Complement Alternative Pathway׳s Activation in Patients With Lupus Nephritis ☆ ☆☆

Abstract Objective The aim of this study was to detect the spectrum of complement activation pathways in circulation and to assess their correlations with clinical and pathologic features in a large lupus nephritis cohort from China. Materials and Methods Plasma levels of C1q, mannose-binding lectin, C4d, Bb, C3, C3a, C5a and soluble C5b-9 were detected by enzyme-linked immunosorbent assay in 222 patients with active biopsy-proven lupus nephritis, 34 patients with lupus nephritis at remission, 82 patients with active systemic lupus erythematosus without renal involvement and 39 normal controls. The correlations between levels of complement components and clinicopathological features of these patients were further analyzed. Results Plasma levels of C1q and C3 significantly decreased, and the levels of Bb, C3a, C5a and soluble C5b-9 were significantly elevated in patients with active lupus nephritis compared with those in remission, active systemic lupus erythematosus without renal involvement group and normal controls. In the lupus nephritis group, soluble C5b-9 levels were inversely correlated with C1q and C4d levels ( r = −0.412, P r = −0.221, P = 0.002, respectively), but more strongly correlated with the level of Bb ( r = 0.546, P P = 0.017) in the lupus nephritis group. Conclusions Our findings suggested that the activation of the complement alternative pathway might play a more important role in the pathogenesis of lupus nephritis, and factor Bb might be a useful marker for evaluating renal disease activity and outcomes.