What is the role of T-cells in immunity?

• A. Develop in the thymus and differentiate into effector T cells and memory T cells.
• B. Produce antibodies against pathogens.
• C. Engulf and digest pathogens directly.
• D. Initiate allergic responses by histamine release.

Answer: (A)

T cells are central to cell-mediated immunity. They originate from precursors in the bone marrow but mature in the thymus, where they become trained to recognize infected or abnormal cells. After maturation, they differentiate into effector T cells—such as helper T cells, which coordinate other immune responses by releasing cytokines, and cytotoxic T cells, which directly kill infected or abnormal cells—and into memory T cells, which persist long-term and enable a faster, stronger response if the same pathogen reappears. This combination of thymic maturation and formation of both effector and memory pools is exactly what describes their role.

Other immune actions are handled by different cells: antibodies are produced by B cells, phagocytes like macrophages and neutrophils engulf pathogens, and histamine release driving allergic symptoms comes from mast cells and basophils.