The Journal of Immunology, Vol 152, Issue 6 2995-3005, Copyright © 1994 by American Association of Immunologists

ARTICLES

Sublytic complement attack exposes C-reactive protein binding sites on cell membranes

YP Li, C Mold and TW Du Clos
Department of Microbiology, University of New Mexico School of Medicine, Albuquerque 87131.

C-reactive protein (CRP) is an acute phase serum protein synthesized by the liver. CRP has been localized to acute inflammatory sites and has been postulated to facilitate the removal of damaged cells. CRP binds to a number of ligands that may be present in inflammatory sites, and the extent to which individual ligands are involved in its binding to tissue sites is unknown. Complement activation is important in the tissue damage in many inflammatory conditions causing cell membrane damage and recruitment of inflammatory cells. This paper describes the binding of CRP to complement-damaged cell membranes. Raji cells activate the alternative complement pathway resulting in the deposition of C3b and membrane attack complexes (MAC) on the cell membrane. However, Raji cells are relatively resistant to killing by human complement. Treatment of Raji cells with human serum led to calcium- dependent phosphocholine-inhibitable CRP binding. CRP binding was eliminated by depletion of C3, C5, or C8 and reduced by depletion of C9 from serum. CRP binding preceded cell death and co-localized with MAC on cell membranes. CRP binding to complement-treated liposomes required phosphatidylcholine in addition to the MAC indicating that membrane phospholipids rather than the MAC proteins provide the binding sites for CRP. However, for both liposomes and Raji cells disruption of the lipid bilayer by complement attack was required for CRP binding to occur. These results support the hypothesis that CRP binding at sites of inflammation may be mediated by exposed phospholipids on damaged cell membranes.

This article has been cited by other articles:

				A. Agrawal, M. J. Simpson, S. Black, M. P. Carey, and D. Samols A C-Reactive Protein Mutant That Does Not Bind to Phosphocholine and Pneumococcal C-Polysaccharide J. Immunol., September 15, 2002; 169(6): 3217 - 3222. [Abstract] [Full Text] [PDF]

				K. Yasojima, C. Schwab, E. G. McGeer, and P. L. McGeer Generation of C-Reactive Protein and Complement Components in Atherosclerotic Plaques Am. J. Pathol., March 1, 2001; 158(3): 1039 - 1051. [Abstract] [Full Text] [PDF]

				H. Jarva, T. S. Jokiranta, J. Hellwage, P. F. Zipfel, and S. Meri Regulation of Complement Activation by C-Reactive Protein: Targeting the Complement Inhibitory Activity of Factor H by an Interaction with Short Consensus Repeat Domains 7 and 8-11 J. Immunol., October 1, 1999; 163(7): 3957 - 3962. [Abstract] [Full Text] [PDF]

				W. Koenig, M. Sund, M. Frohlich, H.-G. Fischer, H. Lowel, A. Doring, W. L. Hutchinson, and M. B. Pepys C-Reactive Protein, a Sensitive Marker of Inflammation, Predicts Future Risk of Coronary Heart Disease in Initially Healthy Middle-Aged Men : Results From the MONICA (Monitoring Trends and Determinants in Cardiovascular Disease) Augsburg Cohort Study, 1984 to 1992 Circulation, January 19, 1999; 99(2): 237 - 242. [Abstract] [Full Text] [PDF]

				J. Torzewski, M. Torzewski, D. E. Bowyer, M. Frohlich, W. Koenig, J. Waltenberger, C. Fitzsimmons, and V. Hombach C-Reactive Protein Frequently Colocalizes With the Terminal Complement Complex in the Intima of Early Atherosclerotic Lesions of Human Coronary Arteries Arterioscler. Thromb. Vasc. Biol., September 1, 1998; 18(9): 1386 - 1392. [Abstract] [Full Text] [PDF]