ObjectiveTo explore the effect of bone mesenchymal stem cells (MSCs) on cell proliferation and miRNA155 expression of activated T lymphocytes in the oneway mixed lymphocyte reaction (MLR) system.MethodsMSCs were isolated from SD rats and cultured in vitro.Cells were identified with a flow cytometer for the expression of CD11b/c, CD34, CD44 and CD90.The differentiation ability of MSCs was identified by osteogenic and adipogenic induction.The oneway MLR system was established with T lymphocytes isolated from the spleens of SD rats by immunomagnetic beads and inactivated mononuclear cells solated from the spleens of Wistar rats.The effect of MSCs on cell proliferation and miRNA155 expression of activated T lymphocytes in the oneway MLR system were respectively detected by CCK8 assay and rea1time PCR.ResultsCultured MSCs were negative for CD11b/c and CD34 \[(85.1%±0.6%) and (98.0%±0.8%), respectively\] but positive for CD44 and CD90 \[(98.9%±0.8%) and (98.1%±0.9%), respectively\].The cells had the ability of osteogenic and adipogenic differentiation.The proliferation and miRNA155 expression of activated T lymphocytes in the oneway MLR could be significantly inhibited by MSCs in a dosedependent manner.ConclusionsThe expression of miRNA155 in activated T lymphocytes can be downregulated by MSCs, which may play an important role in the regulaton of MSCs on cell proliferation and immune function of T lymphocytes.