Serologic and biochemical studies of the Ia system of the mouse H-2 gene complex. Further evidence for I-C subregion.

Three antisera were made against B10.A(5R) tissues to show the presence of an I-Cd subregion in that strain: 1) B10 anti-B10.A(5R) [anti-Dd, I-Cd]; 2) (B10 times C3H.9L) F1 anti-B10.A(5R) [anti-Ddi1; 3) (B10 times HTI)F1 anti-B10.A(5R) [anti-I-Cd]. Serologic analyses of the antisera clearly showed the presence of an Id segment in B10.A(5R) and provided further evidence for the existence of a new I-C subregion. These anti-I-Cd sera define the Ia.7 specificity and analyses of several recombinants map Ia.7 within the I-C subregion. Ia.7 is present in I-Ck, I-Cd and Ip strains. Biochemical analyses showed that the Ia.7 molecule has a molecular weight of 31,000 and is distinct from the 46,000 m.w. H2K or D molecules. The possible roles of the I-C region in immune response, mixed lymphocyte reaction, and graft-vs-host reaction are discussed.