IM Lecture 12 T-cell Receptor

Question: What is the primary function of cortical epithelial cells in the thymus?

Answers: a) To produce antibodies. b) To present antigens to maturing T cells. c) To facilitate T cell proliferation. d) To induce negative selection.

• Question: What role does the thymus play in T cell development?

• Answers: a) It is the site where B cells mature. b) It is not involved in T cell development. c) It is required for the development of T cells. d) It is only involved in the development of memory T cells.

• Question: What happens to the thymus with age?

• Answers: a) It increases in size and functionality. b) It remains unchanged throughout life. c) It becomes weaker and produces fewer functional T cells. d) It becomes the primary site for memory T cell production.

• Question: Where do mature T cells primarily originate from?

• Answers: a) Spleen b) Bone marrow c) Lymph nodes d) Thymus

• Question: What is the role of RAG proteins in T cell development?

• Answers: a) They promote cell proliferation. b) They are essential for α and β chain rearrangements. c) They deactivate the Notch signaling pathway. d) They are involved in the development of memory T cells.

• Question: Which type of T cells recognize MHC-bound peptides in lymphoid organs?

• Answers: a) γδ-T cells b) αβ-T cells c) Double-negative T cells d) Double-positive T cells

• Question: What is the fate of a T cell with unproductive β-chain rearrangements at the Cβ1 locus?

• Answers: a) It undergoes apoptosis. b) It differentiates into a γδ-T cell. c) It can be rescued by rearrangements at the Cβ2 locus. d) It remains as a double-positive thymocyte.

• Question: What determines the T cell restriction specificity in the thymus?

• Answers: a) The bone marrow b) The MHC haplotype expressed in the thymus c) The type of antigen-presenting cells present d) The presence of AIRE protein

• Question: What leads to the differentiation of double-positive thymocytes into either CD4+ or CD8+ T cells?

• Answers: a) Interaction with antigen-presenting cells b) Positive selection in the thymus c) Negative selection process d) Binding to either MHC class I or II molecules

Question: What role do RAG proteins play in T cell development?

Answers: a) They facilitate cell proliferation. b) They are involved in α and β chain rearrangements of the TCR. c) They suppress the production of autoantibodies. d) They activate the Notch signaling pathway.

Question: What is the role of TdT (Terminal deoxynucleotidyl transferase) in T cell development?

Answers: a) It aids in cytokine production. b) It inserts N nucleotides in somatic recombination. c) It activates mature T cells. d) It suppresses the immune response.

Question: What is the outcome of Notch signaling in T cell development?

Answers: a) It initiates the apoptosis of T cells. b) It differentiates thymocytes into Pro-T cells. c) It suppresses the TCR expression. d) It activates B cell development.

Question: What distinguishes αβ-T cells from γδ-T cells?

Answers: a) αβ-T cells are involved in antibody production, while γδ-T cells are not. b) αβ-T cells recognize MHC-bound peptides, whereas γδ-T cells recognize soluble antigens. c) γδ-T cells participate in cytotoxicity, while αβ-T cells do not. d) γδ-T cells recognize MHC-bound peptides, whereas αβ-T cells recognize soluble antigens.

Question: Why are most T cells αβ-T cells rather than γδ-T cells?

Answers: a) Because γδ-T cells are only produced in response to specific infections. b) Because the γ and δ chains are more complex to synthesize than α and β chains. c) Because cell proliferation occurs after β chain rearrangement, favoring αβ-T cell development. d) Because γδ-T cells convert into αβ-T cells during maturation.

Question: What determines whether a T cell rearrangement is productive or non-productive?

Answers: a) The ability of the T cell to bind to an antigen. b) Whether the rearrangement results in a functional TCR. c) The presence of cytokines during T cell development. d) The type of coreceptors expressed on the T cell.

Question: What is the significance of junctional diversity in TCR development?

Answers: a) It determines the specificity of the T cell for MHC molecules. b) It leads to the proliferation of T cells in the thymus. c) It contributes to the diversity of the TCR repertoire. d) It helps in the differentiation of T cells into either CD4+ or CD8+ cells.

Question: What is the role of positive selection in T cell development?

Answers: a) It eliminates autoreactive T cells. b) It ensures T cells recognize foreign antigens with high affinity. c) It ensures T cells can recognize peptide-MHC molecules with low affinity. d) It induces the proliferation of T cells.

Question: What is the fate of T cells that bind the peptide-MHC complex with very high affinity during negative selection?

Answers: a) They become memory T cells. b) They undergo apoptosis. c) They differentiate into regulatory T cells. d) They are exported to peripheral tissues.

Question: How do regulatory T cells (Tregs) prevent autoimmunity?

Answers: a) By producing cytokines that enhance immune responses. b) By emitting suppression signals to inhibit activation of autoreactive T cells. c) By binding to foreign antigens with high affinity. d) By converting into effector T cells.

• Question: What is the fate of a thymocyte if it fails positive selection in the thymus?

• Answers: a) It becomes a regulatory T cell. b) It is killed. c) It remains as a double-positive thymocyte. d) It differentiates into a γδ-T cell.

• Question: Which cells are involved in resistance at epithelial surfaces and wound healing?

• Answers: a) γδ-T cells b) αβ-T cells c) Double-negative T cells d) Double-positive T cells

• Question: What is the significance of the CD4 and CD8 molecules during T cell development?

• Answers: a) They determine whether a T cell becomes a helper or cytotoxic T cell. b) They are involved in antigen recognition. c) They have no significant role in T cell development. d) They are only expressed after T cells leave the thymus.

• Correct Answer: a) They determine whether a T cell becomes a helper or cytotoxic T cell.

• Explanation: During T cell development in the thymus, the expression of CD4 and CD8 molecules is crucial. Initially, thymocytes express both (double-positive), but as they mature, they become single-positive, expressing either CD4 or CD8. This expression determines their differentiation into either helper T cells (CD4+) or cytotoxic T cells (CD8+).

• Question: What leads to junctional diversity in TCR gene rearrangements?

• Answers: a) The addition of N and P nucleotides. b) The rearrangement of V, D, and J segments. c) The duplication of gene segments. d) The deletion of non-functional segments.

• Question: What is the role of AIRE (AutoImmune REgulator) in the thymus?

• Answers: a) It promotes the proliferation of thymocytes. b) It ensures the expression of all “self” molecules in the thymus. c) It has no role in T cell development. d) It induces the apoptosis of thymocytes.

• Question: What is Di George’s syndrome?

• Answers: a) Overproduction of functional T cells. b) A condition with an absent or underdeveloped thymus. c) Hyperactive thymic epithelial cells. d) Excessive production of γδ-T cells.