B antigen

B antigen

Transfusion medicine A major blood group–ABO antigen which defines the blood type B, and assumes that the codominant allele at the ABO locus is B or H; B antigens are highly immunogenic; when a B unit of packed red cells is transfused into an A or O recipient, the natural antibodies present in the recipient are capable of evoking a severe or fatal hemolytic transfusion reaction. Cf A antigen, Bombay phenotype, H antigen.