Ia antigenic specificities are oligosaccharide in nature: hapten-inhibition studies.
We have previously reported that the Ia specificities, coded for by the I region within the H-2 complex, appear to consist predominantly of carbohydrate. This conclusion was reached by examining low molecular weight Ia-bearing oligosacharides isolated from mouse serum. We now report hapten-inhibition studies which indicate that the binding of both allogeneic and xenogeneic anti-Ia antibodies to the Ia glycoproteins found predominantly on B lymphocytes can be specifically inhibited by certain free sugars. Both inhibition assays revealed that the specificity for the following Ia antigens resides predominantly in the following sugars: (a) Ia.1: N-acetyl-D-mannosamine or related sugars; (b) Ia.3: alpha-D-galactose and related sugars; (c) Ia.7: L-fucose;  and (d) Ia.15: N-acetyl-D-glucosamine. It seems likely that these sugars are found at the terminal nonreducing ends of the carbohydrate portion of the Ia-bearing glycoproteins present in the lymphocyte membrane. In contrast, several public and private H-2 antigenic specificities did not appear to be sugar defined. These studies imply that at least some of the Ia genes from both the I-A and I-C subregions of the I region code for glycosyl transferases which modify oligosaccharide structure and impart specificity to the Ia antigens by alteration of their terminal sugar residues.
D000818:Animals; D000937:Antigen-Antibody Reactions / Q000187:drug effects; D001402:B-Lymphocytes / Q000276:immunology; D000939:Epitopes; D006027:Glycosides / Q000032:analysis / Q000494:pharmacology; D006241:Haptens; D007518:Isoantibodies; D007519:Isoantigens / Q000032:analysis*; D051379:Mice; D009005:Monosaccharides / Q000032:analysis / Q000494:pharmacology; D009844:Oligosaccharides / Q000032:analysis* / Q000494:pharmacology; D013329:Structure-Activity Relationship
D000939:Epitopes; D006027:Glycosides; D006241:Haptens; D007518:Isoantibodies; D007519:Isoantigens; D009005:Monosaccharides; D009844:Oligosaccharides