CD4 and graft versus host disease: On the other hand, Yi demonstrated that IL‐27 favoured the protective effect of human placenta–derived mesenchymal stromal cells (hPMSC) in GVHD therapy by increasing CD4+ IL‐10+ IFN‐γ+ T cells production,10 up‐regulation of IL‐27 combined with rapamycin promoted IL‐10+CD4+ T cells effect in prolonging cardiac allograft survival,11 which suggested that IL‐27 and IL‐27Rα inhibited allorejection.