KLRK1 and Hepatic fibrosis: Mice with NK cell-specific knockout metabotropic glutamate receptor 5 (mGluR5) have aggravated CCl4-induced liver fibrosis compared to wild-type mice. In contrast, activation of mGluR5 can increase NK cell cytotoxicity against activated HSCs by upregulating the expression of anti-fibrotic genes, such as PRF1 (perforin), KLRK1 (killer cell lectin-like receptor K1), and IFN-γ production.