Microbial Metabolites and Gut Immunology.

The intestine is the largest peripheral lymphoid organ in animals, including humans, and interacts with a vast array of microorganisms called the gut microbiota. Comprehending the symbiotic relationship between the gut microbiota and our immune system is essential not only for the field of immunology but also for understanding the pathogenesis of various systemic diseases, including cancer, cardiometabolic disorders, and extraintestinal autoimmune conditions. Whereas microbe-derived antigens are crucial for activating the intestinal immune system, particularly T and B cells, as environmental cues, microbes and their metabolites play a critical role in directing the differentiation of these immune cells. Microbial metabolites are regarded as messengers from the gut microbiota, since bacteria have the ability to produce unique molecules that humans cannot, and many immune cells in the intestine express receptors for these molecules. This review highlights the distinct relationships between microbial metabolites and the differentiation and function of the immune system.

Treatment of autoimmune pancreatitis with the anecdotes of the first report.

The first case that led researchers to put forward a new concept of autoimmune pancreatitis (AIP) was treated with steroids by gastroenterologists in Tokyo Women's Medical University. It is important to differentiate AIP from pancreatic cancer before treatment with steroids is started. Today, steroids are standard therapy for AIP worldwide. In the Japanese consensus guidelines, steroid therapy is indicated for symptomatic AIP. After management of glucose levels and obstructive jaundice, oral prednisolone is initiated at 0.6 mg/kg/day for 2-4 weeks and is gradually tapered to a maintenance dose of 2.5-5 mg/day over 2-3 months. To prevent relapse, maintenance therapy with low-dose prednisolone is used. For relapsed AIP, readministration or increased doses of steroids are effective. The presence of proximal bile duct stenosis and elevated serum IgG4 levels may be predictive of relapse of AIP. It is necessary to verify the validity of the Japanese regimen of steroid therapy for AIP. The necessity, drugs, and duration of maintenance therapy for AIP need to be clarified by prospective studies.

Cancer metastasis is accelerated through immunosuppression during Snail-induced EMT of cancer cells.

Epithelial-mesenchymal transition (EMT) is a key step toward cancer metastasis, and Snail is a major transcription factor governing EMT. Here, we demonstrate that Snail-induced EMT accelerates cancer metastasis through not only enhanced invasion but also induction of immunosuppression. Murine and human melanoma cells with typical EMT features after snail transduction induced regulatory T cells and impaired dendritic cells in vitro and in vivo partly through TSP1 production. Although Snail(+) melanoma did not respond to immunotherapy, intratumoral injection with snail-specific siRNA or anti-TSP1 monoclonal antibody significantly inhibited tumor growth and metastasis following increase of tumor-specific tumor-infiltrating lymphocytes and systemic immune responses. These results suggest that inhibition of Snail-induced EMT could simultaneously suppress both tumor metastasis and immunosuppression in cancer patients.