ROLE OF HEMICHROME BINDING TO ERYTHROCYTE-MEMBRANE IN THE GENERATION OF BAND-3 ALTERATIONS IN BETA-THALASSEMIA-INTERMEDIA ERYTHROCYTES

Nine splenectomized, hematologically well-compensated beta-thalassemia intermedia patients randomly chosen from a pool of 60 similar patient s were studied. Membrane proteins solubilized with nondenaturing deter gent C(12)E(8) were gel filtered on Sepharose CL-6B (Pharmacia Fine Ch emicals, Uppsala, Sweden). Fractions containing higher than 4,000-kD m olecular-weight aggregates were isolated and analyzed. Four patients h ad remarkably increased amounts of membrane-bound hemichromes and Igs. In those patients, band 3 underwent oxidative modifications such as a ggregation and a decrease in sulfhydryl groups. The other five patient s had low amounts of membrane-bound hemichromes and less modifications of band 3. The same band-3 modifications could be reproduced by chall enging normal membranes with artificially generated hemichromes or wit h hemolysates prepared from thalassemic erythrocytes of the high-hemic hrome group. Addition of reduced glutathione to the challenged membran es did not hinder hemichrome binding, but prevented oxidative modifica tions of band 3 and Ig binding to high-molecular-weight band-3 aggrega tes. Hemichrome binding to band 3, hemichrome-mediated oxidation of of band-3 cytoplasmic domains, generation of high-molecular-weight band- 3 aggregates, and enhanced opsonization by anti-band-3 antibodies is a possible sequence of events leading to phagocytic removal of erythroc ytes in thalassemia. (C) 1995 by The American Society of Hematology.