Role of helper T cells (CD4+) in adaptive immunity?

• A. They kill infected cells directly.
• B. They activate B cells, cytotoxic T cells, and macrophages via cytokine signaling.
• C. They produce antibodies.
• D. They present antigens to T cells.

Answer: (B)

Helper T cells coordinate the adaptive immune response by signaling other cells through cytokines. When a CD4+ T cell sees antigen on MHC class II molecules presented by an antigen-presenting cell, it becomes activated and releases cytokines that boost the activity of many partners. This includes helping B cells mature and switch to different antibody types, so antibodies are produced effectively; aiding cytotoxic T cells to expand and function more robustly in targeting infected cells; and activating macrophages to enhance their ability to engulf and destroy pathogens. They don’t kill cells directly—that job belongs to cytotoxic T cells and NK cells. They also don’t produce antibodies themselves—that’s the role of B cells and plasma cells. Antigen presentation to CD4+ T cells is done by professional APCs, not by the helper T cells themselves. Through these signals, helper T cells orchestrate both humoral and cellular aspects of immunity.