An erythrocyte and serum antigen with a specificity antithetical to the mouse C4 associated H-2.7 antigen.

Repeated immunization of intra-H-2 recombinant strain A.TBR16 with lymphoid tissue from strain A.TBR13 produced an antiserum that agglutinated the erythrocytes from inbred strains of mice carrying the b, d, r, q, u, wr7, w13, w17, w19, and w21 haplotypes of the H-2 complex. The antiserum was negative with erythrocytes of strains carrying the haplotypes f, j, k, p, and s. This pattern of reactivity among fifteen H-2 haplotypes is unlike the strain distribution for any known H-2 erythrocyte antigen, and is exactly antithetical to the S region-controlled H-2.7 antigen. An examination of 12 intra-H-2 recombinant haplotypes mapped the genetic determinant controlling the new antigen to the IC or S regions of the H-2 complex. In addition, hemagglutination inhibition studies revealed the antigen was also expressed in serum and plasma. The serologic, genetic, and tissue distribution data suggest the gene controlling the newly defined antigen is allelic to the gene controlling the H-2.7 antigen.