Development of T cells takes place in which region?

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

Answer: (A)

T-cell maturation happens in the thymus. Immature T-cell precursors come from the bone marrow and migrate to the thymus, where they undergo the processes that shape a functional T-cell repertoire. In the thymic cortex they undergo positive selection to ensure they can recognize self-MHC molecules, and in the medulla they undergo negative selection to eliminate cells that react too strongly to self-antigens. This education in the thymus produces naive T cells that then travel to peripheral lymphoid tissues to respond to infections. Other organs play different roles: the bone marrow is where hematopoietic cells originate (and where B cells mature), while the spleen and lymph nodes are sites for antigen encounter and T-cell activation rather than their initial development.