Eosinophil depletion suppresses radiation-induced small intestinal fibrosis.

Radiation-induced intestinal fibrosis (RIF) is a serious complication after abdominal radiotherapy for pelvic tumor or peritoneal metastasis. Herein, we show that RIF is mediated by eosinophil interactions with α-smooth muscle actin-positive (α-SMA) stromal cells. Abdominal irradiation caused RIF especially in the submucosa (SM) of the small intestine, which was associated with the excessive accumulation of eosinophils in both human and mouse.

IL-10-producing CD4(+) T cells negatively regulate fucosylation of epithelial cells in the gut.

Fucosylated glycans on the surface of epithelial cells (ECs) regulate intestinal homeostasis by serving as attachment receptors and a nutrient source for some species of bacteria. We show here that epithelial fucosylation in the ileum is negatively regulated by IL-10-producing CD4(+) T cells. The number of fucosylated ECs was increased in the ileum of mice lacking T cells, especially those expressing αβ T cell receptor (TCR), CD4, and IL-10.

The mucosal immune system for vaccine development.

Mucosal surfaces are continuously exposed to the external environment and therefore represent the largest lymphoid organ of the body. In the mucosal immune system, gut-associated lymphoid tissues (GALTs), including Peyer's patches and isolated lymphoid follicles, play an important role in the induction of antigen-specific immune responses in the gut. GALTs have unique organogenesis characteristics and interact with the network of dendritic cells and T cells for the simultaneous induction and regulation of IgA responses and oral tolerance.

Innate lymphoid cells regulate intestinal epithelial cell glycosylation.

Fucosylation of intestinal epithelial cells, catalyzed by fucosyltransferase 2 (Fut2), is a major glycosylation mechanism of host-microbiota symbiosis. Commensal bacteria induce epithelial fucosylation, and epithelial fucose is used as a dietary carbohydrate by many of these bacteria. However, the molecular and cellular mechanisms that regulate the induction of epithelial fucosylation are unknown.

Blockade of TLR3 protects mice from lethal radiation-induced gastrointestinal syndrome.

High-dose ionizing radiation induces severe DNA damage in the epithelial stem cells in small intestinal crypts and causes gastrointestinal syndrome (GIS). Although the tumour suppressor p53 is a primary factor inducing death of crypt cells with DNA damage, its essential role in maintaining genome stability means inhibiting p53 to prevent GIS is not a viable strategy. Here we show that the innate immune receptor Toll-like receptor 3 (TLR3) is critical for the pathogenesis of GIS.

Nutritional components regulate the gut immune system and its association with intestinal immune disease development.

The gut is equipped with a unique immune system for maintaining immunological homeostasis, and its functional immune disruption can result in the development of immune diseases such as food allergy and intestinal inflammation. Accumulating evidence has demonstrated that nutritional components play an important role in the regulation of gut immune responses and also in the development of intestinal immune diseases. In this review, we focus on the immunological functions of lipids, vitamins, and nucleotides in the regulation of the intestinal immune system and as potential targets for the control of intestinal immune diseases.

An essential role for the N-terminal fragment of Toll-like receptor 9 in DNA sensing.

Toll-like receptor 9 (TLR9) is an innate immune sensor for microbial DNA that erroneously responds to self DNA in autoimmune disease. To prevent autoimmune responses, Toll-like receptor 9 is excluded from the cell surface and silenced until the N-terminal half of the ectodomain (TLR9N) is cleaved off in the endolysosome. Truncated Toll-like receptor 9 (TLR9C) senses ingested microbial DNA, although the precise role of the truncation remains controversial.

Microbe-dependent CD11b+ IgA+ plasma cells mediate robust early-phase intestinal IgA responses in mice.

Intestinal plasma cells predominantly produce immunoglobulin (Ig) A, however, their functional diversity remains poorly characterized. Here we show that murine intestinal IgA plasma cells can be newly classified into two populations on the basis of CD11b expression, which cannot be discriminated by currently known criteria such as general plasma cell markers, B cell origin and T cell dependence. CD11b(+) IgA(+) plasma cells require the lymphoid structure of Peyer's patches, produce more IgA than CD11b(-) IgA(+) plasma cells, proliferate vigorously, and require microbial stimulation and IL-10 for their development and maintenance.