T-cell Development and Tolerance
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Questions and Answers

Where do T-cells primarily mature?

  • Bone marrow
  • Spleen
  • Thymus (correct)
  • Lymph nodes

    • Which cells in the thymus play a crucial role in guiding T-cell development?

  • Thymic epithelial cells (correct)
  • Macrophages
  • Dendritic cells
  • B-cells

    • What process allows T-cells to recognize antigens presented via HLA?

  • Positive selection (correct)
  • Negative selection
  • Re-arrangement of HLA proteins
  • Differentiation into B-cells

    • What happens to T-cells with TCRs that bind self-antigens with high affinity?

    <p>Undergo negative selection</p> Signup and view all the answers

    Which of the following is NOT a characteristic of the thymus?

    <p>Surrounded by a thick capsule</p> Signup and view all the answers

    In T-cell development, where do lymphoid progenitors divide under the influence of IL-7?

    <p>Bone marrow</p> Signup and view all the answers

    What is the main characteristic that differentiates T-cell development from B-cell development in terms of maturation location?

    <p>Maturation in thymus</p> Signup and view all the answers

    Where are double negative 3 (DN3) cells mostly found during T-cell development in the thymus?

    <p>In the cortex</p> Signup and view all the answers

    What happens if a developing T-cell in the thymus has a useless beta chain of the TCR?

    <p>The cell dies</p> Signup and view all the answers

    What is the phenotype of a developing T-cell immediately after both TCR chains have been recombined?

    <p>Double positive (DP)</p> Signup and view all the answers

    What happens if a DP (double positive) cell in the thymus interacts with thymic epithelial cells expressing self-antigens with very low affinity?

    <p>Death of the DP cell</p> Signup and view all the answers

    What is the consequence when DP cells interact with thymic epithelial cells expressing self-antigens with high affinity?

    <p>Death of the DP cell</p> Signup and view all the answers

    What is the fate of DN cells that do not rearrange their beta chain correctly in the thymus?

    <p>Death of the DN cell</p> Signup and view all the answers

    What happens to a DP T-cell with 'low-medium' affinity for a thymic epithelial cell's HLA bound to self antigen during positive selection?

    <p>It is allowed to survive</p> Signup and view all the answers

    What happens to a DP T-cell with 'high' affinity for a thymic epithelial cell's HLA bound to self antigen during negative selection?

    <p>It is killed</p> Signup and view all the answers

    What happens to some T-cells that recognize self during negative selection?

    <p>They become regulatory T-cells</p> Signup and view all the answers

    What determines whether a DP cell expresses CD4 or CD8 co-receptor after surviving positive and negative selection?

    <p>Interaction with medullary TECs</p> Signup and view all the answers

    During positive selection, what leads to a DP T-cell being allowed to survive?

    <p>'Low-medium' affinity for thymic epithelial cell's HLA bound to self antigen</p> Signup and view all the answers

    What provides the driving force for lymph to enter lymph capillaries?

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

    Which duct drains the right arm, thoracic region, and right head/neck into the blood system?

    <p>Right lymphatic duct</p> Signup and view all the answers

    What happens to external pressure when lymph enters lymph capillaries?

    <p>It dissipates</p> Signup and view all the answers

    What is the role of trunks in the lymphatic system?

    <p>Combine vessels after exiting lymph nodes</p> Signup and view all the answers

    During T-cell development, beta chain of the TCR is shuffled before the alpha chain

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

    95% of T-cells do not survive positive and negative selection

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

    Choice of CD8 or CD4 receptors occurs in the cortex of the thymus

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

    Where does central tolerance occur?

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

    What are the consequences of defects in AIRE gene?

    <p>Autoimmune diseases</p> Signup and view all the answers

    Which of the following is the major polarizing cytokine for T-reg cells?

    <p>TGF-B</p> Signup and view all the answers

    What happens when CD28 of Th cell binds to B7 (CD80/86) of CD4+ T-reg cells?

    <p>Apoptosis of T-reg cell</p> Signup and view all the answers

    CTLA-4 is expressed on Th cells. Which ligand of the T-reg cell does it bind to with high affinity?

    <p>B7 (CD80/86)</p> Signup and view all the answers

    Which of the following receptors is expressed on T-reg cells in high levels?

    <p>IL-2R</p> Signup and view all the answers

    Which of the following antibodies plays a role in maintaining barrier integrity against microbial invasion?

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

    Which of the following diseases is associated with deficiencies in both the IL-2R-alpha gene and the CTLA-4 gene?

    <p>Type 1 DM (diabetes mellitus)</p> Signup and view all the answers

    Which of the following is true regarding the spleen?

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

    Which of the following signals do B-cells need to be activated without the help of Th cells?

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

    Where does the thoracic duct drain into?

    <p>Left subclavian vein and left internal jugular</p> Signup and view all the answers

    Study Notes

    T-Cell Maturation and Development

    • T-cells primarily mature in the thymus.
    • Thymic epithelial cells play a crucial role in guiding T-cell development.
    • T-cells recognize antigens through a process that involves the interaction with Human Leukocyte Antigen (HLA).

    Affinity and Selection

    • T-cells with TCRs that bind self-antigens with high affinity typically undergo apoptosis (negative selection).
    • Characteristics of the thymus include its role in T-cell development, while a lack of lymphatic drainage is NOT a characteristic.
    • Lymphoid progenitors divide under the influence of IL-7 in the thymus.

    Differences in T-Cell and B-Cell Development

    • T-cell maturation occurs in the thymus, whereas B-cells mature in the bone marrow.

    Development Stages in Thymus

    • Double negative 3 (DN3) cells are found in the thymus during T-cell development, particularly in the subcapsular zone.
    • Developing T-cells with a useless beta chain of the TCR typically fail to progress in development.
    • After TCR chain recombination, a developing T-cell is termed a double positive (DP) T-cell.

    Positive and Negative Selection Outcomes

    • DP cells interacting with self-antigens at low affinity survive positive selection.
    • High affinity interactions result in apoptosis during negative selection.
    • DN cells not correctly rearranging their beta chain will be eliminated.

    Co-Receptor Expression and Selection Processes

    • The expression of CD4 or CD8 co-receptors in a DP cell is determined by the type of TCR and selection outcome.
    • DP T-cells survive positive selection through weak interactions with thymic epithelial cells.

    Lymphatic System

    • The driving force for lymph entry into capillaries is the pressure gradient.
    • The right lymphatic duct drains lymph from the right arm, thoracic region, and right head/neck into the bloodstream.
    • When lymph enters capillaries, external pressure decreases.

    Functions of Lymphatic Trunks

    • Trunks in the lymphatic system serve as major conduits for draining lymph and transporting immune cells.

    Central Tolerance and AIRE Gene

    • Central tolerance, where self-reactive T-cells are eliminated, occurs in the thymus.
    • Defects in the AIRE gene lead to autoimmunity due to impaired negative selection.

    T-Cell Regulation and Signaling

    • The major polarizing cytokine for T-reg cells is IL-2.
    • Binding of CD28 on Th cells to B7 (CD80/86) on T-reg cells enhances regulation.
    • CTLA-4 binds to CD80/86 with high affinity on T-reg cells.

    Immune Response and Antibody Function

    • T-reg cells express high levels of CD25.
    • Antibodies such as IgA contribute to maintaining barrier integrity against pathogens.
    • Combined deficiencies in IL-2R-alpha and CTLA-4 genes can lead to severe immune dysfunction.

    Spleen and B-Cell Activation

    • The spleen plays a key role in filtering blood and activating immune responses.
    • B-cells can be activated without Th cells through direct antigen recognition and signal transduction.

    Lymphatic Drainage

    • The thoracic duct drains lymph into the venous system at the junction of the left subclavian and internal jugular veins.

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    Related Documents

    Immunology T-cell Development and Tolerance (BMS 150) PDF

    Description

    Learn about the mechanisms of positive and negative selection in T-cell development. Understand how T-cells with varying affinities for self antigens survive or are eliminated in the thymus.

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