Blood group B antigen (B antigen)

The Blood group B antigen is a complex carbohydrate structure expressed on the surface of erythrocytes, endothelial cells, and epithelial cells in individuals with blood type B or AB (StatPearls, NBK554381). It is synthesized by the action of the ABO glycosyltransferase, specifically the B transferase, which attaches an alpha-1,3-linked galactose residue to the H antigen precursor (UniProt, P12432). In clinical medicine, the B antigen is a primary barrier to safe blood transfusion and organ transplantation because individuals with type A or O blood produce pre-existing IgM antibodies against it. These anti-B antibodies can cause rapid, life-threatening intravascular hemolysis if B-positive blood is administered to an incompatible recipient. Research into the B antigen includes the use of specific alpha-galactosidase enzymes to strip the terminal galactose, effectively converting B-type blood into universal O-type blood (Nature Microbiology, s41564-019-0469-7). Additionally, the expression of B antigens on non-erythroid tissues influences susceptibility to various pathogens and the risk of developing certain cardiovascular and oncological conditions (PubMed, 32107131). Management of this target is essential in desensitization protocols for ABO-incompatible organ transplants using therapies like Rituximab and plasmapheresis.

Other names

B substanceABO blood group B antigenGal-alpha-1,3-(Fuc-alpha-1,2)-Gal-beta-1,3/4-GlcNAcType B carbohydrate antigen

Antibody-mediated agglutination and hemolysis; enzymatic cleavage of the terminal alpha-1,3-galactose residue to convert B antigen to H antigen (Type O).