Apelin expression is downregulated in T cells in a murine model of chronic colitis.

Apelin (APL), an endogenous ligand for APJ, has been reported to be upregulated in a murine model of acute colitis induced by sodium dextran sulfate, as well as inflammatory bowel diseases (IBD) in humans. However, the mechanisms and functions of APL/APJ axis in the pathogenesis of IBD are unclear. We herein analyzed CD4+ T cells to determine the functions of APL in a murine model of chronic colitis induced in Rag deficient mice (Rag-/-). In colonic tissues of wild-type mice (WT), we found that APL was expressed especially in the lamina propria lymphocytes, where CD4+ T cells are dominant, rather than the epithelial cells. Unexpectedly, the APL expression was rather downregulated in the colonic tissue of the chronic colitis group compared to the control groups (Rag-/- before colitis induction and WT). The APL expression was downregulated when naïve T cells were differentiated into effecter T cells. A lack of APL resulted in decreased naïve T cells and increased effecter T cells in secondary lymphoid organs. A synthetic APL peptide, [Pyr1]-APL-13, increased IL-10 and decreased IFN-γ productions by effecter T cells. Administration of [Pyr1]-APL-13 improved survival rate in association with lessened colitis severity and decreased pro-inflammatory cytokine production. This is the first report showing immunological function of APL specifically on T cells, and these results indicate that APL/APJ axis may be a novel therapeutic target for IBD.

Immunoglobulin A-specific deficiency induces spontaneous inflammation specifically in the ileum.

OBJECTIVE: Although immunoglobulin A (IgA) is abundantly expressed in the gut and known to be an important component of mucosal barriers against luminal pathogens, its precise function remains unclear. Therefore, we tried to elucidate the effect of IgA on gut homeostasis maintenance and its mechanism. DESIGN: We generated various IgA mutant mouse lines using the CRISPR/Cas9 genome editing system. Then, we evaluated the effect on the small intestinal homeostasis, pathology, intestinal microbiota, cytokine production, and immune cell activation using intravital imaging. RESULTS: We obtained two lines, with one that contained a <50 base pair deletion in the cytoplasmic region of the IgA allele (IgA tail-mutant; IgAtm/tm) and the other that lacked the most constant region of the IgH α chain, which resulted in the deficiency of IgA production (IgA-/-). IgA-/- exhibited spontaneous inflammation in the ileum but not the other parts of the gastrointestinal tract. Associated with this, there were significantly increased lamina propria CD4+ T cells, elevated productions of IFN-γ and IL-17, increased ileal segmented filamentous bacteria and skewed intestinal microflora composition. Intravital imaging using Ca2+ biosensor showed that IgA-/- had elevated Ca2+ signalling in Peyer's patch B cells. On the other hand, IgAtm/tm seemed to be normal, suggesting that the IgA cytoplasmic tail is dispensable for the prevention of the intestinal disorder. CONCLUSION: IgA plays an important role in the mucosal homeostasis associated with the regulation of intestinal microbiota and protection against mucosal inflammation especially in the ileum.

CEACAM1 specifically suppresses B cell receptor signaling-mediated activation.

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) expressed in T cells may regulate immune responses in the gut. In addition to T cells, B cells are also an important population in the gut-associated lymphoid tissues that orchestrate mucosal homeostasis. However, the role of CEACAM1 in B cells has not been elucidated. We herein analyzed mature B cells to determine the functions of CEACAM1. Flow cytometry revealed high expression of CEACAM1 on B cells in secondary lymphoid tissues. Cytokine production induced by activation of B cell receptor (BCR) signaling was suppressed by CEACAM1 signaling in contrast to that associated with either Toll-like receptor 4 or CD40 signaling. Confocal microscopy revealed co-localization of CEACAM1 and BCR when activated with anti-Igµ F(ab')2 fragment. Overexpression of CEACAM1 in a murine B cell line, A20, resulted in reduced expressions of activation surface markers with decreased Ca2+ influx after BCR signal activation. Overexpression of CEACAM1 suppressed BCR signal cascade in A20 cells in association with decreased spontaneous proliferation. Our results suggest that CEACAM1 can regulate BCR-mediated mature B cell activation in lymphoid tissues. Therefore, further studies of this molecule may lead to greater insights into the mechanisms of immune responses within peripheral tissues and the potential treatment of inflammatory diseases.

Indolent T cell lymphoproliferative disorder with villous atrophy in small intestine diagnosed by single-balloon enteroscopy.

Chronic diarrhea is one of the major symptoms in gastroenterology. However, this may be caused by pathologic conditions for which the diagnosis is critical. Villous atrophy, as an endoscopic lesion, accompanied by chronic diarrhea can occasionally be observed in the patients with inflammatory diseases of the gastrointestinal (GI) tract. Herein, we present a case with persistent diarrhea accompanied by intestinal wall thickening without any other significant endoscopic features other than villous atrophy in the jejunum and the ileum, where we diagnosed as an indolent T cell lymphoproliferative disorder (T-LPD) of the GI tract, defined in the 2016-2017 revised World Health Organization classification, via single-balloon enteroscopy (SBE). Interestingly, we found the same lymphocyte infiltration from the distal third portion of the duodenum, where gastroscopy could not reach, via SBE, even though no endoscopic findings were observed such as villous atrophy. Since infiltrating cells in the intestinal tissues were CCR4+, mogamulizumab was administered with resulting durable symptomatic remission for more than 2 years. Patients with persistent diarrhea may have serious small intestinal disorder including not only chronic inflammatory diseases but also lymphoid neoplasmic conditions including T-LPD of GI tract.

B cell activation in the cecal patches during the development of an experimental colitis model.

Although previous studies have suggested that appendix seems to be involved in the colitis, the role of this in the pathogenesis remains unclear. In this study, we assessed the importance of appendiceal lymphoid follicles, specifically the cecal patches (CP) in mice, using an experimental colitis model. Treatment with oxazolone resulted in ulcerations particularly at CP with follicular expansion as well as colitis. The colitis was attenuated by either appendectomy or the absence of mature B cells. We therefore established an intravital imaging system accompanied by the fluorescence resonance energy transfer technology to analyze the dynamic immune response of CP B cells. Our observation revealed frequent Ca2+ signaling in CP B cells during the early phase of colitis development. These findings suggested that the CP B cells may be involved in the pathogenesis of colitis including inflammatory bowel diseases in humans.

Ventral simultanagnosia and prosopagnosia for unfamiliar faces due to a right posterior superior temporal sulcus and angular gyrus lesion.

We report a patient with ventral simultanagnosia, prosopagnosia for "unfamiliar faces" (dorsal prosopagnosia), spatial agraphia, and constructional disorder, particularly on the left spatial side, due to a lesion in the right posterior superior and middle temporal gyri and angular gyrus. The patient showed impairment of fundamental visual and visuospatial recognition, such as in object size, configuration, and horizontal point location, which probably underlay the mechanism of simultanagnosia and prosopagnosia. This case also suggests that the coexistence of simultanagnosia and prosopagnosia results from a right hemispheric insult, and damage to the temporoparietal area interrupts the incorporation of spatial information into object recognition. This disconnection of information flow, together with impaired object recognition per se, may impair the parallel processing of multiple objects, leading to object-by-object or part-by-part recognition.