These data are consistent with a model in which host-reactive CD8 T cells entering host epithelial compartments following alloSCT are induced to express CD103 by bioactive TGFβ, a cytokine known to promote CD103 expression by CD8 T cells[12] and which is ubiquitous at GVHD target sites such as the gut epithelium [13]. The gene discussed is CD8A; the disease is graft versus host disease.