TNFR and LTbetaR agonists induce follicle-associated epithelium and M cell specific genes in rat and human intestinal epithelial cells.

M cells assist mucosal immune surveillance by transcytosis of particles to underlying lymphoid tissue, but the mechanisms of M cell differentiation are poorly understood. To develop a better defined cell culture model of M cell differentiation, we treated human (Caco-2BBe) and rat (IEC-6) intestinal epithelial cell lines with lymphotoxin beta receptor (LTbetaR) and TNF receptor (TNFR) agonists. Treated cells were studied for regulation of genes associated with M cell and follicle-associated epithelium (FAE). We found that LTbetaR and TNFR agonists induce transcription of FAE-specific genes (Ccl20 and Lamb3) in Caco2-BBe cells and IEC-6 cells as well as rodent M cell specific genes such as Sgne-1/Scg5, Cldn4, and Gp2. The cytokines have distinct but complementary effects; TNFR agonists mainly induced FAE-specific genes, while the LTbetaR agonist induced M cell specific genes. The combination of cytokines showed additive induction of the FAE-associated Ccl20, Lamb3 and a surprising induction of CD137/Tnfrsf9. On the other hand TNF agonists appeared to suppress expression of some LTbetaR-induced genes. Functionally, cytokine treatment led to the reorganization of microvilli and Claudin-4 redistribution. These studies suggest complex interactions between these cytokines in the context of either inflammation or tissue differentiation.