Helper T cells are central to immunity because they
- A. activate B cells and cytotoxic T cells by secreting cytokines
- B. engulf and digest bacteria
- C. secrete large amounts of antibody
- D. produce histamine during an allergic reaction
Explanation
Helper T cells sit at the centre of the response, recognising antigen presented by macrophages and then releasing chemical signals that switch on both the antibody producing and the cell killing arms. Their loss is why HIV, which destroys them, disables immunity as a whole rather than only one part of it. Engulfing bacteria is the job of phagocytes and histamine comes from mast cells.