Structural studies of the protein portion of the H-2-linked Ia glycoprotein antigens of the mouse: tryptic peptide comparison of products from the I-A and I-C subregions of B10.HTT

In antigens from the I-A⁸ and I.C(κ) subregions of the B10.HTT (H-2(t3)) strain of mice were isolated by indirect immunoprecipitation of arginine-labeled, nonionic detergent-solubilized materials. After biochemical purification the electrophoretically homogeneous 28,000 dalton glycoprotein β chains from the Ia precipitates were digested with trypsin and the resultant radiolabeled tryptic peptides were compared by analytical ion exchange chromatography. These comparisons reveal that the β chains of Ia antigens from the A (I-A(s) and C (I-C(κ)) subregions of B10.HTT share only two out of 12 to 14 of their arginine tryptic peptides. Thus these noncross-reactive Ia antigens are structurally quite diverse, and would possess sufficient structural variability to account for their lack of antigenic cross-reactivity.