Single-cell RNA sequencing (scRNA-seq) of cells expressing T cell receptor β-chains (TCRβ) from the livers of mice with NASH showed that CD8+ T cells had gene expression profiles related to cytotoxicity and effector-function (for example, Gzmk and Gzmm) and inflammation markers (for example, Ccl3) with elevated exhaustion traits (for example, Pdcd1 and Tox) (Fig. 1d, e). The gene discussed is PDCD1; the disease is metabolic dysfunction-associated steatohepatitis.