COMPLEMENT-DEPENDENT BINDING OF C-REACTIVE PROTEIN COMPLEXES TO HUMANERYTHROCYTE CR-1

C-reactive protein (CRP) is an acute phase serum protein that binds to phosphocholine (PC) on phospholipids and polysaccharides and to prote in components of chromatin and small nuclear ribonucleoproteins. Compl exes 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 particip ation of complement and complement receptors in clearance of soluble C RP complexes has not been examined, We have used PC-conjugated BSA to prepare complexes containing either IgG antibody or CRP, We found simi lar complement-mediated binding of both types of complexes to human er ythrocyte complement receptors (CR1, CD35). We also found that serum d eficient in C4A or C4B supported binding of CRP and IgG complexes to e rythrocytes. These findings indicate that complexes between CRP and so luble ligands may be cleared by the erythrocyte CR1 pathway described for soluble immune complexes. (C) 1996 Academic Press, Inc.