Wright blood system

The Wright blood system is a pair of antigens, Wr(a) and Wr(b), carried on the Band 3 glycoprotein AE1 inherited through various alleles of the gene SLC4A1. Wr(a) is a low-frequency antigen found on the RBCs of approximately 1: 1000 Caucasians. Anti-Wr(a) can be naturally occurring or can be the result of red cell alloimmunization. It has been reported to be present in 1:25 to 1:100 healthy blood donors and even higher proportion of hospital patients. Incompatibility due to anti-Wr(a) can cause acute or delayed hemolytic transfusion reactions or hemolytic disease of the fetus and newborn (HDFN) if the patient is challenged with antigen positive blood.