Biochemical comparison of MHC antigens isolated from mutant C3HfB/HeN and parent C3H/HeN mice.

H-2K antigen heavy chains were isolated from C3HfB/HeN and C3H/HeN spleen cells by immunoprecipitation and high pressure liquid chromatography and were compared by tryptic peptide mapping. Glycopeptides obtained from 3H-glucosamine-labeled H-2Kk (C3H) and H-2Kkv1 (C3Hf) heavy chains were found to be identical, indicating that previously observed differences between the two molecules are due to alterations in amino acid sequence. I-A subregion antigen alpha- and beta-chains were also isolated from C3H and C3Hf spleen cells by immunoprecipitation and SDS-polyacrylamide gel electrophoresis, and were compared by tryptic peptide mapping analyses. Material isolated from 3H-glucosamine-labeled cells revealed that I-A alpha- and beta-chains were glycosylated, and antigens from C3H and C3Hf mice contained identical glycopeptides. Similar analyses of I-A antigen alpha- and beta-chains isolated from C3H and C3Hf spleen cells labeled with 3H-arginine or 3H-lysine revealed no differences in the amino acid sequences of the I-A antigens of these two strains. These findings indicate that all of the unique immunologic properties of mutant C3Hf cells can be attributed to modifications of the amino acid sequence of the MHC K locus gene product.