Eicosapentaenoic acid modulates the immune response but has no effect on a mimic of antigen-specific responses

It has been suggested that the omega-3 polyunsaturated fatty acid eicosapentaenoic acid (EPA) has immunosuppressive effects and that these may be detrimental in some circumstances. Many studies have used high-fat diets or have concentrated on one aspect of immune function, such as mitogen-induced proliferation. In the present study we assessed the effect of high-purity EPA provided as a novel diester with propane-1,3-diol, which was delivered orally within the normal dietary fat content.

Mitogen-induced proliferation and a mimic of antigen-specific splenocyte proliferation were examined. Proinflammatory cytokine production in response to lipopolysaccharide ex vivo was also measured. Balb/c mice were fed a fat-free diet to which was added oil to make up 5% of the final diet weight by using corn oil or 95% pure EPA as a diester with propane-1,3-diol (4%, plus 1% corn oil).

There was no difference in food consumption or weight gain between mice fed the control and EPA-enriched diets for 10 or 24 d. There was a significant decrease in the splenocyte proliferation index in animals fed the EPA-enriched diet after 10 and 24 d when stimulated by concanavalin A (P<0.05), but no difference when cells were stimulated with anti-CD3 and interleukin-2. There was a significant increase in the production of tumor necrosis factor by splenocytes of mice fed the EPA-enriched diet when stimulated by lipopolysaccharide (P<0.0005). However, there was no difference in ex vivo lipopolysaccharide-stimulated production of interleukin-6 between the two diets at either time point (P>0.05).

The present study found that, rather than producing a generalized immunosuppression, the administration of approximately 10 g of EPA/kg of body weight has more subtle effects in modulating the immune system. The observed effects of EPA may explain some of its reported beneficial effects in inflammatory conditions without producing detrimental effects on antigen-specific immunosurveillance.