T cells in a suppressor circuit and non-T:non-B cells bear different I-J determinants.

T cells involved in the generation of suppressor activity bear an I-J-subregion controlled determinant (e.g., J1) which is distinct from that (e.g., J2) found on non-T:non-B accessory cells. T-cell subsets examined include Ly-1 inducer and Ly-1,2 acceptor cells which collaborate to generate suppressor activity in the in vitro sheep red blood cell antibody system. Non-T:non-B accessory cells examined include accessory cells involved in concanavalin-A induced, T-cell proliferative responses and in in vitro antibody responses to sheep red blood cells. These results provide evidence for serologic and genetic complexity of the I-J subregion of the murine H-2 gene complex.