Primary cytotoxic T-cell response in vitro against Mls antigens in NZB-mice

NZB-mice have a T cell hyperreactivity based on a primary response to minor histocompatibility antigens (MIH) on target cells identical to NZB on the H-2 complex (MHC). We tested the idea that a single MIH difference on MHC identical target cells is sufficient to elicit such a primary response in vitro. Cytotoxic T lymphocyte (CTL) response and activated T-helper cell (THC) frequencies were evaluated. NZB x CBA/J (Mls a/d) and NZB x CBA/Ca (Mls a/b) hybrids, which differ only at the M-locus, were raised. A primary cytotoxic response in the direction Mls b anti Mls d, but not vice versa was observed in vitro. In the assay used no unusual THC frequencies against Mls d could be demonstrated. The results favour cellular hyperreactivity in NZB which can be elicited by a single MIH antigen alone.