ANTI C1Q ANTIBODIES CORRELATE SIGNIFICANTLY WITH CRYOGLOBULINS IN PATIENTS WITH SYSTEMIC LUPUS ERYTHEMATOSUS AND URTICARIAL VASCULITIS

Background: Anti-C1q antibodies have been described in systemic lupus erythematosus (SLE) as well as in other connective tissue diseases. In SLE they have been considered as a marker for disease activity and presence of nephritis. The highest prevalence of anti-C1q antibodies was found in urticarial vasculitis (UVS), where they can be used as a diagnostic marker. No study has focused on the association of anti-C1q and cryoglobulins with clinical and biological features of the diseases. Objectives: The aim of the study was to evaluate the prevalence of anti-C1q antibodies in patients with the mixed cryoglobulinemia and to analyze association of concomitant presence of anti-C1q antibodies and cryoglobulins with clinical and biological features. Methods: We have determined anti-C1q antibodies by commercial ELISA (Euroimmun, GmbH). Cryoglobulins were searched using standard technique and quantified with a qualitative scale of values from + to ++++. Concentrations of C3 and C4 complement components were determined by turbidimetry. The study population included 20 patients with SLE, 6 patients with UVS and 8 patients with isolated cryoglobulinemic vasculitis (CV). The risk for the development of nephritis with different laboratory features (anti-C1q, cryoglobulin, low C4) was estimated by regression analysis. Results: Anti-C1q antibodies were detected in 100% of UVS, 30% of SLE and in 25% of CV patients. Cryoglobulins were present in all of UVS and CV patients and in 55% of SLE patients. A significant correlations (p<0.01) both in presence and concentration of anti-C1q antibodies with cryoglobulins were observed. Patients with UVS had higher concentration of anti-C1q in comparison with SLE (p<0.01) and CV (p<0.05) patients. Patients with CV had significantly higher cryoglobulin concentrations in comparison with SLE (p<0.001) and UVS (p<0.01) patients. Univariate analysis showed that patients with low C4 fraction of complement have higher risk of nephritis. By logistic regression analysis low C4 levels appeared as an independent risk factor for renal disease (OR=7.55, p=0.0145). Conclusion: This study shows a strong association of anti-C1q antibodies with cryoglobulins in patients with SLE and UVS. Possible pathogenic role of anti-C1q antibodies, and cryoglobulins remains confined to local deposits in tissues. They seem to be essential, but not sufficient for the development of nephritis. The presence of cryoglobulin-C1q complexes are able to induce activation of classical complement pathway necessary for the development of nephritis. Disclosure of Interest: None declaredCitation: Annals of the Rheumatic Diseases, volume 68, supplement 3, year 2009, page 376Session: Humoral aspects Autoantibodies (Poster Presentations )