Binding of IgA to erythrocytes from patients with IgA nephropathy.
Primate erythrocytes (RBCs) may be involved in the transport and processing of C3b-containing immune complexes (IC). Compared to RBCs from healthy controls, increased amounts of IgA were detectable on RBCs from 7 of 17 patients with IgA nephropathy (IgA NP). There was no difference in the amount of IgG or IgM. The highest amount of RBC-bound IgA corresponded to 6 ng IgA/10(8) cells. The mechanisms involved in the binding of IgA to RBCs were investigated in vitro. Isolated IgA1 or IgA2 did not bind to RCBs from a patient with IgA deficiency. In contrast, incubation of RBCs with a polyethyleneglycol (PEG) precipitate of serum from a patient with IgA NP which contained IgA-IC resulted in IgA1 binding. However, this binding was not inhibited by monoclonal anti-CR1 or by an excess of IgG or IgM. Factor I did not cause release of IgA from RBCs from patients with IgA NP. Heat-aggregated IgA1 also bound to RBCs and this binding was not affected by the presence of complement. We conclude that minute amounts of IgA-IC are bound to RBCs by a complement- and Fc receptor-independent mechanism. The quantity of IgA-IC associated with RBC is so small that it is unlikely to represent an important in vivo route of IgA-IC transport or processing.
Matsuda
S
S
Department of Microbiology and Pediatrics, University of Alabama, Birmingham 35294.
Waldo
F B
FB
Czerkinsky
C
C
Moldoveanu
Z
Z
Mestecky
J
J
D000936:Antigen-Antibody Complex / Q000032:analysis* / Q000276:immunology; D002478:Cells, Cultured; D003176:Complement C3 / Q000032:analysis / Q000276:immunology; D004912:Erythrocytes / Q000276:immunology*; D005922:Glomerulonephritis, IGA / Q000097:blood* / Q000276:immunology; D006801:Humans; D007070:Immunoglobulin A / Q000032:analysis* / Q000276:immunology; D007074:Immunoglobulin G / Q000032:analysis; D007075:Immunoglobulin M / Q000032:analysis
D000936:Antigen-Antibody Complex; D003176:Complement C3; D007070:Immunoglobulin A; D007074:Immunoglobulin G; D007075:Immunoglobulin M