What is the main function of T cells in the immune response?

• A. Produce antibodies
• B. Produce cytokines that regulate both innate and adaptive immunity
• C. Participate actively in phagocytosis
• D. Respond to target cells without prior exposure

Answer: (B)

T cells primarily act as coordinators of the immune response, using cytokines to regulate and shape both the innate and adaptive branches. Helper T cells release a variety of cytokines that activate macrophages, help B cells mature and class-switch antibodies, and guide cytotoxic T cell responses. Regulatory T cells secrete signals that keep the immune response from running amok, preventing excessive inflammation and autoimmunity. While cytotoxic T cells can kill infected cells, their activity is driven by the cytokine milieu created by other T cells and innate cells.

Antibody production is the job of B cells, not T cells, so that choice doesn’t fit. Phagocytosis is performed by macrophages and neutrophils, not T cells. And responding to target cells without prior exposure describes innate-like surveillance (as seen with natural killer cells), whereas T cells require antigen presentation and activation. So the statement that best captures what T cells do is that they produce cytokines that regulate both innate and adaptive immunity.