Dependence of epithelial growth of the small intestine on T-cell activation during weaning in the rat

Background & Aims: Intestinal crypt hyperplasia is associated with local T-cell activation in both clinical and experimental examples of immunologically mediated enteropathy. This suggests that T cell-derived factors may be trophic for epithelial proliferation in the intestine postnatally. The purpose of this study was to investigate T-cell activity during weaning in the rat and to investigate immune dependence of intestinal growth on T-cell activation. Methods: The expression of interleukin-2 receptor (IL-2R) by mesenteric lymph node T cells was investigated from days 14 to 160 of life. Rats were treated with monoclonal antibodies against the IL-2R that were nonblocking (control) or blocking (experimental) from day 7, and intestinal growth was assessed at days 19, 25, and 29 of life. Results: The mean +/- SEM of T cells expressing the IL-2R during weaning (days 15-28) was 6.1% +/- 0.3% compared with 3.3% +/- 0.3% at other ages (P < 0.001). The small intestine in vats treated with blocking antibody had reduced crypt length and mitotic count compared with control animals. Conclusions: Weaning is associated with activation of T cells, and blockade of the IL-2R reduces intestinal growth.