IL17A and graft versus host disease: They used sorted CD3+ T cells in NHP and CD4+ and CD8+ T cells in humans in both supervised and unsupervised gene expression analyses for the identification of pathways controlling GVHD, and discovered three transcriptional hallmarks of breakthrough aGVHD that are not observed in hyperacute GVHD: (1) T cell persistence rather than proliferation, (2) a highly inflammatory programming, (3) a T helper (Th)/Tc1-mediated dysfunction driven by inflammatory IL-17 dominated pathways (38).