Band 3 protein clustering on human erythrocytes promotes binding of naturally occurring anti-band 3 and anti-spectrin antibodies.
Recognition of senescent and oxidatively stressed human erythrocytes appeared to be initiated by band 3 clustering, followed by bivalent binding of naturally occurring anti-band 3 autoantibodies (anti-band 3 NAbs), and complement deposition. The number of RBC-associated anti-band 3 NAbs was, however, low compared to the total amount of IgG that bound in vitro to RBC containing band 3 oligomers. This implied the involvement of yet other types of NAb, among which we focussed on anti-spectrin NAbs, since eluates from RBC of thalassemic patients contained these NAbs. Binding of affinity-purified anti-band 3 and anti-spectrin NAbs was studied to RBC on which band 3 oligomers were generated by exoplasmic cross-linking. This pretreatment increased binding not only of (125)I-iodinated anti-band 3, but also of anti-spectrin NAbs by 7-10-fold at 0 degrees C in the presence of nearly physiological IgG and HSA concentrations. Binding of anti-spectrin NAbs was not to spectrin as judged from surface-labeling of RBCs that were pretreated with cross-linker. Binding was dose and time dependent in both cases. Moreover, binding of anti-spectrin NAbs was not competed by high concentrations of anti-band 3 NAbs and anti-spectrin NAbs even stimulated binding of anti-band 3 F(ab')(2) by 30%. This suggests that anti-spectrin NAbs bound to band 3 or a protein associated with band 3 by virtue of their inherent polyreactivity.
Hornig
R
R
Institute of Biochemistry, Swiss Federal Institute of Technology, ETH-Zentrum, CH 8092 Zurich, Switzerland.
Lutz
H U
HU
D001457:Anion Exchange Protein 1, Erythrocyte / Q000737:chemistry / Q000276:immunology* / Q000378:metabolism*; D000937:Antigen-Antibody Reactions; D001323:Autoantibodies / Q000097:blood*; D003432:Cross-Linking Reagents; D004905:Erythrocyte Aging; D004912:Erythrocytes / Q000276:immunology* / Q000378:metabolism*; D006801:Humans; D007113:Immunity, Innate; D066298:In Vitro Techniques; D046911:Macromolecular Substances; D018384:Oxidative Stress; D011485:Protein Binding; D013049:Spectrin / Q000276:immunology*
D001457:Anion Exchange Protein 1, Erythrocyte; D001323:Autoantibodies; D003432:Cross-Linking Reagents; D046911:Macromolecular Substances; D013049:Spectrin