【Objective】 The study was aimed to study the effects of mesenchymal stem cells (MSC) in hematopoietic stem cell transplantation for sensitized recipients. 【Methods】 Bone marrow cells derived from BALB/c mice were cultured in vitro. The molecular markers and the function of MSC were detected by flow cytometry. A murine model of sensitization was established by transfusion of allogeneic spleen cells. MSC labeled with green fluorescent dye were transplanted into nonsensitized and sensitized recipients

and the homing of MSC in vivo was monitored at different time points post transplantation. Additionally

sensitized BALB/c mice under irradiation were transplanted with syngeneic MSC and allogeneic bone marrow cells

and the rate of survival was monitored daily. 【Results】 The results showed that the fourth passage of MSC presented typical spindleshape morphology. The MSC were lack of expression of hematopoietic cell markers but with expression of adherent markers. Fortyeight hours post transplantation

the homing of MSC was found mainly in bone morrow of nonsensitized recipient and spleen of sensitized recipient

respectively. The hematopoietic stem cell transplantation showed that all the sensitized recipients died at 12 to 16 days after receiving syngeneic MSC and allogeneic bone marrow cells

with a median of 14 days. 【Conclusion】 Successfully cultured murine MSC in vitro. The MSC mainly homed to spleen of sensitized recipient post transplantation

furthermore

MSC could not enhance engraftment of allogeneic hematopoietic stem/progenitor cells in sensitized recipients.