Here, we investigated possible heterogeneity of naive CD8+ T cells, particularly in a context of inflammatory disease models, such as inflammatory bowel disease (IBD) and graft-versus-host disease (GVHD), where CD8+ T cells have been reported to differentiate into type 17 cytotoxic (Tc17) effector cells and cause immunopathological symptoms in mice and humans11–16. This evidence concerns the gene CD8A and graft versus host disease.