Identification of activated T cell receptor γδ lymphocytes in the liver of tumor-bearing hosts

T cell receptor (TcR)γδ cells are known to be a minor population of T lymphocytes in the blood (< 10%) and other peripheral lymphoid organs in healthy donors. We demonstrated here that a large proportion of TcRγδ cells, i.e., up to 30% of mononuclear cells (MNC) were detectable in the liver, but not other lymphoid organs of cancer patients. More importantly, the majority of such TcRγδ cells (> 70%) were shown to be lymphoblastic by electron microscopy. An activation marker of T lymphocytes, Leu-19 (CD56) was also highly expressed on the hepatic TcRγδ cells. The possibility of hepatic TcRγδ cells being activated was further examined in mice. C3H/He mice injected with syngeneic tumor cells were demonstrated to have an increased number of liver MNC; such MNC showed an ability to proliferate in vitro. These mice eventually had a considerable proportion of TcRγδ cells in the liver, showing activation markers, the Ia and LFA-1 antigens. These results suggest that the liver may be an important organ for activation and probably expansion of TcRγδ cells especially in tumor bearing hosts.