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 (LDHB) and IgG2a myeloma protein is remarkably similar (1, 2). The similarity is explained by our recent work, demonstrating that both antigens, when presented in the context of cell surface Ek (Ek alpha Ek beta) molecules, generate strong suppression that causes nonresponsiveness to all mouse strains expressing this molecule. The suppression is mediated by antigen-specific, Ek-restricted Lyt-1+2+ suppressor T (Ts) cells, which act by inhibiting the proliferation of A(A alpha A beta)-restricted, Lyt-1+2- (possibly T helper [Th]) cells specific for the same antigen (3-5). However, the question of why the Ek molecule, in combination with two structurally unrelated proteins, preferentially induces Ts cells has remained unanswered. We demonstrate here that the anti-LDHB and anti-IgG2a Ts cells are fully cross-reactive, which indicates that the LDHB + Ek and IgG2a + Ek determinants recognized by these cells are very similar or identical.