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

Abstract

Objective: Systemic lupus erythematosus (SLE) is a multisystem inflammatory disease characterized by the 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 2 groups (low disease activity [SLE Disease Activity Index (SLEDAI) score ≤4, n = 88] and 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 enzyme-linked immunosorbent assay. Results: Levels of anti–ficolin-2 autoantibodies were significantly higher in SLE patients as compared to healthy subjects and associated with SLEDAI score. They were found to be positive in 61 of 165 SLE patients (37%). The 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 nonproliferative 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 serologic biomarker for the diagnosis of active lupus with renal manifestations.