Which of the following statements about negative selection during lymphocyte development is most accurate?
A. The mechanism of negative selection is the death of cells whose antigen receptors are not stimulated by self antigens.
B. The mechanism of negative selection is apoptosis actively induced by antigen-receptor recognition of self antigens.
C. Negative selection ensures a self MHC restricted repertoire of T lymphocytes.
D. Negative selection occurs only in T cell maturation and not in B cell maturation.
E. The major mechanism of negative selection is inhibition of antigen receptor expression.
ANS: B. Negative selection is a mechanism that promotes a self-tolerant lymphocyte repertoire for both B and T cells. It occurs in the generative lymphoid organs (bone marrow and thymus) when developing lymphocytes express antigen receptors that bind strongly to self antigens. The major mechanism is actively induced apoptosis; immature lymphocytes that receive strong antigen receptor-mediated signals are particularly susceptible to death by apoptosis. Positive selection in the thymus promotes a self-MHC-restricted T cell repertoire.
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