Cell-mediated immune injury in the intestine

Epithelial adaptation clearly occurs during the course of intestinal cell-mediated immune responses to alloantigens. The adaptive response is similar to that seen in a number of enteropathies, namely villus atrophy, crypt hypertrophy, and crypt cell hyperplasia. In human fetal gut, polyclonal activation of lamina propria CD4+ T cells produces the same epithelial adaptive responses. Although these data provide overwhelming evidence that cell-mediated immune responses can cause enteropathy, the demonstration of antigen-specific T cells in the lamina propria of patients with enteropathy is still lacking, even in a disease as well-characterized as celiac disease. Epithelial adaptation in experimental and clinical situations, however, must involve a change in the mechanisms and mediators involved in normal intestinal homeostasis, such as epidermal growth factor and transforming growth factor-alpha and -beta, and in the interactions between epithelial cells and the underlying stromal cells.