Haplotype‐specific suppressor T cells mediating linked suppression of immune responses elicited by third‐party H‐2 alloantigens

Abstract Specific suppressor T cells (Ts) were induced in vitro by incubation of mouse spleen/lymph node cells with allogeneic heat‐treated cells. These Ts inhibit mixed lymphocyte reaction (MLR) in a haplotype‐specific manner. Ts also suppress cell proliferation induced by third‐party H‐2 alloantigens provided these are expressed on the same cell surface as at least some of the H‐2 antigens used for Ts activation. Ts activated by H‐2 plus non‐H‐2 alloantigens suppress an MLR induced by irrelevant H‐2 alloantigens if these are expressed on the same cell surface as the non‐H‐2 alloantigens used for Ts activation. Products of the H‐2 region or non‐H‐2 alloantigens which are not able to stimulate cell proliferation do not activate Ts. These Ts are first demonstrable after 4 days of incubation of lymphoid cells with heat‐treated allogeneic cells and they inhibit MLR only if added at the very beginning of the culture. Exogenous interleukin 2 does not overcome suppression and the suppression is not due to a cytotoxic effect, since heat‐treated cells do not elicit cell proliferation or cytotoxic cells. Moreover, the specific Ts differ in their Thy‐1 + ,Ly‐1 + ,2 − phenotype from Ly‐2 + allospecific cytotoxic cells. Thus specific Ts could be induced in vitro , which demonstrate linked suppression for third‐party H‐2 alloantigens provided these are expressed on the same cell surface as the antigens used for Ts activation.