Increased serum levels of a proliferation-inducing ligand in patients with bullous pemphigoid.

BACKGROUND B cells have been demonstrated to have critical roles in developing autoimmune bullous diseases. Recently identified tumor necrosis factor-like molecules, B cell-activating factor of the TNF family (BAFF) and a proliferation-inducing ligand (APRIL) are essential molecules for B cell development, survival, and proliferation. Although the functions of APRIL have not been fully evaluated, recent studies suggest that circulating levels of APRIL are increased in various autoimmune diseases, including systemic lupus erythematosus and rheumatoid arthritis. OBJECTIVES To determine serum APRIL levels in patients with pemphigus vulgaris (PV) and bullous pemphigoid (BP), and compare those with clinical findings and laboratory findings. PATIENTS/METHODS Sera from 15 PV patients, 43 BP patients, and 15 normal controls were subjected to ELISA assays to measure serum APRIL, BAFF, Dsg3, and BP180 levels. RESULTS AND CONCLUSIONS Circulating APRIL levels were significantly elevated in BP patients but not in PV patients, and correlated with serum BAFF levels. Our study revealed that serum APRIL levels tended to be increased in the quite early stage of disease. In conclusion, circulating APRIL levels may be a useful marker for early activation of autoimmune diathesis, and furthermore, an effective therapeutic target molecule in patients with BP.