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Questions and Answers
What is the primary function of primary lymphoid organs?
Which immune cells are produced in the bone marrow?
What role do lymph nodes play in the immune response?
How do secondary lymphoid organs differ from primary lymphoid organs?
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Which of the following statements about the thymus is correct?
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What is the primary role of the immune system?
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Which statement correctly describes non-specific/innate immunity?
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What distinguishes specific/adaptive immunity from non-specific/innate immunity?
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How does the immune system respond to foreign tissues such as transplants?
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What are Pathogen-Associated Molecular Patterns (PAMPs)?
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What is the primary function of Toll-Like Receptors (TLRs)?
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Which of the following is NOT a stage of inflammation?
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Which process involves phagocytes moving across the capillary wall?
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What do neutrophils form during the process of eliminating bacteria?
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What role do chemokines play during the inflammatory response?
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What is a consequence of neutrophils dying after killing bacteria?
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Which of the following is a characteristic of PAMPs?
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What is the primary function of MHC I molecules?
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Which of the following cells are classified as antigen-presenting cells (APCs)?
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Which best describes the relationship between T-cell receptors and MHC II proteins?
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What antigen characteristics are crucial for eliciting an immune response?
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What role do macrophages play in the immune system?
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In which scenario might a natural killer cell become activated?
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What is the first step in the antigen presentation process by APCs?
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Which statement best describes the uniqueness of MHC molecules among individuals?
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What type of immune cell is primarily responsible for destroying multicellular parasites?
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Which cells secrete cytokines to activate other immune cells?
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Where are neutrophils produced?
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Which of the following immune cells can transform into macrophages?
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What is the function of plasma cells?
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Which type of T cell directly destroys virus-infected cells?
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What role do mast cells play in the immune response?
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Which of the following is NOT a component of the second line of defense in innate immunity?
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Which of the following factors are involved in the process of inflammation?
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Which feature distinguishes specific/adaptive immunity from non-specific/innate immunity?
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Which cells are considered professional antigen-presenting cells (APCs)?
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What type of immune response involves the release of chemicals such as histamine?
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What is a primary function of neutrophils during an immune response?
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What role do memory cells play in the immune response?
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Which of the following best describes clonal expansion in lymphocytes?
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What is the primary outcome of the interaction between antibodies and FC receptors?
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During a secondary immune response, which factor contributes to a more rapid antibody production?
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Which component of the antibody is responsible for its specificity to an antigen?
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What is the role of Natural Killer (NK) Cells in the immune system?
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During the activation of Helper T Cells, what role do cytokines play?
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What is the main difference between the innate immune system and the adaptive immune system?
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Which cells are primarily responsible for the direct attack against infected body cells?
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How do macrophages assist in the immune response?
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What triggers the recruitment of neutrophils during an immune response?
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What type of T Cell is involved in linking the innate to the adaptive immune system?
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Which statement best summarizes the function of plasma cells?
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What is the role of Recombination Activating Genes (RAGs) in B cell development?
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Which of the following proteins is specifically important for the rearrangement of DNA during B cell development?
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What is produced when the heavy-chain primary RNA transcript undergoes processing?
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What stage comes directly after the formation of the pre-B cell?
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What is the purpose of the surrogate light chain in B cell development?
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Which component is responsible for the rearrangement of the D and J gene segments in B cells?
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Which option correctly describes the sequence of B cell maturation from progenitor to functional cell?
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What chain is formed in a B cell after the successful rearrangement of immunoglobulin genes?
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What is the role of Helper T Cells (TH) in the immune response?
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Which process allows for the variation in the antibodies produced by B cells?
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What initiates the Membrane Attack Complex (MAC) in the complement cascade?
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What type of immunity involves the use of antibodies produced by another organism?
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What is one of the primary roles of humoral immunity involving antibodies?
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Memory cells are formed as a result of what process during the adaptive immune response?
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Which component of the immune system is primarily responsible for the direct attack on antigen-bearing cells?
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What is an important function of antigen-presenting cells (APCs) in the immune system?
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Which region of the B-Cell Receptor is responsible for determining the specificity of the antibody?
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What role do RAG1 and RAG2 proteins play in B cell development?
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Which process is mediated by Terminal deoxynucleotidyl transferase (TdT) during B cell maturation?
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Which type of B cell is characterized by the expression of a fully formed B cell receptor?
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What component's rearrangement occurs first during B cell receptor development?
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What is the primary function of B cells once they have differentiated into plasma cells?
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Which of the following sequences occurs in B cell receptor maturation?
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Which segment influences the diversity of antibody specificity in B cells?
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What is the purpose of the heavy-chain primary RNA transcript in B cell maturation?
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Which stage of B cell development occurs just before the B cell becomes fully immunocompetent?
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During which process are gene segments spliced out to enable B cell receptor diversity?
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Which of the following features is unique to mature B cells compared to their precursors?
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Which component of B cell receptors is responsible for recognizing and binding to antigens?
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What is the primary cause of decreased resistance to infection globally?
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What results from the negative selection process in T cell development?
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Which T cell type is primarily responsible for recognizing endogenous antigens?
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Which immune response mechanism involves the displacement of CD28 by CTLA4?
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Which type of hypersensitivity involves symptoms appearing 12-72 hours after exposure?
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What role do MHC proteins play in organ transplantation?
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What condition is characterized by an absence of both B and T cells?
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Which of the following statements is true regarding the ABO blood group system?
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What occurs during anaphylaxis related to allergic reactions?
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Which factors affect the body's resistance to infections?
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What is a common outcome for lymphocytes during the development of tolerance?
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What do mast cells release during an allergic reaction?
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How does stress influence the immune system?
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What is the primary mechanism of immune tolerance?
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Study Notes
The Immune System
- The immune system encompasses the entire body and its various organs through lymph and blood
- It protects against pathogens (Bacteria, Viruses, Parasites) and altered body cells (Cancer)
- It can potentially attack healthy cells by mistake, leading to autoimmune disorders or attacking transplanted tissues
- The immune system has two main branches: Non-specific (Innate) and Specific (Adaptive)
Strategies for Protection
- Non-Specific/Innate immunity:
- The body's first line of defense
- Does not require recognition of a specific pathogen
- Same response each time it encounters a pathogen
- Specific/Adaptive immunity:
- Requires recognition of a specific pathogen
- Faster response with repeated exposure to the same pathogen
Components of the Immune System - Lymphoid Organs
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Primary Lymphoid Organs:
- Locations where stem cells divide and immune cells develop
- Bone Marrow: Produces blood cells (B cells and immature T cells), matures B cells
- Thymus: Located above the heart, matures T cells, contains T cells, dendritic cells, epithelial cells, and macrophages
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Secondary Lymphoid Organs:
- Sites where most immune responses occur
- Lymph Nodes: Scattered throughout the body, filter microbes, macrophages phagocytize microbes in lymph
- Spleen: Largest lymphoid organ, removes microbes and old erythrocytes
- Lymphoid Nodules: Small aggregations of lymphoid tissue found in different locations
- Tonsils: Lymphoid tissue in the throat
- Peyer’s Patches and MALT (Mucosal-Associated Lymphoid Tissues): Found in the intestines
- Appendix: Small, finger-shaped pouch that extends from the colon
Immune Cells
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Leukocytes (white blood cells):
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Lymphoid Cells:
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T Cells:
- Cytotoxic T-Cells (CD8+): Destroy virus-infected cells, cancer cells, and transplanted tissues
- Helper T-Cells (CD4+): Secrete cytokines to activate B cells, cytotoxic T cells, NK cells, and macrophages
- Regulatory T-Cells (CD4+): Suppress the immune system to prevent autoimmune reactions
- B Cells: Produce antibodies
- NK Cells (Natural Killer Cells): Bind and kill virus-infected cells and cancer cells
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T Cells:
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Myeloid Cells:
- Macrophage: Phagocytize microbes and debris, present antigens to T cells
- Dendritic Cells: Phagocytize microbes and present antigens to T cells
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Lymphoid Cells:
Immune Cells - Myeloid Lineage
- Eosinophils: Destroy parasites
- Basophils: Release histamine and other chemicals
- Mast Cells: Release histamine and other chemicals
- Neutrophils: Highly mobile phagocytes that are the first responders to an infection
- Monocytes: Become macrophages and dendritic cells
Specific Role of Immune Cells
- Neutrophils: Phagocytize bacteria, release chemicals, and die in the process of killing bacteria
- Basophils: Release histamine in blood similar to mast cells in tissues
- Eosinophils: Destroy multicellular parasites, participate in allergic reactions
- Monocytes: Migrate to tissues and become macrophages
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Lymphocytes:
- B cells: Initiate antibody-mediated immune responses by binding antigens to their surface receptors
- T cells (TH and TC): Recognize specific antigens and activate other immune cells
- Cytotoxic T Cells (CD8+): Directly kill target cells by binding to antigens on their surface
- Helper T Cells (CD4+): Secrete cytokines that help activate other immune cells
- Macrophages: Phagocytize microbes and debris, release toxic chemicals, present antigens to T cells, and contribute to inflammation
- Dendritic Cells: Phagocytize microbes and present antigens to T cells, also known as "professional APCs"
- Mast Cells: Release histamine and other chemicals involved in inflammation, found in tissues
- Plasma Cells: Secrete antibodies
Major Histocompatibility Complex (MHC)
- Two classes:
- MHC I: Found on all nucleated cells, presents internal antigens (antigens from within the cell)
- MHC II: Found on antigen-presenting cells (macrophages, dendritic cells, B cells), presenting antigens from outside the cell
- Only identical twins share the same MHC molecules
Antigen Presenting Cells
- Present exogenous antigens (antigens taken up from outside the cell) with MHC II molecules. This process involves:
- Ingesting the antigen
- Digesting it into peptide fragments
- Binding peptide fragments to MHC II molecules
- Inserting these complexes onto the cell surface
Adaptive Immune Response
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Antigen Requirements:
- Reactivity: The ability of an antibody to bind specifically to the antigen that provoked it
- Immunogenicity: The ability of an antigen to stimulate an immune response and trigger antibody production
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Antigen-Presenting Cells (APCs):
- Dendritic cells: Professional antigen-presenting cells
- Macrophages: Phagocytize microbes and present antigens to Helper T cells
- B Lymphocytes: Present antigens to Helper T cells
Host Defenses
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Non-Specific/Innate Immunity:
- The body's first line of defense against pathogens
- No memory of previous encounters with pathogens
- First Line of Defense: Physical barriers like skin, mucous membranes, and cilia
- Second Line of Defense: Cellular factors (phagocytes, natural killer cells) and Humoral factors (inflammation, antimicrobial substances, interferons)
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Specific/Adaptive Immunity:
- Involves memory of previous encounters with pathogens
- B cells and T cells are the main players
- Requires recognition of specific foreign materials
- Much stronger and more effective than innate immunity
Inflammation
- Non-specific response to tissue damage
- Signs and Symptoms: Redness, heat, pain, swelling
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Stages:
- Vasodilation: Widening of blood vessels to increase blood flow
- Emigration of Phagocytes: Phagocytes move from the bloodstream to the site of inflammation
- Tissue Repair: Damaged tissue is repaired
- Trigger: Toll-like receptors (TLRs) on macrophages recognize Pathogen-Associated Molecular Patterns (PAMPS) on microbes, initiating the inflammatory response
Toll-Like Receptors (TLRs)
- Transmembrane receptors that are highly conserved in evolution
- Recognize PAMPs on microbes (e.g., lipopolysaccharides of gram-negative bacteria, peptidoglycans of gram-positive bacteria)
- Extracellular domain recognizes pathogens
- Intracellular signaling domain initiates downstream signaling cascades
The Inflammatory Response
- Neutrophils are attracted to the site of inflammation by chemokines
- Adhesion of neutrophils to blood vessel walls (margination)
- Neutrophils cross blood vessel walls (diapedesis)
- Neutrophils phagocytize bacteria and release toxic chemicals
- NETs (Neutrophil Extracellular Traps): Chromatin bound to proteins released by neutrophils
The Major Histocompatibility Complex (MHC)
- Presents antigens to T cells
- MHC I: Found on all nucleated cells
- MHC II: Found on antigen-presenting cells
Immunology Lecture 3
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Immune System Defense: The immune system defends the body against specific microbes and foreign substances through a complex process involving both non-specific (innate) and specific (adaptive) immunity.
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Innate Immune System: The innate immune system is the body's first line of defense and is characterized by non-specific responses to pathogens.
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Natural Killer Cells: Natural killer (NK) cells are important in innate immunity. They attack cells that lack MHC Class I expression, which is often seen in tumor cells and virally infected cells. They release granzymes and perforin when activated by the interaction between their antibody and the FC receptor.
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Phagocytic Cells: Phagocytic cells play a crucial role in eliminating invading pathogens.
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Fixed-Tissue Macrophages: These cells are resident in tissues, acting as sentinels against microbes and foreign substances. They recognize pathogen-associated molecular patterns (PAMPs) through Toll-like receptors (TLRs) and release signals for neutrophil recruitment.
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Neutrophils: These cells are also a major part of the innate immune system and are recruited to sites of infection. They undergo margination, emigration, and NET formation to trap and kill invading pathogens.
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Dendritic Cells: Dendritic cells are professional antigen-presenting cells (APCs) that bridge the innate and adaptive immune systems. They express MHC Class II molecules and present antigens to T cells in lymph nodes, promoting the immune response.
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Adaptive Immune System: The adaptive immune system provides a specific and targeted defense against pathogens that have bypassed the innate immune system.
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B and T Lymphocytes: B and T lymphocytes are key players in adaptive immunity. They are responsible for recognizing and responding to specific antigens.
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Helper T Cells (TH): Helper T cells play a central role in activating both B cells and cytotoxic T cells, coordinating the immune response.
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B Cells: B cells differentiate into plasma cells, which produce and secrete antibodies. Antibodies contribute to the humoral response, targeting pathogens and activating the complement system.
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Cytotoxic T Cells (TC): Cytotoxic T cells directly attack infected cells, cancerous cells, or foreign cells. They are part of cell-mediated immunity.
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Antigen Presentation: Antigen-presenting cells (APCs) process and present antigens to helper T cells (TH). The interaction between the APC and the TH is central to the activation of the adaptive immune response.
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Helper T Cell Activation: Helper T cell activation requires several steps:
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Antigen Recognition: The helper T cell (TH) must recognize the specific antigen presented by the APC via MHC Class II molecules.
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Co-Stimulation: The TH must receive co-stimulatory signals from the APC.
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Cytokine Production: The APC produces cytokines that further stimulate the TH.
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Lymphocyte Activation and Differentiation: Activation of helper T cells leads to the production of cytokines, which in turn, activates B cells and cytotoxic T cells. This results in the differentiation of B cells into plasma cells, secreting antibodies, and the activation of cytotoxic T cells to kill infected cells.
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Memory Cells: Upon activation, lymphocytes generate memory cells, which retain the capability of recognizing and responding more rapidly to the same antigen upon re-exposure. This mechanism ensures a faster and more efficient response during subsequent infections.
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Antibody Production: Antibodies are produced by plasma cells in response to antigen stimulation. They consist of two regions:
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FAB Region: This region binds to the specific antigen.
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FC Region: This region interacts with other immune cells and proteins, triggering downstream immune responses.
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Immunoglobulin Gene Rearrangement: Lymphocytes generate diverse antigen receptors through a process called immunoglobulin gene rearrangement. This process involves:
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Recombination Activating Genes (RAGs): These genes are responsible for rearranging immunoglobulin gene segments.
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Terminal deoxynucleotidyl transferase (TdT): This enzyme introduces random nucleotides, further diversifying the receptor repertoire.
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APCs and Lymphocytes
- Antigen-Presenting Cells (APCs) activate lymphocytes in the lymph nodes
- T helper cells (TH) are the first to demonstrate specificity
- TH cells are required to activate B and TC cells
- Both T and B cells create memory cells
Antibodies
- Antibodies have a variable region (FAB) and a constant region (FC)
- Antibodies have different classes with varying functions
- Antibodies can undergo class switching (e.g., IgM to IgG)
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Active immunity occurs from exposure to an antigen through infection or vaccination
- Natural active immunity occurs through infection
- Artificial active immunity occurs through vaccination
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Passive immunity occurs from receiving antibodies
- Natural passive immunity occurs through mother to fetus or mother to infant through breast milk
- Artificial passive immunity occurs through antibody injection
Humoral and Cellular Immunity
- Humoral immunity involves antibodies
- Antibodies can guide phagocytes, activate the complement system, and neutralize free antigen
- Cellular immunity involves cytotoxic T cells (TC)
- TC cells directly attack antigen-bearing cells
Complement System
- The complement system is a complex cascade of proteins that help to destroy pathogens
- Membrane Attack Complex (MAC) forms holes in the cell wall of microbes, leading to cell death
How Lymphocytes Develop Specific Receptors
- T and B cells undergo a process called immunocompetence to develop antigen receptors
- B cells undergo immunoglobulin gene rearrangement to create unique B cell receptors
- RAG1 and RAG2 are recombination activating genes involved in gene rearrangement
- TdT (Terminal deoxynucleotidyl transferase) adds nucleotides during rearrangement
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Clonal deletion or clonal inactivation eliminates cells that recognize self-antigens
- This leads to immune tolerance
MHC Class I and II
- MHC I and II molecules are important in immune responses
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MHC Class I presents endogenous antigens (produced by the body cell)
- Involved in the activation of cytotoxic T cells (TC)
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MHC Class II presents exogenous antigens (foreign material)
- Involved in the activation of helper T cells (TH)
Activation of Cytotoxic T Cells
- TC cells recognize antigens presented by MHC I
- TH cells (specifically TH1) assist in activating TC cells
Checkpoint Inhibition
- Checkpoint inhibitors regulate the immune response
- CTLA4 and PD-1 are checkpoint inhibitors that can displace CD28 from B7, limiting activation signals
Factors that Affect Immune Response
- Malnutrition
- Preexisting disease
- Stress
- Sleep deprivation
- Exercise
Immunodeficiency Diseases
- SCID (Severe Combined Immunodeficiency Disease)
- AIDS (Acquired Immunodeficiency Syndrome)
Harmful Immune Responses
- Tissue/Graft Rejection
- Transfusion Reactions
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Allergy (hypersensitivity)
- Immediate hypersensitivity
- Delayed hypersensitivity
- Autoimmune diseases
- Excessive Inflammatory Responses
Other Key Factors
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Transfusion Reactions
- Related to ABO and Rh blood group antigens
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Anaphylaxis
- Severe allergic reaction resulting from widespread mast cell activation
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Autoimmune Diseases
- Immune system attacks self-proteins
- Examples: Type 1 diabetes, rheumatoid arthritis, multiple sclerosis, myasthenia gravis
Tissue Grafts and Organ Transplantation
- MHC proteins on donor cells are foreign to the recipient
- Drugs that kill actively dividing lymphocytes are used to prevent rejection
- Cyclosporine blocks cytokine production from helper T cells.
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Description
Explore the intricate details of the immune system, including its main components and functions. Learn about the two branches of immunity: Non-specific (Innate) and Specific (Adaptive), and the role of lymphoid organs. This quiz will enhance your understanding of how the body defends itself against pathogens.
