Immunoprivileged status of the liver is controlled by Toll-like receptor 3 signaling

The liver is known to be a classical immunoprivileged site with a relatively high resistance against immune responses. Here we demonstrate that highly activated liver-specific effector CD8(+) T cells alone were not sufficient to trigger immune destruction of the liver in mice. Only additional innate immune signals orchestrated by TLR3 provoked liver damage. While TLR3 activation did not directly alter liver-specific CD8(+) T cell function, it induced IFN-alpha and TNF-alpha release. These cytokines generated expression of the chemokine CXCL9 in the liver, thereby enhancing CD8(+) T cell infiltration and liver disease in mice. Thus, nonspecific activation of innate immunity can drastically enhance susceptibility to immune destruction of a solid organ.