Anti-D1(b) as a red cell autoantibody

Background: It is known that some ''warm''-reactive autoantibodies are directed against epitopes on the red cell anion exchanger, protein band 3. Some such antibodies (but not all) recognize Wr(b). It is also known that Di(a) and Di(b) represent an amino acid polymorphism of band 3. Study Design and Methods: Autoantibodies from 119 patients were tested against Di(b-) red cells. Seventy-four of these autoantibodies were subsequently adsorbed with Di(b-) red cells. Results: All 119 autoantibodies initially reacted with the Di(b-) red cells, which showed that none contained only anti-Di(b). Among the 74 adsorbed with Di(b-) red cells, two were found to contain an unadsorbed anti-Di(b) component. Conclusion: No example of autoanti-Di(b) as the only autoantibody present was found among the 119 samples tested. However, 2 (2.7%) of 74 autoantibodies subjected to adsorption with Di(b-) red cells were seen to contain an anti-Di(b) component. This low incidence of autoanti-Di(b) is in marked contrast to the high incidence of autoanti-Wr(b), although both antibodies define epitopes associated with the red cell anion exchanger, band 3.