Inhibition of lymphocyte proliferation by free fatty acids. II. Toxicity of stearic acid towards phytohaemagglutinin-activated T cells.

Studies were performed to further characterize the effects of saturated fatty acids on murine T lymphocyte proliferation. Flow cytometry was used to show that the inhibitory effects of stearic acid (18:0) on [3H]thymidine uptake can be correlated with changes in cellular DNA content. Additional studies using flow cytometry and fluorescein diacetate as a viability stain showed that exogenous 18:0 was toxic for phytohemagglutinin (PHA)-stimulated T cells, whereas the viability of unstimulated T cells was less affected by 18:0. The inhibitory effects of 18:0 on T cell proliferation were evident as early as 4 hr after fatty acid addition and after a 10-hr exposure, the effects of 18:0 could not be reversed by washing the cells or by adding oleic acid (18:1). It is proposed that the inhibitory effects of 18:0 are dependent upon PHA-induced changes in T cell lipid metabolism.