Effects of orally ingested Bifidobacterium longum on the mucosal IgA response of mice to dietary antigens

To study the effects of lactic acid bacteria on the mucosal defence against dietary protein antigens, we compared the mucosal IgA responses to beta-lactoglobulin (beta-LG) of two groups of mice fed a whey protein diet with and without a culture condensate of Bifidobacterium longum. Both total IgA and anti-beta-LG IgA levels in tissue extracts of the small intestinal wall were significantly higher in mice fed the B. longum diet for 2 weeks than in control ones. Peyer's patch (PP) cells from B. longum-fed mice had a much larger increase in in vitro IgA production than ones from control mice. Furthermore, the in vitro IgA response to beta-LG was detected only when PP cells from B. longum-fed mice were assayed. These results suggest that orally ingested lactic acid bacteria may protect a host from invasion of the intestinal mucosa by dietary antigens that have escaped enzymatic digestion in the intestine.