Liver sinusoidal blood containing natural killer-like cells.

Rat liver sinusoidal washout cells were examined. These cells, which are marginated in sinusoids, could be washed out by simple flushing of the vasculature with culture media without enzymes and under physiological portal pressure. They revealed, in comparison to peripheral blood mononuclear cells, high cytotoxic activity commonly attributed to the natural killer (NK) and natural cytotoxic (NC) cells, and were found to be anti-asialo-GM1-negative. Liver sinusoidal cytotoxic cell (LSCC) activity has been found to be associated with the large granular lymphocytes in low-density cells in OX8-positive as well as in OX8-negative populations. The mononuclear cells washed out from the liver microvasculature could be stimulated with NK-sensitive targets to release soluble factors which selectively lyse YAC-1 tumour cells and inhibit growth of normal haematopoietic granulocyte-macrophage colony-forming cells in vitro. The cytotoxic cell population in the liver turned out to be blood-borne in origin and not resident. Our findings suggest that liver sinusoidal cytotoxic cells represent an NK population with a predilection for marginating in the liver and may be important in eliminating tumour or virus infected cells passing through the liver from the circulation. The mechanism of their accumulation in liver sinusoids remains unclear.