[Effect of glycosphingolipids on the activity of natural killer cells].

The effects of exogenous glycosphingolipids on the cytotoxic activity of natural killer (NK) cells and on the sensitivity of target cells were studied. Incubation of splenocytes with gangliosides of the hemato-series (GM3 and GD3) or with their precursor, LacCer, decreases the cytotoxic NK-activity, whereas some other acidic and neutral glycolipids do not possess such capability. On the other hand, incubation of target (YAC lymphoma) cells with glycolipids of the hemato-series increases the sensitivity of these cells to the cytotoxic action of NK-cells. A comparison of the ganglioside profiles of two YAC call lines differing in their NK-sensitivity revealed the presence of a GD3-like component in the highly sensitive cell line and the absence of this ganglioside in low sensitive target cells. It is assumed that gangliosides of the hemato-series are components of the acceptor complex on the surface of the target cells and that shedding of these gangliosides (especially, of GD3) by tumour cells is one possible mechanism of NK-activity suppression during malignant growth.