Dietary n‐3 PUFA affect TcR‐mediated activation of purified murine T cells and accessory cell function in co‐cultures

Summary Diets enriched in n‐3 polyunsaturated fatty acids (PUFA) suppress several functions of murine splenic T cells by acting directly on the T cells and/or indirectly on accessory cells. In this study, the relative contribution of highly purified populations of the two cell types to the dietary suppression of T cell function was examined. Mice were fed diets containing different levels of n‐3 PUFA; safflower oil (SAF; control containing no n‐3 PUFA), fish oil (FO) at 2% and 4%, or 1% purified docosahexaenoic acid (DHA) for 2 weeks. Purified (>90%) T cells were obtained from the spleen, and accessory cells (>95% adherent, esterase‐positive) were obtained by peritoneal lavage. Purified T cells or accessory cells from each diet group were co‐cultured with the alternative cell type from every other diet group, yielding a total of 16 different co‐culture combinations. The T cells were stimulated with either concanavalin A (ConA) or antibodies to the T cell receptor (TcR)/CD3 complex and the costimulatory molecule CD28 (αCD3/αCD28), and proliferation was measured after four days. Suppression of T cell proliferation in the co‐cultures was dependent upon the dose of dietary n‐3 PUFA fed to mice from which the T cells were derived, irrespective of the dietary treatment of accessory cell donors. The greatest dietary effect was seen in mice consuming the DHA diet (P = 0·034 in the anova; P=0·0053 in the Trend Test), and was observed with direct stimulation of the T cell receptor and CD28 costimulatory ligand, but not with ConA. A significant dietary effect was also contributed accessory cells (P = 0·033 in the Trend Test). We conclude that dietary n‐3 PUFA affect TcR‐mediated by T cell activation by both direct and indirect (accessory cell) mechanisms.