Liver-Resident NK Cells Control Antiviral Activity of Hepatic T Cells via the PD-1-PD-L1 Axis.

The tolerogenic microenvironment of the liver is associated with impaired hepatic T cell function. Here, we examined the contribution of liver-resident natural killer (LrNK) cells, a prominent hepatic NK cell compartment, to T cell antiviral responses in the liver. The number of virus-specific T cells increased in LrNK-cell-deficient mice during both acute and chronic lymphocytic choriomeningitis virus infection. Upon infection with adenovirus, hepatic T cells from these mice produced more cytokines, which was accompanied by reduced viral loads. Transfer of LrNK cells into LrNK-cell-deficient or wild-type mice inhibited hepatic T cell function, resulting in impaired viral clearance, whereas transfer of conventional NK cells promoted T cell antiviral responses. LrNK-cell-mediated inhibition of T cell function was dependent on the PD-1-PD-L1 axis. Our findings reveal a role for LrNK cells in the regulation of T cell immunity and provide insight into the mechanisms of immune tolerance in the liver.