Background: T-cell hypersensitivity is implicated in the tissue damage in a variety of gastrointestinal diseases. The aim of this study was to characterize the spectrum of pathological changes induced by T-cell activation in explants of fetal human small intestine, to modulate the pathology by immunological intervention, and to define the cellular pathways in intestinal damage.
Methods: Explants of fetal human small intestine were cultured with pokeweed mitogen in the presence or absence of dexamethasone or FK506. Pathological changes were then assessed by morphology or on frozen sections.
Results: Activation of lamina propria T cells produced variable mucosal damage that could be classified into two main types. Some explants showed villous atrophy and crypt hyperplasia whereas in others there was almost total mucosal destruction. This latter appearance predominated in explants from older specimens. Explants that were destroyed contained high numbers of T cells and activated macrophages. FK506 could completely inhibit mucosal damage, especially in younger specimens, whereas dexamethasone, even at high doses, prevented mucosal destruction, but individual explants continued to show villus atrophy and crypt hyperplasia.
Conclusions: These results indicate that there is a quantitative relationship between mucosal cell-mediated immunity and the pathological outcome and that large numbers of activated macrophages in the mucosa can result in tissue destruction.