Influence of C1q on the Interaction of Model Immune Complexes with Human Platelets

Sloand, James A.; Mehta, R.; Schmer, G; Rosenfeld, Stephen I.

doi:10.1006/clin.1995.1106

Cited by 1 publication

(4 citation statements)

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“…46,47 The aggregation induced by polyacrylic acid-IgG complexes was completely abolished by C1q at a concentration similar to that used in the present study. 47 IgG adsorbed to a hydrophobic surface, as in our model system, may also be considered as an immune complex model at the macro-scale, previously shown capable of potent activation of complement 28,30 and inflammatory cells. 31- This approach mimics inflammatory conditions where immune complexes deposit on the vascular endothelium and other tissue surfaces, eventually resulting in platelet activation and thrombus formation.…”

Section: Discussionsupporting

confidence: 61%

“…Furthermore, aggregated C1q may induce platelet aggregation, which is blocked by antibodies against the platelet C1q receptor 45 . In contrast, C1q has been shown to inhibit platelet aggregation induced by IgG immune complexes 46 , 47 . The aggregation induced by polyacrylic acid‐IgG complexes was completely abolished by C1q at a concentration similar to that used in the present study 47 .…”

Section: Discussionmentioning

confidence: 46%

“…The present ellipsometry data illustrate that C1q binds to pre‐adsorbed IgG, and it is possible that the C1q/IgG complex inhibits the subsequent platelet binding to IgG. Sloand et al 47 proposed different mechanisms whereby platelet aggregation is inhibited by C1q/IgG complexes. For example, C1q associated to immune complexes may prevent platelet aggregation by exclusively binding to the C1q receptor and not to the FcγRIIa receptor, thereby preventing crosslinking of FcγRIIa molecules.…”

Section: Discussionmentioning

confidence: 58%

“…In contrast, C1q has been shown to inhibit platelet aggregation induced by IgG immune complexes 46 , 47 . The aggregation induced by polyacrylic acid‐IgG complexes was completely abolished by C1q at a concentration similar to that used in the present study 47 . IgG adsorbed to a hydrophobic surface, as in our model system, may also be considered as an immune complex model at the macro‐scale, previously shown capable of potent activation of complement 28 , 30 and inflammatory cells 31 , 32 , 33 .…”

Section: Discussionmentioning

confidence: 99%

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C‐reactive protein and C1q regulate platelet adhesion and activation on adsorbed immunoglobulin G and albumin

et al. 2008

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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 FccRs. 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.

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