In this study, we isolated CML patient-derived Flk1(+)CD31(-)CD34(-) mesenchymal stem cells (MSCs) and detected their biological characteristics and immunological regulation using fluorescence in situ hybridization (FISH) analysis, fluorescence activated cell sorting (FACS), enzyme-linked immunoadsorbent assay, mixed lymphocyte reaction assays.     ///    The capacity of patient Flk1(+)CD31(-)CD34(-) MSCs to inhibit T lymphocyte activation and proliferation was impaired in vitro.     ///    "CML patient-derived Flk1(+)CD31(-)CD34(-) MSCs had normal morphology, phenotype and karyotype while appeared impaired in immuno-modulatory function. "