Thymocyte Development of Humanized Mice Is Promoted by Interactions with Human-Derived Antigen Presenting Cells upon Immunization.

Immune responses in humanized mice are generally inefficient without co-transplantation of human thymus or HLA transgenes. Previously, we generated humanized mice via the intra-bone marrow injection of CD133+ cord blood cells into irradiated adult immunodeficient mice (IBMI-huNSG mice), which could mount functional immune responses against HTLV-1, although the underlying mechanisms were still unknown. Here, we investigated thymocyte development in IBMI-huNSG mice, focusing on the roles of human and mouse MHC restriction. IBMI-huNSG mice had normal developmental profiles but aberrant thymic structures. Surprisingly, the thymic medulla-like regions expanded after immunization due to enhanced thymocyte expansion in association with the increase in HLA-DR+ cells, including CD205+ dendritic cells (DCs). The organ culture of thymus from immunized IBMI-huNSG mice with a neutralizing antibody to HLA-DR showed the HLA-DR-dependent expansion of CD4 single positive thymocytes. Mature peripheral T-cells exhibited alloreactive proliferation when co-cultured with human peripheral blood mononuclear cells. Live imaging of the thymus from immunized IBMI-huNSG mice revealed dynamic adhesive contacts of human-derived thymocytes and DCs accompanied by Rap1 activation. These findings demonstrate that an increase in HLA-DR+ cells by immunization promotes HLA-restricted thymocyte expansion in humanized mice, offering a unique opportunity to generate humanized mice with ease.

Experimental gastric endoscopic submucosal dissection: training in a porcine model.

BACKGROUND: Endoscopic submucosal dissection (ESD) requires special skills and a long procedure time for a quality-controlled procedure. A universal training system remains to be established. Hands-on courses in animal models before advancing to the human colon appear to be essential, especially in Europe. The learning curve is a prerequisite in ESD, in order to improve technical outcomes and decrease the rate of procedural adverse events. METHODS: In the experimental research center of ELPEN Pharmaceuticals, 18 European endoscopists, inexperienced at ESD, performed gastric ESDs in porcine models. The course lasted two days and was conducted under the supervision of experts. RESULTS: A total of 72 of 76 ESDs were completed en bloc (94.7%). The procedural time and cutting speed differed significantly between the first and second day: 48±4.4 vs. 43±4.8 min (P=0.0045), and 1.38±0.20 vs. 1.63±0.23 cm2/min (P=0.0033), respectively. The complications were not significantly different between the two groups: five (13.88%) vs. four (11%) episodes of bleeding (P>0.05). The perforation rate was similar, at two episodes per day (5.55%). We documented an acceptable rate of en bloc resections and complications. CONCLUSION: ESD demands a new level of endoscopic skills in Europe. A formal sequential training program, using porcine models, may benefit countries with a low volume of cases.

Hypermethylation of MST1 in IgG4-related autoimmune pancreatitis and rheumatoid arthritis.

The serine/threonine kinase Mst1 plays important roles in the control of immune cell trafficking, proliferation, and differentiation. Previously, we reported that Mst1 was required for thymocyte selection and regulatory T-cell functions, thereby the prevention of autoimmunity in mice. In humans, MST1 null mutations cause T-cell immunodeficiency and hypergammaglobulinemia with autoantibody production. RASSF5C(RAPL) is an activator of MST1 and it is frequently methylated in some tumors. Herein, we investigated methylation of the promoter regions of MST1 and RASSF5C(RAPL) in leukocytes from patients with IgG4-related autoimmune pancreatitis (AIP) and rheumatoid arthritis (RA). Increased number of CpG methylation in the 5' region of MST1 was detected in AIP patients with extrapancreatic lesions, whereas AIP patients without extrapancreatic lesions were similar to controls. In RA patients, we detected a slight increased CpG methylation in MST1, although the overall number of methylation sites was lower than that of AIP patients with extrapancreatic lesions. There were no significant changes of the methylation levels of the CpG islands in the 5' region of RASSF5C(RAPL) in leukocytes from AIP and RA patients. Consistently, we found a significantly down-regulated expression of MST1 in regulatory T cells of AIP patients. Our results suggest that the decreased expression of MST1 in regulatory T cells due to hypermethylation of the promoter contributes to the pathogenesis of IgG4-related AIP.