ABSTRACT
<p><b>OBJECTIVE</b>To investigate the effect of ATO on the proportion of Treg in the peripheral blood of patients with severe aplastic anemia (SAA) in vitro.</p><p><b>METHODS</b>The peripheral blood of 20 newlydiagnosed patients were collected, and the peripheral blood monomuclear cells (PBMNC) were extracted. After the PBMNC were treated with ATO of different concentrotions (0, 1, 2.5 and 5 µmol/L) for 96 hours, the proportion of CD44 CD25CD127 regulatatory T cells (Treg) were detected by flow cytometry. The expression levels of Foxp3 mRNA were detected by RT-PCR, and the levels of IFN-γ,IL-4,IL-17 and TGF-β1 were detected by ELTSA to verify the results of flow cytomery.</p><p><b>RESULTS</b>ATO significantly increased the proportion of Treg (P<0.01) at the concentration of 2.5 and 5 µmol/L, and the rising degree of Treg proportion improved with the increasing ATO concentration(r= 0.524). Treg proportion increased at a concentration of 1 µmol/L, but without statistical significance (P>0.05). At 1(P<0.05), 2.5(P<0.01) and 5 µmol/L(P<0.01), ATO significantly up-regulated the expression of Foxp3 mRNA, and the increase of Foxp3 mRNA positively and linearly correlated with the increase of Treg cell-frequency(r=0.523). ATO significantly reduced the levels of IFN-γ (at ATO 1,2.5 and 5 µmol/L, P<0.01), IL-4 (at ATO 2.5 µmol/L, P<0.01; at ATO 5 µmol/L, P<0.01) and IL-17(at ATO 2.5 µmol/L, P<0.05; at ATO 5 µmol/L, P<0.01). ATO had no significant effect on TGF-β1 at 1(P>0.05) and 2.5 µmol/L (P>0.05), but significantly reduced TGF-β1 level at 5 µmol/L (P<0.05).</p><p><b>CONCLUSION</b>ATO can mediate the immune regulation through up-regulating the proportion of Treg in peripheral blood of patients with SAA and reducing the levels of IFN-γ, IL-4 and IL-17.</p>