Which statement best describes how peripheral tolerance helps prevent autoimmunity?

• A. Clonal deletion of self-reactive T cells in the thymus
• B. Peripheral tolerance includes anergy, regulatory T cell suppression, and immune privilege
• C. All self-reactive cells are eliminated in the bone marrow
• D. It has no role in autoimmunity

Answer: (B)

Peripheral tolerance keeps self-reactive cells under control after they exit primary lymphoid organs. It works best by making self-reactive T cells unresponsive (anergy) when they encounter self-antigen without the right costimulatory signals, by regulatory T cells that actively suppress autoreactive responses, and by immune privilege in certain tissues where immune activity is limited to prevent damage. These mechanisms prevent autoimmunity without requiring the complete removal of all self-reactive cells from the periphery. Central tolerance in the thymus handles many self-reactive T cells during development, and bone marrow processes govern B cell tolerance there, so saying all self-reactive cells are eliminated in the bone marrow isn’t accurate. Overall, the combination of anergy, regulatory T cell suppression, and immune privilege best describes how peripheral tolerance helps prevent autoimmunity.