Complement-dependent binding of C-reactive protein complexes to human erythrocyte CR1.
C-reactive protein (CRP) is an acute phase serum protein that binds to phosphocholine (PC) on phospholipids and polysaccharides and to protein components of chromatin and small nuclear ribonucleoproteins. Complexes between CRP and ligands activate complement and bind to receptors on phagocytic cells. Although complement is required for CRP-mediated clearance or phagocytosis of ligand-coated erythrocytes, the participation of complement and complement receptors in clearance of soluble CRP complexes has not been examined. We have used PC-conjugated BSA to prepare complexes containing either IgG antibody or CRP. We found similar complement-mediated binding of both types of complexes to human erythrocyte complement receptors (CR1, CD35). We also found that serum deficient in C4A or C4B supported binding of CRP and IgG complexes to erythrocytes. These findings indicate that complexes between CRP and soluble ligands may be cleared by the erythrocyte CR1 pathway described for soluble immune complexes.
Department of Microbiology, University of New Mexico, Albuquerque 87131, USA.
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D000936:Antigen-Antibody Complex / Q000378:metabolism; D002097:C-Reactive Protein / Q000378:metabolism*; D003181:Complement C4 / Q000494:pharmacology; D003165:Complement System Proteins / Q000378:metabolism*; D004912:Erythrocytes / Q000737:chemistry* / Q000276:immunology*; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology; D011233:Precipitin Tests; D011485:Protein Binding; D017463:Receptors, Complement 3b / Q000097:blood*
D000936:Antigen-Antibody Complex; D003181:Complement C4; D007074:Immunoglobulin G; D017463:Receptors, Complement 3b; D003165:Complement System Proteins; D002097:C-Reactive Protein