High-Dose Dexamethasone Inhibits BAFF Expression in Patients with Immune Thrombocytopenia

B-cell activating factor belonging to the TNF family (BAFF) is elevated in several autoimmune diseases including immune thrombocytopenia (ITP). High-dose dexamethasone (HD-DXM) has shown its clinical efficacy in ITP patients. The plasma BAFF concentration and BAFF mRNA were measured in ITP patients before and after oral administration of 40 mg/day DXM for four consecutive days by enzyme-linked immunosorbent assay (ELISA) and real-time quantitative PCR. Moreover, we evaluated the effects of DXM on BAFF expression and proliferation of lymphocytes by ELISA, real-time quantitative PCR and cell proliferation respectively in in vitro experiment. Both plasma BAFF concentration and BAFF mRNA were significantly increased in active ITP patients at pretherapy when compared with controls (P < 0.001). After 4-day treatment with HD-DXM, the BAFF and BAFF mRNA were decreased, and lower than that for controls. In in vitro assays, we found DXM-inhibited BAFF, IFN-gamma expression, and the proliferation of lymphocytes in a dose-dependent manner. These results suggest that BAFF expression is increased in ITP patients with active disease, and DXM is an effective inhibitor of BAFF production. As immunosuppressant, DXM may play its role in ITP treatment partly through regulating BAFF expression.