CD4 and graft versus host disease: This was unexpected because the frequencies of donor CD4 and CD8 T cells producing TNFα and/or IFNγ, two key pathogenic cytokines involved in aGvHD, were equally diminished when co-transferred with iTregs (Figure 3B) and because the absolute numbers of these cytokine producing donor T cells were significantly reduced upon rIL-27 pre-stimulated iTreg transfer (Figure 3C), which is consistent with the notion that Tregs prevent GvHD development by inhibiting allo-reactive T cell expansion (36).