OBJECTIVETo investigate the correlation of immunologic thrombocytopenia(ITP) pathogenesis with the abnormal expression of IL-21, and to explore the association of high-dose dexamethasone (HD-DEX) treatment with the IL-21 expression.

METHODS26 newly diagnosed ITP patients and 24 healthy controls were enrolled in this study. The mononuclear cells and serum were obtain from density gradient centrifugation in the newly diagnosed ITP patients before HD-DXM treatment, and the samples of healthy controls were also used for assays. The protein and mRNA expression of IL-21 on peripheral blood mononuclear cells(MNC) were determined by flow cytometry and real-time reverse-transcription polymerase chain reaction. Plasma levels of IL-21, IFN-γ and IL-4 were determined by enzyme-linked immunoabsorbent assay (ELISA).

RESULTSIL-21 expression on mononuclear cells was significantly higher in ITP patients (13.07%) than that in normal controls (8.2%), the ratio of IL-21/GAPDH mRNA expression on MNC was significantly higher in ITP patients (9.524±0.97) than that in normal controls (3.701±0.60, P<0.01). After HD-DXM therapy, the ratio of IL-21/GAPDH mRNA decreased significantly (5.87±1.21) as compared with the level before treatment. Significantly high levels of serum IL-21, IFN-γ and lower IL-4 were found in ITP patients, as compared with healthy controls. Serum IL-21 and IFN-γ levels in ITP patients decreased significantly after HD-DXM administration (P<0.01), while post-treatment levels of IL-4 were increased significantly, compared with the levels before treatment (P<0.01).

CONCLUSIONTherapeutic effect of DXM on ITP associates with down-regalation of IL-21 expression. The increased expression of IL-21 involves in the pathogenesis of ITP.