Sa1769 TRIF Confers Expansion of Unique Innate Lymphoid Cell Populations During Enteric Infection With Gram-Negative Bacteria

Abstract

Background: Increasing evidence has highlighted an important contribution of innate lymphoid cells (ILCs) to host defense against enteric pathogens. We have found that mice deficient in TIR-domain-containing adapter-inducing interferon-β (TRIF) (TrifLPS2 mice) have an increased susceptibility to Gram-negative enteropathogens due to defective induction of IFNs in macrophages and natural killer (NK) cells. Since other subsets of ILCs also express IFN-γ, this study examined the role of TRIF signaling in the regulation of IFN-γ expressing ILCs during enteric infection with a Gram-negative enteropathogen Yersinia enterocolitica. Method: WT and TrifLPS2 mice were orally infected with Y. enterocolitica. Four days post infection, IFN-γ expressing ILCs were analyzed in the mesenteric lymph nodes (MLN), Peyer's patches (PPs), and the small intestinal lamina propria by flow cytometry. The single cell suspensions of mononuclear cells were isolated from these organs and incubated with PMA and ionomycin for four hours in the presense of golgiplug. Specific surface markers and intracellular cytokines were stained. IFN-γ expressing ILCs were characterized by NKp46+IL-17-IL-22cells (include NK cells: ILC1), NKp46+IL-22+ cells (IL-22+ILC3), and NKp46-IL-17+ cells (IL-17+ILC3) within IFN-γ+CD3population. The expression of cytokines that are involved in the activation of ILCs (IL-12p35, IL-23p19, and IL-15) and IFN-β were analyzed in the MLN and PPs by real-time PCR. Results: WT mice had significantly greater population of IFN-γ+CD3cells in the MLN and PPs compared to TrifLPS2 mice: the population of these cells in the small intestine was similar between WT and TrifLPS2 mice. In the MLN, ILC1 was dominant in IFN-γ+CD3population, which was significantly greater in WT mice compared to TrifLPS2 mice. Whereas the number of ILC3 (both IL-22+ and IL-17+) in the MLN was similar between WT and TrifLPS2 mice. On the other hand, IL-22+ILC3 was more abundant in the small intestine than other ILCs, which was greater in TrifLPS2 mice compared to WT mice: there were no differences between WT and TrifLPS2 mice in the number of ILC1 or IL-17+ILC3. In the PPs, ILC1 was more abundant than ILC3. IL-22+ILC3 population in the PPs was slightly greater in TrifLPS2 mice than WT mice. Defective expression of IFN-γ, IL-12p35, and IL-15 in the MLN and PPs was found in TrifLPS2 mice suggesting the involvement of these cytokines in observed differences in ILC expansion. Conclusion: Taken together, TRIF signaling regulates IFN-γ expressing ILC1 expansion in the MLN and IL-22+ILC3 expansion in the small intestine and PPs during enteric infection with Y. enterocolitica. Establishing the role of TRIF signaling in intestinal ILC expansion may contribute to the managements of infectious as well as inflammatory diseases in the intestine.