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T Cell Selection Mechanism – Quiz

T Cell Selection Mechanism – Quiz

25 Multiple Choice Questions

1. T cell positive and negative selection occur primarily in which organ? Bone marrow
Thymus
Spleen
Lymph nodes

2. Positive selection of T cells occurs mainly in the: Thymic cortex
Thymic medulla
Peripheral blood
Bone marrow sinusoids

3. Negative selection of T cells predominantly occurs in the: Thymic medulla
Thymic cortex only
Lymph node follicles
Spleen red pulp

4. Positive selection ensures that developing T cells: Do not recognize any MHC molecules
Can bind self MHC with appropriate, moderate affinity
Are completely self-reactive
Express both BCR and TCR

5. Thymocytes that fail to recognize self MHC at all undergo: Positive selection
Negative selection
Death by neglect
Peripheral tolerance

6. T cells that bind self peptide–MHC with very high affinity in the thymus are: Positively selected
Negatively selected and deleted
Ignored and exported to periphery
Immediately activated as effector cells

7. Double-negative (DN) thymocytes are defined by which surface phenotype? CD4⁺CD8⁺
CD4⁻CD8⁻
CD4⁺CD8⁻
CD4⁻CD8⁺

8. Double-positive (DP) thymocytes express: CD4 and CD19
CD4 and CD8
CD3 only
Neither CD4 nor CD8

9. Positive selection of CD4⁺ helper T cells is driven by recognition of: Peptide–MHC class I on cortical epithelial cells
Peptide–MHC class II on cortical epithelial cells
Free antigen in the thymic medulla
Lipopolysaccharide only

10. Positive selection of CD8⁺ cytotoxic T cells is driven by recognition of: Peptide–MHC class I
Peptide–MHC class II
Soluble antibodies
CD40–CD40L interactions alone

11. The strength of TCR signaling during selection is a key determinant of: Whether the thymocyte undergoes positive or negative selection
B cell isotype switching
Neutrophil chemotaxis
Mast cell degranulation

12. Negative selection contributes primarily to which immunologic outcome? Central tolerance to self antigens
Class switching
Isotype-specific memory
Fever generation

13. Which thymic cells express a wide range of tissue-restricted self antigens to mediate negative selection? Cortical thymic epithelial cells (cTECs)
Medullary thymic epithelial cells (mTECs)
Hepatocytes
Osteoclasts

14. The transcription factor AIRE is important in the thymus because it: Drives expression of tissue-restricted antigens in mTECs
Recombines TCR genes
Activates complement cascade
Controls neutrophil lifespan

15. A T cell that survives both positive and negative selection will typically leave the thymus as: CD4⁺CD8⁺ double-positive cell
CD4⁺ or CD8⁺ single-positive mature T cell
B cell precursor
NK cell

16. Failure of negative selection is most likely to result in: Severe combined immunodeficiency
Autoimmune disease
Neutropenia
Complement deficiency

17. During positive selection, thymocytes interact primarily with: Medullary dendritic cells
Cortical thymic epithelial cells presenting self peptide–MHC
Peripheral macrophages
Red blood cells

18. Negative selection can be induced by which thymic antigen-presenting cells? Only cortical epithelial cells
Medullary epithelial cells and dendritic cells (and sometimes B cells)
Platelets
Hepatocytes

19. The term “β-selection” in thymocyte development refers to: Selection based on expression of a functional TCRβ chain
Selection of B cell heavy chain
Selection based on IgM expression
Selection of NK cell receptors

20. Double-positive thymocytes that receive excessively strong TCR signals to self peptide–MHC typically undergo: Clonal expansion
Apoptosis (negative selection)
Class switching
IgE production

21. The movement of positively selected thymocytes from cortex to medulla is important because: It exposes them to a broader array of self antigens for negative selection
It allows B cell maturation
It terminates TCR expression
It induces antibody secretion

22. “Death by neglect” during T cell development is best described as: Apoptosis of cells that receive no or very weak TCR signals
Death of cells that bind too strongly to self
Necrosis due to infection
Clearance by macrophages in the spleen only

23. Central tolerance is primarily established by: Positive selection alone
Negative selection of self-reactive T cells in the thymus
Peripheral anergy only
Class-switch recombination

24. A mature T cell that has successfully completed thymic selection will have which of the following characteristics? Strongly self-reactive
Non-reactive to any MHC
Capable of recognizing foreign peptide presented on self MHC, but tolerant to most self antigens
Expresses both BCR and TCR

25. A defect in thymic negative selection is most likely associated with which clinical finding? Recurrent infections due to T cell deficiency
Autoantibodies and multi-organ autoimmunity
Isolated IgA deficiency
Hemolytic anemia from G6PD deficiency

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