The composition of intestinal bacteria affects the level of luminal IgA.

An essential role of several specific intestinal bacteria in the intestinal IgA level is suggested. Fecal IgA concentration in mice from one breeder was significantly higher than that in mice from two other breeders. The level of segmented filamentous bacteria and four particular clostridia in mice from the former breeder are of particular importance in developing the IgA production and secretion system.