PURPOSE OF THE STUDY.
Intraepithelial lymphocytes (IELs) are immune cells with unique but incompletely understood properties related to epithelial barrier defense. This study builds off the authors’ previous work with specialized T-cell populations and investigates how these interesting cells develop and function.
Studies were performed in mice.
The authors used gene expression studies and transgenic mouse models to characterize factors involved with IEL development, survival, and function in the gastrointestinal tract.
In contrast to other lymphocyte populations, IELs were found to express high levels of a transcription factor known as aryl hydrocarbon receptor (Ahr). In Ahr-deficient mice, IELs developed and were recruited normally to the intestines and skin, but their survival was markedly diminished and they eventually disappeared as the animals matured. Previous studies had shown Ahr to bind to plant-derived nutrients found naturally in cruciferous vegetables, and therefore the authors investigated whether diet affected Ahr signaling and, consequently, IEL development. Feeding wild-type mice a synthetic diet devoid of Ahr ligands resulted in the disappearance of intestinal IELs similar to that seen in transgenic mice lacking Ahr expression; and the IELs returned when a single specific Ahr ligand was added to the synthetic diet. Finally, IELs appeared to be important for intestinal health, since their absence was associated with increased intestinal bacterial burdens, resulting in abnormal immune activation and increased susceptibility to chemical-induced colitis.
Diet-derived compounds activate Ahr-signaling pathways to maintain proper intestinal immune function.
This article presents another reason to eat your vegetables: proper functioning of the intestinal immune system. The authors demonstrate that specific dietary compounds found in cruciferous vegetables like broccoli, cauliflower, and cabbage are essential for the survival of IELs, which maintain the delicate balance between immune reactivity and tolerance to the intestinal microbiota. These provocative findings provide a potential mechanism by which diets low in fruits and vegetables may predispose people to immune dysregulation and the occurrence of intestinal inflammatory diseases. Furthermore, this article highlights how the environment can have dramatic effects on immune system development and function.
- Copyright © 2012 by the American Academy of Pediatrics