A histomorphometric classification system for normal and inflamed mouse duodenum-Quali-quantitative approach

Gut-associated intestinal lymphoid tissue, the largest secondary lymphoid organ in the human body, constantly samples antigens from the gut lumen, presenting as a default response the activation of TCD4⁺ FOXP3⁺ regulatory T cells that secrete a profile of anti-inflammatory cytokines maintaining gut homeostasis denominated from an immunological perspective as mucosal tolerance. However, when antigens are sampled in an inflammatory setting, the immune response may either be protective, in the case of harmful pathogens, or cause further inflammatory reactions as in food allergy, inflammatory bowel diseases, coeliac disease or food protein-induced enterocolitis syndrome. Therefore, there is a need for accurate and consistent experimental models. However, a drawback in comparing these models is the lack of a classification system similar to that which is already used for humans. Thus, the aim of this work was to propose a classification system of the small intestinal histomorphology in experimental mice. To do this we used a mouse antigen-specific gut inflammation model developed by our research group. Duodenum sections stained with haematoxylin-eosin and Alcian blue were scanned using the APERIO scanning system and analysed with the ImageScope^® software. The evaluated parameters were villus area, villus height and width, enterocyte count, mononuclear intra-epithelial leucocyte and goblet cell counts, and architectural and cellular ratios. Food-sensitized animals challenged with a diet containing the corresponding food allergen presented, as for humans, time-dependent shortened and widened villi accompanied by leucocyte infiltrate and loss of goblet cells. With these data, we were able to establish a classification system for experimental intestinal inflammation in mice thus permitting better comparisons among and between experiments than has been possible previously.