Induction of T cell responses in nonresponder mice by abolishing suppression with monoclonal antibodies recognizing a region-controlled, T cell-specific determinants

Mouse strains carrying the k allele at loci A(β), A(α), E(β), and E(α) are nonresponders to lactate dehydrogenase B (LDH(B)) and to allotypic determinants of IgG2a myeloma proteins (for example, UPC10 used in this study). The nonresponsiveness to these antigens is caused by T suppressor (Ts) cells that prevent antigen-primed T helper (Th) cells from proliferating. We demonstrate here that monoclonal antibodies specific for an A region-controlled molecule selectively expressed on T cells (A-T) are capable of inducing anti-LDH(B) and anti-UPC10 responses of primed T cells from nonresponder strains. A monoclonal anti-J antibody that cross-reacts with the A-T molecule also induces responsiveness, whereas another J-specific antibody that lacks this cross-reactivity fails to do so. The mechanism of response induction is blocking of the interaction between the Ts cell or its factor (TsF) and the target of suppression, the antigen-specific Lyt-1⁺2^- (Th) cell. The blocking occurs at the level of the Ts cell and the TsF. The data indicate that Ts cells and TsF carry a unique, A region-controlled molecule that is not only functionally analogous but also serologically similar to the J molecule.