DOCOSAHEXAENOIC ACID-INDUCED ALTERATION OF THY-1 AND CD8 EXPRESSION ON MURINE SPLENOCYTES

Here we test whether the incorporation of docosahexaenoic acid (DHA, 2 2:6), an (n - 3) fatty acid, into lymphocyte membranes affects the exp ression of the surface proteins Thy-1.2 and CD8. DHA was incorporated into splenocytes by three methods: feeding mice diets containing menha den (fish) oil, fusing splenocytes with DHA-containing phosphatidylcho line vesicles, and culturing splenocytes with DHA. Thy-1.2 and CD8 exp ression were measured by flow cytometry and complement-mediated lysis using a panel of monoclonal antibodies. As (n - 3) fatty acid incorpor ation into the lymphocytes increased, the expression of one Thy-1.2 ep itope and one CD8 epitope decreased; the expression of two CD8 epitope s increased. Although diet-induced changes in surface protein expressi on may result from selective migration of cell populations or the diet 's effect on protein biosynthesis, fusion with lipid vesicles demonstr ated that DHA-containing phospholipids can mediate a direct and immedi ate effect, The decrease in Thy-1.2 expression was sustained for more than a week after removal of (n - 3) fatty acids from the diet, most l ikely due to retention of membrane-bound (n - 3) fatty acids. Because Thy-1.2 and CD8 participate in T cell activation, modulation of their expression by DHA suggests that DHA, when serving as a membrane struct ural element, may alter immune function.