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What is antagonism in the context of cytokines?

  • The ability of one cytokine to stimulate the action of another
  • The ability of one cytokine to inhibit the action of another (correct)
  • The ability of one cytokine to bind to a receptor on a responsive target cell
  • The ability of one cytokine to evoke a biological activity

    • What is the primary function of cytokines?

  • To stimulate or inhibit the activation of immune cells
  • To evoke particular biological activities after binding to a receptor on a responsive target cell (correct)
  • To regulate the intensity and duration of immune responses
  • To regulate the secretion of antibodies

    • What is the role of hematopoietic stem cells (HSCs)?

  • To regulate the secretion of cytokines
  • To continuously replenish and replace all classes of blood cells (correct)
  • To generate only T-lymphocytes and B-lymphocytes
  • To stimulate or inhibit the activation of immune cells

    • What is the function of Common Lymphoid Progenitor (CLP) cells?

    <p>To give rise to T-lymphocytes, B-lymphocytes, and natural killer (NK) cells</p> Signup and view all the answers

    What is the function of Granulocytes and Macrophages (GM) progenitor?

    <p>To give rise to myeloblasts that mature into granulocytes</p> Signup and view all the answers

    What is the role of cytokines in immune response?

    <p>To regulate the intensity and duration of immune responses</p> Signup and view all the answers

    What is the function of cytokines in hematopoiesis?

    <p>To regulate hematopoiesis</p> Signup and view all the answers

    What is the function of Dendritic Cells (DCs)?

    <p>To arise from either Common Lymphoid Progenitor (CLP) or Common Myeloid Progenitor (CMP)</p> Signup and view all the answers

    Which type of chemokine serves as a chemoattractant?

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

    Which cytokine receptor family includes Interleukin-1 and Macrophage colony stimulating factor (M-CSF)?

    <p>Immunoglobulin (Ig) superfamily receptors</p> Signup and view all the answers

    Which cytokine is produced by the TH1 subset of T cells and has antiviral and antiparasitic activities?

    <p>IFN-γ</p> Signup and view all the answers

    What is the primary function of IFN-γ in macrophages?

    <p>Increase microbicidal activity</p> Signup and view all the answers

    What is the effect of IFN-γ on the TH2 population?

    <p>Inhibit the expansion of the TH2 population</p> Signup and view all the answers

    What is the role of IFN-γ in the expression of class II MHC proteins?

    <p>Upregulate the expression of class II MHC proteins</p> Signup and view all the answers

    What is the duration of IFN-γ secretion by T cells?

    <p>Transient, reaching its peak at approximately 24 h after cell stimulation</p> Signup and view all the answers

    Which cytokine is involved in the differentiation of Tc CD8+ cells?

    <p>IFN-γ</p> Signup and view all the answers

    What is the cause of reduced expression of the 55-kDa α subunit of the IL-2 receptor?

    <p>Dramatic reduction in the expression</p> Signup and view all the answers

    Which of the following is NOT a problem with cytokine therapies?

    <p>Well-established pharmacokinetics</p> Signup and view all the answers

    What is a characteristic of adaptive immunity?

    <p>Antigen specificity</p> Signup and view all the answers

    What is the function of B-lymphocytes in the immune response?

    <p>Produce antibodies to recognize and bind to antigens</p> Signup and view all the answers

    What is the characteristic of antibodies produced by B-lymphocytes?

    <p>Same antigen-binding sites with different tail regions</p> Signup and view all the answers

    What is the function of cytokines in the immune response?

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

    What is the name of the immune response mediated by certain types of T-lymphocytes?

    <p>Cell Mediated Immune response</p> Signup and view all the answers

    Where do B cells mature?

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

    What is the rate at which plasma cells secrete antibodies?

    <p>2000 molecules per second</p> Signup and view all the answers

    What is the function of CD4 T lymphocytes in the antibody-mediated arm?

    <p>To recognize pathogen's antigens and produce cytokines</p> Signup and view all the answers

    What is the primary function of antibodies in the immune response?

    <p>To combat extracellular pathogens and their toxins</p> Signup and view all the answers

    What is the role of antigen-presenting cells (APCs) in the antibody-mediated arm?

    <p>To present antigens to helper T cells</p> Signup and view all the answers

    What is the function of T cells in the cell-mediated arm?

    <p>To recognize the antigen-MHC class I complex</p> Signup and view all the answers

    What is the name of the receptor found on the surface of T cells?

    <p>T-cell receptor (TCR)</p> Signup and view all the answers

    Where do T cells mature?

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

    What is the name of the process by which antibodies help eliminate pathogens?

    <p>Enhanced phagocytosis</p> Signup and view all the answers

    What is the maximum molecular weight of cytokines in kDa?

    <p>30</p> Signup and view all the answers

    What is the primary function of cytokines?

    <p>To mediate cell interactions and communications</p> Signup and view all the answers

    Which type of cytokine is produced by monocytes?

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

    What determines the specificity of an immune response?

    <p>Ag recognition by B and T cells</p> Signup and view all the answers

    What is the characteristic of cytokines in terms of their action duration?

    <p>They act for a limited period of time</p> Signup and view all the answers

    What is the term for cytokines that act on cells at a distance?

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

    What is the term for cytokines that have greater than additive effects when combined?

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

    What is the term for cytokines that can act on more than one cell?

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

    Study Notes

    Cytokines and Their Functions

    • Cytokines are low molecular weight proteins (<30 kDa) secreted by cells that mediate interactions and communications between cells.
    • They are responsible for regulating intensity and duration of immune responses, development of cellular and humoral immune responses, stimulating or inhibiting cell activation, proliferation, and differentiation.
    • Cytokines can induce the synthesis of other cytokines, resulting in cascades of cytokine activity.

    Classification of Cytokines

    • Cytokine families include:
      • Hematopoietic family
      • Interferon family
      • Tumor necrosis factor (TNF) family
      • Chemokine family
    • Cytokine receptor families include:

      • Immunoglobulin (Ig) superfamily receptors, which are involved in cell-cell interactions and are characterized by their Ig-like domains.

      • Class I cytokine receptor family (hematopoietin receptor family), which includes receptors for cytokines that stimulate the growth and differentiation of hematopoietic cells.

      • Class II cytokine receptor family (interferon receptor family), which is responsible for responding to viral infections and triggering an antiviral response.

      • Tumor necrosis factor (TNF) receptor family, which plays a crucial role in regulating cell survival, differentiation, and apoptosis.

      • Chemokine receptor family, which is involved in the recruitment of immune cells to sites of inflammation.

      • Immunoglobulin (Ig) superfamily receptors, which are structurally related to antibodies and bind to cytokines, leading to activation of various signaling pathways.

      • Class I cytokine receptor family (hematopoietin receptor family), characterized by the presence of a conserved Trp-Ser-X-Trp-Ser (WSXWS) motif in their extracellular domains, and include receptors for cytokines such as erythropoietin, granulocyte-colony stimulating factor, and interleukin-2.

      • Class II cytokine receptor family (interferon receptor family), which includes receptors for interferons and interleukin-10, and is characterized by the presence of a conserved motif in their extracellular domains.

      • Tumor necrosis factor (TNF) receptor family, which includes receptors for TNF-α, Fas ligand, and TNF-related apoptosis-inducing ligand (TRAIL), and plays a crucial role in regulating apoptosis and inflammation.

      • Immunoglobulin (Ig) superfamily receptors

      • Class I cytokine receptor family (hematopoietin receptor family)

      • Class II cytokine receptor family (interferon receptor family)

      • Tumour Necrosis factor (TNF) receptor family

      • Chemokine receptor family

    Cytokine Secretion by TH1 and TH2 Subsets

    • T helper 1 (TH1) subset (CD4+ T cells) produce IFN-γ, which:

      • Activates macrophages, stimulating microbicidal activity
      • Up-regulates major histocompatibility complex (MHC) class II expression
      • Induces the production of IgG2a antibodies
      • Enhances the activity of natural killer cells and cytotoxic T cells

    • T helper 2 (TH2) subset (CD4+ T cells) produce IL-4, IL-5, and IL-13, which:

      • Promote the production of IgE antibodies
      • Stimulate the growth and differentiation of eosinophils
      • Induce the production of mucin by goblet cells in the respiratory tract

    • T helper 1 (TH1) subset (CD4+ T cells) produce IFN-γ, which:

      • Activates macrophages, stimulating microbicidal activity
      • Up-regulates class II MHC expression
      • Induces antibody-class switching to IgG and supports phagocytosis and complement fixation
      • Promotes differentiation of Tc CD8+ cells
      • Inhibits TH2 population expansion

    Adaptive Immunity

    • Acts selectively and specifically through:
      • Antigen specificity
      • Diversity
      • Self/non-self recognition
      • Immunological memory
    • Works through two mechanisms:
      • Humoral immune response (antibody production by B-lymphocytes)
      • Cell-mediated immune response (mediated by T-lymphocytes)

    B Cells and Antibody Production

    • B lymphocytes recognize antigens through membrane-bound immunoglobulins (B-cell receptors)

    • Antigen presentation and activation of naive B cells stimulate clonal expansion and differentiation into:

      • Antibody-secreting plasma cells
      • Memory B cells, which can rapidly respond to future encounters with the same antigen

    • Antibody production involves:

      • Class switching, allowing for the production of different antibody classes (IgM, IgG, IgA, etc.) with distinct functions
      • Somatic hypermutation and affinity maturation, leading to the generation of high-affinity antibodies

    • B cells mature in the bone marrow and express antigen-binding receptors (membrane-bound antibodies)

    • Activated B cells differentiate into plasma cells, secreting large amounts of antibodies

    • Antibodies have a unique antigen-binding site and can have different tail regions

    • Effector B cells can secrete antibody while still small lymphocytes, but the end stage is a large plasma cell secreting antibodies at a rate of about 2000 molecules per second

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