Abstract:ObjectiveTo investigate the role of miR-155 in the differentiation and function of Th17 cells in peripheral blood of patients with ulcerative colitis (UC) to clarify the mechanism of miR-155 in UC. Methods Sixteen patients with active UC from June 2016 to June 2017 were enrolled.By immunomagnetic beads,CD4⁺T lymphocytes were isolated from mononuclear cells from the peripheral blood of UC patients and were divided into three groups:control group,miR-155 group and miR-155 inhibition group.The proportion of Th17 cells was detected by flow cytometry,the expression of miR-155-3p in cells was determined by RT-PCR,and the levels of interleukin(IL)-17A and IL-6 in supernatant of cultured peripheral CD4⁺T lymphocytes were measured using enzyme-linked immunosorbent assay(ELISA)． Results After Th17 cells being cultured and intervented for 24 hours,the proportion of Th17 cells ［(16.73±4.41)% vs (5.69±1.78)%］ and the expression of miR-155(1.97±0.56 vs 0.89±0.33) significantly increased in miR-155 group compared with control group(P<0.01)，and the proportion of Th17 cells［(2.03 ± 0.78)% vs (5.69 ± 1.78)%］ and the expression level of mir-155-3p (0.57 ± 0.16 vs 0.89 ± 0.33) in miR-155 inhibition group were significantly lower than those in control group(P<0.01).The levels of IL-17A and IL-6 in the cultured supernatant in miR-155 group were also significantly higher than those in control group and in miR-155 inhibition group (all P<0.01). ConclusionmiR-155 is involved in the regulation of CD4⁺T lymphocytes by promoting the differentiation and function of Th17 cells and plays an important role in the pathogenesis of UC.