Objective: To investigate the significance of serum anti-C1q Ab of evaluation of lupus nephritis activity and its curative effects of cyclophophamide therapy on lupus nephritis (LN).
Methods: The level of serum anti-C1q antibody of 75 patients with LN was examined by enzyme-linked immunosorbent assay (ELISA) of the 75 patients the incipient cases had never received corticosteroid and immunosuppressant and the recurrent cases had stopped the immunosuppressant treatment for more than 3 months and were treated, if so, with prednisone with the dosage </= 10 mg/d. Thirty-one patients underwent renal biopsy. The patients underwent treatment of cyclophophamide. The relationships between serum anti-C1q Ab level and lupus nephritis activity, renal pathohistology, as well as laboratory parameters were analyzed, followed by further regular follow-up to investigate its influence to the curative effect.
Results: Fifty-five of the 75 patients (73.3%) were anti-C1q Ab positive with the level of (92 U/ml +/- 41 U/ml). The mean time of conversion of urinary protein into negative was 9 months in the positive C1q positive group and 6 months in the C1q negative group. One year after, 25% of those with positive C1q antibody failed to convert into urinary protein negative, and 90% of those with negative C1q antibody converted into urinary protein negative. One year after, 32% of those whose serum C1q antibody remained positive 1 month after the treatment failed to convert into urinary protein negative, and 91% of those whose serum C1q antibody remained positive 1 month after the treatment converted into urinary protein negative. The serum anti-C1q Ab level was positively correlated with the lupus nephritis clinical active index, proteinuria, and titer of anti-dsDNA, and was negatively correlated with the levels of serum C3 and C4. Renal biopsies showed a positive correlation between the serum anti-C1q Ab level and the activity index of renal pathohistology. Multivariate analysis showed that the serum anti-C1q Ab level after treatment were associated with the curative effect and prognosis of LN.
Conclusion: Serum anti-C1q Ab is not only a good index of lupus nephritis activity, but also reflects renal involvement and curative effect. That serial measurement of serum anti-C1q Ab may provide better clinical strategies for the therapy.