Abstract
Rats were fed for 12 weeks on a low fat (LF; 2.5% by weight) diet or on one of five high fat (20% by weight) diets; the latter contained hydrogenated coconut oil (HCO), olive oil (OO), safflower oil (SO), evening primrose oil (EPO) or menhaden (fish) oil (MO). Feeding the EPO or MO diets resulted in inhibition of mitogen-stimulated spleen lymphocyte proliferation compared with feeding any of the other diets; in addition, feeding the OO diet resulted in inhibition of proliferation compared with feeding the LF diet. Feeding the OO, EPO or MO diets resulted in inhibition of spleen lymphocyte natural killer (NK) cell activity compared with feeding the LF or HCO diets; feeding the SO diet resulted in inhibition of NK cell activity compared with feeding the HCO diet. There was no effect of dietary lipid manipulation upon the proportion of T-cells or of CD4+ or CD8+ cells in the spleen. The level of expression of CD2 on CD4+ and CD8+ spleen lymphocytes was decreased by MO feeding compared with feeding the LF, HCO, SO or EPO diets; OO feeding decreased the level of expression of CD2 on CD4+ spleen lymphocytes compared with feeding the LF diet. The level of expression of LFA-1 was decreased on both CD4+ and CD8+ spleen lymphocytes from animals fed the OO or MO diets compared with that on lymphocytes from animals fed some of the other diets. Following mitogenic stimulation the level of expression of CD8, CD2, ICAM-1, LFA-1 and the interleukin-2 receptor was lower on spleen lymphocytes from animals fed the MO diet and, for some of the markers, on those from animals fed the OO or EPO diets. These observations indicate that diets containing MO, OO and EPO exert immunomodulatory effects by influencing the expression of important molecules upon the lymphocyte surface. This may occur through effects on signal transduction pathways and/or gene expression.