Site differences of Toll-like receptor expression in the mucous epithelium of rat small intestine
Youhei Mantani1, Aosa Kamezaki1, Kankanam Gamage Sanath Udayanga1, Ei-ichirou Takahara1, Wang-Mei Qi2, Junichi Kawano1, Toshifumi Yokoyama1, Nobuhiko Hoshi1 and Hiroshi Kitagawa1
1Department of Bioresource Science, Graduate School of Agricultural Science and
2Department of Bioresource and Agrobioscience, Graduate of Science and Technology, Kobe University, Kobe, Japan.
Offprint requests to: Hiroshi Kitagawa, Laboratory of Animal Histophysiology, Graduate School of Agricultural Science, Kobe University, Kobe 657-8501, Japan. e-mail: hkitagaw@kobe-u.ac.jp
Summary. Toll-like receptors (TLRs) are known to recognize pathogen-associated molecular patterns and might function as receptors to detect microbes. In this study, the distribution of TLR-2, -4 and -9 were immunohistochemically investigated in the rat small intestine. As a result, TLR-2 was detected in the striated borders of villous columnar epithelial cells throughout the small intestine, except for the apices of a small number of intestinal villi. TLR-4 and -9 were detected in the striated borders of the villous columnar epithelial cells only in the duodenum. TLR-4-immunopositive minute granules were found in the apical cytoplasms of epithelial cells, subepithelial spaces and blood capillary lumina. TLR-2 and -4 were detected in the striated borders of undifferentiated epithelial cells and in the luminal substances of the intestinal crypts throughout the small intestine, but TLR-9 was not detected in the crypts throughout the small intestine. Only TLR-4 was detected in the secretory granules of Paneth cells in both the jejunal and ileal intestinal crypts. These findings suggest that duodenal TLRs might monitor indigenous bacteria proliferation in the upper alimentary tract, that TLR-2 might also monitor the proliferation of colonized indigenous bacteria throughout the small intestine, that the lack of TLR-2 at the villous apices might contribute to the settlement of indigenous bacteria, and that TLR-2 and -4 are secreted from intestinal crypts. Histol Histopathol 26, 1295-1303 (2011)
Key words: Epithelium, Immunohistochemistry, Rat, Small intestine, Toll-like receptors
DOI: 10.14670/HH-26.1295