Immune Response Types and Cells
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Questions and Answers

What percentage of peripheral blood lymphocytes do natural killer cells (NK cells) typically comprise?

  • 15-20%
  • 20-25%
  • 5-10%
  • 10-15% (correct)

    • Which of the following statements correctly describes the recognition capabilities of natural killer cells?

  • NK cells only recognize viral antigens.
  • NK cells require pre-sensitization to target cells.
  • NK cells utilize a broad recognition mechanism for ill-defined molecules. (correct)
  • NK cells recognize self-class I MHC complexes.

    • Which markers are primarily used to identify natural killer cells?

  • CD16 and CD56 (correct)
  • CD3 and CD19
  • CD4 and CD8
  • CiR and CD28

    • What role does CD8+ T cell play in the recognition of antigens?

    <p>Serves as a coreceptor for class I MHC-restricted recognition.</p> Signup and view all the answers

    Which categories do the MHC gene products fall into?

    <p>Class I, Class II, and Class III</p> Signup and view all the answers

    How do class II MHC molecules present antigens?

    <p>By internalizing and processing exogenous antigens in endosomes.</p> Signup and view all the answers

    Which components are encoded by class III MHC genes?

    <p>Components of the complement system</p> Signup and view all the answers

    Which of the following cells are CD4+ T cells primarily associated with?

    <p>Helper functions for class II MHC presentation</p> Signup and view all the answers

    What is the primary function of CD8+ T cells?

    <p>To kill infected or cancerous cells</p> Signup and view all the answers

    What is necessary for the complete activation of T cells during antigen recognition?

    <p>Engagement of TCR and CD28 coactivation</p> Signup and view all the answers

    Which immunoglobulin is primarily found on the surface of all B cells as an antigen receptor?

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

    What role do macrophages have in the immune response?

    <p>They produce cytokines and secrete toxic metabolites</p> Signup and view all the answers

    What characterizes dendritic cells in the immune system?

    <p>They possess dendritic processes and large amounts of class II MHC molecules</p> Signup and view all the answers

    What is the consequence of T cells not receiving the second signal required for activation?

    <p>They will undergo apoptosis or become anergic</p> Signup and view all the answers

    What is the role of CD21 on B cells?

    <p>It acts as a complement receptor and binds to Epstein-Barr virus</p> Signup and view all the answers

    Which immunoglobulin classes make up approximately 95% of plasma immunoglobulins secreted by plasma cells?

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

    What is the primary function of innate immunity?

    <p>To prevent entry of environmental microbes and recognize them</p> Signup and view all the answers

    Which of the following describes the composition of a T cell receptor (TCR)?

    <p>Composed of α and β polypeptide chains linked by disulfide bonds</p> Signup and view all the answers

    Which type of immunity is primarily responsible for defense against extracellular microbes?

    <p>Humoral immunity</p> Signup and view all the answers

    What is the CD4:CD8 ratio indicative of in T-lymphocytes?

    <p>Higher presence of CD4 T-cells compared to CD8 T-cells</p> Signup and view all the answers

    Which cytokines are produced specifically by T-helper-1 (TH1) cells?

    <p>IL-2 and interferon-γ (IFN-γ)</p> Signup and view all the answers

    How are the different subsets of T-lymphocytes (CD4 and CD8) characterized?

    <p>By the type of antigen presented by MHC molecules</p> Signup and view all the answers

    What role do natural killer (NK) cells play in the immune system?

    <p>Directly killing virus-infected and tumor cells</p> Signup and view all the answers

    What is a primary characteristic of somatic rearrangement of TCR genes?

    <p>It generates diversity in T cell receptors</p> Signup and view all the answers

    What characterizes the immediate phase of a Type I hypersensitivity reaction?

    <p>Vasodilatation and exudation due to the release of vasoactive amines</p> Signup and view all the answers

    Which mechanism is NOT involved in Type II hypersensitivity reactions?

    <p>Direct cytotoxicity by eosinophils</p> Signup and view all the answers

    What is a common outcome of Type III hypersensitivity reactions?

    <p>Antigen-antibody complex deposition leading to inflammation</p> Signup and view all the answers

    In Type IV hypersensitivity, which cells are primarily activated in the delayed type response?

    <p>CD4+ T cells and CD8+ T cells</p> Signup and view all the answers

    Which of the following is an example of a Type II hypersensitivity reaction?

    <p>Transfusion reactions and autoimmune hemolytic anemia</p> Signup and view all the answers

    Which diseases are primarily associated with Type III hypersensitivity reactions?

    <p>Systemic lupus erythematosus and polyarteritis nodosa</p> Signup and view all the answers

    Which role do CD8+ T cells play in Type IV hypersensitivity?

    <p>Direct cell cytotoxicity mainly in graft rejection</p> Signup and view all the answers

    Which statement is true regarding the late phase of Type I hypersensitivity reactions?

    <p>It lasts for days and is characterized by leukocyte influx</p> Signup and view all the answers

    Study Notes

    Immune Response Types

    • Innate Immunity: Always present, acts immediately
      • Barriers: Skin, mucous membranes
      • Cells: Phagocytes (neutrophils, macrophages), NK cells
      • Proteins: Complement system
    • Adaptive Immunity: Develops after exposure to specific pathogens
      • Cell-Mediated Immunity: T cells (thymus-derived) target intracellular pathogens
      • Humoral Immunity: B cells (bone marrow-derived) produce antibodies to fight extracellular pathogens

    Cells of the Immune System

    • T-Lymphocytes (T cells): 60-70% of circulating lymphocytes
      • TCR (T cell receptor): Recognizes specific antigens
      • CD4 and CD8: Coreceptors that aid in antigen recognition
        • CD4: Recognizes Class II MHC molecules on antigen presenting cells
        • CD8: Recognizes Class I MHC molecules on infected cells
      • T helper cells (TH):
        • TH1: Produce cytokines for cell-mediated immunity (e.g., IFN-γ)
        • TH2: Produce cytokines for antibody production (e.g., IL-4, IL-5)
    • B-Lymphocytes (B cells): 10-20% of circulating lymphocytes
      • BCR (B cell receptor): Recognizes specific antigens leads to the production of antibodies (IgM, IgG, IgA, IgE, IgD)
    • Macrophages: Phagocytic cells that play a role in both innate and adaptive immunity
      • Antigen presentation to T cells via MHC II
      • Secrete cytokines
      • Destroy tumor cells
    • Dendritic Cells and Langerhans' Cells: Antigen presenting cells found in tissues (lymphoid tissue, skin)
      • Efficient antigen presentation with poor phagocytic activity
    • Natural Killer (NK) Cells: Part of the innate immune system
      • Kill infected or cancerous cells without prior sensitization.
      • Express CD16 and CD56
      • Release Interferon-gamma (IFN-γ)

    Main Histocompatibility Complex (MHC)

    • MHC I: Expressed on all nucleated cells
      • Presents internalized antigens to CD8+ cytotoxic T cells
    • MHC II: Expressed on antigen presenting cells (APCs)
      • Presents exogenous antigens to CD4+ helper T cells

    Hypersensitivity Reactions

    • Type I (Immediate): Allergic reactions, rapid response
      • Release of histamine and other vasoactive amines from mast cells
    • Type II (Cytotoxic): Antibodies directed at antigens on cell surfaces
      • Opsonization and phagocytosis
      • Antibody-dependent cellular cytotoxicity (ADCC)
      • Antibody-mediated cellular dysfunction
    • Type III (Immune Complex): Immune complexes deposit in tissues
      • Inflammatory response
    • Type IV (Delayed): Initiated by T cells
      • Delayed-type hypersensitivity (DTH)
      • Cell-mediated cytotoxicity

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