Purpose: This study evaluated the correlation of anti-β2-glycoprotein I (anti-β2-GPI) antibodies with complement activation in patients with idiopathic membranous nephropathy (IMN).
Methods: Thirty-two IMN patients with positive anti-β2-GPI antibody were enrolled, and 32 age- and sex-matched IMN patients with negative anti-β2-GPI antibody were randomly enrolled as controls. The frozen serum samples of these 64 patients were collected for detection of anti-phospholipase A2 receptor (PLA2R) antibody and the activity of three complement pathways. Paraffin specimens of the kidney tissues of these 64 patients were collected for immunohistochemical staining of C4d.
Results: IMN patients with positive anti-β2-GPI antibody had a significant decline of the residual complement activity of alternative pathway than those with negative anti-β2-GPI antibody (37.4 ± 21.2% vs 65.7 ± 50.5%, P = 0.021). The positive rate of kidney C4d staining in IMN patients with and without anti-β2-GPI was 65.6 and 81.2%, with no significant difference (P = 0.257). Patients with and without anti-β2-GPI had the same positive rate of anti-PLA2R antibody.
Conclusion: Anti-β2-GPI antibody was associated with alternative complement activation in patients with IMN.
Keywords: Anti-PLA2R; Anti-β2GPI; C4d; Complement activation; Idiopathic membranous nephropathy.