IFNG and chronic graft versus host disease: With these efforts, we can continuously monitor the dynamic change of immune status (not only plasma IFN-γ, IL-4, Il-10, IL-12 levels, but also the Th1, and Th2 frequencies within total CD4+ T cells simultaneously) and then to establish the relationship between kinetics of immune status and the clinical activity of both acute and chronic GVHD.