Mechanistic understandings of liver damage in NASH are incomplete. In this article, using a preclinical mouse model that displays key features of human NASH, M. Dudek et al. (Technical University of Munich, Germany) found an indispensable role for T cells in liver immunopathology. The authors detected hepatic accumulation of CD8 T cells with phenotypes that combined tissue residency with effector and exhaustion characteristics in NASH mice and in patients with NASH. Activation of CD8 T cells during NAFL and NASH are attributed to metabolic signals such as acetate and extracellular ATP.