Further Evidence for the Presence of A Antigen on Group B Erythrocytes through the Use of Specific Exoglycosidases

Abstract

Certain antibodies have shown the ability to detect small amounts of A antigenic structures on certain group B cells. These rare cells that reverse group as B, are designated here as B(A) cells. Among the anti-A antibodies capable of detecting these cells are MHO4 (an IgM murine monoclonal antibody) and polyclonal anti-A derived from blood group O donors. The latter (anti-A, B) have been adsorbed exhaustively with normal B cells, to deplete the serum of antibodies to group B antigen. The cell specificity detected by these antibodies can be removed only by an alpha-N-acetylgalactosaminidase (A-zyme) but not by an alpha-galactosidase (B-zyme). Inhibition studies show that these reactions can be inhibited by A secretor saliva and cannot be inhibited by B secretor saliva. Moreover, papain treatment of normal group B cells not previously agglutinable with these antibodies, now causes these cells to become reactive, and this specificity, too, is removed only by A-zyme. These results suggest that low levels of blood group A antigen are being recognized by these antibodies and that these structures can exist not only on B(A) cells but on all group B erythrocytes.

Further Evidence for the Presence of A Antigen on Group B Erythrocytes through the Use of Specific Exoglycosidases

“…They fail to react with normal group B cells (native) and with native or papaintreated group O cells. The B(A) reactions have been re ported to be specifically inhibited by A substance [1].We report here confirmation of the A-specific inhibition of MH04 anti-A and polyclonal anti-A from O serum ad sorbed with B cells and present further evidence for the presence of A antigens on group B cells, obtained through the use of highly purified exoglycosidases [5]. The glyco sidases used in these studies were an a-galactosidase (B-zyme) obtained from green coffee beans [6] and an a-N-acetylgalactosaminidase (A-zyme) isolated from chicken liver [7].…”

Many genetically defined ABO subgroups exhibit characteristic flow cytometric patterns

“…Due to the weak reactions seen with B RBCs, which can also be observed in tube assays or the column agglutination test (gel cards), ES‐15 was previously deemed to be an anti‐A,B monoclonal reagent 44 . However, the specificity of this reactivity was confirmed by treatment of group B RBCs with exoglycosidase specific for A antigen after which these cells typed and stained negatively with ES‐15 20,21 . We were unable to reproduce the weak B reactivity once reported 45 in group A 1 RBCs with the anti‐B clone BS‐85.…”

“…As expected when tested with anti‐A, group A 1 , A 2 , A 1 B, and A 2 B RBCs were clearly positive and group O RBCs negative. Group B RBCs were very weakly but still distinctly positive when tested with anti‐A due to the small amount of A antigen naturally present on B RBCs 21 . When testing with anti‐B, positive reactions were seen with B, A 1 B, and A 2 B RBCs while negative reactions were obtained with A 1 , A 2 , and O RBCs.…”

“…We have developed a highly sensitive flow cytometric method to detect A and B antigens 20 . Subgroup RBCs were used as weak positive controls and A antigens present in low amounts on normal group B RBCs 21 could be detected clearly. This method was used successfully for quality assessment after the enzymatic conversion of group A or B RBCs to cells typing serologically as blood group O with all monoclonal ABO typing reagents tested 20 .…”

The A1 (B) phenomenon: a monoclonal anti‐B (BS‐85) demonstrates low levels of B determinants on A1 red cells

“…The use of A1 (B)-enhanced tests, especially protease enzymes, demonstrated the presence of a little B on all adult AI red cells just as protease enzyme B (A) tests have demonstrated a little A on all adult B cells (Beck et al, 1987;Stroup & Treacy, 1987;Voak et al, 1988;Goldstein et al, 1989). We could not however, demonstrate A1 (B) reactions with A2 RBC and it would appear that A2 transferase enzymes do not have the capacity to transfer galactose to available H sites on A2 RBC, or alternatively do not produce sufficient B antigen to be detectable.…”