Impaired vitamin A-mediated mucosal IgA response in IL-5 receptor-knockoutmice

To clarify actions of vitamin A on mucosal immunity associated with interle ukin-5 (IL-5), we examined effects of vitamin A on mucosal IgA level in IL- 5 receptor alpha -chain-knockout (IL-5R alpha (-/-)) mice. Daily supplement ation of retinyl acetate (1 mg/mouse) increased Th2 cytokine levels and a n umber of their positive cells in the small intestinal mucosa of IL-5R alpha (-/-) mice, as observed in wild-type or IL-5R alpha (+/-) mice. Wild-type and heterozygous mice increased the IgA level and a number of IgA-containin g cells in the mucosa in response to the vitamin A treatment, but not in IL -5R alpha (-/-) mice. Retinyl acetate increased anti-cholera toxin (CT) IgA level in the mucosa of wild-type mice, improving their survival rate after an exposure to 0.4 mg of CT. However, retinyl acetate failed to induce res istance to CT toxicity in IL-5R alpha (-/-) mice. Our results suggest that IL-5 may play an important role in an action of vitamin A on mucosal IgA sy stem. (C) 2001 Academic Press.