AbstractThe effects of anti‐Lyt‐2 antibodies at different levels of lectin‐induced cytotoxic T lymphocyte (CTL) responses have been analyzed. Induction of interleukin 2 (T cell growth factor) reactivity (“step 1”) by three different lectins was profoundly inhibited by anti‐Lyt‐2 antibodies. Also lectin‐dependent cytotoxicity of polyclonally induced CTL was significantly inhibited by anti‐Lyt‐2 antibodies, whereas the interjacent IL2‐dependent proliferation of “step 1”‐induced CTL precursors was unaffected by these antibodies. The anti‐Lyt‐2‐mediated inhibition was selective and specific to the target cell determinants and limited to the events in CTL responses which require interactions with the lectins. These results parallel those obtained in antigen‐induced responses and indicate that antigens and lectins induce CTL responses by interacting with the same type of membrane receptor complex containing Lyt‐2 molecules and antigen‐specific receptors. It follows that T cell mitogenic lectins do not appear to deliver trigger