Association of Extrathymic Pathway of T Cell Differentiation with Anti-tumor Immunity : Specific Activation of the Hepatic Extrathymic Pathway and Analysis of Anti-tumor Cytotoxicity in Mice Bearing with Syngeneic Tumors

The thymus is the major central organ for T cell differentiation in the body. However attention was recently focused on an association of extrathymic T cells with various immune response. The liver is a major site for such extrathymic T cell differentiation. Cumulative evidences revealed that extrathymic T cells in the liver comprise cells with TCR of intermediate intensity and contain autoreactive clones. These extrathymic T cells were activated with aging and under conditions of bacterial stimulation and autoimmune diseases. In the present study, it was investigated how regular T cells were activated in mice injected with viable syngeneic tumors. It was demonstrated that specific activation of extrathymic T cells in the liver and acquisition of anti-tumor cytotoxicity were induced in these mice. The present results suggested that extrathymic T cells played an important role on tumor immunity in the host-defense mechanisms