ObjectiveTo investigate the effects of trichostatin A(TSA) and sodium butyrate(NaB), histone deacetylase inhibitors, on the balance of Th1/Th2 after differentiation of peripheral blood CD4+T cells. MethodsPeripheral CD4+T cells were grown in vitro and were divided into TSA group, NaB group, and CON group. The concentrations of IL-4 and IFN-γ (Th1/Th2 factors) in the supernatants were examined by ELISA in each group 48 h later; the expressions of IL-4 and IFN-γ were analyzed by qRT-PCR; and the T-lymphocytes in peripheral blood (PBL) were measured by flow cytometry. Results ELISA showed that the supernatant IFN-γ and IL-4 levels in the TSA and NaB groups were significantly higher than those in the CON group 48 h after treatment with TSA(0.33 μmol/L) and NaB(1.4 mmol/L); real-time quantitative PCR also showed that the expressions of IFN-γ and IL-4 mRNA in TSA and NaB groups were significantly higher than those in the CON group(3.121, 2.31; P<0.05). However, flow cytometry showed that the ratios of IFN-γ+ cells/IL-4+ cells were significantly higher in TSA and NaB groups than that in the CON group((1.931,1.551;P<0.05) .ConclusionTreatment with TSA and NaB, both histone deacetylase inhibitors,can induce a shift of Th1/ Th2 cell balance toward Th1 cells in peripheral CD4+T cells.