Association between anti-β2 glycoprotein I antibodies and renal glomerular C4d deposition in lupus nephritis patients with glomerular microthrombosis: a prospective study of 155 cases

Glomerular microthrombosis (GMT) is a common vascular change in patients with lupus nephritis (LN). The mechanism underlying GMT is still unknown. In our previous study, we found that the level of IgG anti-beta 2 glycoprotein I (beta 2GPI) antibodies was higher in the LN-GMT group than in the LN-non-GMT group, which indicated that anti-beta 2GPI antibodies may play a role in GMT formation. Many studies have demonstrated that the activation of the classical complement pathway may play a critical role in fetal loss and aPL-induced thrombosis formation. To investigate whether complement activation plays a role in GMT formation and to evaluate its relationship with aPL, we prospectively investigated deposition of C4d in 155 renal biopsy specimens of LN patients. The results revealed a strong relationship between the intensity of glomerular C4d staining and the presence of microthrombi (p < 0.001). The detection rate of IgG anti-beta 2GPI antibodies was higher in the LN-GMT group than in the LN-non-GMT group (p < 0.05). Further, the intensity of glomerular C4d staining was significantly related with IgG anti-beta 2GPI antibodies (p < 0.05). The results of our study suggest that anti-beta 2GPI antibodies may play a role in GMT formation, and this process might involve complement activation. Lupus (2010) 19, 1195-1203.