Immunology Lecture 2-5: Innate Immune, Antibody, Lymphocytes, T Cells and MHC

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Questions and Answers

Which of the following cytokines is NOT produced by Th17 cells?

  • IL-22
  • IL-10 (correct)
  • IL-21
  • IL-17

Which of the following is NOT a function of Treg cells?

  • Activate CD8+ T cells to kill target cells (correct)
  • Suppress proliferation of responder cells
  • Suppress antibody production from B cells
  • Suppress cytokine production of responder cells

Which type of T cell primarily helps B cells to produce antibodies?

  • Th1
  • Treg
  • Th2 (correct)
  • Th17

Which of the following is NOT a cytokine produced by Th1 cells?

<p>IL-4 (D)</p> Signup and view all the answers

Which type of T cell primarily helps CD8+ T cells become cytotoxic?

<p>Th1 (B)</p> Signup and view all the answers

Which of the following cytokines is NOT directly involved in the differentiation of naïve CD4+ T cells into effector T cell subtypes?

<p>IL-10 (A)</p> Signup and view all the answers

Which type of effector T cell primarily contributes to the suppression of immune responses?

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

Which of the following is NOT a mechanism by which Treg cells suppress immune responses?

<p>Directly killing target cells through cytotoxic mechanisms (C)</p> Signup and view all the answers

Which molecules are involved in presenting peptides to T cells?

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

What is the total number of signals required for T cell activation?

<p>2 (B)</p> Signup and view all the answers

What type of T cells are classified as cytotoxic lymphocytes?

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

Which of the following correctly represents the structure of MHC class I?

<p>Heterodimer with beta-2 microglobulin (A)</p> Signup and view all the answers

What do CD4+ T cells primarily recognize?

<p>MHC II molecules (B)</p> Signup and view all the answers

Which term best describes the genes encoding MHC class I and II molecules?

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

What is the function of co-stimulatory molecules during T cell activation?

<p>To provide the second signal for activation (B)</p> Signup and view all the answers

Which subtype of T cell is primarily involved in helping B cells and CD8+ T cells?

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

What type of signal is recognized by the T cell receptor (TCR)?

<p>Peptide-MHC complexes (D)</p> Signup and view all the answers

Which cells express MHC class II molecules?

<p>Specialized antigen presenting cells (B)</p> Signup and view all the answers

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Study Notes

T Cell Antigen Recognition

  • Peptides are displayed by cells in the context of highly polymorphic MHC molecules
  • T cells recognize peptides with their T cell receptors

MHC Molecules

  • MHC I:
    • Associates with β2 microglobulin
    • Expressed on all nucleated cells
    • Displays peptides from endogenously expressed proteins
  • MHC II:
    • Expressed on specialized antigen-presenting cells (APCs): monocytes, macrophages, dendritic cells, and B lymphocytes
    • Displays peptides from exogenously derived proteins

Sources of Peptides Loaded into MHC Class I and II

  • MHC class I: viruses and other intracellular pathogens
  • MHC class II: extracellular pathogens and proteins

Structure and Function of MHC Molecules

  • Highly polymorphic genes encoding MHC class I and II
  • MHC molecules are heterodimers (α and β chains) for MHC I and II

T Cell Receptors (TCRs)

  • T cells are defined by expression of the T cell receptor
  • TCRs are membrane-bound heterodimers (α and β chains) with variable and constant domains
  • TCR genes undergo rearrangements from germline before translation
  • Two subtypes: αβ and γδ

T Cell Activation

  • Activation of T cells requires two signals: Signal 1 (TCR-MHC interaction) and Signal 2 (co-stimulation)
  • Co-stimulatory molecules (CD28 and CD86) are upregulated on APCs by 'danger signals' (infection and inflammation)

CD8 T Cells

  • Recognize peptides presented by MHC I
  • Cytotoxic T cells that can kill target cells (virally infected or cancerous cells)

CD4 T Cells

  • Recognize peptides presented by MHC II
  • Can differentiate into different kinds of effector T cells with distinct functions:
    • Th1: produce IFN-γ and help activate CD8 T cells and macrophages
    • Th2: produce IL-4 and help activate B cells
    • Th17: produce IL-17 and help fight extracellular pathogens
    • Treg: suppress immune responses and maintain self-tolerance

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