Serum Complement Activation on Heterologous Platelets Is Associated With Arterial Thrombosis in Patients With Systemic Lupus Erythematosus and Antiphospholipid Antibodies

Lupus. 2009 May;18(6):530-8. doi: 10.1177/0961203308099974.


Complement plays a major role in inflammation and thrombosis associated with systemic lupus erythematosus (SLE) and the antiphospholipid syndrome (APS). A cross-sectional retrospective analysis was performed to evaluate serum complement fixation on platelets and thrombotic incidence using banked sera and clinical data from patients with SLE (n = 91), SLE with antiphospholipid antibodies (aPL) or APS (n = 78) and primary aPL (n = 57) or APS (n = 96). In-situ complement fixation was measured as C1q and C4d deposition on heterologous platelets using an enzyme-linked immunosorbent assay approach. Platelet activation by patient serum in the fluid phase was assessed via serotonin release assay. Enhanced in-situ complement fixation was associated with the presence of IgG aPL and IgG anti-beta2 glycoprotein 1 antibodies (P < 0.05) and increased platelet activation (P < 0.005). Moreover, enhanced complement fixation, especially C4d deposition on heterologous platelets, was positively associated with arterial thrombotic events in patients with SLE and aPL (P = 0.039). Sera from patients with aPL possess an enhanced capacity for in-situ complement fixation on platelets. This capacity may influence arterial thrombosis risk in patients with SLE.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Antiphospholipid Syndrome / blood*
  • Antiphospholipid Syndrome / complications
  • Arterial Occlusive Diseases / blood
  • Arterial Occlusive Diseases / epidemiology
  • Arterial Occlusive Diseases / etiology*
  • Blood Platelets / metabolism*
  • Complement Activation / physiology*
  • Complement C1q / metabolism
  • Complement C4 / metabolism
  • Cross-Sectional Studies
  • Female
  • Humans
  • Immunoassay
  • Incidence
  • Lupus Erythematosus, Systemic / blood*
  • Lupus Erythematosus, Systemic / complications
  • Male
  • Middle Aged
  • Platelet Activation / physiology*
  • Retrospective Studies
  • Risk Factors
  • Thrombosis / blood
  • Thrombosis / epidemiology
  • Thrombosis / etiology*
  • United States / epidemiology


  • Complement C4
  • Complement C1q