Suppressive mechanisms of EPA on human T cell proliferation

In vivo and in vitro experiments show that polyunsaturated fatty acids (PUF As) including eicosapentaenoic acid (EPA) inhibit mitogen- or antigen-stimu lated proliferation of T cells in rodents and humans. However, the exact ma nner and mechanisms by which PUFA inhibits T cell proliferation is not clea r. In the present study, we investigated the suppressive effects of EPA, an n-3 PUFA, on PHA stimulated human peripheral blood T cells, Our results sh owed that EPA suppresses mitogen- or antigen-stimulated human T cell prolif eration by at least 2 steps; step 1) EPA suppresses T cell proliferation by inhibiting IL-2R alpha expression and IL-2 production; step 2) EPA induces cell death of blast T cells without reducing the expression of IL-2R alpha . We also showed that EPA selectively stimulates the cell death of blast T cells but not resting T cells, The suppressive effect of EPA was mediated v ia the production of reactive oxygen products, because EPA-stimulated H2O2 production and the suppressive effect of EPA was restored by addition of ca talase or NAG. These results taken together suggest that such immunosuppres sive effects of EPA may explain the apparent benefits of EPA-enriched diets for patients with inflammatory disorders.