ASTAXANTHIN, A CAROTENOID WITHOUT VITAMIN-A ACTIVITY, AUGMENTS ANTIBODY-RESPONSES IN CULTURES INCLUDING T-HELPER CELL CLONES AND SUBOPTIMALDOSES OF ANTIGEN

Astaxanthin, a carotenoid without vitamin A activity, enhances T-depen dent antigen (Ag)-specific humoral immune responses. We examined carot enoid actions on T-helper (Th) cell activity in a direct manner with r econstitution experiments; spleen Th cells were replaced with Ag-speci fic Type 1 and Type 2 (Th1 and Th2) Th cell clones. The Ag for the Th1 and Th2 clones were pigeon cytochrome C and rabbit gamma-globulin, re spectively. Astaxanthin and beta-carotene augmented the number of IgM antibody (Ab)-secreting cells when unprimed B cells were incubated wit h Th clones and stimulated with suboptimal doses of Ag specific for ea ch Th clone. The number of IgG Ab-secreting cells were greater with us e of in vivo primed B cells than with unprimed B cells in both Th clon es. Astaxanthin but not beta-carotene augmented the number of IgG Ab-s ecreting cells when primed B cells and Th cell clones were stimulated with suboptimal doses of Ag specific for each Th clone. In the presenc e of optimal doses of Ag for each Th clone, neither carotenoid augment ed the number of Ab-secreting cells. Astaxanthin and beta-carotene may enhance the actions of both Th1 and Th2 cells for humoral immune resp onses with suboptimal Ag challenges; certain carotenoids may help main tain Ag-mediated immune responses at optimal levels.