【Objective】 To observe the effect of infusion of bone marrow mesenchyma1 stem cells (MSC) combined with natural killer cells (NK) on acute graft versus host disease (aGVHD) after allogeneic bone marrow transplantation (alloBMT) in mice and investigate the preliminary mechanism. 【Methods】 Bone marrow cells isolated from C57BL/6 mice were cultured to MSC in vitro. NK cells were separated from spleen cells in C57BL/6 mice through magnetic beads. Allogeneic bone marrow transplantation models were established with BALB/c mice as recipients and C57BL/6 mice as donors. Forty BALB/c mice were divided into 4 groups at randoms i.e.: MSC combined with NK group

MSC group

NK group and medium control group. According to GVHD scores

GVHD pathological changes in the liver

spleen and gut

and average survival time

aGVHD were valued. The concentrations of IFNγ and IL12 in the serum were detected through ELISA assay. The expression rates of CD11c and CD86 on the surface of spleen cells were detected through flow cytometry. 【Results】 According to GVHD scores

GVHD pathological changes in the liver

spleen and gut

and average survival time

compared to blank control group

the aGVHD manifestations of MSC combined with NK group

MSC group and NK group were alleviated

especially in MSC combined with NK group. The IFNγ concentration of NK group was higher than that of MSC combined with NK group

MSC group and medium control group. The IL12 concentration of MSC combined with NK group was lower than that of NK group and medium control group respectively

and MSC group was lower than medium control group. The numbers of both immature dendritc cells (CD11c+CD86-) and mature dendritic cells (CD11c+CD86+) of spleen in MSC combined with NK group were lower than those of MSC group

NK group and medium control group. 【Conclusion】 Infusion of bone marrow mesenchyma1 stem cells combined with natural killer cells decreased the number of dendritic cells

alleviated acute graft versus host disease and prolonged survival time in mice.