Background & Aims: Interleukin (IL)-15 exerts functional effects on ly
mphocytes similar to those of IL-2, IL-15 is expressed by nonlymphoid
cells and may integrate these cells into classical immune responses, T
he aim of this study was to characterize the expression of IL-15 by in
testinal epithelial cells and determine the functional roles of IL-15
within the mucosal immune system. Methods: Rat IL-15 was cloned from a
rat jejunal library, Expression of IL-15 in rat and human intestinal
epithelial cells was assessed by Northern and Western blotting, Tyrosi
ne kinase activation in response to IL-15 in intestinal epithelial cel
ls was determined by immunoprecipitation, Results: Rat and human intes
tinal epithelial cells express IL-15 messenger RNA, IL-15 activates St
at3 and stimulates the proliferation of intestinal epithelial cells, T
he relevance of the observations for intestinal epithelial cell functi
on in vivo was supported by the demonstration of transcripts for IL-15
in primary human intestinal epithelial cells. Conclusions: IL-15 is e
xpressed by intestinal epithelial cells and may be able to regulate in
testinal epithelial cell function, These experiments suggest that IL-1
5 is an important mediator that could integrate intestinal epithelial
cell function with the intestinal immune system.