Ann Rheum Dis 63:1478-1482 doi:10.1136/ard.2003.017939
  • Extended report

High avidity anti-β2-glycoprotein I antibodies in patients with antiphospholipid syndrome

  1. S Čučnik1,
  2. T Kveder1,
  3. I Križaj2,
  4. B Rozman1,
  5. B Božič3
  1. 1University Medical Centre, Department of Rheumatology, Ljubljana, Slovenia
  2. 2Jožef Stefan Institute, Department of Biochemistry and Molecular Biology, Ljubljana
  3. 3Department of Clinical Biochemistry, Faculty of Pharmacy, University of Ljubljana
  1. Correspondence to:
    Assistant Professor B Božič
    University Medical Centre, Department of Rheumatology, Vodnikova 62, SI-1000 Ljubljana;
  • Accepted 18 January 2004


Objective: To evaluate avidity of IgG anti-β2-glycoprotein I antibodies (anti-β2-GPI) in patients with antiphospholipid syndrome (APS) and systemic lupus erythematosus (SLE) in relation to thrombosis, and to demonstrate a possible affinity maturation of IgG anti-β2-GPI during the disease course.

Methods: 64 sera from 32 patients (18 with primary or secondary APS, 14 with SLE without APS) and their respective IgG fractions or affinity purified anti-β2-GPI were studied by anticardiolipin (aCL) and anti-β2-GPI enzyme linked immunosorbent assay and by chaotropic assay.

Results: Six, 12, and 14 patients had high, low, and heterogeneous avidity IgG anti-β2-GPI, respectively. In 12 patients an increase in antibody avidity was observed over a period of between four and 12 years. More patients with APS were in the high avidity than in the low avidity anti-β2-GPI group, while the opposite was observed for SLE alone (both p<0.05). The most common clinical feature among patients with high avidity anti-β2-GPI was thrombosis, mainly venous thrombosis (p<0.05 and p<0.02, respectively, v the low avidity anti-β2-GPI group).

Conclusions: Patients with APS with or without SLE may have anti-β2-GPI of high, low, or heterogeneous avidity. High avidity anti-β2-GPI appear to be associated with thrombosis and APS, while in pure SLE low avidity anti-β2-GPI may prevail. Monitoring of avidity may help elucidate the role of anti-β2-GPI affinity maturation in the pathogenesis of APS.