Effect of fatty acid modifications of cultured hepatoma cells on susceptibility to complement-mediated cytolysis.

The fatty acid composition of Morris Hepatoma 7777 cells was modified by exposure to culture media that were supplemented with 0.1 to 0.36 mM oleic or linoleic acid for 5 days. Changes occurred in the fatty acid composition of both the cellular phospholipid and the neutral lipid fractions. Exposure to linoleic acid caused a large increase in the polyunsaturated fatty acid content of the cell lipids, whereas enrichment in monoenoic fatty acids occurred when the cells were exposed to high levels of oleic acid. Cellular phospholipid content decreased, cholesterol content did not change, and triglyceride content increased as a result of fatty acid supplementation. The fatty acid-modified cells showed increased susceptibility to complement-mediated cytolysis as compared with control cells grown in unsupplemented culture media. The extent of the increase in susceptibility to cytolysis depended on the degree of lipid modification and also on the cell number and antibody titer used in the assay. Cells enriched with linoleic acid were the most susceptible, but oleic acid enrichment also produced increased susceptibility to immune cytolysis. The kinetic study showed that the initial rate of cytolysis was higher in fatty acid-modified cells than in the control cells. There was no difference in the osmotic fragility of the control and fatty acid-modified cells. These results indicate that changes in the lipid composition of a target cell can influence its susceptibility to complement-dependent cytolysis.