Evidence that Con A induces cytotoxicity in the same subclass of T cells as does alloimmunization.

We have studied the induction of cytoxic activity in murine T cells by the T cell mitogen Con A. Here we report the results of experiments that indicate that this cytotoxicity develops in the same class of T cells potentially activatable to cytotoxicity by immunization with allogeneic cells. Cytotoxic activity does not result from activation of cells of the T-helper class by PHA, and extensive reduction of the proportion of cells of the T-helper class by in vivo treatment with ATS does not comparably reduce the cytotoxicity developed in response to Con A. The Con A-activated cytotoxic cell sediments as a large cell. Furthermore, spleen cell populations previously immunized to alloantigens in vivo develop greatly increased cytotoxicity specific for the alloantigen of the immunizing haplotype after culture with Con A in vitro.