Ir-associated murine alloantigens: Serological and chemical definition of la 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 la antigens associated with the H-2b haplotype in several H-2 antisera. Two new la specificities, la.8 and la.9, both determined by genes in the Ir-IA 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 la.9 and to distinguish it chemically from la.7 in a membrane preparation from a strain possessing both specificities.