The Immune System Overview
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Questions and Answers

What is the primary function of primary lymphoid organs?

  • Site where immune cells mature and stem cells divide. (correct)
  • Store immune cells for later use.
  • Filter microbes from the body.
  • Produce antibodies in response to infections.

Which immune cells are produced in the bone marrow?

  • Natural killer cells and memory T-cells.
  • B-cells and immature T-cells. (correct)
  • Immature T-cells and dendritic cells.
  • Macrophages and plasma cells.

What role do lymph nodes play in the immune response?

  • Mature B-cells and release them into the bloodstream.
  • Produce antibodies before an infection occurs.
  • Filter microbes and facilitate phagocytosis. (correct)
  • Store old erythrocytes and dead cells.

How do secondary lymphoid organs differ from primary lymphoid organs?

<p>Secondary organs are involved in immune responses, while primary organs are for cell maturation. (C)</p> Signup and view all the answers

Which of the following statements about the thymus is correct?

<p>It atrophies after the maturation of immune cells. (A)</p> Signup and view all the answers

What is the primary role of the immune system?

<p>To protect the body from pathogens and altered cells (D)</p> Signup and view all the answers

Which statement correctly describes non-specific/innate immunity?

<p>Acts as the first-line of defense without recognizing pathogens (A)</p> Signup and view all the answers

What distinguishes specific/adaptive immunity from non-specific/innate immunity?

<p>It requires pathogen recognition and improves upon subsequent exposure (B)</p> Signup and view all the answers

How does the immune system respond to foreign tissues such as transplants?

<p>By mounting an immune response to reject the foreign tissue (D)</p> Signup and view all the answers

What are Pathogen-Associated Molecular Patterns (PAMPs)?

<p>Molecules recognized as harmful by the immune system (A), Unique structures essential for microbial physiology (C)</p> Signup and view all the answers

What is the primary function of Toll-Like Receptors (TLRs)?

<p>To recognize microbial patterns through PAMPs (A)</p> Signup and view all the answers

Which of the following is NOT a stage of inflammation?

<p>Activation of T cells (C)</p> Signup and view all the answers

Which process involves phagocytes moving across the capillary wall?

<p>Diapedesis (B)</p> Signup and view all the answers

What do neutrophils form during the process of eliminating bacteria?

<p>Neutrophil Extracellular Traps (NETs) (B)</p> Signup and view all the answers

What role do chemokines play during the inflammatory response?

<p>They attract phagocytes to the site of infection. (A)</p> Signup and view all the answers

What is a consequence of neutrophils dying after killing bacteria?

<p>They form Neutrophil Extracellular Traps. (A)</p> Signup and view all the answers

Which of the following is a characteristic of PAMPs?

<p>They are conserved structures across different microbes. (A)</p> Signup and view all the answers

What is the primary function of MHC I molecules?

<p>To express on all nucleated cells (A)</p> Signup and view all the answers

Which of the following cells are classified as antigen-presenting cells (APCs)?

<p>B cells (D)</p> Signup and view all the answers

Which best describes the relationship between T-cell receptors and MHC II proteins?

<p>T-cell receptors recognize antigens only when bound to MHC II (C)</p> Signup and view all the answers

What antigen characteristics are crucial for eliciting an immune response?

<p>Immunogenicity and Reactivity (B)</p> Signup and view all the answers

What role do macrophages play in the immune system?

<p>They serve as professional APCs presenting antigens with MHC II (A)</p> Signup and view all the answers

In which scenario might a natural killer cell become activated?

<p>When MHC I is absent or altered (C)</p> Signup and view all the answers

What is the first step in the antigen presentation process by APCs?

<p>Ingest the antigen (A)</p> Signup and view all the answers

Which statement best describes the uniqueness of MHC molecules among individuals?

<p>Only identical twins share the same MHC molecules (B)</p> Signup and view all the answers

What type of immune cell is primarily responsible for destroying multicellular parasites?

<p>Eosinophils (C)</p> Signup and view all the answers

Which cells secrete cytokines to activate other immune cells?

<p>Helper T cells CD4+ (A)</p> Signup and view all the answers

Where are neutrophils produced?

<p>Bone marrow (B)</p> Signup and view all the answers

Which of the following immune cells can transform into macrophages?

<p>Monocytes (D)</p> Signup and view all the answers

What is the function of plasma cells?

<p>To secrete antibodies (B)</p> Signup and view all the answers

Which type of T cell directly destroys virus-infected cells?

<p>Cytotoxic T cells CD8+ (A)</p> Signup and view all the answers

What role do mast cells play in the immune response?

<p>Secreting histamine and other chemicals (D)</p> Signup and view all the answers

Which of the following is NOT a component of the second line of defense in innate immunity?

<p>Antibody production (D)</p> Signup and view all the answers

Which of the following factors are involved in the process of inflammation?

<p>All of the above (D)</p> Signup and view all the answers

Which feature distinguishes specific/adaptive immunity from non-specific/innate immunity?

<p>Ability to produce antibodies (B)</p> Signup and view all the answers

Which cells are considered professional antigen-presenting cells (APCs)?

<p>Dendritic cells (A)</p> Signup and view all the answers

What type of immune response involves the release of chemicals such as histamine?

<p>Non-specific inflammatory response (A)</p> Signup and view all the answers

What is a primary function of neutrophils during an immune response?

<p>Phagocytosis of pathogens (C)</p> Signup and view all the answers

What role do memory cells play in the immune response?

<p>They expand the pool of lymphocytes for quicker response to antigens. (B)</p> Signup and view all the answers

Which of the following best describes clonal expansion in lymphocytes?

<p>The replication of lymphocytes with specific receptors for an antigen. (A)</p> Signup and view all the answers

What is the primary outcome of the interaction between antibodies and FC receptors?

<p>Release of Granzymes and Perforin by NK cells. (B)</p> Signup and view all the answers

During a secondary immune response, which factor contributes to a more rapid antibody production?

<p>Higher concentration of specific memory cells available. (D)</p> Signup and view all the answers

Which component of the antibody is responsible for its specificity to an antigen?

<p>The FAB region of the antibody. (D)</p> Signup and view all the answers

What is the role of Natural Killer (NK) Cells in the immune system?

<p>Identify and destroy virus-infected cells (A)</p> Signup and view all the answers

During the activation of Helper T Cells, what role do cytokines play?

<p>They enhance the cellular response of T Cells and B Cells (C)</p> Signup and view all the answers

What is the main difference between the innate immune system and the adaptive immune system?

<p>Only adaptive immunity has memory for previously encountered antigens (C)</p> Signup and view all the answers

Which cells are primarily responsible for the direct attack against infected body cells?

<p>Cytotoxic T Cells (D)</p> Signup and view all the answers

How do macrophages assist in the immune response?

<p>They present antigens and activate T Cells (B)</p> Signup and view all the answers

What triggers the recruitment of neutrophils during an immune response?

<p>The Danger signal from macrophages (A)</p> Signup and view all the answers

What type of T Cell is involved in linking the innate to the adaptive immune system?

<p>Helper T Cells (B)</p> Signup and view all the answers

Which statement best summarizes the function of plasma cells?

<p>They produce and secrete antibodies (C)</p> Signup and view all the answers

What is the role of Recombination Activating Genes (RAGs) in B cell development?

<p>They are involved in immunoglobulin gene rearrangement. (B)</p> Signup and view all the answers

Which of the following proteins is specifically important for the rearrangement of DNA during B cell development?

<p>TdT (C)</p> Signup and view all the answers

What is produced when the heavy-chain primary RNA transcript undergoes processing?

<p>Heavy-chain messenger RNA (D)</p> Signup and view all the answers

What stage comes directly after the formation of the pre-B cell?

<p>Mature B cell (D)</p> Signup and view all the answers

What is the purpose of the surrogate light chain in B cell development?

<p>To stabilize the pre-B cell receptor. (B)</p> Signup and view all the answers

Which component is responsible for the rearrangement of the D and J gene segments in B cells?

<p>RAG1 (C)</p> Signup and view all the answers

Which option correctly describes the sequence of B cell maturation from progenitor to functional cell?

<p>Pro-B cell → Pre-B cell → Mature B cell → Plasma cell (A)</p> Signup and view all the answers

What chain is formed in a B cell after the successful rearrangement of immunoglobulin genes?

<p>Heavy chain (C)</p> Signup and view all the answers

What is the role of Helper T Cells (TH) in the immune response?

<p>Activate B and Cytotoxic T Cells. (A)</p> Signup and view all the answers

Which process allows for the variation in the antibodies produced by B cells?

<p>Class-switching (B)</p> Signup and view all the answers

What initiates the Membrane Attack Complex (MAC) in the complement cascade?

<p>Activation of C1 by antigen-antibody complexes (C)</p> Signup and view all the answers

What type of immunity involves the use of antibodies produced by another organism?

<p>Passive artificial immunity (A)</p> Signup and view all the answers

What is one of the primary roles of humoral immunity involving antibodies?

<p>To guide phagocytes and activate complement systems. (D)</p> Signup and view all the answers

Memory cells are formed as a result of what process during the adaptive immune response?

<p>Clonal selection (B)</p> Signup and view all the answers

Which component of the immune system is primarily responsible for the direct attack on antigen-bearing cells?

<p>Cytotoxic T Cells (A)</p> Signup and view all the answers

What is an important function of antigen-presenting cells (APCs) in the immune system?

<p>Activating T Cells. (C)</p> Signup and view all the answers

Which region of the B-Cell Receptor is responsible for determining the specificity of the antibody?

<p>Variable region (C)</p> Signup and view all the answers

What role do RAG1 and RAG2 proteins play in B cell development?

<p>Mediate V(D)J recombination (A)</p> Signup and view all the answers

Which process is mediated by Terminal deoxynucleotidyl transferase (TdT) during B cell maturation?

<p>Adding nucleotides at gene junctions (B)</p> Signup and view all the answers

Which type of B cell is characterized by the expression of a fully formed B cell receptor?

<p>Mature B cell (A)</p> Signup and view all the answers

What component's rearrangement occurs first during B cell receptor development?

<p>D segments (D)</p> Signup and view all the answers

What is the primary function of B cells once they have differentiated into plasma cells?

<p>Antibody secretion (C)</p> Signup and view all the answers

Which of the following sequences occurs in B cell receptor maturation?

<p>Heavy chain rearrangement, light chain rearrangement, and expression of B cell receptor (B)</p> Signup and view all the answers

Which segment influences the diversity of antibody specificity in B cells?

<p>Variable region (A)</p> Signup and view all the answers

What is the purpose of the heavy-chain primary RNA transcript in B cell maturation?

<p>To produce a precursor for mature mRNA (A)</p> Signup and view all the answers

Which stage of B cell development occurs just before the B cell becomes fully immunocompetent?

<p>Mature B cell (C)</p> Signup and view all the answers

During which process are gene segments spliced out to enable B cell receptor diversity?

<p>Gene rearrangement (B)</p> Signup and view all the answers

Which of the following features is unique to mature B cells compared to their precursors?

<p>Ability to secrete antibodies (B)</p> Signup and view all the answers

Which component of B cell receptors is responsible for recognizing and binding to antigens?

<p>Variable region (C)</p> Signup and view all the answers

What is the primary cause of decreased resistance to infection globally?

<p>Protein-calorie malnutrition (A)</p> Signup and view all the answers

What results from the negative selection process in T cell development?

<p>Destruction of T cells that recognize self-proteins (D)</p> Signup and view all the answers

Which T cell type is primarily responsible for recognizing endogenous antigens?

<p>Cytotoxic T cells (C)</p> Signup and view all the answers

Which immune response mechanism involves the displacement of CD28 by CTLA4?

<p>Checkpoint inhibition (B)</p> Signup and view all the answers

Which type of hypersensitivity involves symptoms appearing 12-72 hours after exposure?

<p>Delayed hypersensitivity (D)</p> Signup and view all the answers

What role do MHC proteins play in organ transplantation?

<p>Cause tissue rejection (B)</p> Signup and view all the answers

What condition is characterized by an absence of both B and T cells?

<p>SCID (A)</p> Signup and view all the answers

Which of the following statements is true regarding the ABO blood group system?

<p>Group A has Anti-B antibodies (B)</p> Signup and view all the answers

What occurs during anaphylaxis related to allergic reactions?

<p>Activation of mast cells leads to systemic symptoms (A)</p> Signup and view all the answers

Which factors affect the body's resistance to infections?

<p>Nutrition and sleep (A)</p> Signup and view all the answers

What is a common outcome for lymphocytes during the development of tolerance?

<p>Clonal deletion of self-reactive cells (B)</p> Signup and view all the answers

What do mast cells release during an allergic reaction?

<p>Histamine (B)</p> Signup and view all the answers

How does stress influence the immune system?

<p>Decreases the production of antibodies (C)</p> Signup and view all the answers

What is the primary mechanism of immune tolerance?

<p>Clonal deletion of self-reactive lymphocytes (A)</p> Signup and view all the answers

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

  • 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
  • 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

  • Leukocytes (white blood cells):
    • Lymphoid Cells:
      • 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
    • Myeloid Cells:
      • Macrophage: Phagocytize microbes and debris, present antigens to T cells
      • Dendritic Cells: Phagocytize microbes and present antigens to T 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
  • 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

  • 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
  • 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

  • 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)
  • 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
  • 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

  • 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.

  • Innate Immune System: The innate immune system is the body's first line of defense and is characterized by non-specific responses to pathogens.

  • 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.

  • Phagocytic Cells: Phagocytic cells play a crucial role in eliminating invading pathogens.

    • 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.

    • 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.

    • 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.

  • Adaptive Immune System: The adaptive immune system provides a specific and targeted defense against pathogens that have bypassed the innate immune system.

  • B and T Lymphocytes: B and T lymphocytes are key players in adaptive immunity. They are responsible for recognizing and responding to specific antigens.

    • Helper T Cells (TH): Helper T cells play a central role in activating both B cells and cytotoxic T cells, coordinating the immune response.

    • 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.

    • Cytotoxic T Cells (TC): Cytotoxic T cells directly attack infected cells, cancerous cells, or foreign cells. They are part of cell-mediated immunity.

  • 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.

  • Helper T Cell Activation: Helper T cell activation requires several steps:

    • Antigen Recognition: The helper T cell (TH) must recognize the specific antigen presented by the APC via MHC Class II molecules.

    • Co-Stimulation: The TH must receive co-stimulatory signals from the APC.

    • Cytokine Production: The APC produces cytokines that further stimulate the TH.

  • 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.

  • 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.

  • Antibody Production: Antibodies are produced by plasma cells in response to antigen stimulation. They consist of two regions:

    • FAB Region: This region binds to the specific antigen.

    • FC Region: This region interacts with other immune cells and proteins, triggering downstream immune responses.

  • Immunoglobulin Gene Rearrangement: Lymphocytes generate diverse antigen receptors through a process called immunoglobulin gene rearrangement. This process involves:

    • Recombination Activating Genes (RAGs): These genes are responsible for rearranging immunoglobulin gene segments.

    • Terminal deoxynucleotidyl transferase (TdT): This enzyme introduces random nucleotides, further diversifying the receptor repertoire.

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)
  • Active immunity occurs from exposure to an antigen through infection or vaccination
    • Natural active immunity occurs through infection
    • Artificial active immunity occurs through vaccination
  • 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
  • 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
  • MHC Class I presents endogenous antigens (produced by the body cell)
    • Involved in the activation of cytotoxic T cells (TC)
  • 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
  • Allergy (hypersensitivity)
    • Immediate hypersensitivity
    • Delayed hypersensitivity
  • Autoimmune diseases
  • Excessive Inflammatory Responses

Other Key Factors

  • Transfusion Reactions
    • Related to ABO and Rh blood group antigens
  • Anaphylaxis
    • Severe allergic reaction resulting from widespread mast cell activation
  • 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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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.

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