Where do T cells complete their maturation?

• A. Thymus
• B. Spleen
• C. Red bone marrow
• D. Lymph nodes

Answer: (A)

T cell maturation completes in the thymus. While their precursors originate in the red bone marrow, they migrate to the thymus to finish development, undergoing a selection process that ensures they can recognize self-MHC molecules and do not react strongly to self-antigens. Positive selection in the thymic cortex favors thymocytes that can interact with self-MHC, and negative selection in the medulla eliminates those that are strongly self-reactive. Once maturation is complete, these T cells move to peripheral lymphoid tissues to participate in immune responses. The spleen and lymph nodes are sites of immune activation, not maturation, and red bone marrow is where lymphoid precursors begin, not where they complete maturation.