Background There is a lack of serum markers for effective evaluation of renal lesion severity of systemic lupus erythematosus (SLE). Recent studies show that anti-Clq antibody has been associated with SLE and lupus nephritis (LN), but there were few data about the relationship between anti-Clq antibody and renal pathology of LN.
Objectives To investigate the relationship between serum anti - Clq antibody and the disease activity of SLE as well as renal pathological characteristic.
Methods Anti-C1q Ab were measured by enzyme-linked immunosorbant assay (ELISA) in 128 patients with SLE (including 58 cases with LN and 70 cases without LN), 103 patients with other autoimmune diseases (disease control group) and 60 healthy individuals (healthy control group). Renal biopsy was conducted in all LN patients.
Results Prevalence of anti-C1q was 31.3% (40/128) in patients with SLE, significantly higher than that in disease control group and healthy control group (31.3% vs.4.9% (5/103), P<0.01; 31.3% vs. 0 (0/60), P<0.01). And the positive rate of anti-C1q Ab was significantly higher in patients with active SLE (37/54,68.5%), LN (35/58, 60.3%) and active LN (32/36, 88.9%) in comparison with patients with inactive SLE (3/64,4.7%), non-LN (5/60,8.33%) and inactive LN (3/22,13.6%), respectively. The incidence of renal involvement in SLE patients with positive anti-C1q Ab was higher than that in anti-C1q Ab negative group (87.5% vs 29.5%, P<0.05). 12 cases of renal biopsies were classified as WHO Class II. 13 cases Class III,18 cases Class IVCand 15 cases Class V. The serum anti-C1q Ab level in Class IV LN patients (63±10 RU/ml) was higher than that in Class II/III/V LN patients (P<0.01). There was no significant difference of the anti-C1q Ab level among the other pathological types of LN.The serum C1qAb level was significantly higher in the LN patients with renal deposition of C1q (++), IgG positive and C3 positive, in comparison with the deposition of C1q (+/−), IgG negative and C3 negative, respectively (P<0.05). The elevated levels of anti-C1qAb was significantly positively correlated with the deposition of C1q, IgG and C3 in the kidney.
Conclusions The serum anti-C1q antibody, a simple and non-invasive marker, can reflect the disease activity of SLE, especially with regard to renal involvement. It is useful for SLE to predict renal lesion, particularly diffuse proliferative LN (iclass IV).
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Disclosure of Interest None declared