Immunology MHC and T Cell Activation
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Immunology MHC and T Cell Activation

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Questions and Answers

Which type of cells express Class I MHC molecules?

  • Dendritic cells
  • B lymphocytes
  • All nucleated cells (correct)
  • Macrophages

    • What is the primary cytokine that stimulates Class II MHC expression in antigen-presenting cells?

  • TNF-α
  • IFN-γ (correct)
  • IL-1
  • IL-6

    • What aspect of MHC molecules is primarily responsible for their polymorphism?

  • Ig-like domains
  • Peptide-binding cleft (correct)
  • Cytoplasmic regions
  • Transmembrane domains

    • Which molecule enhances the activation of CD4+ T cells?

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

    Class II MHC molecules are exclusively expressed on which type of cells?

    <p>Dendritic cells and macrophages</p> Signup and view all the answers

    What characterizes Class I MHC molecules compared to Class II?

    <p>They contain an α chain and β2-microglobulin.</p> Signup and view all the answers

    Which of the following best describes the structural components of Class II MHC molecules?

    <p>Two polymorphic chains</p> Signup and view all the answers

    Which cytokines have a similar effect on Class I MHC molecules?

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

    What is the primary role of MHC molecules in the immune response?

    <p>To bind and display peptides for T cell recognition.</p> Signup and view all the answers

    Which class of MHC molecules is found on all nucleated cells?

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

    How do variations in MHC molecules affect T cell recognition?

    <p>They influence peptide binding and overall T cell recognition.</p> Signup and view all the answers

    What type of cells primarily expresses MHC class II molecules?

    <p>Macrophages, dendritic cells, and B cells.</p> Signup and view all the answers

    Which of the following is considered the most effective APC for initiating T cell responses?

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

    What is the significance of T cell maturation in relation to MHC molecules?

    <p>It ensures T cells recognize only MHC molecules with bound antigens.</p> Signup and view all the answers

    What is the main function of antigen presenting cells (APC)?

    <p>To capture antigens and present them to lymphocytes.</p> Signup and view all the answers

    In the context of T lymphocytes activation, how is peptide-MHC complex recognition crucial?

    <p>It prevents T cells from responding to self-antigens.</p> Signup and view all the answers

    What are co-stimulators in the context of T cell activation?

    <p>Membrane bound molecules on APCs that stimulate T cells</p> Signup and view all the answers

    How do dendritic cells (DCs) capture antigens from the bloodstream?

    <p>They sample antigens that circulate in the bloodstream</p> Signup and view all the answers

    What triggers the activation of dendritic cells, turning them into mature DCs?

    <p>Cytokines produced in response to microbes</p> Signup and view all the answers

    What is the function of adjuvants in the immune response?

    <p>To increase the expression of co-stimulators and cytokines</p> Signup and view all the answers

    Which receptors do resting tissue-resident dendritic cells primarily use to capture antigens?

    <p>C-type lectins</p> Signup and view all the answers

    What chemokine receptor do mature dendritic cells express after activation?

    <p>CCR7</p> Signup and view all the answers

    What role do proteasomes play in the processing of cytosolic proteins?

    <p>They yield peptides that can bind to class I MHC molecules.</p> Signup and view all the answers

    Which cell type is primarily responsible for presenting antigens to CD4+ helper T cells?

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

    What is the role of pinocytosis in dendritic cells?

    <p>To non-specifically internalize fluid-phase molecules</p> Signup and view all the answers

    Which process is responsible for generating peptides displayed on class II MHC molecules?

    <p>Enzymatic degradation of internalized proteins in lysosomes.</p> Signup and view all the answers

    What is the function of the transporter associated with antigen processing (TAP)?

    <p>To translocate peptides generated by proteasomes into the ER.</p> Signup and view all the answers

    What type of proteins are primarily degraded by lysosomes for class II MHC presentation?

    <p>Internalized proteins from the extracellular environment.</p> Signup and view all the answers

    Which statement accurately describes the stability of class I MHC molecules?

    <p>They are structurally stable when bound to peptides generated in the cytosol.</p> Signup and view all the answers

    How do extracellular bacteria interact with the cytosolic pathway for MHC presentation?

    <p>They inject proteins directly into the cytosol.</p> Signup and view all the answers

    Which type of proteins are primarily processed by class I MHC molecules?

    <p>Cytosolic proteins that undergo proteasomal degradation.</p> Signup and view all the answers

    What distinguishes the pathways of class I and class II MHC molecules in antigen processing?

    <p>Class I MHC presents peptides from proteasomal degradation while class II MHC presents lysosomal peptides.</p> Signup and view all the answers

    What is the primary role of the invariant chain (Ii) in the biosynthesis of Class II MHC molecules?

    <p>It occupies the peptide-binding clefts before peptide loading.</p> Signup and view all the answers

    Which molecule is responsible for editing the peptide repertoire presented by Class II MHC molecules?

    <p>HLA-DM</p> Signup and view all the answers

    Where do Class II MHC complexes present foreign antigens for recognition?

    <p>On the surface of dendritic cells</p> Signup and view all the answers

    What characterizes immunodominant peptides in relation to MHC molecules?

    <p>They bind with high affinity to available Class I and Class II MHC molecules.</p> Signup and view all the answers

    What is the initial location of Class II MHC molecule synthesis?

    <p>Endoplasmic reticulum (ER)</p> Signup and view all the answers

    Which type of T cell is primarily recognized by Class II MHC molecules?

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

    What happens to the invariant chain (Ii) during the processing of Class II MHC molecules?

    <p>It dissociates under the action of proteolytic enzymes.</p> Signup and view all the answers

    How do dendritic cells present antigens from intracellular microbes?

    <p>By endocytosing vesicular antigens for Class I pathway presentation.</p> Signup and view all the answers

    Study Notes

    Introduction

    • MHC molecules are responsible for presenting peptides to CD4+ and CD8+ T cells
    • Variation in MHC molecules influences both peptide binding and T cell recognition

    MHC I and MHC II

    • MHC I is present on all nucleated cells and presents peptides to CD8+ T cells
    • MHC II is present on dendritic cells, macrophages and B cells and presents peptides to CD4+ T cells

    Antigen Presenting Cells (APCs)

    • APCs are specialized cells responsible for displaying antigens to lymphocytes
    • Dendritic Cells (DCs) are the most effective APCs for activating naïve T cells
    • Macrophages and B cells are better for activating previously activated helper T cells
    • APCs express class II MHC molecules and co-stimulators that signal T cell activation

    Co-stimulators and Adjuvants

    • Co-stimulators are APC molecules that are required to fully activate T cells in addition to antigen presentation
    • Adjuvants are microbial products that enhance APC co-stimulator expression and improve antigen presentation

    Dendritic Cell Role in Antigen Capture and Presentation

    • DCs are located in epithelial tissues and capture antigens entering the body
    • DCs use receptors like C-type lectins to capture microbes and process them for binding to MHC molecules
    • Once activated, DCs express chemokine receptor CCL7 and migrate to the lymph nodes where they stimulate T cells

    MHC Molecule Expression

    • Class I molecules are expressed on all nucleated cells and present antigens from viruses and tumors
    • Class I expression is increased by IFN- alpha and Beta
    • Class II molecules are expressed on APCs and are regulated by cytokines like IFN-gamma

    MHC Pathway of Antigen Processing and Presentation

    • Class I MHC pathway processes internal proteins primarily derived from viruses and other intracellular pathogens via proteasomes
    • Peptides generated by proteasomes are transported into the ER by the TAP transporter and bind to MHC I molecules
    • Class II MHC pathway processes externally derived proteins that have been endocytosed and degraded via lysosomes
    • Degraded peptides bind to MHC II molecules within endosomal vesicles

    Immunodominance of Peptides

    • Protein antigens are processed to generate multiple peptides, but only some are immunodominant
    • Immunodominant peptides are the ones that bind best to the available MHC molecules and are recognized by T cells

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    Related Documents

    Antigen Presentation to T Lymphocytes & MHC Molecules (PDF)

    Description

    This quiz covers the critical roles of MHC molecules in presenting peptides to T cells, as well as detailing the functions of antigen presenting cells (APCs) such as dendritic cells, macrophages, and B cells. Learn about the relationship between co-stimulators and adjuvants in T cell activation. Test your knowledge on these essential immunological concepts.

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