Anti‐C1q antibodies are associated with systemic lupus erythematosus global activity but not specifically with nephritis: A controlled study of 126 consecutive patients

Abstract

Objective. Several studies have shown that antiC1q antibodies correlate with the occurrence and activity of nephritis in systemic lupus erythematosus (SLE). However, the significance of anti-C1q antibodies in SLE has not been fully characterized. The aim of this study was to investigate associations between anti-C1q antibodies and clinical and serologic parameters of SLE.Methods. An enzyme-linked immunosorbent assay kit was used to measure anti-C1q antibodies in the sera of 126 consecutive patients with active SLE who were admitted to our university hospital from 2007 through 2009. Sera obtained from patients with high titers of anti-C1q antibodies at the initial evaluation (n ‫؍‬ 20) were reevaluated following treatment. Control sera were obtained from patients with other autoimmune diseases and from normal healthy control subjects (n ‫؍‬ 20 in each group). Associations between anti-C1q antibodies and clinical and serologic parameters of SLE were statistically analyzed.Results. Anti-C1q antibodies were detected in the sera of 79 of 126 patients with SLE. The prevalence and titers of anti-C1q antibodies were significantly (P < 0.0001) higher in SLE patients than in patients with rheumatoid arthritis, patients with systemic sclerosis, and normal healthy control subjects. The prevalence and titers of anti-C1q antibodies were not significantly associated with active lupus nephritis (P ‫؍‬ 0.462 and P ‫؍‬ 0.366, respectively). Anti-C1q antibody titers were significantly correlated with SLE Disease Activity Index 2000 scores and the levels of anti-doublestranded DNA antibodies, C3, C4, CH50, and C1q (P < 0.0001 for all comparisons). Moreover, anti-C1q antibody titers significantly decreased as clinical disease was ameliorated following treatment (P ‫؍‬ 0.00097).Conclusion. These findings indicate that anti-C1q antibodies are associated with SLE global activity but not specifically with active lupus nephritis.

Application of Fluorescent Monocytes for Probing Immune Complexes on Antigen Microarrays

“…In the diagnosis of SLE high titers of Ro-SSA [40], dsDNA [41] and C1q [42] specific IgG autoantibodies are considered among the most specific markers, while ssDNA specific IgG appears in many inflammatory disorders and in normal subjects as well [43]. In our experiments, comparing detection of immune complexes by secondary antibodies against human IgG and IgM with U937 cells, we found positive correlation between cell and IgG but not IgM signals (Table 1).…”

PTX3, Anti-PTX3, and Anti-C1q Autoantibodies in Lupus Glomerulonephritis

“…Anti-dsDNA antibodies have been widely used as a clinical biomarker of LGLN occurrence or relapse [17,18]. Furthermore, anti-C1q antibodies have recently emerged as perpetuators of renal inflammation [19][20][21][22], yet their pathogenetic potential is currently being challenged [23][24][25]. Unfortunately, no reliable biomarkers able to predict LGLN in SLE patients have been identified to date [26].…”

Anti-C1q antibodies as a follow-up marker in SLE patients

“…In addition, it was reported that levels of anti-C1q antibodies decreased after successful treatment of lupus nephritis [25]. However, these findings are in contrast to data found by Katsumata et al describing that anti-C1q antibodies were associated with SLE global disease activity but not specifically with active lupus nephritis [26]. Taken together, the value of anti-C1q in SLE patients as follow-up marker is controversial and data on the correlation between anti-C1q levels and changes in disease activity within individual patients are lacking.…”