Lung type 2 innate lymphoid cells express cysteinyl leukotriene receptor 1, which regulates T sub(H)2 cytokine production

Background: Cysteinyl leukotrienes (CysLTs) contribute to asthma pathogenesis, in part through cysteinyl leukotriene receptor 1 (CysLT1R). Recently discovered lineage-negative type 2 innate lymphoid cells (ILC2s) potently produce IL-5 and IL-13. Objectives: We hypothesized that lung ILC2s might be activated by leukotrienes through CysLT1R. Methods: ILC2s (Thy1.2 super(+) lineage-negative lymphocytes) and CysLT1R were detected in the lungs of wild-type, signal transducer and activator of transcription 6-deficient (STAT6 super(-/-)), and recombination-activating gene 2-deficient (RAG2 super(-/-)) mice by means of flow cytometry. T sub(H)2 cytokine levels were measured in purified lung ILC2s stimulated with leukotriene D sub(4) (LTD sub(4)) in the presence or absence of the CysLT1R antagonist montelukast. Calcium influx was measured by using Fluo-4 intensity. Intranasal leukotriene C sub(4), D sub(4), and E sub(4) were administered to naive mice, and levels of ILC2 IL-5 production were determined. Finally, LTD sub(4) was coadministered with Alternaria species repetitively to RAG2 super(-/-) mice (with ILC2s) and IL-7 receptor-deficient mice (lack ILC2s), and total ILC2 numbers, proliferation (Ki-67 super(+)), and bronchoalveolar lavage fluid eosinophil numbers were measured. Results: CysLT1R was expressed on lung ILC2s from wild-type, RAG2 super(-/-), and STAT6 super(-/-) naive and Alternaria species-challenged mice. In vitro LTD sub(4) induced ILC2s to rapidly generate high levels of IL-5 and IL-13 within 6 hours of stimulation. Interestingly, LTD sub(4), but not IL-33, induced high levels of IL-4 by ILC2s. LTD sub(4) administered in vivo rapidly induced ILC2 IL-5 production that was significantly reduced by montelukast before treatment. Finally, LTD sub(4) potentiated Alternaria species-induced eosinophilia, as well as ILC2 accumulation and proliferation. Conclusions: We present novel data that CysLT1R is expressed on ILC2s and LTD sub(4) potently induces CysLT1R-dependent ILC2 production of IL-4, IL-5, and IL-13. Additionally, LTD sub(4) potentiates Alternaria species-induced eosinophilia and ILC2 proliferation and accumulation.