Co-culture with intestinal epithelial organoids allows efficient expansion and motility analysis of intraepithelial lymphocytes

Background Intraepithelial lymphocytes (IELs) in the intestine play important roles in the regulation of local immune responses. Although their functions have been studied in a variety of animal experiments, in vitro studies on spatiotemporal behaviors of IELs and their interaction with intestinal epithelial cells (IECs) have been hampered due to the lack of a suitable culture system. In this study, we aimed at developing a novel co-culture system of IELs with IECs to investigate dynamic interaction between these two populations of cells in vitro. Methods We optimized experimental conditions under which murine IELs can be efficiently maintained with IECs cultured as three-dimensional organoids. We then tested the effect of IL-2, IL-7, and IL-15 on the maintenance of IELs in this co-culture system. By time-lapse imaging, we also examined the dynamic behaviors of IELs. Results IELs can be expanded with epithelial organoids in the presence of IL-2, IL-7, and IL-15. IELs were efficiently maintained within and outside of organoids showing a similar to four-fold increase in both alpha beta T and gamma delta T IELs for a period of 2 weeks. Four-dimensional fluorescent imaging revealed an active, multi-directional movement of IELs along the basolateral surface of IECs, and also their inward or outward migration relative to organoid structures. Cell tracking analysis showed that alpha beta T and gamma delta T IELs shared indistinguishable features with regard to their dynamics. Conclusions This novel co-culture method could serve as a unique tool to investigate the motility dynamics of IELs and their temporal and spatial interaction with IECs in vitro.