Increased serum APRIL differentially correlates with distinct cytokine profiles and disease activity in systemic lupus erythematosus patients.

Cytokines play an important role in the pathogenesis of systemic lupus erythematosus (SLE). Among the cytokines that regulate B cell homeostasis is a proliferation-inducing ligand (APRIL). This study aimed to determine whether serum levels of APRIL are raised in patients with SLE and correlate with disease activity or proinflammatory cytokines production, or both. Serum APRIL, interleukin-17 (IL-17), IL-4 and interferon gamma (IFN-γ) levels were measured in forty patients with SLE and 30 healthy controls. Disease activity was assessed by SLE disease activity index (SLEDAI), and results were correlated with serum APRIL levels. Serum APRIL levels were significantly higher in patients with SLE than in healthy controls. Positive correlation was found between serum APRIL levels and total SLEDAI score and anti-dsDNA antibody titers. Moreover, serum APRIL levels was significantly higher in patients with arthritis, mucocutaneous manifestations and proteinuria. APRIL is increased in patients with active SLE accompanying the increase of IL-17 and IFN-γ. Significant positive correlations between serum levels of APRIL and IL-17 and IFN-γ and a negative correlation between serum levels of APRIL and IL-4 were found. The results suggest that APRIL may be an important marker of disease activity in patients with SLE. We provide the analyses of APRIL levels in patients with SLE, suggesting new tools for the diagnosis, prognosis and possible therapeutic management of SLE.