Differential expression of Toll-like receptor-2, -4 and -9 in follicle-associated epithelium from epithelia of both follicle-associated intestinal villi and ordinary intestinal villi in rat Peyer’s patches

Abstract

The expressions of Toll-like receptor (TLR) -2, -4 and -9 were immunohistochemically investigated in the follicle-associated epithelium (FAE), and epithelia of the follicle-associated intestinal villus (FAIV) and ordinary intestinal villus (IV) in rat Peyer’s patch regions with no bacterial colonies on the mucous membranes. TLR-2 was expressed in the striated borders of microvillous columnar epithelial cells (MV) in both FAIV and IV except in the apices. However, TLR-2 expression in the striated borders was weaker in the epithelium of the follicular side of FAIV (f-FAIV) than in epithelia of IV and the anti-follicular side of FAIV. TLR-4 and -9 were not expressed in the FAIV and IV. In the FAE, TLR-2, -4 and -9 were not expressed in the striated borders of MV, but the roofs of some typical M-cells were immunopositive for all TLRs. Especially, no TLR-positive MV were found at the FAE sites where M-cells appeared most frequently. In the follicle-associated intestinal crypt (FAIC), immunopositivity for all TLRs was observed in the striated borders of MV and the luminal substances. In conclusion, the lower levels of TLR-2 in both FAE and the epithelium of f-FAIV probably reduce recognition of indigenous bacteria. TLR-2, -4 and -9 appear not to participate directly in differentiation of MV into M-cells, because TLRs were not expressed in any MV in the upstream region of M-cells in FAE with no settlement of indigenous bacteria in the rat Peyer’s patches.

The role of toll like receptor 9 in maintaining gut homeostasis

“…Transcriptional modulation of pattern recognition receptors in chronic colitis in mice is accompanied by Th1 and TH17 responses[14].Site-specifi c expression of TLR9 is also more distinct in the small intestine than colon. Specifi cally, while small intestinal ordinary villi are immune-negative for TLR9, the roof of M-cells of follicle-associated epithelium are immune-positive for TLR9[15]. Taken together, these data suggest that cellspecifi c TLR9 expression may be constitutive or inducible and its function may be pro-or anti-infl ammatory depending on whether the TLR9 examined is located on the surface or within the endosome.…”

Effects of the expansion of bacterial colonies into the intervillous spaces on the localization of several lymphocyte lineages in the rat ileum

“…The following two types of mucosa were investigated: 1) ordinary mucosa, which were defined as mucosa without any mucosal lymphatic tissue such as Peyer’s patches, isolated lymphatic follicles or cryptopatches; and 2) follicle-associated mucosa (FAM), which accompanied the parafollicular area under the muscularis mucosae in Peyer’s patches in the rat ileum. Then, the intestinal villus was classified into two groups: intestinal villus in the ordinary mucosa (IV) and intestinal villus in FAM (IV-FAM), including the follicle-associated intestinal villus (FAIV), which we defined as the intestinal villus just adjacent to the lymphatic follicle in our previous study [48]. Moreover, the intestinal crypts were classified into two groups: intestinal crypts in the ordinary mucosa (IC) and intestinal crypts in FAM (IC-FAM), including follicle-associated intestinal crypts (FAIC), which we defined as intestinal crypts just adjacent to the lymphatic follicle in our previous study [48] (Fig.…”

Mechanism of M-cell differentiation accelerated by proliferation of indigenous bacteria in rat Peyer’s patches

“…For the detection of RANK, RANKL or cleaved caspase-3, the tissue blocks from another 10 rats were immersion-fixed in 4.0% paraformaldehyde fixative in PB for 1 hr at 4°C. Then, all tissue blocks were snap-frozen in liquid nitrogen with reference to the embedding method described previously [ 28 ]. Four micrometer-thick sections were cut using a Coldtome CM1950 (Leica Biosystems, Nussloch, Germany) and were placed on slide glasses precoated with 2% 3-aminopropyltriethoxysilane (Shin-Etsu Chemical, Tokyo, Japan) and stored at −30°C until use.…”

“…An LF consists of a dome area, follicular area, parafollicular area and follicle-associated epithelium (FAE); the FAE is composed of predominant microvillous columnar epithelial cells (MV), rare goblet cells and a few M-cells [ 3 , 4 , 18 , 28 ]. The M-cell is a specialized epithelial cell that functions in the transportation of antigenic substances from the intestinal lumen to the subepithelial immunocompetent cells, thereby initiating mucosal immune responses [ 17 , 18 ].…”

“…In a previous study, based on the finding that stimulation from indigenous bacteria on the FAE activate the differentiation into M-cells [ 4 ], we speculated that the pinocytosis of MV for the differentiation into M-cells was related to the receptors for bacterial recognition, specifically the Toll-like receptors (TLR) -2, -4 and -9 [ 28 ], which recognize the peptidoglycan, lipoprotein and lipoteichoic acid (TLR-2), the lipopolysaccharide (TLR-4) and the unmethylated CpG sequences (TLR-9) in DNA, respectively [ 1 , 12 ]. However, no MV, which are the precursor cells of M-cells, express TLR-2, -4 or -9 in the LFs that lack bacterial colonies on the FAE [ 28 ]. On the other hand, the expressions of TLRs in the epithelia are increased by stimulation with TLR-ligands in the murine colon [ 6 , 14 ] and bovine mammary [ 11 ].…”