Subsequently, PD-1 is upregulated in the intrahepatic CD8+ T cells and they stop producing IFNγ, start expressing granzyme B (GrB) and undergo massive expansion [21] thereby mediating a necroinflammatory liver disease and terminating viral gene expression whereupon the intrahepatic CD8+ T cell population contracts, liver disease abates and IFNγ production returns [21]. The gene discussed is CD8A; the disease is liver disorder.