In addition, GvHD induced the NK/CD8+ T cell-associated effector molecules granzyme A and B and perforin (Gzma, Gzmb and Prf1) in donor Treg (in all organs, but again most evident in colon) suggesting that one of their protective mechanisms in GvHD involves the killing of donor Tconv or APC34–36 (for expression profiles of individual genes across all samples see Supplementary Fig. 4d). This evidence concerns the gene PRF1 and graft versus host disease.