Dietary fructooligosaccharides up-regulate immunoglobulin A response and polymeric immunoglobulin receptor expression in intestines of infant mice

We examined whether or not dietary fructooligosaccharides (FOS) in infancy can have a beneficial effect on the mucosal immune system. Newborn BALB/c mice, accompanied by their dams until 21 days of age, were fed either a control diet based on casein [FOS(-) diet group] or a FOS(-) diet supplemented with 5% (w/w) FOS [FOS(+) diet group]. Total IgA levels in tissue extracts from the intestines of mice in the FOS(+) diet group at 38 days of age were about twofold higher (P < 0.05) than those in the FOS(-) diet group in the jejunum, ileum and colon. Ileal and colonic polymeric immunoglobulin receptor (pIgR) expression in the FOS(+) diet group at 36 days of age was 1.5-fold higher than in the FOS(-) diet group (P < 0.05). Consistent with these results, the ileal IgA secretion rate of the FOS(+) diet group at 37 days of age was twofold higher than that of the FOS(-) diet group (P < 0.05). Moreover, the percentage of B220(+)IgA(+) cells in Peyer's patches (PP) was significantly higher in the FOS(+) diet group than in the FOS(-) diet group (6.2% versus 4.3%, P < 0.05), suggesting that isotype switching from IgM to IgA in PP B cells might be enhanced in vivo. Taken together, our findings suggest that dietary FOS increases the intestinal IgA response and pIgR expression in the small intestine as well as the colon in infant mice.