ObjectiveTo investigate the expression of CD4+CD25highCD127lowTreg (Treg) and related cytokines in peripheral blood of COPD patients with pulmonary hypertension and explore its clinical significance. MethodsPeripheral blood lymphocytes and serum were collected from 65 COPD patients with chronic pulmonary hypertension (the CPH group) and 20 COPD patients with normal pulmonary artery pressure (the control group). Flow cytometry was used to detect the Treg/CD4+ T cells and calculate its ratio, enzyme-linked immunosorbent assay was used to detect the serum contents of interleukin (IL)-6,IL-10 and tumor necrosis factor α (TNF-α). ResultsTreg can be detected in the peripheral blood of patients of COPD with or without PH, however, the Treg ratio in the CPH group was significantly lower than that in the control group [(7.41±1.12)% vs. (9.04±2.11)%, P<0.05]. Compared with the control group, the IL-10 level was significantly lower [(4.47±0.88)pg/mL vs. (5.18±0.26)pg/mL], while IL-6and TNF-α contents were significantly higher in the CPH group [(7.49±0.95)pg/mL vs. (6.76±0.35)pg/mL, (28.61±9.16)pg/mL vs. (19.64±4.85)pg/mL, P<0.05]. There was a positive correlation between Treg ratio and serum IL-10 level (r=0.41, P<0.05), and negative correlation between Treg ratio and TNF-α or IL-6 contents (r=0.45 or 0.37,P<0.05). The Treg ratio of the patients with severe pulmonary hypertension was lower than that in the patients with mild pulmonary hypertension [(7.42±1.03)% vs. (10.47±2.55)%,P<0.05). ConclusionsContents of Treg and IL-10 decrease while IL-6 and TNF-α increase in peripheral blood of COPD patients with pulmonary hypertension. It suggests that Treg cells and related cytokines may involve in the pathogenesis and progression of CPH. Treg may becomea potential biological prognosis indicator and treatment target of CPH in the future.