Carotenoid action on cloned, effector-stage murine thelper cell activities

T-helper (Th) cells are key regulators of the immune system and are likely targets for the immunomodulating action of carotene ids. Astaxanthin, a carotenoid without provitamin A activity, enhances T-helper (Th) cell clonemediated antibody (Ab) production with suboptimal antigen (Ag) challenges in rodent animal models, Th clones are in the stage of effector Th cells and produce large amounts of cytokines. Two major subsets, Thl and Th2 cells, are defined on the basis of cytokine production,. Thl cells produce iL-2 and IFNy, and Th2 cells produce IL-4 and IL-5. In this study, we examine the effects of carotenoids (astaxanthin and -carotene) on cytokine production (protein and mRNA levels of IFNy, IL-4 and IL-5). A.E7 cells and CDC35 cells are Thl and Th2 clones, respectively. Irradiated primed or naive spleen cells are the source of Agpresenting cells (APC). In the incubation of Thl cells with primed spleen cells, astaxanthin suppresses IFNy protein and mRNA expression. Also, -carotene suppresses the expression of IFNy protein. Neither carotenoid affects IFNy production with the use of naive (unprimed) spleen cells. Neither astaxanthin nor -carotene alters IL-4 or IL-5 protein or mRNA expression by the Th2 clone. Other carotenoids with various antioxidant activities (zeaxanthin, lutein, lycopene, and cantaxanthin) do not suppress IFNy production by A.E7 cells. Astaxanthin's suppressive action on IFNy production by Thl cells may explain its enhancing action on Thl clone-mediated Ab production; IFNy suppresses humoral immune responses.