CD4 and graft versus host disease: However, hPMSCs downregulated the expression of PD-1 in CD4+IL-10+ T cells by regulating the crosstalk between the Nrf2 and NF-κB signaling pathways, which inhibited CD4+IL-10+ T cell apoptosis, thus promoting the generation of CD4+IL-10+ T cells and further mitigating the inflammatory response of GVHD.