BAFF and APRIL expression as an autoimmune signature of membranous nephropathy

Background: Based on the fact that B-cell activating factor (BAFF) and a proliferation-inducing ligand (APRIL) have a regulatory role in B cell biology, excessive levels of these cytokines can promote autoimmune pathogenesis. However, the expression and implication remain unresolved in cases of membranous nephropathy (MN). Results: The plasma BAFF levels of the primary MN patients were higher than those of healthy controls but lower than those of secondary MN patients, whereas the APRIL levels were similar between the MN patients and healthy controls. The BAFF levels were higher in relapse cases, whereas the APRIL levels were higher in the patients who did not experience remission compared with the counterpart patients. The ectopic expression of BAFF and APRIL was observed in the glomeruli or circulating B cells of MN patients, and this high expression trend was similar to that of lupus patients. Conclusions: Expression profile of BAFF and APRIL in MN is similar to that of other autoimmune disease, which affects the kidney outcomes. Methods: Plasma BAFF and APRIL levels were measured upon kidney biopsy in patients with primary (n = 89) and secondary MN (n = 13), and the results were compared with the levels in healthy controls (n = 111). The kidney outcomes (e.g., remission and relapse) were traced for the median of 3 years. Aberrant expression of the cytokines was evaluated in the kidney and circulating B cells using immunohistochemistry and flow cytometry analyses, respectively.