Reactivity of autoantibodies of autoimmune hemolytic anemia with recombinant rhesus blood group antigens or anion transporter band3.

The specificity of autoantibodies in autoimmune hemolytic anemia (AIHA) has been studied using the serological procedure and immunoprecipitation technique with rare phenotype red cells. We attempted to analyze specificity using recombinant rhesus (Rh) blood group and band3 antigens expressed on erythroleukemic cell lines, KU812E. The autoantibody eluates were isolated by the acid elution procedure from the red cells of 20 AIHA patients. The recombinant Rh antigens, RhD, cE, ce, CE, and chimera antigens CE-D and D-CE, were obtained by retroviral cDNA transduction into KU812E cells, and the cell line expressing the antigens was cloned. Band3 cDNA was also obtained and introduced into KU812E and cloned KU812 expressing RhcE. The reactivities of AIHA eluates with recombinant Rh and band3 antigens were studied by flow cytometry. Fifteen eluates reacted with at least one of the RhcE, ce, or CE antigens, and four eluates reacted with RhD. Seven eluates with strong Rh specificity were studied further using chimera antigen. Five eluates showed reduced or lost reactivity, although two eluates reacted identically with the chimera antigens as wild type. These results indicated that conformational epitopes constituted by RhD or CE specific exofacial peptide loops are important for autoantibodies in most cases. Seven eluates reacted with band3, five exclusively. The coexpression study of RhcE and band3 did not enhance the expression of either antigen nor the reactivity with patient eluates, indicating that association of Rh and band3 was not involved in the appearance of autoantigen. Copyright 2001 Wiley-Liss, Inc.