Therefore, although the absolute number of regulatory T cells, conventional T cells, Th17 cells, or Th1 cells were significantly lower in G-BM compared to G-PB, the ratio of conventional T cells to CD4+CD25highCD127-/low Treg cells was significantly lower in G-BM compared to G-PB, which could partially contribute to the lower incidence of acute GVHD in G-BM transplantation compared to G-PB transplantation. Here, CD4 is linked to acute graft versus host disease.