Clinical relevance of glomerular IgM deposition in patients with lupus nephritis

Abstract

Background The aim of the study was to investigate the clinical relevance of IgM deposition in patients with LN in a large cohort. Results 217 patients with renal biopsy–proven lupus nephritis were enrolled. The associations between glomerular IgM deposition and clinicopathological parameters were further analyzed. IgM deposition was positively correlated with glomerular C1q and C3 deposition moderately (r = 0.436, P < 0.001; r = 0.408, P < 0.001, respectively), and inversely correlated with plasma levels of C3 and CFH mildly (r=-0.138, P = 0.043; r=-0.147, P = 0.037, respectively). By multivariate analysis, we found that glomerular IgM deposition independently contributes to glomerular C3 deposition in patients with lupus nephritis (OR = 2.002, 95% CI: 1.295–3.094, P = 0.002). In addition, we also found that patients with IgM 0+-2 + had similar plasma CFH levels, but in patients with IgM3+-4+, plasma CFH levels were significantly lower (300.4 ± 155.8µg/ml vs. 429.9 ± 187.5µg/ml, P < 0.001). Furthermore, patients with high density of glomerular IgM and low levels of CFH had heavier proteinuria, higher serum creatinine and lower plasma C3 levels (5.7 ± 3.1g/d vs. 4.7 ± 3.5g/d, P = 0.037;150.1 ± 121.0µmol/L vs. 105.6 ± 97.1µmol/L, P = 0.005; 0.3 ± 0.2µg/L vs. 0.4 ± 0.2µg/L, P = 0.04, respectively), comparing with those with low density of glomerular IgM and low levels of CFH. Conclusions Our results suggested IgM might bind to injury-associated epitopes and be involved in disease progression and provided a possible relevance of CFH and IgM in the process of alternative pathway (AP) activation.