Dynamic migration of γδ intraepithelial lymphocytes requires occludin

gamma delta intraepithelial lymphocytes (IELs) are located beneath or between adjacent intestinal epithelial cells and are thought to contribute to homeostasis and disease pathogenesis. Using in vivo microscopy to image jejunal mucosa of GFP gamma delta T-cell transgenic mice, we discovered that gamma delta IELs migrate actively within the intraepithelial compartment and into the lamina propria. As a result, each gamma delta IEL contacts multiple epithelial cells. Occludin is concentrated at sites of gamma delta IEL/epithelial interaction, where it forms a ring surrounding the gamma delta IEL. In vitro analyses showed that occludin is expressed by epithelial and gamma delta T cells and that occludin derived from both cell types contributes to these rings and to gamma delta IEL migration within epithelial monolayers. In vivo TNF administration, which results in epithelial occludin endocytosis, reduces gamma delta IEL migration. Further in vivo analyses demonstrated that occludin KO gamma delta T cells are defective in both initial accumulation and migration within the intraepithelial compartment. These data challenge the paradigm that gamma delta IELs are stationary in the intestinal epithelium and demonstrate that gamma delta IELs migrate dynamically to make extensive contacts with epithelial cells. The identification of occludin as an essential factor in gamma delta IEL migration provides insight into the molecular regulation of gamma delta IEL/epithelial interactions.