Food sensitized pediatric patients show colonic cow's milk protein-specific Th2 cells.

Abstract

Food allergies have become a health concern worldwide. Around 6-10% of children are allergic to cow´s milk proteins. We have previously characterized colorectal polyps in patients sensitized to food allergens. These polyps are classified as inflammatory and present a Th2 environment, with elevated IL-13 and IL-4 and are a site of IgE synthesis. In this study, we characterized and isolated cow´s milk protein-specific T cell lines and T cell clones from the lamina propria of polyps from patients sensitized to these proteins. Isolated T cells responded to cow´s milk proteins similarly to peripheral blood T cells, showing antigen-specific cell proliferation and Th2 cytokines release in vitro. T cell clones obtained were all CD4+ T cells and expressed the membrane TCRαβ receptor and secreted higher IL-4, IL-5 and IL-13 amounts than unstimulated cells, whereas IFN-γ secretion remained unchanged. Remarkably, the gut homing chemokine receptor CCR9 was augmented in cow's milk-specific peripheral and lamina propria T cells, and CCL25 was found to be expressed in the inflammatory polyp tissue and not in the adjacent mucosa. In conclusion, we isolated and characterized cow´s milk-specific lamina propria CD4+ Th2 cells from colonic inflammatory polyps. CCR9 expression on these cells, along with increase secretion of CCL25 in the polyp, favor recruitment and cow's milk specific allergic response within the inflammatory polyp tissue. Our findings may be critical to understand the underlying mechanism that promotes IgE synthesis in the colon of cow´s milk proteins allergic patients, contributing to the development of novel T cell-targeted immunotherapies.