Investigating the movement of intestinal intraepithelial lymphocytes using an organoid co-culture system

Abstract

The small intestine, which is lined by a single layer of intestinal epithelial cells, is the main site of nutrient absorption. It is continuously exposed to food antigens, and also several bacteria and microorganisms. Intestinal intraepithelial lymphocytes (IELs) are T cells that are interspersed between epithelial cells, above the basement membrane. This makes them one of the first immune cells to encounter and provide defence against invasive microbes. Studies have shown the important contribution of IELs patrolling along the epithelium to the immunosurveillance of the guts. However, little is known about how these immune cells move.

Intestinal organoids are three-dimensional structures of epithelial cells that mimic the gut epithelium in vitro. In this study a murine IEL-organoid co-culture system was established to study IEL movement. It has been shown that it is possible to keep them together in culture for long-term and by performing bright field and confocal microscopy imaging of the co-culture, I was able to visualize IEL movements. Indeed, IELs were observed to be highly motile inside organoids similar to previous studies. IL-15, a chemokine which is known to promote IEL proliferation and survival, can also affect IEL chemokinesis and chemotaxis. When IL-15 bindings was blocked, IEL movement was reduced. I also performed an analysis of IEL proteomic data for molecules regulated by IL-15 that could be involved in IEL migration. The expression of several adhesion molecules and chemokine receptors was either upregulated or downregulated which showed a potential involvement in IEL movement and retention within the epithelium. I showed that one way in which IL-15 drives IEL migration is potentially through a chemokine receptor, CXCR6. Results from the migration assay showed that IEL were chemoattracted and migrated towards CXCL16, the ligand of CXCR6. CXCL16 is expressed by stressed epithelial cells, and could be a mechanism for IELs to be attracted to sites of intestinal damage.

Date of Award	2021
Original language	English
Supervisor	Mahima Swamy (Supervisor) & Inke Nathke (Supervisor)