Ornithine decarboxylase supports ILC3 responses in infectious and autoimmune colitis through positive regulation of IL-22 transcription

Group 3 innate lymphoid cells (ILC3s) are RORγT+ lymphocytes that are predominately enriched in mucosal tissues and produce IL-22 and IL-17A. They are the innate counterparts of Th17. While Th17 lymphocytes utilize unique metabolic pathways in their differentiation program, it is unknown whether ILC3s make similar metabolic adaptations. We employed single-cell RNA sequencing and metabolomic profiling of intestinal ILC subsets to identify an enrichment of polyamine biosynthesis in ILC3s, converging on the rate-limiting enzyme ornithine decarboxylase (ODC1). In vitro and in vivo studies demonstrated that exogenous supplementation with the polyamine putrescine or its biosynthetic substrate, ornithine, enhanced ILC3 production of IL-22. Conditional deletion of ODC1 in ILC3s impaired mouse antibacterial defense against C. rodentium infection, which was associated with a decrease in anti-microbial peptide production by the intestinal epithelium. Furthermore, in a model of anti-CD40 colitis, deficiency of ODC1 in ILC3s markedly reduced the production of IL-22 and severity of inflammatory colitis. We conclude that cell-intrinsic polyamine biosynthesis facilitates efficient defense against enteric pathogens as well as augments autoimmune colitis, thus representing an attractive target to modulate ILC3 function in intestinal disease. Untreated (n=2), IL23-stimulated (n=2), putrescine-treated (n=2), and IL-23-stimulated and putrescine-treated (n=2) MNK-3. WT CCR6+ ILC3 (n=2) and ODC1 KO CCR6+ ILC3 (n=2).