ObjectiveTo investigate the expression of PD-L1 on Treg cells and the correlation with the frequency of peripheral blood Treg in patients with HIV-Ⅰ. MethodsPeripheral blood from 36 patients with HIV-Ⅰ(patients without antiretroviral therapy, HIV-Ⅰinfection group) and 16 healthy persons ( control group ) was collected, PBMCs were abstracted, flow cytometry was used to test the expression of PD-L1 on regulatory T cells(Treg) and calculate the Treg frequency. ResultsThe expression of PD-L1 on Treg cells in the HIV-Ⅰinfection group was significantly lower than that in the control group (P＜0.01), that was a positive correlation between the expression of PD-L1 on Treg cells and Treg frequency on peripheral blood T cells of CD3+, CD4+ in patients with HIV-Ⅰ(r=0.6305，P＜0.01). ConclusionsThe up-regulated expression of PD-L1on Treg may be associated with the increased frequency of Treg in patients with HIV-Ⅰ.

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