Which organ releases T cells into circulation?

• A. Tonsils
• B. Thymus
• C. Thyroid
• D. Splenic trabeculae

Answer: (B)

T cells mature in the thymus, a specialized organ where they go through development and selection. Once they have matured, they exit the thymus and enter the bloodstream to circulate to peripheral tissues and lymphoid organs. The tonsils are secondary lymphoid tissue involved in antigen exposure, not a site of T cell maturation or release. The thyroid is an endocrine gland producing hormones, not involved in T cell development. Splenic trabeculae are structural components of the spleen; while the spleen houses immune cells, it does not serve as the source from which mature T cells are released into circulation. Thus, the thymus is the organ responsible for releasing mature T cells into the circulation.