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.
Correct Answer: c) It is required for the development of T cells.
Simplified Explanation: The thymus is crucial for T cell maturation and differentiation.
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.
Correct Answer: c) Because cell proliferation occurs after β chain rearrangement, favoring αβ-T cell development.
Explanation: Most T cells are αβ-T cells because after the β chain is produced, the thymocyte proliferates, ensuring that subsequent T cells in this lineage express the same β chain. This proliferation favors the development of αβ-T cells over γδ-T cells.
Question: Where do mature T cells primarily originate from?
Answers: a) Spleen b) Bone marrow c) Lymph nodes d) Thymus
Correct Answer: b) Bone marrow
Simplified Explanation: T cells start as progenitor cells in the bone marrow and then mature in the thymus.
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
Correct Answer: b) The MHC haplotype expressed in the thymus
Simplified Explanation: The MHC molecules in the thymus influence the type of MHC molecules T cells will recognize later on.
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
Correct Answer: b) αβ-T cells
Simplified Explanation: αβ-T cells play a key role in immune responses by recognizing MHC-presented peptides.
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.
Correct Answer: b) They are involved in α and β chain rearrangements of the TCR.
Explanation: RAG proteins (Recombination Activating Genes) are essential for the rearrangement of α and β chains in the T cell receptor (TCR), which is a crucial step in T cell development and ensures the diversity of the TCR repertoire.
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
Correct Answer: d) Binding to either MHC class I or II molecules
Simplified Explanation: The type of MHC molecule a thymocyte binds to determines whether it becomes a CD4+ or CD8+ T cell.
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.
Correct Answer: c) It can be rescued by rearrangements at the Cβ2 locus.
Simplified Explanation: Unsuccessful β-chain rearrangements can be corrected through a secondary rearrangement process at the Cβ2 locus.
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.
Correct Answer: c) It contributes to the diversity of the TCR repertoire.
Explanation: Junctional diversity is crucial for TCR development as it involves the addition of N and P nucleotides at the junctions of gene segments during TCR gene rearrangement. This process greatly increases the diversity of the TCR repertoire, enabling a broad range of antigen recognition.
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.
Correct Answer: c) It becomes weaker and produces fewer functional T cells.
Simplified Explanation: As we age, the thymus shrinks and becomes less effective in producing new T cells.
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.
Correct Answer: a) The addition of N and P nucleotides.
Explanation: Junctional diversity in TCR gene rearrangements is primarily generated by the addition of N (nucleotide) and P (palindromic) nucleotides during the recombination process. This diversity contributes to the vast repertoire of TCR specificities.
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.
Correct Answer: b) αβ-T cells recognize MHC-bound peptides, whereas γδ-T cells recognize soluble antigens.
Explanation: αβ-T cells primarily recognize antigens presented by MHC molecules in lymphoid organs and are involved in cytotoxic responses, while γδ-T cells recognize soluble antigens and play roles in immune responses at epithelial surfaces.
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.
Correct Answer: b) They undergo apoptosis.
Explanation: During negative selection in the thymus, T cells that bind to the peptide-MHC complex with very high affinity are eliminated through apoptosis. This process prevents the development of autoreactive T cells that could potentially cause autoimmune diseases
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.
Correct Answer: b) It differentiates thymocytes into Pro-T cells.
Explanation: Notch signaling is crucial in T cell development. When thymocytes in the thymus bind to thymic epithelium, Notch signaling is activated, which then initiates the differentiation of these thymocytes into Pro-T cells.
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.
Correct Answer: b) It ensures the expression of all “self” molecules in the thymus.
Explanation: AIRE is a crucial protein in the thymus that regulates the expression of a wide variety of genes, ensuring that "self" antigens are presented in the thymus. This expression is essential for the negative selection of T cells, preventing autoimmunity.
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.
Correct Answer: b) By emitting suppression signals to inhibit activation of autoreactive T cells.
Explanation: Regulatory T cells (Tregs) play a key role in maintaining immune tolerance by emitting suppression signals. These signals inhibit the activation and differentiation of naïve T cells that recognize self-antigens, thereby preventing autoimmunity.
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.
Correct Answer: b) It inserts N nucleotides in somatic recombination.
Explanation: TdT plays a critical role in T cell development by adding N (nontemplated) nucleotides to the DNA during somatic recombination. This process increases the diversity of the T cell receptor repertoire.
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.
Correct Answer: b) To present antigens to maturing T cells.
Explanation: Cortical epithelial cells in the thymus are involved in the positive selection of T cells, where they present antigens to maturing T cells to ensure that these cells can recognize foreign antigens presented by MHC molecules.
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.
Correct Answer: b) Whether the rearrangement results in a functional TCR.
Explanation: A T cell rearrangement is considered productive if it results in the formation of a functional T cell receptor (TCR). Non-productive rearrangements do not produce a functional TCR and often lead to cell apoptosis or further rearrangement attempts.
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.
Correct Answer: b) They are essential for α and β chain rearrangements.
Simplified Explanation: RAG proteins help rearrange TCR genes, allowing for diverse T cell receptor formation.
Question: Which cells are involved in resistance at epithelial surfaces and wound healing?
Correct Answer: a) γδ-T cells
Explanation: γδ-T cells are involved in resistance at epithelial surfaces, wound healing, and control of inflammation. They recognize soluble antigens and play a unique role in the immune system.
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+).
Correct Answer: c) It is automatically deleted.
Explanation: When the α-chain gene of the TCR is rearranged, the δ locus, which is situated within the α locus, is automatically deleted. This deletion ensures that the cell does not express both αβ and γδ receptors.
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.
Correct Answer: b) It is killed.
Explanation: If a thymocyte fails positive selection, which ensures that T cells can recognize peptide-MHC molecules with low affinity, it will not survive. This process is crucial for the development of functional 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.
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.
Correct Answer: c) It ensures T cells can recognize peptide-MHC molecules with low affinity.
Explanation: Positive selection in the thymus ensures that T cells can recognize peptide-MHC complexes with sufficient, but not overly high, affinity. This process is critical for the development of T cells that are functional and capable of responding to foreign antigens presented by MHC molecules.
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.
Correct Answer: b) A condition with an absent or underdeveloped thymus.
Explanation: Di George’s syndrome is characterized by the absence or underdevelopment of the thymus, leading to a severe deficiency in T cells and associated immune
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