Identification of commensal bacteria coated with secretory immunoglobulin A

　A part of commensal intestinal bacteria in mammal including human, mouse, bovine and pig are coated with secretory immunoglobulin A (S‒IgA). It has been suggested from our previous research that S‒IgA coating of commensal bacteria occur in bacterial group specific manner in human and mouse intestine. Thus, identification of S‒IgA‒coated bacterial genera/species would certainly help to elucidate the interaction between S‒IgA and commensal intestinal bacteria. However, the method to identify the genera/species of S‒IgA‒coated bacteria has not been established. To identify S‒IgA‒coated bacterial composition, we developed the method combining immunohistochemical detection of S‒IgA and subsequent 16S rRNA targeted fluorescence in situ hybridization (FISH) analysis. Furthermore, human and mice fecal S‒IgA coated bacterial composition was evaluated by this newly developed method with ten frequently‒used FISH probes. Fecal S‒IgA‒coated bacterial composition was successfully analyzed with this method and this analysis suggested that Enterobacteriaceae was preferably coated with S‒IgA whereas Bacteroides/Prevotella and Lactobacillus/ Enterococcus groups seemed to be poorly coated with S‒IgA. This method will be applied to confirm whether interaction between S‒IgA and commensal intestinal bacteria relate to symptom of inflammatory bowel diseases.

研究紹介 (Research Report)