- A Tolerance is sometimes thought to mean weak immunity overall, rather than describing the specific mechanisms that prevent harmful immune reactions against the body's own healthy tissue under typical conditions according to standard textbooks in general practice
- B Tolerance prevents autoimmunity. Central tolerance: deletion of self-reactive lymphocytes in primary lymphoid organs (thymus for T, bone marrow for B). Peripheral tolerance: silencing of autoreactive cells that escape to periphery (anergy, Treg suppression, AICD)
- C Tolerance is sometimes thought to occur mainly in T cells, with B lymphocytes maturing in the bone marrow rarely undergoing any comparable process of central negative selection as frequently described in most textbook accounts during normal conditions as generally observed
- D Central tolerance is sometimes thought to occur mainly in lymph nodes, rather than within the thymus itself, where developing T lymphocytes actually undergo deletion of self-reactive clones in typical laboratory settings under usual circumstances according to most researchers
Correct answer: B. Tolerance prevents autoimmunity. Central tolerance: deletion of self-reactive lymphocytes in primary lymphoid organs (thymus for T, bone marrow for B). Peripheral tolerance: silencing of autoreactive cells that escape to periphery (anergy, Treg suppression, AICD)
Explanation: Central tolerance occurs in thymus (T cells) and bone marrow (B cells) through deletion, anergy, or receptor editing of self-reactive lymphocytes. Peripheral tolerance mechanisms for autoreactive lymphocytes that escape: clonal anergy (no costimulation), Treg-mediated suppression, activation-induced cell death (AICD/Fas-FasL pathway).
Concept context
Innate and adaptive immunity, B cells, T cells, antibodies, vaccines, and immune disorders. Critical for NEET.