The level of CD_4~+ Foxp3~+ regulatory T cells in patients with childhood acute leukemia and its relationship with the minimal residual disease of leukemia

Objective To study the regulatory T cells (Treg-cell) frequencies in patients with childhood acute leukemia and evaluate its clinical application value by investigating the relationship between the increasing numbers of Treg cells and minimal residual disease of leukemia (MRD), Methods Foxp3-FITC/CD_(25)-PE/CD_4-PerCP/CD_3-APC four-color staining flow cytometry was established to identify Treg cells. Treg cells frequencies both in 10 healthy controls and in 33 patients with newly diagnosed childhood acute leukemia ( B-ALL 17 cases, T-ALL 9 cases, AML 7 cases) were detected. The possibility of the accumulation of Treg cells being the prognostic marker for acute leukemia was evaluated by comparing the results of Treg cells frequency with that of MRD. Results The percentage of Treg cells in CD_4~+ CD_3~+ T cells was M = 8. 09% in normal bone marrows, which was significantly different from the results in the bone marrows of newly diagnosed childhood acute leukemia ( M = 12.77% , U = 3.41, P < 0.01 ), but it showed no significantly differences among B-ALL, T-ALL and AML groups. No association was observed between the expression of Treg cells and clinical-biologic characteristics studied. In addition, Treg cells frequency in MRD positive group was significantly different from that in MRD continuously negative group ( M = 14. 74% vs M=11.3%, t =252.5,P<0.05). Conclusions Consistent with results from solid tumor, the study identifies a significantly increased numbers of Treg cells in patients with childhood acute leukemia. The situation of accumulation of Treg cells is closely associated with MRD results during chnical remission. High level of Treg cells may cause poor prognosis and increase the possibility of relapse. Key words: Regulatory T cell;  Leukemia, acute;  Minimal residual disease;  Prognosis;  Flow cytometry