APRIL Level as a Marker of Disease Activity in Treated Rheumatoid Arthritis Patients: Association with Disease Activity and Anti-CCP Antibody.

Rheumatoid arthritis (RA) is a chronic autoimmune disease with joint inflammation and autoantibody production. Cytokines play an important role in the pathogenesis of RA. Among the cytokines that regulate B cell homeostasis is the "A Proliferation-Inducing Ligand" (APRIL). To determine the differences in APRIL in response to treatment in anti- cyclic citrllinated peptides (anti-CCP) positive versus anti-CCP negative patients with established RA. Concentrations of APRIL in sera of 10 anti-CCP positive RA patients, 18 anti-CCP negative RA patients, and 12 healthy controls were measured by enzyme-linked immunosorbent assay (ELISA) at treatment initiation and after 6 months of treatment with methotrexate and hydroxychloroquine. Correlations between serum anti-CCP, C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), 28-joint Disease Activity Score (DAS28), and serum level of APRIL were analyzed. Serum APRIL levels were increased in rheumatoid arthritis patients in comparison with healthy volunteers. APRIL correlated positively with disease activity; swollen joint count, visual analog score and simplified disease activity index (all P < 0.05). In addition, APRIL was significantly higher in patients with positive anti-CCP. After treatment, APRIL levels significantly decreased in the anti-CCP positive RA patients than in anti-CCP negative RA patients. In conclusions, serum APRIL may be a good predictor marker for joint injury and therapeutic response in patients with RA.