Rat liver contains a distinct blood-borne population of NK cells resistant to anti-asialo-GM1 antiserum.

A high level of anti-tumoral (NK) cytotoxicity was observed in the mononuclear population washed out from the liver microvasculature in rat. The level of cytotoxicity against K562 and YAC1 cells, percentage of large granular lymphocytes (LGL) and of OX8+ cells was significantly higher than in the inflowing portal and also caval blood. A low concentration of adherent, phagocytic and OX6+(Ia) cells and a higher level of cytotoxicity after removal of adherent cells ruled out the possibility of liver macrophages to be responsible for the cytotoxicity. Surprisingly, the liver-sequestered NK population turned to be resistant to anti-asialo-GM1 antiserum. Thus, liver microvasculature contains a significant number of cells with characteristics of NK cells which constitute a functionally distinct NK population.