except erythrocytes and trophoblasts.

    <p>True</p> Signup and view all the answers

    CD4+ T cells recognize antigens in the context of self-class I molecules.

    <p>False</p> Signup and view all the answers

    Cell-mediated reactions are a specific function of the adaptive immune response.

    <p>True</p> Signup and view all the answers

    HLA-D consists of three sub-regions: HLA-DP, HLA-DQ, and HLA-DR, which are associated with class II MHC molecules.

    <p>True</p> Signup and view all the answers

    The genes encoding Class III MHC molecules have apparent roles in the immune system.

    <p>False</p> Signup and view all the answers

    The HLA complex is primarily located on the long arm of chromosome 6 in humans.

    <p>False</p> Signup and view all the answers

    MHC class II molecules interact with CD8+ T lymphocytes during antigen presentation.

    <p>False</p> Signup and view all the answers

    HLA-B27 is associated with autoimmune diseases such as ankylosing spondylitis.

    <p>True</p> Signup and view all the answers

    The major histocompatibility complex (MHC) plays no role in organ/tissue transplantation.

    <p>False</p> Signup and view all the answers

    What is the role of defensins in innate immunity?

    <p>Defensins are antimicrobial molecules produced by epithelial cells to protect against microbial invasion.</p> Signup and view all the answers

    How does the adaptive immune system enhance the body's defense compared to the innate immune system?

    <p>The adaptive immune system provides specific and long-lasting protection through memory and prior exposure to antigens.</p> Signup and view all the answers

    Identify the primary function of CD8+ T cells in cellular immunity.

    <p>CD8+ T cells function as cytotoxic T lymphocytes (CTLs) that destroy host cells infected by microbes or cancerous cells.</p> Signup and view all the answers

    What distinguishes primary lymphoid organs from secondary lymphoid organs in the immune system?

    <p>Primary lymphoid organs, such as the thymus and bone marrow, are sites of lymphocyte development, while secondary lymphoid organs are where adaptive immune responses occur.</p> Signup and view all the answers

    Explain the role of regulatory T lymphocytes in the immune response.

    <p>Regulatory T lymphocytes suppress the immune response to prevent overactivity and maintain tolerance.</p> Signup and view all the answers

    What is the main characteristic of humoral immunity?

    <p>Humoral immunity is primarily mediated by B lymphocytes and their production of antibodies to protect against extracellular microbes and toxins.</p> Signup and view all the answers

    Describe the two main components of adaptive immunity.

    <p>Adaptive immunity consists of humoral immunity mediated by B cells and cellular immunity mediated by T cells.</p> Signup and view all the answers

    How do secondary lymphoid organs facilitate the generation of adaptive immunity?

    <p>Secondary lymphoid organs, such as lymph nodes and the spleen, concentrate antigens and allow naïve lymphocytes to encounter them.</p> Signup and view all the answers

    What is the first antibody produced by plasma cells upon activation?

    <p>IgM</p> Signup and view all the answers

    Explain the role of CD16 in the function of Natural Killer (NK) cells.

    <p>CD16 is an Fc receptor for IgG, allowing NK cells to mediate antibody-dependent cellular cytotoxicity (ADCC).</p> Signup and view all the answers

    Describe how NK cells differentiate between normal and abnormal cells.

    <p>NK cells use inhibitory receptors that recognize MHC class I molecules on healthy cells to avoid attacking them.</p> Signup and view all the answers

    What happens to B cells after they are stimulated by an antigen?

    <p>They develop into plasma cells, which secrete antibodies.</p> Signup and view all the answers

    Identify the primary locations where mature B cells are distributed in the body.

    <p>Mature B cells are primarily found in peripheral blood, lymph nodes, spleen, and mucosa-associated lymphoid tissues.</p> Signup and view all the answers

    Outline the method by which NK cells induce apoptosis in target cells lacking MHC molecules.

    <p>NK cells use perforins to create holes in the target cell membrane, leading to apoptosis.</p> Signup and view all the answers

    What distinguishes the B-cell receptor (BCR) components on mature B cells?

    <p>BCRs are composed of IgM and IgD with unique antigen specificity.</p> Signup and view all the answers

    How do Natural Killer cells comprise a certain percentage of the human peripheral lymphoid cell population?

    <p>NK cells account for about 5% to 15% of the total human peripheral lymphoid cells.</p> Signup and view all the answers

    Describe the immediate role of innate immunity in response to pathogens.

    <p>Innate immunity provides immediate initial protection against invading pathogens through general defenses that do not require prior exposure.</p> Signup and view all the answers

    What are the key characteristics that differentiate innate immunity from adaptive immunity?

    <p>Innate immunity is present at birth, non-specific, and does not have memory, while adaptive immunity is developed through exposure, highly specific, and has memory.</p> Signup and view all the answers

    Explain the term 'memory' in the context of adaptive immunity and its absence in innate immunity.

    <p>In adaptive immunity, memory allows for a quicker and more effective response upon re-exposure to the same antigen, which is absent in innate immunity.</p> Signup and view all the answers

    How does innate immunity trigger the adaptive immune response?

    <p>Innate immunity detects pathogens and activates various signals and cells that prompt the adaptive immune system to respond specifically.</p> Signup and view all the answers

    Discuss the importance of recognizing self from non-self antigens in the immune system.

    <p>Recognition of self from non-self antigens is crucial to avoid attacking the body's own tissues and to mount appropriate immune responses against pathogens.</p> Signup and view all the answers

    In the context of immunity, what does the term 'cell-mediated reactions' refer to?

    <p>Cell-mediated reactions involve immune cells (like T cells) directly attacking infected or abnormal cells without relying on antibodies.</p> Signup and view all the answers

    Identify and explain the significance of one major dysfunction that can occur in the immune system.

    <p>One major dysfunction is the failure to recognize self-antigens, leading to autoimmune diseases where the immune system attacks the body's own cells.</p> Signup and view all the answers

    What role do antibodies play in the immune response and how does their formation occur?

    <p>Antibodies are proteins produced by B cells that specifically bind to antigens, neutralizing pathogens and marking them for destruction.</p> Signup and view all the answers

    What are two key functions of macrophages?

    <p>Antigen recognition and phagocytosis.</p> Signup and view all the answers

    How does opsonization enhance the immune response?

    <p>Opsonization enhances phagocytosis by coating pathogens with opsonins like immunoglobulins.</p> Signup and view all the answers

    Identify a major function of cytokines in the immune system.

    <p>Cytokines act as messenger molecules that mediate communication between immune cells.</p> Signup and view all the answers

    What cytokines are mainly produced by CD4+ T lymphocytes?

    <p>IL-2, IL-4, IL-5, IL-17, and IFN-.</p> Signup and view all the answers

    What are colony-stimulating factors characterized by in terms of their function?

    <p>They stimulate hematopoiesis and increase leukocyte numbers during immune responses.</p> Signup and view all the answers

    Explain the significance of Major Histocompatibility Complex (MHC) in the immune system.

    <p>MHC molecules present antigens on cell surfaces, enabling T cells to recognize and respond to pathogens.</p> Signup and view all the answers

    What types of cytokines are produced rapidly in response to microbes?

    <p>Cytokines of innate immunity, such as TNF, IL-1, and IL-12.</p> Signup and view all the answers

    Differentiate between the roles of opsonins and cytokines in the immune response.

    <p>Opsonins enhance phagocytosis by coating pathogens, while cytokines mediate communication and activate immune cells.</p> Signup and view all the answers

    What are the primary functions of MHC class I molecules?

    <p>MHC class I molecules are integral to the immune response to intracellular infections and tumors, interacting with CD8+ T lymphocytes during antigen presentation.</p> Signup and view all the answers

    How are MHC class II molecules primarily expressed and what is their function?

    <p>MHC class II molecules are expressed on professional antigen-presenting cells like B lymphocytes and dendritic cells, and they assist in presenting antigens to CD4+ T cells.</p> Signup and view all the answers

    Describe the genes that encode the human major histocompatibility complex and their significance.

    <p>The genes encoding MHC molecules are located on the short arm of chromosome 6 and are significant for ensuring effective immune responses and transplant compatibility.</p> Signup and view all the answers

    What is the main distinguishing feature of MHC class III molecules?

    <p>MHC class III molecules encode components of the complement system and cytokines, playing a lesser-known role in the immune system.</p> Signup and view all the answers

    Explain the relationship between HLA and autoimmune diseases.

    <p>Certain HLA alleles are associated with the predisposition to autoimmune diseases, indicating a genetic link between HLA and immune system dysfunction.</p> Signup and view all the answers

    Why are MHC molecules critical in organ/tissue transplantation?

    <p>MHC molecules are critical in organ/tissue transplantation because they help determine compatibility between donor and recipient, influencing transplant acceptance or rejection.</p> Signup and view all the answers

    What is the role of CD4+ T cells in relation to MHC class II molecules?

    <p>CD4+ T cells recognize antigens presented by MHC class II molecules and function as helper cells, crucial for activating both B cells and other immune responses.</p> Signup and view all the answers

    Describe the differences in antigen presentation between MHC class I and class II molecules.

    <p>MHC class I molecules present antigens to CD8+ T cells, while MHC class II molecules present to CD4+ T cells, indicating distinct roles in immune responses.</p> Signup and view all the answers

    Match the components of the immune system with their primary functions:

    <p>Epithelial Barriers = Mechanical barriers against microbes NK cells = Destroy abnormal host cells B lymphocytes = Produce antibodies Macrophages = Phagocytosis of pathogens</p> Signup and view all the answers

    Match the types of immunity with their characteristics:

    <p>Innate immunity = Immediate response to pathogens Humoral immunity = Mediated by B cells and antibodies Cell-mediated immunity = Involves T lymphocytes Adaptive immunity = Long-lasting memory response</p> Signup and view all the answers

    Match the primary lymphoid organs with their functions:

    <p>Thymus = Development of T cells Bone marrow = Production of B cells Lymph nodes = Site of adaptive immune responses Spleen = Filters blood and responds to blood-borne pathogens</p> Signup and view all the answers

    Match the types of T cells with their roles:

    <p>CD8+ T cells = Cytotoxic response against infected cells Regulatory T cells = Suppress immune responses Helper T cells = Assist B cells in antibody production Memory T cells = Provide long-term immunity</p> Signup and view all the answers

    Match the types of lymphocytes with their categories:

    <p>B lymphocytes = Humoral immunity CD4+ T cells = Helper T cells Neutrophils = Innate immunity Dendritic cells = Antigen presentation</p> Signup and view all the answers

    Match the types of immune responses with their descriptions:

    <p>Primary immune response = First exposure to an antigen Secondary immune response = Response to a re-exposure Innate immune response = Non-specific and immediate Adaptive immune response = Specific and memory-based</p> Signup and view all the answers

    Match the immune system cells with their characteristics:

    <p>Neutrophils = First responders to infection Basophils = Involved in allergic responses Macrophages = Phagocytosis and antigen presentation Eosinophils = Defense against parasites</p> Signup and view all the answers

    Match the types of adaptive immune responses with their targets:

    <p>Humoral immunity = Extracellular microbes and toxins Cell-mediated immunity = Intracellular microbes and tumors Regulatory T cells = Control excessive immune responses Memory B cells = Long-term pathogen recognition</p> Signup and view all the answers

    Match the following B cell functions with their corresponding descriptions:

    <p>Production of antibodies = Secretion of various antibody classes like IgG, IgA Antigen presenting cell = Processing and presenting antigens to T cells Development into plasma cells = Transformation after stimulation by antigen Receptor specificity = Unique recognition of specific antigens</p> Signup and view all the answers

    Match the following markers or molecules with their associated cells:

    <p>CD16 = Natural Killer Cells IgM = Initial antibody produced by plasma cells CD56 = Surface marker for identifying NK cells B-cell Receptor (BCR) = Receptors on B cells composed of IgM and IgD</p> Signup and view all the answers

    Match the following descriptions with the roles of Natural Killer (NK) cells:

    <p>Perforin-granzymes system = Mechanism used to induce apoptosis in abnormal cells ADCC = Killing of IgG-coated target cells Surface receptors = Recognition of MHC class I molecules Inhibitory receptors = Prevent killing of normal host cells</p> Signup and view all the answers

    Match the following types of antibodies to their primary functions:

    <p>IgG = Main antibody for secondary immune response IgA = Found in mucosal areas and secretions IgE = Involved in allergic reactions IgD = Function as a receptor on B cells</p> Signup and view all the answers

    Match the following B Lymphocyte characteristics with their respective details:

    <p>Peripheral distribution = 10% to 20% of circulating lymphocytes Mature site = Found in lymph nodes and spleen Activation = Stimulated by antigens to produce antibodies Unique specificity = Recognize distinct antigens through BCR</p> Signup and view all the answers

    Match the following NK cell recognition methods to their descriptions:

    <p>Inhibitory receptors = Recognize self-MHC to avoid killing healthy cells Activating receptors = Engage with cells lacking MHC markers Antibody-dependent cellular cytotoxicity = CD16 mediates killing of IgG-coated cells Granzyme action = Induces apoptosis in the target cell</p> Signup and view all the answers

    Match the following B cell types after activation with their characteristics:

    <p>Plasma cells = Secrete large amounts of antibodies Memory B cells = Persist for long-term immunity Naive B cells = Undifferentiated and require activation Activated B cells = Have undergone initial antigen exposure</p> Signup and view all the answers

    Match the following immune cells to their respective features:

    <p>B Lymphocytes = Primary producers of antibodies T Lymphocytes = Mediators of cell-mediated immunity Natural Killer Cells = Part of the innate immune response Antigen presenting cells = Present antigens to activate T cells</p> Signup and view all the answers

    Match the following types of immunity with their characteristics:

    <p>Innate Immunity = First line of defense Adaptive Immunity = Requires prior exposure to antigens Natural Immunity = Present from birth Artificial Immunity = Acquired through immunization</p> Signup and view all the answers

    Match the following immune system functions with their descriptions:

    <p>Recognition of self = Distinguishing between body cells and pathogens Memory = Ability to remember past infections Antibody formation = Production of immunoglobulins against pathogens Cell-mediated reactions = Immune response involving T cells</p> Signup and view all the answers

    Match the following types of passive immunity with their sources:

    <p>Maternal Passive Immunity = Transfer of antibodies during pregnancy Artificial Passive Immunity = Transfer of antibodies via serum Natural Passive Immunity = Breast milk antibodies Active Immunity = Body's response to natural infection</p> Signup and view all the answers

    Match the following characteristics of innate immunity with their features:

    <p>Immediate response = Provides quick defense against pathogens Lacks specificity = Does not differentiate between pathogens Triggers adaptive response = Initiates further immune responses No memory = Does not retain information about pathogens</p> Signup and view all the answers

    Match the following cells with their primary roles in the immune system:

    <p>T cells = Cell-mediated immunity B cells = Humoral immunity Natural Killer cells = Targeting infected cells Macrophages = Phagocytosis and antigen presentation</p> Signup and view all the answers

    Match the following types of adaptive immunity with their activation method:

    <p>Active Immunity = Infection or vaccination Passive Immunity = Receiving pre-formed antibodies Natural Immunity = Exposure to pathogens Artificial Immunity = Medical interventions such as vaccines</p> Signup and view all the answers

    Match the following components with their functions in the immune system:

    <p>Antibodies = Bind to antigens for neutralization Cytokines = Facilitate cell communication MHC molecules = Present antigens to T cells Complement proteins = Enhance opsonization and lysis of pathogens</p> Signup and view all the answers

    Match the following types of immune cells with their specific functions:

    <p>B Lymphocytes = Produce antibodies T Helper Cells = Activate B cells and T cells Cytotoxic T Cells = Kill infected cells Regulatory T Cells = Maintain immune tolerance</p> Signup and view all the answers

    Match the following functions of macrophages with their corresponding descriptions:

    <p>Antigen recognition = Identifying and binding to foreign antigens Phagocytosis = Engulfing and destroying pathogens Secretory function = Releasing molecules that mediate immune response Antigen presentation = Showing processed antigens to T cells</p> Signup and view all the answers

    Match the following types of cytokines with their primary functions:

    <p>Cytokines of Innate Immunity = Rapidly produced to mediate inflammation Cytokines of Adaptive Immunity = Promote lymphocyte proliferation Colony-Stimulating Factors = Stimulate formation of blood cell colonies Regulatory cytokines = Help modulate immune responses</p> Signup and view all the answers

    Match the following soluble mediators of immunity with their roles:

    <p>Opsonins = Enhance phagocytosis by coating pathogens Cytokines = Messenger molecules for immune communication Proteins of the complement system = Participate in opsonization and lysis of pathogens Acute phase reactants = Participants in the systemic inflammatory response</p> Signup and view all the answers

    Match the following cytokines with their producing cells:

    <p>TNF = Macrophages IL-2 = CD4+ T lymphocytes IL-1 = Dendritic cells Chemokines = Natural Killer (NK) cells</p> Signup and view all the answers

    Match the following types of immune responses with their associated characteristics:

    <p>Innate immunity = Immediate response to pathogens Adaptive immunity = Involves memory cells for long-lasting defense Humoral immunity = Production of antibodies by B cells Cell-mediated immunity = Involves direct action by T cells</p> Signup and view all the answers

    Match the following components of the major histocompatibility complex (MHC) with their features:

    <p>MHC class I = Present antigens to CD8+ T cells MHC class II = Present antigens to CD4+ T cells MHC class III = Involves complement proteins MHC genes = Located on chromosome 6 in humans</p> Signup and view all the answers

    Match the following types of cells with their immune functions:

    <p>Macrophages = Phagocytosis and antigen presentation Dendritic cells = Initiate adaptive immune response Natural Killer cells = Destroy infected or stressed cells B lymphocytes = Produce antibodies</p> Signup and view all the answers

    Match the following terms related to the immune system with their definitions:

    <p>Opsonization = Coating pathogens to enhance phagocytosis Cytokines = Soluble proteins mediating immune responses Phagocytosis = The ingestion of pathogens by immune cells Acute phase response = Systemic reaction to inflammation or injury</p> Signup and view all the answers

    Match the following class of MHC molecules with their characteristics:

    <p>Class I MHC = Expressed on all nucleated cells and platelets Class II MHC = Expressed only on professional antigen-presenting cells Class III MHC = Encode components of the complement system All MHC molecules = Involved in antigen presentation</p> Signup and view all the answers

    Match the following HLA alleles with the associated conditions:

    <p>HLA-B27 = Ankylosing spondylitis HLA-DQ = Autoimmune endocrinopathies HLA-DR = Rheumatoid arthritis HLA-A = Type 1 diabetes</p> Signup and view all the answers

    Match the MHC classes with their respective T lymphocyte interactions:

    <p>MHC Class I = Interacts with CD8+ T lymphocytes MHC Class II = Interacts with CD4+ T lymphocytes MHC Class III = Not directly involved with T lymphocytes MHC molecules = Required for T cell recognition of antigens</p> Signup and view all the answers

    Match the following phrases with their respective MHC molecule functions:

    <p>MHC Class I = Present intracellular antigens MHC Class II = Assist in activating helper T cells Class I and II = Above functions are critical for immune responses Class III = Involved in cytokine production</p> Signup and view all the answers

    Match the MHC gene loci with their designated classes:

    <p>HLA-A = Class I MHC HLA-B = Class I MHC HLA-DR = Class II MHC HLA-DP = Class II MHC</p> Signup and view all the answers

    Match the statements with their respective MHC classes:

    <p>Class I = Expressed by all nucleated cells Class II = Involved in antigen presentation on B cells Class III = Produces complement components All MHC classes = Facilitate adaptive immune response</p> Signup and view all the answers

    Match the following MHC-related functions with their description:

    <p>Peptide display = Recognition by T lymphocytes Transplantation = Minimizing graft rejection Immune response = Reaction to tumors and infections Disease association = Linking alleles to autoimmune conditions</p> Signup and view all the answers

    Match the following terms with their definitions:

    <p>Antigen presenting cells = Include B cells and dendritic cells HLA complex = Cluster of MHC genes on chromosome 6 CD8+ T lymphocytes = Cytotoxic T cells activated by Class I MHC CD4+ T lymphocytes = Helper T cells activated by Class II MHC</p> Signup and view all the answers

    What is a critical feature of Type I hypersensitivity reactions?

    <p>They typically involve the release of histamines from mast cells.</p> Signup and view all the answers

    What is a characteristic feature of the late-phase reaction in type I hypersensitivity?

    <p>Infiltration of eosinophils and neutrophils</p> Signup and view all the answers

    Which type of antigens can trigger hypersensitivity reactions?

    <p>Antigens that are either endogenous or exogenous</p> Signup and view all the answers

    Which of the following is an example of systemic type I hypersensitivity reaction?

    <p>Anaphylactic shock</p> Signup and view all the answers

    What percentage of the population is typically affected by Type I hypersensitivity reactions?

    <p>10-20%</p> Signup and view all the answers

    Which immunoglobulin is primarily involved in the mediation of Type I hypersensitivity reactions?

    <p>IgE</p> Signup and view all the answers

    What mediators are primarily released in the late-phase reaction of type I hypersensitivity?

    <p>Prostaglandins and leukotrienes</p> Signup and view all the answers

    What role do HLA genes play in hypersensitivity reactions?

    <p>They are associated with genetic susceptibility to hypersensitivity.</p> Signup and view all the answers

    Which type of antibodies is predominantly involved in type II hypersensitivity reactions?

    <p>IgG and IgM</p> Signup and view all the answers

    What is a common effect of the antigen-antibody reaction in type II hypersensitivity?

    <p>Complement-dependent lysis of target cells</p> Signup and view all the answers

    Which of the following best describes the sensitization phase of hypersensitivity reactions?

    <p>It occurs the first time an individual encounters an allergen.</p> Signup and view all the answers

    Which characteristic distinguishes Type II hypersensitivity reactions from Type I?

    <p>Type II reactions are antibody-mediated and often involve IgG or IgM.</p> Signup and view all the answers

    What type of hypersensitivity reaction is characterized by smooth muscle spasms and glandular secretions?

    <p>Type I hypersensitivity</p> Signup and view all the answers

    What is the main consequence of the interaction between allergens and sensitized mast cells in Type I hypersensitivity?

    <p>Release of inflammatory mediators like histamines</p> Signup and view all the answers

    Which of the following cell types is typically infiltrated during a type I hypersensitivity reaction?

    <p>Eosinophils and TH2 cells</p> Signup and view all the answers

    What role do inflammatory mediators play in the context of a localized type I hypersensitivity reaction like hay fever?

    <p>Enhance acute local inflammation</p> Signup and view all the answers

    What is the role of IL-4 in the sensitization phase of hypersensitivity reactions?

    <p>Stimulates B cells to secrete IgE antibodies</p> Signup and view all the answers

    Which of the following best describes the immediate phase response in a hypersensitivity reaction?

    <p>It occurs within minutes and subsides within an hour.</p> Signup and view all the answers

    Which cell type is primarily responsible for the release of mediators during a re-exposure to the allergen?

    <p>Mast cells</p> Signup and view all the answers

    What is the effect of cross-linking IgE on the surface of mast cells?

    <p>It promotes activation and degranulation of mast cells.</p> Signup and view all the answers

    Which cytokine is primarily responsible for eosinophil activation during the sensitization phase?

    <p>IL-5</p> Signup and view all the answers

    During the sensitization process, what is the role of antigen-presenting cells (APCs)?

    <p>They present the antigen to T cells.</p> Signup and view all the answers

    What is the function of TH2 cells in the allergic response?

    <p>They stimulate B cells and eosinophil activity.</p> Signup and view all the answers

    Which of the following components released from mast cells is primarily responsible for increased vascular permeability?

    <p>Histamine</p> Signup and view all the answers

    Which mechanism involves antibody-dependent lysis of target cells through complement activation?

    <p>Cell lysis</p> Signup and view all the answers

    What type of hypersensitivity reaction is characterized by antibody-mediated destruction of cells?

    <p>Type II hypersensitivity</p> Signup and view all the answers

    In which scenario do antibodies cause dysfunction without directly injuring the cell?

    <p>Grave's disease</p> Signup and view all the answers

    What is the primary role of opsonization in phagocytosis?

    <p>To mark cells for recognition by phagocytes</p> Signup and view all the answers

    Which example illustrates a type II hypersensitivity reaction involving blood cells?

    <p>Hemolytic disease of the newborn</p> Signup and view all the answers

    In antibody-dependent cellular cytotoxicity, what is the role of the antibody?

    <p>To link the target cell with immune effector cells</p> Signup and view all the answers

    What is a consequence of autoantibodies binding to cell surface receptors in antibody-mediated dysfunction?

    <p>Inhibition of normal cell function</p> Signup and view all the answers

    Which of the following conditions does NOT represent a type II hypersensitivity reaction?

    <p>Asthma</p> Signup and view all the answers

    What is a crucial requirement for the development of hypersensitivity reactions?

    <p>Prior sensitization to the allergen</p> Signup and view all the answers

    Which type of hypersensitivity reaction is primarily mediated by IgE antibodies?

    <p>Type I hypersensitivity</p> Signup and view all the answers

    What percentage of the population is estimated to experience Type I hypersensitivity reactions?

    <p>10-20%</p> Signup and view all the answers

    Which statement correctly describes the nature of antigens involved in hypersensitivity reactions?

    <p>Both exogenous and endogenous antigens can be involved</p> Signup and view all the answers

    Which feature distinguishes Type IV hypersensitivity from Types I, II, and III?

    <p>Cell-mediated response</p> Signup and view all the answers

    Genetic susceptibility to hypersensitivity diseases often involves which type of genes?

    <p>HLA genes</p> Signup and view all the answers

    Which of the following best describes the timing of a Type I hypersensitivity reaction?

    <p>Occurs within minutes (5-10 minutes)</p> Signup and view all the answers

    What role do mast cells play in Type I hypersensitivity reactions?

    <p>Bind IgE antibodies</p> Signup and view all the answers

    What is the primary role of TH2 cells once activated by sensitizing antigens?

    <p>They secrete cytokines that stimulate B cells and eosinophils.</p> Signup and view all the answers

    Which type of antibody is produced as a result of B cell activation by IL-4 from TH2 cells?

    <p>IgE</p> Signup and view all the answers

    What triggers the immediate phase response upon re-exposure to an allergen?

    <p>Cross-linking of IgE molecules on mast cells or basophils.</p> Signup and view all the answers

    Which of the following describes a characteristic of mast cells in allergic reactions?

    <p>They contain granules that release mediators upon activation.</p> Signup and view all the answers

    What is the general time frame for the development of the immediate phase response after re-exposure to an allergen?

    <p>5 to 30 minutes</p> Signup and view all the answers

    What types of allergic reactions can be seen in genetically susceptible individuals?

    <p>Multiple types including asthma, hay fever, and food allergies</p> Signup and view all the answers

    Which cytokine released by TH2 cells primarily activates eosinophils?

    <p>IL-5</p> Signup and view all the answers

    What is a consequence of mast cell degranulation during a type I hypersensitivity reaction?

    <p>Vasodilation and increased vascular permeability</p> Signup and view all the answers

    What is the role of IgG and IgM in type II hypersensitivity reactions?

    <p>They activate the complement system leading to cell lysis.</p> Signup and view all the answers

    Which mechanism leads to the phagocytosis of cells coated with antibodies?

    <p>Opsonization by antibodies and complement proteins.</p> Signup and view all the answers

    In which condition do antibodies act as agonists, stimulating the target cell's activity?

    <p>Grave’s disease.</p> Signup and view all the answers

    What type of hypersensitivity reaction is characterized by cell lysis due to antibody binding to cell surface antigens?

    <p>Type II hypersensitivity.</p> Signup and view all the answers

    Which mechanism illustrates antibody-dependent cellular cytotoxicity (ADCC)?

    <p>Linking of NK cells to target cells without phagocytosis.</p> Signup and view all the answers

    What is a common cause of hemolytic anemia related to type II hypersensitivity?

    <p>Incompatible blood transfusion.</p> Signup and view all the answers

    Which of the following correctly describes the consequences of antibody-mediated cellular dysfunction?

    <p>Impairment of cell function without inflammation.</p> Signup and view all the answers

    How do opsonized cells become targets for macrophages?

    <p>Via specific receptors for antibody and complement.</p> Signup and view all the answers

    What is a primary characteristic of the late-phase reaction in a type I hypersensitivity response?

    <p>Infiltration of eosinophils and neutrophils</p> Signup and view all the answers

    Which type of hypersensitivity reaction is characterized by the presence of antibodies targeting specific antigens on cell surfaces?

    <p>Type II hypersensitivity</p> Signup and view all the answers

    What type of cell is primarily involved in the immediate hypersensitivity reactions such as hay fever and asthma?

    <p>Mast cells</p> Signup and view all the answers

    What clinical condition may result from systemic type I hypersensitivity reactions?

    <p>Anaphylactic shock</p> Signup and view all the answers

    Which mediators are typically released during the late-phase reaction of type I hypersensitivity?

    <p>Cytokines and leukotrienes</p> Signup and view all the answers

    In an antibody-mediated type II hypersensitivity reaction, which of the following effects is NOT a consequence of the antigen-antibody reaction?

    <p>Allergic inflammation</p> Signup and view all the answers

    Which cells are primarily involved in the infiltration seen during late-phase type I hypersensitivity reactions?

    <p>Eosinophils and TH2 cells</p> Signup and view all the answers

    Which antibody is most commonly associated with IgG-dependent type II hypersensitivity reactions?

    <p>IgG</p> Signup and view all the answers

    Study Notes

    Immunity: Protection Against Disease

    • Immunity: The body's defense mechanism against pathogens.
    • Immune System: Consists of cells (leukocytes) & molecules that combat microbes.
    • Immune Response: Collaborative reaction of cells & molecules to pathogens.

    Functions of the Immune System

    • Recognizes "self" from "non-self" antigens (foreign substances).
    • Mounts a specific response to non-self antigens.
    • Retains memory of previously encountered non-self antigens.
    • Produces antibodies (immunoglobulins, Ig).
    • Orchestrates cell-mediated reactions.

    Types of Immunity

    • Innate Immunity (Natural/Native): First line of defense.

      • Present at birth.
      • Immediate protection against invaders.
      • Lacks specificity; highly effective.
      • Triggers adaptive immunity.
      • No memory response.

    • Adaptive Immunity: Second Line of defense.

      • Acquired over time through exposure.
      • Slower to develop, but more powerful.
      • Requires prior antigen exposure.
      • Highly specific to targets.
      • Long-lasting protection (memory).

    Components of Innate Immunity

    • Epithelial Barriers: Skin, gastrointestinal & respiratory tracts act as physical & chemical barriers (defensins).
    • Humoral: Complement system (proteins that help in destruction of pathogens).
    • Cellular: Includes:
      • Neutrophils
      • Macrophages
      • Natural Killer (NK) cells.

    Components of Adaptive Immunity

    • Humoral Immunity: Protects against extracellular microbes & toxins.

      • Mediated by B lymphocytes (bone marrow-derived).
      • Produces antibodies (Ig).

    • Cell-mediated (Cellular) Immunity: Defends against intracellular microbes & cancer.

      • Mediated by T lymphocytes (thymus-derived).

    Major Organs of the Immune System

    • Primary Lymphoid Organs:

      • Thymus: Site of T cell development.
      • Bone Marrow: Produces all blood cells, including naïve B cells.

    • Secondary Lymphoid Organs: Where adaptive immune responses occur.

      • Lymph Nodes
      • Spleen
      • Mucosal & Cutaneous Lymphoid Tissues

    Cells of the Immune System

    • Lymphocytes:
      • T Lymphocytes:
        • CD4+ T cells (Helper T cells): Activate other immune cells.
          • Th1 Cells: Promote cell-mediated immunity.
          • Th2 Cells: Promote humoral immunity.
        • CD8+ T cells (Cytotoxic T cells): Destroy infected cells.
        • Regulatory T cells: Suppress immune responses.
      • B Lymphocytes: - Produce antibodies. - Act as antigen-presenting cells.
        • Natural Killer (NK) Cells: Kill infected or cancerous cells without prior sensitization.
    • Monocytes and Macrophages: Phagocytose pathogens, present antigens, and release inflammatory mediators.
    • Mast Cells and Basophils: Release histamine and other inflammatory mediators.
    • Neutrophils and Eosinophils: Phagocytose pathogens and release enzymes to kill them.

    Soluble Mediators of Immunity

    • Opsonins: Coat pathogens to enhance phagocytosis.
    • Cytokines: Signaling molecules that regulate immune responses.
      • Innate Immunity Cytokines: TNF, IL-1, IL-12, chemokines.
      • Adaptive Immunity Cytokines: IL-2, IL-4, IL-5, IL-17, IFN-γ.
      • Colony-Stimulating Factors: Stimulate hematopoiesis (blood cell production).
    • Complement System Proteins: A cascade of proteins that leads to lysis of pathogens, inflammation, and opsonization.

    Major Histocompatibility Complex (MHC)

    • Function: Present peptides from pathogens to T cells for recognition.
    • MHC Genes: Encode MHC molecules, located on chromosome 6.
    • Human Leukocyte Antigen (HLA) System: The human MHC system.
      • Class I MHC Molecules: Expressed on all nucleated cells. Present peptides to CD8+ T cells.
      • Class II MHC Molecules: Expressed on antigen-presenting cells. Present peptides to CD4+ T cells.
      • Class III MHC Molecules: Encode complement proteins, cytokines, and other proteins.

    HLA and Disease Association

    • Certain HLA alleles are linked to specific diseases:
      • Inflammatory Diseases: Ankylosing spondylitis.
      • Autoimmune Diseases: Autoimmune endocrinopathies.
      • Inherited Metabolic Errors: Various genetic conditions.

    Immunity

    • Immunity protects the body against diseases.
    • The immune system comprises cells and molecules that defend against pathogens.
    • The immune response is a coordinated reaction to infectious agents.

    Immune System Functions

    • Recognizes self from non-self antigens.
    • Mounts a specific response to non-self antigens.
    • Retains memory of previously encountered non-self antigens.
    • Produces antibodies.
    • Facilitates cell-mediated reactions.

    Types of Immunity

    • Innate Immunity: Present at birth and provides immediate initial protection.
      • Does not require prior exposure to foreign antigens.
      • Lacks specificity but is highly effective.
      • Triggers the adaptive immune response.
    • Adaptive Immunity: Acquired through exposure to antigens.
      • Slower to develop but more powerful than innate immunity.
      • Highly specific and provides long-lasting protection (memory).

    Innate Immunity Components

    • Epithelial barriers act as mechanical barriers and produce antimicrobial molecules (defensins).
    • Humoral component: Complement.
    • Cellular component: Neutrophils, macrophages, and natural killer (NK) cells.

    Adaptive Immunity Components

    • Humoral Immunity: Protects against extracellular microbes and toxins.
      • Mediated by B lymphocytes and their antibodies (immunoglobulins, Ig).
    • Cell-mediated Immunity: Responsible for defense against intracellular microbes and cancers.
      • Mediated by T lymphocytes.

    Organs of the Immune System

    • Primary lymphoid organs:
      • Thymus: T cell development.
      • Bone marrow: Production of all blood cells, including naïve B cells.
    • Secondary lymphoid organs:
      • Lymph nodes, spleen, and mucosal/cutaneous lymphoid tissues: Sites of adaptive immune responses.

    Immune System Cells

    • Lymphocytes:
      • T lymphocytes (T cells):
        • CD4+ T cells (helper T cells):
          • Express CD4 molecule.
          • Assist other immune cells (B cells, macrophages) in fighting infection.
          • Secrete cytokines that regulate the immune response.
        • CD8+ T cells (cytotoxic/killer T cells):
          • Express CD8 molecule.
          • Directly destroy infected or cancerous cells.
        • Regulatory T cells:
          • Suppress immune responses to prevent overreaction.
      • B lymphocytes (B cells):
        • Mature in the bone marrow.
        • Produce antibodies (IgM, IgG, IgD, IgA, IgE) upon activation by antigen.
        • Function as antigen-presenting cells.
      • Natural Killer (NK) cells:
        • Large granular lymphocytes.
        • Kill virus-infected cells and tumor cells without prior sensitization.
        • Use ADCC (Antibody-dependent cellular cytotoxicity) and perforin-granzymes system.
    • Monocytes and Macrophages:
      • Immature macrophages in circulation.
      • Phagocytose pathogens.
      • Secrete cytokines and proteins involved in wound healing.
      • Present antigens to T cells.

    Soluble Mediators of Immunity

    • Opsonins:
      • Coat pathogens to enhance phagocytosis.
      • Include immunoglobulins and complements.
    • Cytokines:
      • Short-acting soluble proteins secreted by immune cells.
      • Mediate communication between immune cells.
      • Classified based on their functions (innate immunity, adaptive immunity, colony-stimulating factors).
    • Complement System:
      • Group of proteins that activate a cascade of reactions leading to pathogen destruction.

    Major Histocompatibility Complex (MHC)

    • Membrane-bound proteins encoded by MHC genes.
    • Present peptides to T cells.
    • Critical for T-cell immunity.
    • In humans, MHC genes are located on chromosome 6 and called HLA (human leukocyte antigen) complex.

    MHC Molecules

    • Class I MHC: Expressed on all nucleated cells and platelets.
      • Involved in the immune response to intracellular infections, tumors, and allografts.
      • Interact with CD8+ T lymphocytes during antigen presentation.
    • Class II MHC: Expressed on antigen-presenting cells (B lymphocytes, macrophages, dendritic cells) and activated T cells.
      • Involved in antigen processing and presentation.
      • Recognized by CD4+ T lymphocytes (helper cells).
    • Class III MHC:
      • Encode components of the complement system, cytokines, and other proteins.

    HLA and Disease Association

    • Certain HLA alleles are associated with specific diseases.
      • Inflammatory diseases (e.g., ankylosing spondylitis linked to HLA-B27).
      • Autoimmune diseases (e.g., autoimmune endocrinopathies linked to DR locus alleles).
      • Inherited errors of metabolism.

    Immunity

    • Immunity is the body's defense system against infectious agents.

    Immune System

    • The immune system is a collection of cells and molecules responsible for defending the body.
    • Key functions include:
      • Recognizing self from non-self antigens.
      • Mounting a specific response to non-self antigens.
      • Remembering previously recognized non-self antigens.
      • Antibody formation.
      • Cell-mediated reactions.

    Immune System Diseases

    • Failure or derangement of the immune system results in diseases of the immune system.

    Types of Immunity

    • There are two main categories: innate and adaptive.
      • Innate immunity is present at birth, providing immediate protection.
      • Adaptive immunity is acquired and takes longer to develop.

    Innate Immunity

    • Features:

      • First line of defense.
      • Present at birth.
      • Immediate initial protection.
      • Does not rely on prior contact with foreign antigens.
      • Lacks specificity, but highly effective.
      • Triggers adaptive immune response.
      • No memory.

    • Components:

      • Epithelial barriers: Skin and gastrointestinal/ respiratory tracts act as physical barriers and produce antimicrobial molecules like defensins.
      • Humoral: Includes complement.
      • Cellular: Consists of neutrophils, macrophages, and natural killer (NK) cells.

    Adaptive Immunity

    • Features:

      • Acquired in nature.
      • Second line of defense.
      • More powerful and takes longer to develop than innate immunity.
      • Requires prior exposure to antigens.
      • Recognizes microbial and non-microbial substances.
      • Long-lasting protection (memory).
      • Specific.

    • Components:

      • Humoral immunity: Mediated by B lymphocytes and their antibodies.
      • Cell-mediated (or cellular) immunity: Responsible for defense against intracellular microbes and cancers. Mediated by T lymphocytes.

    Organs of the Immune System

    • Primary lymphoid organs: Where immune cells develop.

      • Thymus: Development of T cells.
      • Bone Marrow: Production of all other blood cells, including naïve B cells.

    • Secondary lymphoid organs: Where adaptive immune responses occur.

      • Lymph nodes: Filter lymph and house lymphocytes.
      • Spleen: Filters blood and houses lymphocytes.
      • Mucosal and cutaneous lymphoid tissues: Immune responses in the lining of the gut and skin.

    Immune System Cells

    • Lymphocytes:

      • T lymphocytes (T cells):
        • CD4+ T cells: Helper T cells that activate other immune cells.
        • CD8+ T cells: Cytotoxic (killer) T cells that destroy infected cells.
        • Regulatory T cells: Suppress the immune response.
      • B lymphocytes (B cells):
        • Develop in bone marrow.
        • Produce antibodies.
        • Function as Antigen Presenting Cells (APCs).
      • Natural Killer Cells (NK cells):
        • Non-phagocytic lymphocytes.
        • Kill virus-infected and tumor cells.
        • Recognize abnormal cells via:
          • Antibody-dependent cellular cytotoxicity (ADCC).
          • Perforin-granzyme system.

    • Monocytes and Macrophages:

      • Monocytes are immature macrophages.
      • Functions:
        • Antigen recognition.
        • Phagocytosis.
        • Secretion of cytokines, collagenase, elastase, fibroblast growth factor, angiogenesis factor, etc.
        • Antigen presentation.

    • Mast cells and basophils: Involved in allergic reactions and inflammation.

    • Neutrophils and eosinophils: Phagocytic cells that fight infections.

    Soluble Mediators of Immunity

    • Opsonins: Molecules that coat pathogens, enhancing phagocytosis.

    • Cytokines:

      • Short-acting soluble proteins that mediate communication between cells.
      • Innate immunity cytokines: Produced by macrophages, dendritic cells, and NK cells.
      • Adaptive immunity cytokines: Produced by CD4+ T lymphocytes.
      • Colony-Stimulating Factors: Stimulate hematopoiesis.

    • Proteins of the complement system: A system of proteins that helps eliminate pathogens.

    Major Histocompatibility Complex (MHC)

    • MHC genes: Located on chromosome 6 in humans.
    • MHC proteins: Membrane-bound proteins that display peptide fragments for recognition by T cells.
    • Human MHC: Called HLA (human leukocyte antigen).

    Importance of MHC

    • Organ/Tissue transplantation: MHC compatibility is crucial for transplant success.
    • Autoimmune diseases: Certain HLA alleles are associated with autoimmune diseases.

    Classification of MHC Molecules

    • Class I MHC:

      • Expressed by all nucleated cells.
      • Encoded by HLA-A, HLA-B, and HLA-C genes.
      • Involved in immune response against intracellular infections, cancers, and allografts.
      • Interact with CD8+ T lymphocytes during antigen presentation.

    • Class II MHC:

      • Expressed by professional antigen-presenting cells (APCs) and activated T cells.
      • Encoded by HLA-DP, HLA-DQ, and HLA-DR genes.
      • Involved in antigen processing and presentation.
      • Interact with CD4+ T lymphocytes.

    • Class III MHC:

      • Encode components of the complement system, cytokines, and other proteins.

    HLA and Disease Association

    • Some diseases are associated with specific HLA alleles:
      • Inflammatory diseases: Ankylosing spondylitis is strongly associated with HLA-B27.
      • Autoimmune diseases: Autoimmune endocrinopathies are associated with DR alleles.
      • Inherited errors of metabolism: Specific HLA alleles can be associated with certain metabolic disorders.

    Immunity

    • Definition: Protection against diseases.
    • Immune System: Collection of cells and molecules responsible for defending the body against pathogens.
    • Immune Response: Coordinated reaction of cells and molecules to infectious agents.
    • Immune System Functions:
      • Recognition of self from non-self antigens.
      • Mounting specific response to non-self antigens.
      • Memory of recognized non-self antigens.
      • Antibody formation.
      • Cell-mediated reactions.
    • Immune System Diseases: Result from failure or derangement of the immune system.

    Types of Immunity

    • Innate (Natural/Native) Immunity:
      • General Features:
        • First line of defense.
        • Present at birth.
        • Provides immediate initial protection.
        • Does not depend on prior contact with foreign antigens.
        • Lacks specificity, but highly effective.
        • Triggers adaptive immune response.
        • No memory.
      • Major Components:
        • Epithelial Barriers: Act as mechanical barriers.
        • Humoral: Comprised by complement.
        • Cellular: Includes neutrophils, macrophages, and NK cells.
    • Adaptive (Specific) Immunity:
      • General Features:
        • Acquired in nature.
        • Second line of defense.
        • Takes more time to develop.
        • More powerful than innate immunity.
        • Prior exposure to antigen is required.
        • Recognizes microbial and non-microbial substances.
        • Long-lasting protection (memory).
        • Specific.
      • Two Main Components:
        • Humoral Immunity: Protects against extracellular microbes and their toxins. Mediated by B lymphocytes and antibodies.
        • Cell-mediated Immunity: Defense against intracellular microbes and cancers. Mediated by T lymphocytes.

    Organs of the Immune System

    • Primary Lymphoid Organs:
      • Thymus: T cell development.
      • Bone Marrow: Production of all other blood cells, including naive B cells.
    • Secondary Lymphoid Organs:
      • Lymph Nodes: Adaptive immune responses.
      • Spleen: Adaptive immune responses.
      • Mucosal and Cutaneous Lymphoid Tissues: Adaptive immune responses.

    Immune System Cells

    • Lymphocytes:
      • T Lymphocytes:
        • CD4+ T Cells: Helper T cells.
        • CD8+ T Cells: Cytotoxic/Killer T cells.
        • Regulatory T Cells: Suppress the immune response.
      • B Lymphocytes:
        • Development: Mature in bone marrow.
        • Distribution: Peripheral blood, lymph nodes, spleen, and mucosa-associated lymphoid tissues.
        • Function: Produce antibodies, antigen presenting cells.
      • Natural Killer (NK) Cells:
        • Function: Kill virus-infected cells and tumor cells without prior exposure.
        • Mechanisms:
          • Antibody-dependent cellular cytotoxicity (ADCC): NK cells lyse IgG-coated target cells.
          • Perforin-granzymes system: NK cells cause apoptosis of target cells.
    • Monocytes, Macrophages, and Dendritic Cells:
      • Monocytes: Immature macrophages.
      • Macrophages: Antigen recognition, phagocytosis, cytokine secretion, antigen presentation.
    • Mast Cells and Basophils:
    • Neutrophils and Eosinophils:

    Soluble Mediators of Immunity

    • Opsonins: Enhance phagocytosis by coating pathogens.
    • Cytokines:
      • Functions: Messenger molecules of the immune system, mediate communication between cells.
      • Classification:
        • Cytokines of Innate Immunity: Produced rapidly by macrophages, dendritic cells, and NK cells.
        • Cytokines of Adaptive Immunity: Produced by CD4+ T cells.
        • Colony-Stimulating Factors: Stimulate hematopoiesis.
    • Complement System: A group of serum proteins that act in concert to bring about the destruction of foreign cells.

    Major Histocompatibility Complex (MHC)

    • Definition: Membrane-bound proteins encoded by MHC genes.
    • Function: Peptide display molecules for recognition by T lymphocytes.
    • Location: Chromosome 6 (short arm).
    • Human MHC: Called Human Leukocyte Antigen (HLA) complex.
    • Importance:
      • Organ/tissue transplantation.
      • Disease association, including inflammatory and autoimmune diseases.

    MHC Classification

    • Class I MHC Molecules:
      • Expression: All nucleated cells and platelets.
      • Encoding Genes: HLA-A, HLA-B, and HLA-C.
      • Functions: Interact with CD8+ T lymphocytes, involved in cytotoxic reactions.
    • Class II MHC Molecules:
      • Encoding Genes: HLA-DP, HLADQ, and HLA-DR.
      • Expression: Professional antigen-presenting cells (B cells, macrophages, dendritic cells).
      • Functions: Interact with CD4+ T lymphocytes, involved in helper T cell responses.
    • Class III MHC Molecules:
      • Encoding Genes: Genes encoding components of the complement system, cytokines and other proteins.

    Hypersensitivity Reactions

    • A type of immune response causing tissue injury, disease, or even death in a sensitized individual.
    • Also known as an exaggerated response to an antigen.
    • Key features:
      • Priming/Sensitization: Prior exposure to the allergen is required for sensitization to occur.
      • Genetic Susceptibility: Predisposition to hypersensitivity may be inherited, especially involving HLA genes.
      • Complex Interaction: Genetic predisposition and exposure play a critical role in developing hypersensitivity towards specific allergens.
      • Antigen Origin: Allergens can be endogenous or exogenous.
      • Exogenous Allergens: Commonly found in dust, pollens, foods, drugs, microbes, chemicals, and blood products.
      • Endogenous Allergens: Self antigens.

    Classification of Hypersensitivity Reactions

    • Type I (Immediate Hypersensitivity): Commonly called allergic or atopic disorders, elicited by allergens from the environment.
    • Type II Hypersensitivity (Antibody-Mediated Disorder): Antibodies directed against specific antigens fixed on cell surfaces, causing lysis of target cells.
    • Type III Hypersensitivity (Immune Complex-Mediated Disorders): Immune complexes formed between antigens and antibodies deposit in tissues, triggering inflammation.
    • Type IV Hypersensitivity (Cell-Mediated or Delayed Type): T cell-mediated immune response, delayed reaction (24-72 hours).

    Type I (Immediate) Hypersensitivity Reactions

    • Characteristics:
      • Affects 10-20% of the population.
      • Rapid reaction occurring within 5-10 minutes.
      • Mediated by IgE antibody.
      • Elevated serum IgE levels in atopic individuals.
      • Occurs in genetically susceptible individuals previously sensitized to the antigen (atopic).
    • Allergens: Many allergens (e.g., house dust mites, pollens, animal danders, molds) are harmless for most people.
    • Examples: Bronchial asthma, hay fever, food allergies.

    Mechanisms of Type I Hypersensitivity Reactions

    • Initial Exposure to Antigen (Sensitization):
      • Exposure: Inhalation, ingestion, or injection of the allergen.
      • Presentation: Allergen presented to T cells by antigen-presenting cells (APCs - macrophages).
      • TH2 Cell Activation: In genetically susceptible people, allergens activate TH2 cells, which secrete cytokines like IL-4, IL-5, and IL-13.
      • IgE Antibody Production: IL-4 from TH2 cells stimulates B cells to produce IgE antibodies.
        • IL-5 activates eosinophils.
        • IL-13 triggers mucus production by epithelial cells.
      • Mast Cell Sensitization by IgE:
        • Mast Cells are concentrated near blood vessels, nerves, and subepithelial tissues.
        • Mast cells have Fc receptors with high affinity for IgE.
        • IgE antibodies attach to mast cells and basophils - this sensitization takes time to develop.
        • First exposure to the allergen does not cause a reaction.
    • Re-exposure to Antigen:
      • Allergen cross-links IgE molecules on the surface of mast cells or basophils, activating degranulation.
      • Mediators Release: Mast cells/basophils release mediators like histamine, cytokines, prostaglandins, and leukotrienes, causing immediate allergic symptoms.
    • Immediate Phase Response:
      • Occurs within 5-30 minutes after exposure, subsides in 60 minutes.
      • Pre-formed mediators (histamine, proteases, chemotactic factors) are released.
      • Characterized by vasodilation, increased vascular permeability, smooth muscle spasm, and glandular secretions.
    • Late-Phase Reaction:
      • Develops 2-8 hours after exposure, lasting for several days.
      • Release of secondary mediators from mast cells (prostaglandins, leukotrienes, cytokines, platelet-activating factor (PAF)).
      • Characterized by tissue infiltration with eosinophils, neutrophils, basophils, monocytes, and TH2 cells.
      • Mucosal epithelial cell damage can occur.

    Examples of Type I Hypersensitivity

    • Localized Type I Hypersensitivity:
      • Hay Fever: Acute inflammation of the nasal & conjunctival mucosae with sneezing, hypersecretion, and runny nose - triggered by pollen or food allergens.
      • Extrinsic Asthma: Wheezing & acute respiratory distress due to bronchospasm and increased mucus secretion, triggered by house dust or animal dander.
    • Systemic Type I Hypersensitivity:
      • Anaphylaxis: Hypotension, widespread urticaria, and dyspnea - can be fatal, often triggered by drugs like penicillin in sensitive individuals.

    Antibody-Mediated (Type II) Hypersensitivity Reactions

    • Definition: Antibodies directed against cell surface antigens cause cell lysis.
    • Characteristics:
      • Antibodies: Mostly IgG, occasionally IgM.
      • Antigens:
        • Endogenous Antigens: Self-antigens.
        • Exogenous Antigens: Can be adsorbed onto cell surfaces, or modified to alter surface antigens (e.g., drug metabolites).
    • Mechanism of Action:
      • Complement-Dependent Hypersensitivity:
        • Complement activation and lysis of the target cell after opsonization and phagocytosis.
        • C3b and IgG/IgM are involved.
      • Antibody-Dependent Cellular Cytotoxicity:
        • Antibody acts as a bridge between NK cells/macrophages and the target cell.
        • Does not involve phagocytosis or complement activation.
        • The NK/macrophages release perforin and granzyme to lyse the target cell.
      • Antibody-Mediated Cellular Dysfunction:
        • Antibody binds to cell surface receptors, disrupting or interfering with their function without causing cell injury or inflammation.

    Mechanisms of Injury in Type II Hypersensitivity Reactions

    • Cell Lysis (Antibody-Dependent):
      • Antibodies against cell membrane antigens activate complement, leading to cell lysis.
      • Examples:
        • Transfusion Reaction: ABO or Rh incompatibility leading to lysis of incompatible donor RBCs.
        • Hemolytic Anemia:
          • Penicillin attaches to RBCs.
          • IgG antibodies are produced against penicillin.
          • Splenic macrophages phagocytose the antibody-coated RBCs.
    • Phagocytosis:
      • Erythrocytes or platelets coated with autoantibodies (with or without complement) are phagocytosed by macrophages.

    Examples of Type II Hypersensitivity Reactions

    • Antibodies to Blood Cells:
      • Autoimmune Hemolytic Anemia: Antibodies against red blood cells.
      • Transfusion Reactions: Reactions against incompatible blood transfusions.
      • Hemolytic Disease of the Newborn (Erythroblastosis Fetalis): Mother produces antibodies against fetal red blood cells, leading to destruction of the infant's red blood cells.
      • Idiopathic Thrombocytopenic Purpura (ITP): Antibodies against platelets, causing platelet destruction.
      • Drug-Induced Cytotoxic Antibodies: Some drugs can bind to cell surfaces and trigger antibody production, leading to cell destruction.
    • Antibodies to Tissue Components:
      • Antibodies to thyroid epithelial cells: Can cause hypothyroidism (Hashimoto thyroiditis) or hyperthyroidism (Grave's disease).

    Hypersensitivity Reactions

    • An exaggerated immune response to an antigen, causing tissue damage, disease, or even death.
    • Requires prior sensitization to the allergen.
    • Almost anything can cause an immune response.
    • Inherited susceptibility genes play a role in developing hypersensitivity.
    • Exogenous Antigens: Substances from outside the body, including dust, pollen, food, drugs, microbes, chemicals, and some blood products.
    • Endogenous Antigens: Self-antigens from within the body.

    Classifications of Hypersensitivity Reactions

    • Type I (Immediate): Also known as allergic or atopic disorders.
    • Type II (Antibody-Mediated): Involves antibodies directed against antigens fixed on cell surfaces.
    • Type III (Immune Complex-Mediated): Caused by the formation of immune complexes.
    • Type IV (Cell-Mediated or Delayed): Involves T-cell responses.

    Type I (Immediate) Hypersensitivity Reactions

    • Characteristics:
      • Occurs within minutes after allergen exposure.
      • Mediated by IgE antibodies.
      • Genetic susceptibility: Occurs in individuals with a genetic predisposition and prior sensitization.
      • Common examples: Bronchial asthma, hay fever, food allergies.

    Mechanism of Type I Hypersensitivity

    • Initial Exposure (Sensitization):

      • Exposure to the allergen through inhalation, ingestion, or injection.
      • The allergen is presented to T cells by antigen-presenting cells (APCs), like macrophages.
      • The T cell differentiates into a TH2 cell.
      • TH2 cells release cytokines, IL-4, IL-5, and IL-13.
      • IL-4 stimulates B cells to produce IgE antibodies.
      • IL-5 activates eosinophils.
      • IL-13 stimulates epithelial cells to produce mucus.
      • IgE antibodies attach to Fc receptors on mast cells and basophils.

    • Re-exposure to Antigen:

      • Allergen cross-links IgE molecules on mast cells or basophils, triggering degranulation.
      • Mast cells and basophils release mediators like histamine, cytokines, prostaglandins, and leukotrienes.

    Phases of IgE Triggered Reactions

    • Immediate Phase Response:

      • Occurs within 5-30 minutes after allergen exposure.
      • Releases preformed mediators like histamine, proteases, and chemotactic factors.
      • Characterized by vasodilation, vascular leakage, smooth muscle spasm, and glandular secretions.

    • Late-Phase Reaction:

      • Develops 2-8 hours after exposure, lasting several days..
      • Releases secondary mediators like prostaglandins, leukotrienes, cytokines, and PAF.
      • Characterized by tissue infiltration with eosinophils, neutrophils, basophils, monocytes, and TH2 cells.
      • Also shows mucosal epithelial cell damage.

    Examples of Type I Hypersensitivity

    • Localized Type I: Hay fever and extrinsic asthma.
    • Systemic Type I (Anaphylactic Reaction): Characterized by hypotension, widespread urticaria, and dyspnea. Can be life-threatening.

    Antibody-Mediated (Type II) Hypersensitivity Reactions

    • Definition: Antibodies directed against specific antigens on cell surfaces cause lysis of target cells.
    • Characteristics:
      • Involves IgG and occasionally IgM antibodies.
      • Antigens can be endogenous or exogenous, which may be adsorbed on cell surfaces or extracellular matrix.
    • Mechanisms of Injury:
      • Complement Dependent: Antibody-mediated activation of complement leading to lysis of target cells; often seen in blood transfusions.
      • Phagocytosis (Opsonization): Antibodies coat cells, making them targets for phagocytosis by macrophages.
      • Antibody-Dependent Cellular Cytotoxicity (ADCC): Antibodies bridge natural killer cells or macrophages to the target cell, leading to cell destruction without phagocytosis or complement activation.
      • Antibody-Mediated Cellular Dysfunction: Antibodies block or dysregulate the function of cell surface receptors.

    Examples of Type II Hypersensitivity

    • Antibodies to Blood Cells: Autoimmune hemolytic anemia, transfusion reactions, hemolytic disease of the newborn (erythroblastosis fetalis), idiopathic thrombocytopenic purpura (ITP), and drug-induced cytotoxic antibodies.
    • Antibodies to Tissue Components: Immune reactions involving thyroid, kidneys, and lungs, for example.

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    Explore the fascinating world of immunity and the immune system. This quiz covers the functions, types, and mechanisms that protect the body from diseases. Test your knowledge on both innate and adaptive immunity and how they work together to defend against pathogens.

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