title: The amount of secreted IgA may not determine the secretory IgA coating ratio of gastrointestinal bacteria.
abstract: It is reported that some, but not all, bacteria in human faeces are coated with secretory immunoglobulin A (S-IgA). We evaluated the proportion of S-IgA-coated bacteria to total intestinal bacteria (S-IgA coating ratio) in the gastrointestinal tract of two different strains of mice supplied by two different suppliers. The S-IgA coating ratio was significantly different in each gastrointestinal segment and between mouse suppliers. The amount of non-bacteria-bound IgA (free IgA) in each gastrointestinal segment indicated that this difference in the S-IgA coating ratio might not be due to the amount of secreted IgA. Furthermore, immunoblotting analysis revealed that only a small amount of IgA (<5% to free-IgA) was used for the coating. This indicates that, although sufficient S-IgA was secreted to coat the entire intestinal population of bacteria, only some part of the bacteria were coated with S-IgA. This study suggests that the amount of luminal S-IgA may not determine the S-IgA coating ratio, and that the amount of IgA coating intestinal commensal bacteria is very small.
authors.affiliation: Laboratory of Nutritional Biochemistry, Department of Bioscience and Chemistry, Faculty of Agriculture, Hokkaido University, Sapporo, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Tsuruta
authors.forename: Ryo
authors.initials: R
authors.lastname: Inoue
authors.forename: Iyori
authors.initials: I
authors.lastname: Nojima
authors.forename: Takamitsu
authors.initials: T
authors.lastname: Tsukahara
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Hara
authors.forename: Takaji
authors.initials: T
authors.lastname: Yajima
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000276:immunology*; D001419:Bacteria / Q000276:immunology*; D005260:Female; D041981:Gastrointestinal Tract / Q000276:immunology* / Q000382:microbiology*; D007071:Immunoglobulin A, Secretory / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL
chemical_list: D000907:Antibodies, Bacterial; D007071:Immunoglobulin A, Secretory