The recruitment of extra-intestinal cells to the injured mucosa promotes healing in radiation enteritis and chemical colitis in a mouse parabiosis model.

Mucosal healing occurs through migration and proliferation of cells within injured epithelium, yet these processes may be inadequate for mucosal healing after significant injury where the mucosa is denuded. We hypothesize that extra-intestinal cells can contribute to mucosal healing after injury to the small and large intestine. We generated parabiotic pairs between wild-type and tdTomato mice, which were then subjected to radiation-induced enteritis and 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis. We now show that as compared with singleton mice, mice with a parabiotic partner were protected against intestinal damage as revealed by significantly reduced weight loss, reduced expression of pro-inflammatory cytokines, reduced enterocyte apoptosis, and improved crypt proliferation. Donor cells expressed CD45-, Sca-1+, c-kit+, and CXCR4+ and accumulated around the injured crypts but did not transdifferentiate into epithelia, suggesting that extra-intestinal cells play a paracrine role in the healing response, while parabiotic pairings with Rag1-/- mice showed improved healing, indicating that adaptive immune cells were dispensable for mucosal healing. Strikingly, ablation of the bone marrow of the donor parabionts removed the protective effects. These findings reveal that the recruitment of extra-intestinal, bone marrow-derived cells into the injured intestinal mucosa can promote mucosal healing, suggesting novel therapeutic approaches for severe intestinal disease.

Histopathological and immunophenotypic features of ipilimumab-associated colitis compared to ulcerative colitis.

BACKGROUND: Use of the immune checkpoint inhibitor ipilimumab is sometimes complicated by ipilimumab-associated colitis (Ipi-AC), an immune-mediated colitis that mimics inflammatory bowel disease. OBJECTIVE: We sought to characterize the histopathologic and immunophenotypic features of Ipi-AC and to directly compare these features to ulcerative colitis (UC). METHODS: This is a retrospective cohort study of 22 patients with Ipi-AC, 12 patients with treatment-naïve UC and five controls with diarrhoea but normal endoscopic findings. Immunohistopathologic features were described, and quantitative immunohistochemistry (IHC) was performed for CD4, CD8, CD20, CD138 and FOXP3. RESULTS: Endoscopic findings in both the Ipi-AC and UC groups included ulcerated, oedematous and erythematous mucosa. Involvement of the GI tract was more diffuse in Ipi-AC. As compared to UC, a smaller proportion of Ipi-AC biopsies had basal plasmacytosis (14% for Ipi-AC vs. 92% for UC, P < 0.0001) and crypt distortion (23% for Ipi-AC vs. 75% for UC, P = 0.003), whereas Ipi-AC biopsies had more apoptotic bodies in the left colon (17.6 ± 15.3 for Ipi-AC vs. 8.2 ± 4.2 for UC, P = 0.011). Cryptitis, ulcerations and crypt abscesses were common in both groups. Biopsy specimens from Ipi-AC had a lower density of CD20-positive lymphocytes than UC (275.8 ± 253.3 cells mm-2 for Ipi-AC vs. 1173.3 ± 1158.2 cells mm-2 for UC, P = 0.022) but had a similar density of CD4, CD8, CD138 and FOXP3-positive cells. CONCLUSIONS: Ipi-AC is a distinct pathologic entity with notable clinical and histopathological differences compared to UC. These findings provide insights into the pathophysiology of immune-related adverse events (iAEs) from ipilimumab therapy.

[Inflammation, malignancy and immunology in gastrointestinal spindle cell tumors: what is beyond GIST?]. / Entzündung, Malignität und Immunologie gastrointestinaler Spindelzelltumoren : Was gibt es abgesehen von GIST noch?

Many mesenchymal tumors and tumefactions associated with the gastrointestinal tract feature prominent inflammatory cells but the mechanisms for the inflammation and the processes themselves remain poorly understood. Such classic lesions include Kaposi sarcoma, inflammatory fibroid polyp, sclerosing mesenteritis and inflammatory myofibroblastic tumor but, more recently, the recognition of IgG4-related fibrosclerosing disease has resulted in modification of the views on pathogenesis and treatment of such inflammatory lesions in many anatomical sites. In some lesions the inflammation may reflect viral influences (Kaposi sarcoma) or a bacterial infectious trigger (IgG4-related fibrosclerosing disease) whereas in others such an interaction is unclear and alterations in various genes have been detected, such as anaplastic lymphoma receptor tyrosine kinase gene rearrangements in inflammatory myofibroblastic tumor and platelet-derived growth factor receptor alpha (PDGFRA) gene mutations in inflammatory fibroid polyp and some gastrointestinal stromal tumors (GIST). Even the inflammatory milieu of GISTs may have an impact on the outcome. This article discusses the practical diagnostic considerations as well as the theoretical background.