Autoantibodies Targeting Ficolin‐2 in Systemic Lupus Erythematosus Patients With Active Nephritis

Objective Systemic lupus erythematosus (SLE) is a multi-system inflammatory disease characterized by production of various autoantibodies. The aim of this study was to investigate the presence of anti-ficolin-2 antibodies in SLE patients and to evaluate the association between the levels of these autoantibodies, clinical manifestations, and disease activity. Methods This is a comparative study using a cohort of 165 SLE patients and 48 healthy subjects. SLE patients were further divided into two groups, with “low disease activity” (SLEDAI score ≤ 4, n = 88) and with “high disease activity” (SLEDAI score > 4, n = 77). Clinical manifestations were defined according to the physician in charge. Active lupus nephritis (LN) was documented by kidney biopsy. Detection of anti-ficolin-2 antibodies was performed by ELISA. Results Levels of the anti-ficolin-2 autoantibodies were significantly higher in SLE patients as compared to healthy subjects and associated with the SLEDAI score. They were found positive in 61/165 (37%) SLE patients. Presence of anti-ficolin-2 antibodies was significantly related only to renal involvement, with a very high prevalence (86%) of anti-ficolin-2 antibodies in SLE patients with active LN. Patients with active proliferative LN had significantly more positive anti-ficolin-2 antibodies than those with non-proliferative LN. The combination of anti-ficolin-2, anti-ficolin-3 and anti-C1q demonstrated a very high specificity (98%) for the diagnosis of active LN. Conclusion Our results support the usefulness of anti-ficolin-2 as a complementary serological biomarker for the diagnosis of active lupus with renal manifestation. This article is protected by copyright. All rights reserved.