In this study, we found that the proportion of CD4+IL-10+ T cells decreased in GVHD patients and the GVHD mouse model, while the PD-1 expression levels in CD4+IL-10+ T cells markedly increased, which suggested that PD-1 expression was associated with the percentage of CD4+IL-10+ T cells and the development of GVHD. Here, CD4 is linked to graft versus host disease.