Thymus and T-Cell Maturation
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Questions and Answers

What is the role of cortical epithelial cells in the thymus?

  • Provide antigens to pre-T lymphocytes for negative selection
  • Serve as a tight layer around the microvasculature in the medulla
  • Directly bind with mature T lymphocytes for selection
  • Secrete cytokines that promote T-cell maturation (correct)

    • Where do mature T lymphocytes exit the thymus from?

  • Venules and efferent lymphatics in the medulla (correct)
  • Cortical epithelial cells in the cortex
  • Capsules surrounding the thymus
  • Tight junctions between thymic epithelial cells

    • What happens to pre-T lymphocytes that recognize self-antigens during thymic selection?

  • Die by apoptosis (correct)
  • Advance to the thymic cortex
  • Differentiate into mature T lymphocytes
  • Undergo negative selection by dendritic cells

    • Which cell population begins to proliferate in the thymic cortex?

    <p>T lymphoblasts not expressing CD4, CD8, or a TCR</p> Signup and view all the answers

    What is the purpose of positive selection in the thymus?

    <p>To allow survival based on binding to MHC molecules</p> Signup and view all the answers

    What determines whether a pre-T lymphocyte will survive and advance to the thymic medulla?

    <p>Recognition of self-antigen presented by dendritic cells</p> Signup and view all the answers

    What is the main function of squamous cortical TECs?

    <p>Contribute to the corticomedullary barrier</p> Signup and view all the answers

    What characterizes the thymic medulla in terms of lymphocytes?

    <p>Fewer and larger, more mature lymphocytes</p> Signup and view all the answers

    What is the function of Hassall corpuscles in the thymic medulla?

    <p>Contain aggregates of TECs responsible for peripheral tolerance</p> Signup and view all the answers

    What distinguishes primary nodules from secondary nodules in lymphoid nodules?

    <p>Uniform cell density and staining</p> Signup and view all the answers

    Which type of medullary TECs supports T lymphocytes, dendritic cells, and macrophages?

    <p>Cytoreticulum TECs</p> Signup and view all the answers

    What is the unique feature of thymic corpuscles?

    <p>Size up to 100 μm in diameter</p> Signup and view all the answers

    What is the main function of squamous thymic epithelial cells in the cortex of the thymus?

    <p>Forming an isolated cortical compartment by lining the connective tissue of the capsule and septa.</p> Signup and view all the answers

    What is the function of stellate thymic epithelial cells in the cortex of the thymus?

    <p>Forming a cytoreticulum for macrophages and developing lymphocytes to attach to.</p> Signup and view all the answers

    Which cells in the cortex of the thymus are responsible for secreting IL-4 and other cytokines that stimulate gene recombination of B cells?

    <p>Plasma cells venules</p> Signup and view all the answers

    What role do squamous thymic epithelial cells play in maintaining the blood-thymus barrier?

    <p>Forming desmosomes and occluding junctions to prevent unregulated antigen exposure.</p> Signup and view all the answers

    Which characteristic distinguishes stellate thymic epithelial cells from squamous TECs?

    <p>Processes containing keratin tonofilaments</p> Signup and view all the answers

    Why are cortical epithelial cells in the thymus considered as antigen-presenting cells (APCs)?

    <p>Expressing MHC class II molecules in addition to MHC class I.</p> Signup and view all the answers

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