Biochemical analysis of gene products of major histocompatibility recombinant haplotypes in the rat.

The gene products of the A and B regions of the rat major histocompatibility system (RT1) have been analyzed by immunoprecipitation and sodium dodecyl sulfate polyacrylamide gel electrophoresis. For antiserum production and as a source of target spleen cells, rat strains were used that differed only for various combinations of the RT1 regions. It could be shown that te RT1.A region, whose serologically detectable products behave like classical transplantation antigens, coded for molecules of 45 000 daltons that were associated with 12 500 dalton molecules. The RT1.B region products, which behave serologically like Ia antigens, consisted of two chains of 31 000 and 27 000 daltons, respectively. Thus, serological and biochemical phenotypes of the RT1 antigens could be matched in accordance with data obtained in other species and could be assigned to particular regions of the RT1 system. The two-peak structure of Ia antigens was only detectable under nonreducing conditions. After reduction, both peaks fused, presumably due to cleavage of intrachain disulfide bonds in the smaller chain.