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The expression and clinical significance of Treg cells in chronic myelocytic leukemia

Yi Cheng, GangOu Yang, Mengyuan Sun, Kai Chang, Renjun Long, Zhongyong Jiang

Regulatory T cell (Treg) can regulate auto-immune response. It counteracts against autogenic or allogenic tumor antigens, and maintains immune tolerance and cell homeostasis via inhibiting various physiological or pathological immune responses. Study has found that Treg cells could inhibit the function of immune effector cells with anti-tumor activity, and played important roles in the immune escape of tumor cells. This study analyzed the expression of Treg in Chronic Myelocytic Leukemia (CML), to discuss their effects on disease treatment efficacy as well as prognosis. A total of 107 CML patients were recruited. Flow cytometry was used to measure the peripheral level of CD4+CD25+Foxp3+ Treg. Using averaged antigen expression level as the cut-off line, patients were divided into high and low level groups, whose treatment efficacy and drug resistance were evaluated. Kaplan-Meier approach was used to plot patient survival curve for comparison of survival rates. CD4+CD25+Foxp3+ Treg was significantly higher in chronic untreated group 6.22 ± 1.88% and accelerative/excess blast group 6.79 ± 2.05% compared with control group 1.81 ± 0.84% or chronic treatment group 2.06 ± 1.13%, p<0.05 in all cases). Patients with high Treg levels had lower levels of 3mCHR (3-month complete hematological remission), 12mCCR (12-month complete cytogenetic remission) and 18mCMR (18-month complete molecular remission), but higher drug resistance level than patients with low Treg levels (p<0.05). Overall survival rate of high-Treg patients was remarkably lower than that in low-Treg group (χ²=4.569, p=0.035). Peripheral level of CD4+CD25+Foxp3+ Treg can affect CML course and prognosis, and has implications for the diagnosis and treatment.