Administering PD-1 antibody to aging mice or non-alcoholic steatohepatitis (NASH) mice lead to the reduction on the number of p16+ cells as well as the activated CD8+ T cell-dependent PD-L1+ population in vivo, ameliorating various aging-related phenotypes (18). The gene discussed is PDCD1; the disease is metabolic dysfunction-associated steatohepatitis.