In vitro induction of F1 hybrid anti-parent cell-mediated cytotoxicity.

Spleen cells from normal (C57BL/6 X DBA/2)F1 mice were sensitized in vitro for 5 days with irradiated C57BL/6 or DBA/2 parental stimulating cells. Effector cells were generated which specifically lysed 51Cr-labeled targets (leukemia or mitogen-stimulated lymphoid cells) H-2-matched with the parental genotype used for sensitization. The response of F1 spleen cells to the C57BL/6 parent was stronger and more reproducible than that to the DBA/2 parent. The kinetics of generation of effector cells were similar for the F1 anti-parent and an F1 anti-allogeneic response. However, the magnitude of the F1 anti-C57BL/6 cytotoxic response was considerably lower than the F1 response to allogeneic cells. The ratio of responder to stimulator cells in the cultures was more critical for the former than for the latter response. Several lots of fetal bovine serum were found to be adequate for supplementing the medium in the induction of J1 hybrid anti-parent and anti-allogeneic cytotoxic effector cells. Based on these and other studies, it would appear that the F1 hybrid anti-parent cytotoxic response provides an in vitro model of murine hemopoietic graft rejection in vivo. This response may be elicited by a mechanism distinct from T cell-mediated cytotoxicity and involve different subpopulations of spleen cells.