Carbohydrate-specific antibodies in normal human sera. II. Structural definition of antigenic determinants

IgG and IgM antibodies against several sugars have been characterized in sera of normal donors by passive hemagglutination and a quantitative hemagglutination inhibition test. These antibodies distinguish between the equatorial and axial OH groups at C2, C3, or C4 positions of the glycopyranose configuration, differences between the anomers, linkage types, changes in the primary alcohol group at C6, and OH substitution. In the examples of antibodies to mannose, galactose, and glucose investigated, specificities were usually directed against the beta-anomers. In disaccharides, the antibodies appeared to react only with 1 of the 2 sugar subunits, but unlike monosaccharides, the glycosidic linkages also seemed to be a part of the reaction site. Thus, the reacting moiety in gentiobiose was beta-D-glucopyranosyl with 1----6 linkage, in cellobiose with beta-D-glucopyranosyl with 1----4 linkage, in meliboise was alpha-D-galactopyranosyl with 1----6 linkage, and in lactose the reaction was directed against beta-D-galactopyranosyl with 1----4 linkage. In the maltose-dependent hemagglutination, alpha-D-glucose appeared to be the main reaction site. ManNAc exemplified the specificity determined by OH group substitution. Antibody to D-Fucose represented example of specificity evolving from substitution of the primary alcohol.