Antigen Processing and Presentation in Immunology
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Questions and Answers

What makes conventional DCs the most efficient APCs for initiating primary T cell responses?

  • Responding to chemokines and migrating preferentially into lymph nodes
  • Expressing high levels of peptide-MHC complexes, costimulators, and cytokines (correct)
  • Transferring internalized proteins from phagosomes into the cytosol
  • Being located in tissues colonized by microbes
  • Which cells are strategically located at sites of entry of microbes and in tissues that may be colonized by microbes?

  • B cells
  • Macrophages
  • Natural killer cells
  • Dendritic cells (DCs) (correct)
  • What allows specialized DCs (cDC1) to efficiently cross-present antigens to CD8+ T cells?

  • Transferring internalized proteins from phagosomes into the cytosol (correct)
  • Expressing high levels of costimulators
  • Being located in lymph nodes
  • Responding to chemokines
  • What is one key property that differentiates mature DCs from other antigen-presenting cells?

    <p>Expressing high levels of peptide-MHC complexes</p> Signup and view all the answers

    What is the primary function of dendritic cells (DCs) in relation to T cell responses?

    <p>Initiating primary T cell responses</p> Signup and view all the answers

    Which DC subset is especially efficient at cross-presentation, presenting ingested antigens on class I MHC molecules to CD8+ T cells?

    <p>Type 1 cDCs (cDC1)</p> Signup and view all the answers

    Which DC subset is the major source of type I IFN and plays an essential role in innate immune responses to viruses?

    <p>Plasmacytoid DCs (pDC)</p> Signup and view all the answers

    Which DC subset presents captured antigens to CD4+ T cells and is crucial for initiating responses of these T cells?

    <p>Type 2 cDCs (cDC2)</p> Signup and view all the answers

    Which DC subset can be induced to develop from monocytes under inflammatory conditions but has unclear roles in immune responses?

    <p>Monocyte-derived DCs (moDC)</p> Signup and view all the answers

    Which type of DC captures antigens and transports them to secondary lymphoid organs, being involved in antigen presentation to naive CD4+ and CD8+ T cells?

    <p>Conventional DCs</p> Signup and view all the answers

    Which cells, located in the epidermis, were among the earliest identified dendritic cells?

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

    Which cells are most effective at capturing and transporting antigens for presentation to naive T cells?

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

    What enhances the antigen-presenting function of APCs?

    <p>Exposure to microbial products</p> Signup and view all the answers

    Which cells are more important for the activation of naive T cells?

    <p>Antigen-presenting cells</p> Signup and view all the answers

    Where are microbes and protein antigens that enter through epithelia concentrated?

    <p>Lymph nodes</p> Signup and view all the answers

    Which organ captures blood-borne antigens mostly?

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

    What is the main function of MHC molecules in antigen processing?

    <p>To bind and display antigens for recognition by T cells</p> Signup and view all the answers

    Why do T lymphocytes recognize cell-associated antigens and not soluble, cell-free antigens?

    <p>Because MHC class I and II molecules only present cell-associated antigens</p> Signup and view all the answers

    Which cell type is the most effective antigen-presenting cell (APC) for activating naive T cells?

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

    Why is it essential for antigen-presenting cells (APCs) to carry antigens to secondary lymphoid organs?

    <p>To concentrate antigens where naive T cells circulate</p> Signup and view all the answers

    What is the primary source of foreign protein antigens that induce T cell-mediated immune responses?

    <p>Intact folded proteins</p> Signup and view all the answers

    Why do most T lymphocytes recognize only short peptides?

    <p>Due to the structure of MHC molecules</p> Signup and view all the answers

    Which immune responses are usually induced by nonprotein antigens?

    <p><strong>Humoral</strong> immune responses are induced by nonprotein antigens.</p> Signup and view all the answers

    What are the additional stimuli provided by APCs to fully activate T cells?

    <p><strong>Costimulators</strong> are provided by APCs to fully activate T cells.</p> Signup and view all the answers

    Which type of lymphocytes recognize peptide antigens displayed by MHC molecules?

    <p><strong>CD4+ and CD8+ T cells</strong> recognize peptide antigens displayed by MHC molecules.</p> Signup and view all the answers

    What process allows DCs to initiate CD8+ T cell responses to the antigens of ingested cells?

    <p>Cross-presentation</p> Signup and view all the answers

    Which pathway involves the proteolytic cleavage of proteins by enzymes in lysosomes and late endosomes?

    <p>Class II MHC pathway</p> Signup and view all the answers

    Which molecule is associated with newly synthesized class II MHC molecules and transported from the ER to endosomal vesicles?

    <p>Invariant chain (Ii)</p> Signup and view all the answers

    What type of proteins generates peptides bound to class II MHC molecules for recognition by CD4+ helper T cells?

    <p>Proteins synthesized by extracellular microbes</p> Signup and view all the answers

    What are the effector mechanisms that eliminate extracellular antigens activated by?

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

    Which type of T cells functions to eliminate cells harboring intracellular infections?

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

    What is the process called when DCs present antigens from virus-infected or tumor cells and prime T cells specific for these antigens?

    <p>Cross-presentation</p> Signup and view all the answers

    Where are peptides generated by proteasomes in the cytosol translocated for binding to newly synthesized class I MHC molecules?

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

    What is the specialized transporter protein called that mediates the translocation of peptides ranging from 8 to 16 amino acids from the cytosol into the endoplasmic reticulum?

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

    Which type of proteasomes are specifically found in immune cells like dendritic cells and other antigen-presenting cells?

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

    Which protein assists in loading peptides onto newly synthesized class I MHC molecules in the endoplasmic reticulum?

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

    Why do peptides preferentially bind to class I rather than class II MHC molecules after being transported into the ER?

    <p>Peptides' affinity for class I MHC</p> Signup and view all the answers

    What stabilizes the Class II MHC molecules on the surface of antigen-presenting cells (APCs)?

    <p>Peptide antigens</p> Signup and view all the answers

    Which type of T cells are activated by helper T lymphocytes to eliminate extracellular antigens?

    <p>B lymphocytes</p> Signup and view all the answers

    What type of antigens are presented to CD8+ cytotoxic T lymphocytes?

    <p>Cytosolic antigens</p> Signup and view all the answers

    What is the essential role of the CD4 coreceptor in the antigen presentation process?

    <p>Recognition of nonpolymorphic regions on class II MHC molecules</p> Signup and view all the answers

    Which cell type recognizes only peptides displayed by major histocompatibility complex (MHC) molecules on APCs?

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

    Which immune response is induced by CD8+ cytotoxic T lymphocytes?

    <p>Killing of antigen-expressing cells</p> Signup and view all the answers

    What enables mature DCs to efficiently activate T lymphocytes?

    <p>High levels of peptide-MHC complexes, costimulators, and cytokines</p> Signup and view all the answers

    Which property makes specialized DCs (cDC1) efficient at cross-presenting antigens?

    <p>Transfer of internalized proteins from phagosomes into the cytosol</p> Signup and view all the answers

    Which cells migrate from epithelia and tissues via lymphatics in response to chemokines?

    <p>Activated DCs</p> Signup and view all the answers

    Which cells are strategically located at the common sites of entry of microbes and foreign antigens?

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

    What is the role of chemokines in the immune response?

    <p>Promote DC migration from epithelia and tissues via lymphatics</p> Signup and view all the answers

    Which type of cells can present peptides derived from cytosolic protein antigens to CD8+ CTLs?

    <p>All nucleated cells</p> Signup and view all the answers

    Which type of antigens are degraded by proteasomes to yield peptides that are displayed on class I MHC molecules?

    <p>Proteins that are present in the cytosol</p> Signup and view all the answers

    Which type of microbes produce antigens in the cytosol of cells?

    <p>Microbes that are present in the cytosol</p> Signup and view all the answers

    Which type of cells can express class II MHC molecules and present antigens to T cells?

    <p>Only endothelial and some epithelial cells</p> Signup and view all the answers

    Which type of cells are involved in the presentation of antigens of ingested microbes to effector T cells?

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

    Which type of cells are involved in the internalization of protein antigens and the presentation of peptides derived from these proteins to helper T cells?

    <p>B lymphocytes</p> Signup and view all the answers

    What is the function of MHC molecules in antigen processing?

    <p>To bind and display peptides for recognition by CD4+ and CD8+ T cells</p> Signup and view all the answers

    Which cell type is the most effective antigen-presenting cell (APC) for activating naive T cells?

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

    What are the additional stimuli provided by APCs to fully activate T cells?

    <p>Second signals or costimulators</p> Signup and view all the answers

    What makes conventional DCs the most efficient APCs for initiating primary T cell responses?

    <p>Their high expression of costimulatory molecules</p> Signup and view all the answers

    What is the main difference between CD4+ and CD8+ T cells in antigen processing?

    <p>CD4+ T cells recognize peptides bound to class II MHC molecules, while CD8+ T cells recognize peptides bound to class I MHC molecules</p> Signup and view all the answers

    Which cell type is crucial for initiating responses of CD4+ T cells?

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

    What type of T cells functions to eliminate cells harboring intracellular infections?

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

    Which DC subset is especially efficient at cross-presentation, presenting ingested antigens on class I MHC molecules to CD8+ T cells?

    <p>cDC1</p> Signup and view all the answers

    Which DC subset can be induced to develop from monocytes under inflammatory conditions but has unclear roles in immune responses?

    <p>Monocyte-derived DCs</p> Signup and view all the answers

    What enhances the antigen-presenting function of APCs?

    <p>High expression of costimulatory molecules</p> Signup and view all the answers

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