To explore the mechanism of reduction of GVHD severity caused by Th subsets, the expression of FoxP3 and CD25 for Treg cells (Figure 7B), IFN-γ for Th1 cells, IL-4 for Th2 cells and IL-17 for Th17 cells were measured by intracellular staining assay (Figure 7C). The gene discussed is IL17A; the disease is graft versus host disease.