Characterization of a monoclonal antibody specific for H type 2 structure of ABO blood group, and its use for measuring H type 2 on human red blood cells.

A monoclonal antibody 3A5 specific for the human red blood cells was produced by immunizing BALB/c mouse with human erythrocyte membranes of group O following the immunization protocol of selectively killing the antigen-stimulated lymphocytes. The monoclonal antibody 3A5 we obtained agglutinated red blood cells regardless of individuals of blood group A, B, or O types, but not those from a person with a rare para-Bombay type which is the H-deficient phenotype. The hemagglutination reaction of 3A5 was not inhibited by saliva from either secretor or nonsecretor individuals. The specificity of 3A5 was studied by adsorption with and elution from synthetic oligosaccharide immunoadsorbents including H disaccharide, and H type 1, 2, 3, and 4 structures. Also, the reactivity of 3A5 with synthetic oligosaccharide-BSA complexes for H type 1, H type 2, Le(a), Le(b), A, and B was determined by an immunoassay. We found that 3A5 did not react with any of these synthetic oligosaccharides except H type 2. From these results, the antigenic epitope recognized by 3A5 was demonstrated to be the H type 2 structure. Additionally, the H type 2 substance on erythrocytes was quantitatively analyzed using 3A5.