Lei Zhou

Fibroblasts exhibit phenotypic and functional heterogeneity in chronic inflammatory diseases, but how these changes impact immune outcomes remains poorly understood. We identified that a fibroblast population expressing insulin-like growth factor 1 (IGF1) was reduced in patients with inflammatory bowel disease (IBD). Using mouse models of intestinal inflammation, we found cross-talk between IGF1-expressing fibroblasts and group 3 innate lymphoid cells (ILC3s). IGF1 stimulation limited the ability of ILC3s to produce C-X-C motif chemokine ligand 10 (CXCL10) and recruit plasmacytoid dendritic cells (pDCs) to restrain gut inflammation. We propose that this regulatory pathway is conserved in human ILC3s but may become impaired in IBD. Our results define that anti-inflammatory fibroblasts safeguard the gut through regulation of an innate lymphocyte–pDC axis.

Innate lymphoid cells (ILCs) are a family of predominantly tissue-resident lymphocytes that critically orchestrate immunity, inflammation, tolerance and repair at barrier surfaces of the mammalian body. Heterogeneity among ILC subsets is comparable to that of adaptive CD4⁺ T helper cell counterparts, and emerging studies demonstrate that ILC biology is also dictated by cellular metabolism that adapts bioenergetic requirements during activation, proliferation or cytokine production. Accumulating evidence in mouse models and human samples indicates that ILCs exhibit profound roles in shaping states of metabolic health and disease. Here we summarize and discuss our current knowledge of the cell-intrinsic and cell-extrinsic metabolic factors controlling ILC responses, as well as highlight contributions of ILCs to organismal metabolism. It is expected that continued research in this area will advance our understanding of how to manipulate ILCs or their metabolism for therapeutic strategies that benefit human health.

Microbial colonization of the mammalian intestine elicits inflammatory or tolerogenic T cell responses, but the mechanisms controlling these distinct outcomes remain poorly understood, and accumulating evidence indicates that aberrant immunity to intestinal microbiota is causally associated with infectious, inflammatory and malignant diseases^{1,2,3,4,5,6,7,8}. Here we define a critical pathway controlling the fate of inflammatory versus tolerogenic T cells that respond to the microbiota and express the transcription factor RORγt. We profiled all RORγt⁺ immune cells at single-cell resolution from the intestine-draining lymph nodes of mice and reveal a dominant presence of T regulatory (T_reg) cells and lymphoid tissue inducer-like group 3 innate lymphoid cells (ILC3s), which co-localize at interfollicular regions. These ILC3s are distinct from extrathymic AIRE-expressing cells, abundantly express major histocompatibility complex class II, and are necessary and sufficient to promote microbiota-specific RORγt⁺ T_reg cells and prevent their expansion as inflammatory T helper 17 cells. This occurs through ILC3-mediated antigen presentation, αV integrin and competition for interleukin-2. Finally, single-cell analyses suggest that interactions between ILC3s and RORγt⁺ T_reg cells are impaired in inflammatory bowel disease. Our results define a paradigm whereby ILC3s select for antigen-specific RORγt⁺ T_reg cells, and against T helper 17 cells, to establish immune tolerance to the microbiota and intestinal health.

RORγt is a lineage-specifying transcription factor that is expressed by immune cells that are enriched in the gastrointestinal tract and promote immunity, inflammation and tissue homeostasis^{1,2,3,4,5,6,7,8,9,10,11,12,13,14,15}. However, fundamental questions remain with regard to the cellular heterogeneity among these cell types, the mechanisms that control protective versus inflammatory properties and their functional redundancy. Here we define all RORγt⁺ immune cells in the intestine at single-cell resolution and identify a subset of group 3 innate lymphoid cells (ILC3s) that expresses ZBTB46, a transcription factor specifying conventional dendritic cells^{16,17,18,19,20}. ZBTB46 is robustly expressed by CCR6⁺ lymphoid-tissue-inducer-like ILC3s that are developmentally and phenotypically distinct from conventional dendritic cells, and its expression is imprinted by RORγt, fine-tuned by microbiota-derived signals and increased by pro-inflammatory cytokines. ZBTB46 restrains the inflammatory properties of ILC3s, including the OX40L-dependent expansion of T helper 17 cells and the exacerbated intestinal inflammation that occurs after enteric infection. Finally, ZBTB46⁺ ILC3s are a major source of IL-22, and selective depletion of this population renders mice susceptible to enteric infection and associated intestinal inflammation. These results show that ZBTB46 is a transcription factor that is shared between conventional dendritic cells and ILC3s, and identify a cell-intrinsic function for ZBTB46 in restraining the pro-inflammatory properties of ILC3s and a non-redundant role for ZBTB46⁺ ILC3s in orchestrating intestinal health.

Tumor necrosis factor (TNF) drives chronic inflammation and cell death in the intestine, and blocking TNF is a therapeutic approach in inflammatory bowel disease (IBD). Despite this knowledge, the pathways that protect the intestine from TNF are incompletely understood. Here we demonstrate that group 3 innate lymphoid cells (ILC3s) protect the intestinal epithelium from TNF-induced cell death. This occurs independent of interleukin-22 (IL-22), and we identify that ILC3s are a dominant source of heparin-binding epidermal growth factor–like growth factor (HB-EGF). ILC3s produce HB-EGF in response to prostaglandin E2 (PGE2) and engagement of the EP2 receptor. Mice lacking ILC3-derived HB-EGF exhibit increased susceptibility to TNF-mediated epithelial cell death and experimental intestinal inflammation. Finally, human ILC3s produce HB-EGF and are reduced from the inflamed intestine. These results define an essential role for ILC3-derived HB-EGF in protecting the intestine from TNF and indicate that disruption of this pathway contributes to IBD.