title: Radioimmunoassay studies of the cross-reacting antibody of human group O sera.
abstract: Cross-reacting antibody was obtained from three recently stimulated group O donors. The biological reactions of cross-reacting antibody were investigated by a study of the binding characteristics of 125I-labelled purified IgG fractions with red cells and by the reactions of whole antiserum or eluates with 125I-labelled blood group glycoproteins. The bulk of cross-reacting antibody activity is restricted to the IgG fraction. Experiments with 125I-labelled IgG and with the radioimmunoassay system revealed that cross-reacting antibody has a higher binding constant than specific anti-A or anti-B. In the radioimmunoassay system complete inhibition of cross-reaction antibody was obtained either with D-galactose or with N-acetyl-D-galactosamine, but the same concentrations of monosaccharides gave only partial inhibition of specific anti-A and anti-B antibodies. The results indicate that cross-reacting antibody binds to a smaller determinant than specific antibody. Investigations with other monosaccharides did not, however, reveal a common inhibitory structure. The ability of cross-reacting antibody to bind to both group A and B antigens may, therefore, be a property of a 'polyfunctional' antibody binding site.
mesh_terms: D000017:ABO Blood-Group System; D000116:Acetylgalactosamine; D000918:Antibody Specificity; D001666:Binding Sites, Antibody; D001667:Binding, Competitive; D003429:Cross Reactions; D005260:Female; D005690:Galactose; D006023:Glycoproteins; D006801:Humans; D007074:Immunoglobulin G / Q000032:analysis / Q000378:metabolism; D007075:Immunoglobulin M / Q000032:analysis; D066298:In Vitro Techniques; D007457:Iodine Radioisotopes; D007518:Isoantibodies / Q000032:analysis; D008297:Male; D011863:Radioimmunoassay
chemical_list: D000017:ABO Blood-Group System; D006023:Glycoproteins; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D007457:Iodine Radioisotopes; D007518:Isoantibodies; D000116:Acetylgalactosamine; D005690:Galactose