Elevated serum APRIL levels in patients with systemic sclerosis: distinct profiles of systemic sclerosis categorized by APRIL and BAFF.

Objective: Elevated serum concentrations of B cell-activating factor belonging to the tumor necrosis factor family (BAFF) are found in systemic sclerosis (SSc) and are associated with the severity of skin sclerosis. We investigated serum levels of a proliferation-inducing ligand (APRIL), a close homolog to BAFF, and its clinical association in patients with SSc as well as its correlation with BAFF.

Methods: Serum APRIL levels from 74 patients with SSc, 25 patients with systemic lupus erythematosus, and 25 healthy subjects were examined by ELISA. Clinical and laboratory measures were compared between SSc patients with elevated serum APRIL levels and those with normal levels. We assessed correlation of serum APRIL and BAFF levels in patients with SSc.

Results: Serum APRIL levels were elevated in SSc patients compared to controls. SSc patients with elevated serum APRIL levels had significantly higher incidences of pulmonary fibrosis than those with normal levels. Serum APRIL levels did not correlate with serum BAFF levels in SSc patients, and there were distinct profiles of SSc categorized by serum APRIL and BAFF levels. High APRIL levels served as a marker for involvement of pulmonary fibrosis and high BAFF levels served as a marker for severe skin sclerosis.

Conclusion: The results suggest that elevated serum APRIL and BAFF levels were differentially associated with disease severity in SSc.