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. Here, CD8A is linked to inflammatory bowel disease.