Concanavalin A stimulation of T-cell cytotoxicity has been shown to be absolutely dependent on helper T-cell collaboration. Thymocytes stimulated with ConA do not differentiate to yield cytotoxic effector cells. However, thymocytes cocultured with irradiated spleen cells as helpers and ConA yield high levels of cytotoxicity. The helper cell bears theta antigens on its surface, is not an adherent cell, and does not require any adherent cell functions in our culture conditions. The ConA-dependent helper cells appear to be polyclonal in specificity. Thus, polyclonal stimulation of cytotoxicity by ConA requires T helper-T precursor collaboration in analogy to antigen-specific T helper-T precursor interactions. Unlike the antigen-specific interacitons, the ConA-driven cytotoxicity does not appear to require linked associative recognition for induction of cytotoxicity.

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