AGED LYMPHOCYTE-PROLIFERATION FOLLOWING INCORPORATION AND RETENTION OF DIETARY OMEGA-3-FATTY-ACIDS

T cell activation involves events at the plasma membrane; therefore, m olecules such as long chain omega-3 fatty acids that alter the structu re of the plasma membrane may affect the activation of aged T cells. I n this project we investigated whether the incorporation of omega-3 fa tty acids (from fish oil), in the presence of vitamin E, improves age- diminished T cell proliferation. Young and old mice were fed diets ric h in either fish (menhaden) oil or saturated fat for various lengths o f time. Splenocytes were harvested from these mice and stimulated in c ulture with either mitogen or the antigen keyhole limpet hemocyanin (f or a secondary response); proliferation was estimated by [H-3]thymidin e incorporation. We found no discernible effect of dietary omega-3 fat ty acids (with vitamin E supplementation) on lymphocyte proliferation stimulated by the mitogens concanavalin A or phytohemaggiutinin. We di d, however, find that the saturated fat diet and the menhaden oil diet in young mice lowered protein kinase C activities in the particulate fractions of spleen cells when compared to chow-fed mice. Middle-aged and old mice were less affected by the experimental diets than young m ice, but they demonstrated decreased protein kinase C activity as well . These alterations did not affect the ability of splenocytes to respo nd to mitogenic stimulation. Fatty acid analysis revealed that lymphoc ytes from mice fed saturated fat for 8.5 months retained significant a mounts of the omega-3 fatty acid docosahexaenoic acid, despite the lac k of dietary omega-3 fatty acids. However, when aged (but not young) l ymphocytes were clonally expanded by antigen in vivo in the presence o f dietary omega-3 fatty acids, they produced a greater secondary proli ferative response than old lymphocytes expanded during a saturated fat diet. Although our results suggest that omega-3 fatty acids may enhan ce aged lymphocyte proliferation, the tenacious retention of these fat ty acids makes comparison with omega-3-depleted lymphocytes difficult.