Type 2 innate lymphoid cells are protective against hepatic ischaemia/reperfusion injury

BACKGROUND AND AIMS: Although type 2 innate lymphoid cells (ILC2s) were originally found to be liver-resident lymphocytes, the role and importance of ILC2 in liver injury remains poorly understood. In the current study, we sought to determine whether ILC2 is an important regulator of hepatic ischaemia/reperfusion injury (IRI). METHODS: ILC2-deficient mice (ICOS-T or NSG) and genetically modified ILC2s were used to investigate the role of ILC2s in murine hepatic IRI. Interactions between ILC2s and eosinophils or macrophages were studied in coculture. The role of human ILC2s was assessed in an immunocompromised mouse model of hepatic IRI. RESULTS: Administration of IL-33 prevented hepatic IRI in association with reduction of neutrophil infiltration and inflammatory mediators in the liver. IL-33-treated mice had elevated numbers of ILC2s, eosinophils, and regulatory T cells. Eosinophils, but not regulatory T cells, were required for IL-33-mediated hepatoprotection in IRI mice. Depletion of ILC2s substantially abolished the protective effect of IL-33 in hepatic IRI, indicating that ILC2s play critical roles in IL-33-mediated liver protection. Adoptive transfer of ex vivo-expanded ILC2s improved liver function and attenuated histologic damage in mice subjected to IRI. Mechanistic studies combining genetic and adoptive transfer approaches identified a protective role of ILC2s through promoting IL-13-dependent induction of anti-inflammatory macrophages and IL-5-dependent elevation of eosinophils in IRI. Furthermore, in vivo expansion of human ILC2s by IL-33 or transfer of ex vivo-expanded human ILC2s ameliorated hepatic IRI in an immunocompromised mouse model of hepatic IRI. CONCLUSIONS: This study provides insight into the mechanisms of ILC2-mediated liver protection that could serve as therapeutic targets to treat acute liver injury. IMPACT AND IMPLICATIONS: We report that type 2 innate lymphoid cells (ILC2s) are important regulators in a mouse model of liver ischaemia/reperfusion injury (IRI). Through manipulation of macrophage and eosinophil phenotypes, ILC2s mitigate liver inflammation and injury during liver IRI. We propose that ILC2s have the potential to serve as a therapeutic tool for protecting against acute liver injury and lay the foundation for translation of ILC2 therapy to human liver disease.