Objective To investigate the regulatory effects of IFN-γon Treg cells from HIV/AIDS patients receiving highly active antiretroviral therapy (HAART) for one year.Methods Thirty HIV/A1DS patients whose CD4+T cells were below 350/μ1 were recruited for HAART therapy.Blood samples were collected at the time points of 0,24,48 weeks after HAART.PBMCs were isolated and randomly divided into two culture groups.One group was cultured directly in medium and another group was co-cultured with IFN-γ (40 pg/ml).The supernatants and cells were separated after 5 days of culture for analysis.The concentrations of IL-12 and CD4+CD25+Foxp3 Treg cells were measured by ELISA and flow cytometry,respectively.Results The levels of IL-12 in the supernatants from the culture without IFN-γ at time points of 0,24,48 weeks after HAART were lower than those from the co-cultured group [(37.02±12.76) vs (41.79± 15.02),t=2.336,P=0.03; (41.76±17.01) vs (47.2±14.26),t=2.702,P=0.014; (48.01± 11.84) vs (53.44± 11.30),t =3.14,P =0.003].The percentages of CD4+ CD25 + Foxp3 Treg cells in CD4+ T cells from the direct-cultured group were higher than those from the co-cultured group at the three time points [(10.41±1.10)％ vs (2.40±1.11)％,t=13.89,P=0.000; (8.33±2.03)％ vs (1.99± 0.86)％,t=12.93,P=0.000; (5.65±1.55)％ vs (1.32±0.73)％,t=10.61,P=0.000].Moreover,the results within the same group at the time points of 0,24,48 weeks upon HAART were also significantly different.Conclusion With the interference of HAART,IL-12 levels were increased,while CD4+CD25+ Foxp3 Treg cells were decreased in patients with HIV/AIDS.IFN-γ plays an important role in this process.