T Cell Receptor and MHC Molecules Quiz
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Questions and Answers

What are the 3 broad classes of T cells?

  • Helper
  • Regulatory
  • Cytotoxic
  • All of the above (correct)

    • Which classes of T cells are CD4?

  • Both A and B (correct)
  • Helper
  • Cytotoxic
  • Regulatory

    • Which classes of T cells are CD8?

  • Helper
  • Regulatory
  • Cytotoxic (correct)
  • None of the above

    • How many antigen binding sites does a T cell receptor have?

    <p>1</p> Signup and view all the answers

    How many hypervariable regions make up the T cell antigen binding site?

    <p>6</p> Signup and view all the answers

    What is the function of the T cell receptor constant regions?

    <p>Provide structure and anchor the receptor to the membrane with the transmembrane region</p> Signup and view all the answers

    What 3 processes are responsible for generating T-cell receptor diversity?

    <p>Somatic recombination, junctional diversity, random association alpha and beta chains</p> Signup and view all the answers

    What gene segments make up the α-chain variable region of the T cell receptor?

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

    What gene segments make up the β-chain variable region of the T cell receptor?

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

    Are the constant regions of the T cell receptor composed of gene segments?

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

    What type of antigen do T cells recognize and what type of molecule must the antigen be presented on?

    <p>Peptides, MHC</p> Signup and view all the answers

    From what location are the presented antigens for MHC class I derived?

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

    From what location are the presented antigens for MHC class II derived?

    <p>Extracellular or endosomal system</p> Signup and view all the answers

    What type of T cells are activated by MHC class I?

    <p>CD8</p> Signup and view all the answers

    What type of T cells are activated by MHC class II?

    <p>CD4</p> Signup and view all the answers

    Which cell types express MHC class I molecules?

    <p>Most cells in the body</p> Signup and view all the answers

    Which cell types express MHC class II molecules?

    <p>Only antigen presenting cells</p> Signup and view all the answers

    Which T cell co-receptor (CD4 or CD8) binds to MHC class I?

    <p>CD8 co-receptor</p> Signup and view all the answers

    Which T cell co-receptor (CD4 or CD8) binds to MHC class II?

    <p>CD4 co-receptor</p> Signup and view all the answers

    What is cross-presentation?

    <p>Dendritic cells present viral antigens taken up from the extracellular environment on MHC class I molecules to activate CD8 T cells</p> Signup and view all the answers

    Why is it necessary for dendritic cells to sometimes use cross presentation?

    <p>It allows dendritic cells to activate CD8 T cells even though they are not infected</p> Signup and view all the answers

    How many different MHC class I and II molecules does each person have for presenting antigens?

    <p>6 MHC I and 6 MHC II</p> Signup and view all the answers

    The MHC genes are the most polymorphic genes in the genome. What does polymorphic mean?

    <p>One gene has many different alleles</p> Signup and view all the answers

    Why is it beneficial for the human population to have such a large number of different MHC alleles?

    <p>The greater the variety of antigens that can be presented, making it unlikely for a pathogen to evade recognition</p> Signup and view all the answers

    How are only 12 MHC molecules in each person able to present such a broad range of antigens from all of the many pathogens encountered by the body?

    <p>MHC molecules have promiscuous binding affinity</p> Signup and view all the answers

    What determines which antigens will bind to a particular MHC molecule?

    <p>The peptides that bind will have the same anchor residues</p> Signup and view all the answers

    What is MHC restriction?

    <p>A T cell receptor is specific for both the antigen and the MHC molecule</p> Signup and view all the answers

    What is a peptide binding motif?

    <p>The sequence of anchor residues that bind to a particular MHC molecule</p> Signup and view all the answers

    Which MHC class I molecules are involved in antigen presentation?

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

    Which MHC class II molecules are involved in antigen presentation?

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

    Study Notes

    T Cell Overview

    • T cells can be classified into three broad categories: Helper, Regulatory, and Cytotoxic.
    • Helper and Regulatory T cells express the co-receptor CD4, while Cytotoxic T cells express CD8.

    T Cell Receptor (TCR) Structure

    • A T cell receptor has a single antigen-binding site.
    • The antigen-binding site consists of six hypervariable regions.
    • Constant regions of the TCR provide structural support and anchor the receptor to the cell membrane.
    • The α-chain variable region is formed from gene segments V and J.
    • The β-chain variable region is formed from gene segments V, D, and J.
    • Constant regions are not composed of gene segments.

    Antigen Recognition and Presentation

    • T cells recognize antigens as peptides presented by Major Histocompatibility Complex (MHC) molecules.
    • MHC class I presents antigens derived from the cytosol, while MHC class II presents antigens derived from the extracellular environment or endosomal system.

    T Cell Activation

    • CD8 T cells are activated by MHC class I molecules.
    • CD4 T cells are activated by MHC class II molecules.
    • MHC class I molecules are expressed by most body cells, which can be infected by intracellular pathogens.
    • MHC class II molecules are primarily expressed by professional antigen-presenting cells: dendritic cells, macrophages, and B cells.

    Co-receptors and Antigen Presentation

    • The CD8 co-receptor binds to MHC class I.
    • The CD4 co-receptor binds to MHC class II.
    • Cross-presentation enables dendritic cells to present extracellular antigens on MHC class I to activate CD8 T cells even if they are not infected.

    Diversity of MHC and T Cells

    • Each person has 6 MHC class I molecules and 6 MHC class II molecules, inherited from both parents.
    • MHC genes are the most polymorphic in the genome, meaning each gene has many different alleles.
    • A large variety of MHC alleles enhances the immune system's ability to present a wide range of antigens, making it less likely for pathogens to evade detection.

    MHC Functionality

    • MHC molecules exhibit promiscuous binding affinity, allowing them to bind a diverse range of peptide antigens.
    • Peptides must have specific anchor residues to bind to a particular MHC molecule, determining which antigens will be presented.
    • MHC restriction refers to the specificity of a T cell receptor for both the antigen and the associated MHC molecule.
    • The peptide binding motif is characterized by the sequence of anchor residues that interact with MHC molecules.

    MHC Class Specificity

    • MHC class I molecules involved in antigen presentation include A, B, and C.
    • MHC class II molecules involved in antigen presentation include DP, DQ, and DR.

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    Description

    Test your knowledge on T cell receptors and MHC molecules with these flashcards. Dive into the specifics of T cell classes and their functions, including the roles of CD4 and CD8 cells. Perfect for students studying immunology or related fields.

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