title: Microbial colonization drives lymphocyte accumulation and differentiation in the follicle-associated epithelium of Peyer's patches.
abstract: Peyer's patches (PPs) are lined by follicle-associated epithelium (FAE) with Ag-transporting M cells. To investigate the spatial relationships of B cells, T cells, and dendritic cells (DCs) in PPs during microbial colonization, their in situ redistribution was examined in germfree (GF) rats exposed to a conventional pathogen-free microflora (conventionalized, CV). Although occasional B and T cells occurred in the FAE of GF rats, it contained mainly immature DCs (CD4(+)CD86(-)), whereas mature DCs (CD86(high)) were seen in the interfollicular zones even under GF conditions. In CV rats, DCs had disappeared from the FAE, which instead contained clusters by B and T cells associated with induction of putative M cell pockets. CD86 was seen neither in the FAE nor in the follicles under GF conditions, but it became apparent on intraepithelial B cells 5 wk after colonization. The level of CD86 on these B cells was comparable to that on germinal center B cells, although the B cell follicles did not show direct contact with the M cell areas. B cells in the follicular mantles acquired Bcl-2 after 12 wk in CV rats, whereas B cells in the FAE did not express Bcl-2 at a substantial level throughout the experimental period. The cellular redistribution patterns and phenotypic characteristics observed after colonization suggested that immature DCs, but not B cells, are involved in Ag presentation during primary immune responses against intestinal bacteria. However, the spatial cellular relationships sequentially being established among DCs, B cells, and T cells in PPs, are most likely important for the induction of post-germinal center B cells subsequently residing within the M cell pockets.
authors.affiliation: Laboratory for Immunohistochemistry and Immunopathology, Institute of Pathology, University of Oslo, Rikshospitalet, Norway.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Yamanaka
authors.forename: Lars
authors.initials: L
authors.lastname: Helgeland
authors.forename: Inger Nina
authors.initials: IN
authors.lastname: Farstad
authors.forename: Hisanori
authors.initials: H
authors.lastname: Fukushima
authors.forename: Tore
authors.initials: T
authors.lastname: Midtvedt
authors.forename: Per
authors.initials: P
authors.lastname: Brandtzaeg
mesh_terms: D000818:Animals; D016175:B-Lymphocyte Subsets / Q000166:cytology / Q000276:immunology / Q000378:metabolism / Q000382:microbiology; D001419:Bacteria / Q000254:growth & development* / Q000276:immunology; D002454:Cell Differentiation / Q000276:immunology; D002465:Cell Movement / Q000276:immunology*; D016130:Immunophenotyping; D007413:Intestinal Mucosa / Q000166:cytology / Q000276:immunology* / Q000382:microbiology*; D016131:Lymphocyte Subsets / Q000166:cytology* / Q000382:microbiology; D010581:Peyer's Patches / Q000166:cytology / Q000276:immunology* / Q000378:metabolism / Q000382:microbiology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis; D051381:Rats; D011919:Rats, Inbred Strains; D016176:T-Lymphocyte Subsets / Q000166:cytology / Q000382:microbiology
chemical_list: D019253:Proto-Oncogene Proteins c-bcl-2