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Intestinal eosinophils are implicated in homeostatic and disease-associated processes, yet the phenotype of intestinal tissue-dwelling eosinophils is poorly defined and their roles in intestinal health or disease remain enigmatic. Here we probed the phenotype and localization of eosinophils constitutively homed to the small intestine of naive mice at baseline, and of antigen-sensitized mice following intestinal challenge. Eosinophils homed to the intestinal lamina propria of naive mice were phenotypically distinguished from autologous blood eosinophils, and constitutively expressed antigen-presenting cell markers, suggesting that intestinal eosinophils, unlike blood eosinophils, may be primed for antigen presentation. We further identified a previously unrecognized resident population of CD11c hi eosinophils that are recovered with intraepithelial leucocytes, and that are phenotypically distinct from both lamina propria and blood eosinophils. To better visualize intestinal eosinophils in situ, we generated eosinophil reporter mice wherein green fluorescent protein expression is targeted to both granule-delimiting and plasma membranes. Analyses of deconvolved fluorescent z-section image stacks of intestinal tissue sections from eosinophil reporter mice revealed eosinophils within intestinal villi exhibited dendritic morphologies with cellular extensions that often contacted the basement membrane. Using an in vivo model of antigen acquisition in antigen-sensitized mice, we demonstrate that both lamina propria-associated and intraepithelium-associated eosinophils encounter, and are competent to acquire, lumen-derived antigen. Taken together these data provide new foundational insights into the organization and functional potential of intestinal tissue-dwelling eosinophils, including the recognition of different subsets of resident intestinal eosinophils, and constitutive expression of antigen-presenting cell markers., (© 2017 John Wiley & Sons Ltd.)

Aims: Differentiated squamous intraepithelial neoplasia (DSIN) has been described in several sites, including the upper aerodigestive tract and vulva, so this study investigated whether it also occurred in the anal canal., Methods and Results: All cases of squamous cell carcinoma (SCC) involving the anal canal diagnosed between 2009 and 2015 at our institution were reviewed. Eighty-six cases were included, and 13 (15%) showed features consistent with DSIN: 10 were 'pure' DSIN, and three were 'mixed' DSIN and squamous intraepithelial lesion. DSIN was characterized by atypical keratinocytes limited to the basal/parabasal layers, acanthosis, and a 'cobblestone' appearance. Among specimens with pure DSIN, the surface was flat in eight cases. In five cases, the DSIN was extensive, and associated with deeply invasive SCC requiring radical surgical resection. Immunohistochemically, the epithelia showing changes consistent with DSIN were p16-negative, whereas the invasive component was p16-positive in 12 cases. Both Ki67 and p53 showed strong nuclear positivity in the basal/parabasal layers of DSIN., Conclusions: Invasive SCC associated with DSIN often presents at an advanced stage of disease, requiring radical surgical treatment. The neoplastic changes in DSIN are limited to the basal/parabasal layers, which may account for the negative diagnoses by anal cytopathology and late clinical diagnosis. The recognition of anal DSIN is important in order to avoid underdiagnosis in superficial biopsies., (© 2015 John Wiley & Sons Ltd.)