“Two common and one severe patient were significantly improved in 2 days after MSC transplantation. Among them, two common and one severe Patient were recovered and discharged in 10 days after treatment. After treatment the peripheral lymphocytes were increased, the C-reactive protein decreased, and the overactivated cytokine-secreting immune cells CXCR3+CD11c+T cells, CXCR3+CD8+T cells, and CXCR3+NK cells dissapeared in 3-6 days. In addition, a group of CD14+CD11c+CD11b mid regulatory DC cell population dramatically increased. Meanwhile the level of TNF-@ was significantly decreased, while IL-10 increased in MSC treatment group compared to the placebo control group. Furthermore, the gene expression profile showed MSC were ACE2 and TMPRSS2 which indicated MSC’s are free from COVID19 infection. Thus, the intravenous transplantation of MSC’s was safe and effective for treatment in patients with COVID-19 pneumonia, especially for the Patients in critically severe conditions.”