Intestinal inflammation observed in IL-2R/IL-2 mutant mice is associated with impaired intestinal T lymphopoiesis

Background & Aims: Although interleukin (IL)-2(-/-) and IL-2R alpha(-/-) mice develop inflammatory bowel disease, IL-2R beta(-/-) animals are apparently free of gut pathology, Intraintestinal T lymphopoiesis is reported to be impaired in IL-2R beta(-/-) mice; we have determined whether this characteristic correlated with the apparent resistance of this mutant strain to intestinal inflammation, This led us to reassess intraintestinal T lymphopoiesis in these 3 mutant strains. Methods: Intestinal histology and intraintestinal T lymphopoiesis were analyzed in unmanipulated mutant mice and in athymic and euthymic radiation chimeras reconstituted with bone marrow derived from IL-2(-/-), IL-2R alpha(-/-), and IL-2R beta(-/-) donors. Results: Intraintestinal T lymphopoiesis was ablated in the 3 mutant strains and was associated with cryptopatch abnormalities. The intestinal mucosa of mice reconstituted with lymphocytes from IL-2R beta(-/-) mice exhibited lesions of both the small and large bowel similar to those observed in the early stages of human gluten enteropathy and acute ulcerative colitis, respectively. Analysis of euthymic and athymic bone marrow radiation chimeras indicated that T cells located in the intestinal mucosa of unmanipulated IL-2(-/-), IL-2R alpha(-/-), and IL-2R beta(-/-) mice are of thymic origin. Conclusions: Null mutations at IL-2/IL-2R alpha and beta loci differentially affect intraintestinal and intrathymic T lymphopoiesis. These conditions are associated with lesions of intestinal inflammation that are mediated by thymus-derived T cells.