Regulation of human lymphocyte proliferation by fatty acids

In the present study, the effect of increasing concentrations of palmitic (PA, C 16:0), stearic (SA, C18:0), oleic (OA, C18:1, n-9), linoleic (LA, C18:2n-6), docosahexaenoic (DHA, C22:6 n-3) and eicosapentaenoic (EPA, C20:5 n-3) acids on lymphocyte proliferation was investigated. The maximal non-toxic concentrations of these fatty acids for human lymphocytes in vitro were determined. It was also evaluated whether these fatty acids at non-toxic concentrations affect IL-2 induced lymphocyte proliferation and cell cycle progression. OA and LA at 25 mu M increased lymphocyte proliferation and at higher concentrations (75 mu M and 100 mu M) inhibited it. Both fatty acids promoted cell death at 200 mu M concentration. PA and SA decreased lymphocyte proliferation at 50 mu M and promoted cell death at concentrations of 100 mu M and above. EPA and DHA decreased lymphocyte proliferation at 25 and 50 mu M being toxic at 50 and 100 mu M, respectively. PA, SA, DHA and EPA decreased the stimulatory effect of IL-2 on lymphocyte proliferation, increasing the percentage of cells in G1 phase and decreasing the proportion of cells in S and G2/M phases. OA and LA caused an even greater pronounced effect. The treatment with all fatty acids increased neutral lipid accumulation in the cells but the effect was more pronounced with PA and DHA. In conclusion, PA, SA, DHA and EPA decreased lymphocyte proliferation, whereas OA and LA stimulated it at non-toxic concentrations. Copyright (c) 2006 John Wiley & Sons, Ltd.