Ir-associated murine alloantigens. Serological and chemical definition of Ia specificities associated with the H-2-b haplotype.

Strains bearing recombinant H-2 haplotypes with known positions of recombination have been used to demonstrate antibodies reacting with Ia antigens associated with the H-2-b haplotype in several H-2 antisera. Two new Ia specificities, Ia.8 and Ia.9, both determined by genes in the Ir-1A subregion, have thus been defined, and the strain distribution of these specificities has been determined. Immunoprecipitation of radio-labeled membrane antigens has been used to characterize Ia.9 and to distinguish it chemically from Ia.7 in a membrane preparation from a strain possessing both specificities.