title: C-reactive protein and C1q regulate platelet adhesion and activation on adsorbed immunoglobulin G and albumin.
abstract: Blood platelets and C-reactive protein (CRP) are both used clinically as markers of ongoing inflammation, and both participate actively in inflammatory responses, although the biological effects are still incompletely understood. Rapidly adhering platelets express receptors for complement factor 1q (C1q) and the Fc part of immunoglobulin G (IgG), and CRP is known to activate/regulate complement via C1q binding, and to ligate FcgammaRs. In the present study, we used normal human IgG pre-adsorbed to a well-characterized methylated surface as a model solid-phase immune complex when investigating the effects of CRP and C1q on platelet adhesion and activation. Protein adsorption was characterized using ellipsometry and polyclonal antibodies, and human serum albumin (HSA) and non-coated surfaces were used as reference surfaces. Platelet adhesion to IgG and HSA was inhibited by both C1q and CRP. Furthermore, CRP (moderately) and C1q (markedly) decreased the spreading of adhering platelets. The combination of C1q and CRP was slightly more potent in reducing cell adhesion to IgG, and also impaired the adhesion to HSA and non-coated surfaces. Platelet production of thromboxane B2 (TXB(2)) was also reduced by C1q both in the presence and absence of CRP, whereas CRP alone had no effect on TXB(2) production. We conclude that CRP and C1q regulate the behaviour of platelets, and that this may be an important immunoregulatory mechanism during inflammatory conditions.
authors.affiliation: Department of Physics, Chemistry and Biology, Materials in Medicine, Division of Applied Physics, Linköping University, Linköping, Sweden. carsk@imv.liu.se
authors.forename: Caroline
authors.initials: C
authors.lastname: Skoglund
authors.forename: Jonas
authors.initials: J
authors.lastname: Wetterö
authors.forename: Thomas
authors.initials: T
authors.lastname: Skogh
authors.forename: Christopher
authors.initials: C
authors.lastname: Sjöwall
authors.forename: Pentti
authors.initials: P
authors.lastname: Tengvall
authors.forename: Torbjörn
authors.initials: T
authors.lastname: Bengtsson
mesh_terms: D001792:Blood Platelets / Q000166:cytology / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D002097:C-Reactive Protein / Q000494:pharmacology*; D048430:Cell Shape; D015922:Complement C1q / Q000494:pharmacology*; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology*; D010718:Phosphatidylserines / Q000378:metabolism; D015539:Platelet Activation / Q000187:drug effects*; D010973:Platelet Adhesiveness / Q000187:drug effects*; D012709:Serum Albumin / Q000378:metabolism*; D013929:Thromboxane B2 / Q000096:biosynthesis / Q000378:metabolism
chemical_list: D007074:Immunoglobulin G; D010718:Phosphatidylserines; D012709:Serum Albumin; D013929:Thromboxane B2; D015922:Complement C1q; D002097:C-Reactive Protein