Modulation of rat and human lymphocyte function by n-6 and n-3 polyunsaturated fatty acids and acetylsalicylic acid.

The effects of in vitro additions of between 10 and 100 microM n-6 and n-3 polyunsaturated fatty acids were examined on the proliferation of stimulated T lymphocytes in culture. For both phytohemagglutinin-induced human blood lymphocytes and concanavalin-A-induced rat splenic lymphocytes, the largest inhibitory effects were obtained with 22:4 n-6 and 22:6 n-3, and to a lesser extent with 20:5 n-3. Arachidonic acid 20:4 n-6, the main eicosanoid precursor, was not inhibitory, it even stimulated rat lymphocyte proliferation. Acetylsalicylic acid stimulated both human and rat lymphocyte proliferation. The effects of moderate decreases in the dietary n-6/n-3 ratio by either linseed oil or fish oil maximum eicosapentaenoic acid (MaxEPA) were determined on rat lymphocyte proliferation and natural killer (NK) cell activity in vitro. Dietary changes did not affect mitogen-induced lymphocyte proliferation in vitro, but proliferation of unstimulated lymphocytes was significantly lowered (4-fold) with the n-3-enriched diets. Dietary fish oil but not linseed oil significantly increased the NK cell activity of rat splenic lymphocytes. The n-3-enriched diets, especially the fish oil diets, reduced the stimulatory effect of in vitro added acetylsalicylic acid (aspirin) on lymphocyte proliferation.