Which organ do T cells mature in?

• A. Spleen
• B. Thymus
• C. Bone marrow
• D. Lymph nodes

Answer: (B)

T cells mature in the thymus. Although their progenitors originate in the bone marrow, they migrate to the thymus to complete their development in a specialized environment. In the thymus, developing T cells undergo T-cell receptor gene rearrangement and progress through stages that test how they recognize self-Mresented peptides. Positive selection in the cortex ensures T cells can interact with self-MHC molecules, while negative selection in the medulla eliminates cells that strongly react to self-antigens. The cells that survive these checks exit as naive T cells ready to respond to pathogens in peripheral lymphoid tissues. Other organs like the spleen and lymph nodes are involved in antigen exposure and activation, and the bone marrow is where hematopoietic precursors originate, not where mature T cells finish development.