Development of a method for the identification of S-IgA-coated bacterial composition in mouse and human feces

Some commensal intestinal bacteria in humans and mice are coated with secretory immunoglobulin A (S-IgA). It has been suggested that the S-IgA coating of commensal bacteria does not occur at random and thus identification of S-IgA-coated bacterial genera/species should help in elucidating the interaction between S-IgA and commensal intestinal bacteria, but no method of identifying the genera/species of S-IgAcoated bacteria has been established. To identify S-IgAcoated bacterial composition, we developed a method combining immunohistochemical detection of S-IgA and subsequent 16S rRNA targeted fluorescence in situ hybridization (FISH) analysis. Human and mouse fecal S-IgA coated bacterial composition was evaluated by this newly developed method with 10 frequently-used FISH probes. Fecal S-IgA-coated bacterial composition was successfully analyzed by this method, and this suggests that Enterobacteriaceae is preferably coated with S-IgA, whereas Bacteroides/Prevotella and Lactobacillus/Enterococcus groups appear to be poorly coated with S-IgA.