Cross-reactivity of suppressor T cells specific for lactate dehydrogenase B and IgG2a myeloma protein

The major histocompatibility complex-controlled immune responsiveness of mice to two unrelated antigens, lactate dehydrogenase B (LDH(B)) and IgG2a myeloma protein is remarkably similar. The similarity is explained by our recent work, demonstrating that both antigens, when presented in the context of cell surface E(k) (E(α)(k)E(β)(k)) molecules, generate strong suppression that causes nonresponsiveness to all mouse strains expressing this molecule. The suppression is mediated by antigen-specific, E(k)-restricted Lyt-1⁺2⁺ suppressor T (Ts) cells, which act by inhibiting the proliferation of A(A(α)A(β))-restricted, Lyt-1⁺2^- (possibly T helper [Th]) cells specific for the same antigen. However, the question of why the E(k) molecule, in combination with two structurally unrelated proteins, preferentially induces Ts cells has remained unanswered. We demonstrate here that the anti-LDH(B) and anti-IgG2a Ts cells are fully cross-reactive, which indicates that the LDH(B) + E(k) and IgG2a + E(k) determinants recognized by these cells are very similar or identical.