Intestinal ILC ‐epithelial cell circuits shaping barrier immunity

Recent studies in 2025 uncovered the crosstalk between intestinal innate lymphoid cells (ILCs) and epithelial cells, highlighting a previously unappreciated role of intestinal ILC-epithelial cell circuit in shaping intestinal barrier immunity. In this article for the Highlights of 2025 Series, we discuss recent advances in understanding the bidirectional crosstalk between intestinal innate lymphoid cells (ILCs) and epithelial cells. These studies uncover previously unappreciated immune-epithelial circuits and regulatory mechanisms that refine how we view epithelial differentiation, mucosal homeostasis and inflammatory disease. The intestinal mucosal epithelium forms a critical physiological barrier that separates the host from the luminal microbiota. Simultaneously, this barrier enables the selective transport of nutrients across the epithelial layer. Far from acting simply as a passive physical barrier, the epithelium comprises specialized cell types that actively shape mucosal immunity. These cells are heterogeneous and include chemosensory tuft cells, key initiators of type 2 immune responses during parasitic infection1 and antigen-transporting microfold (M) cells.2 These epithelial cells communicate with local immune populations in the underlying epithelium, positioning them to dynamically calibrate immune responses. Among the immune populations found in the intestinal lamina propria, innate lymphoid cells (ILCs), particularly ILC2s and ILC3s, are highly enriched. These ILCs act as rapid responders to environmental, microbial and cytokine-derived cues, with their effector functions greatly influencing local immunity in the digestive tract. Although the role of ILCs in helminth defense and diseases such as inflammatory bowel disease (IBD) and ulcerative colitis has been recognized,1, 3 the regulatory interactions between ILCs and epithelial cells that control protective versus pathological responses remain poorly defined. Previous studies have shown a link between ILC3 dysregulation and intestinal inflammatory disease through an IL-23-dependent pathway,4, 5 but the mechanism by which IL-23 reshapes the intestinal epithelium remains unclear. Cineus et al.6 (2025) identified an IL-23-dependent cytokine network through which ILC3s modulate epithelial responsiveness to inflammatory signals, providing direct evidence of ILC3-epithelial crosstalk (Figure 1). In this study, they showed that IL-23-activated ILC3s produced IL-22, which acted on IL-22R+ epithelial cells to induce expression of the IL-6 family cytokine receptor oncostatin M receptor (OSMR). This cascade resulted in priming of epithelial cells to respond to inflammatory signals by sensitizing them to oncostatin M (OSM) derived from inflammatory monocytes and neutrophils.6 The combined action of IL-22 and OSM signals drove proinflammatory epithelial changes and leukocyte recruitment during intestinal inflammation, colitis-associated cancer and Helicobacter hepaticus infection.6 This study showed that ILC3-derived cytokines prime epithelial cells to become more inflammatory, thereby exacerbating mucosal pathology in intestinal inflammatory diseases. In addition to secretory cytokines that drive intestinal epithelial remodeling, ILC3s also utilize contact-dependent signaling through membrane-bound proteins such as the tumor necrosis factor superfamily member receptor activator of NF-κB ligand (RANKL),7 a well-established regulator of epithelial M cell differentiation in the intestine and Peyer's patches.2, 8 Unexpectedly, Xu et al.9 (2025) demonstrated that RANKL-expressing ILC3s synergise with IL-13 to promote tuft cell hyperplasia (Figure 1). Using intestinal organoid models, this group revealed that RelB-dependent RANK signaling induces the expression of Il4ra, Il13ra1 and Stat6, encoding components of the IL-13 receptor complex and its downstream effector pathway.9 This transcriptional program sensitized intestinal stem cells to IL-13 signaling and drove them toward tuft cell differentiation. The authors further showed that RANKL expression on ILC3s is regulated by prostaglandins and neuropeptides.9 Among these mediators, prostaglandin D₂ (PGD₂), previously shown to be produced by intestinal tuft cells during infection,10, 11 was identified as a key epithelial-derived signal that promoted RANKL expression on ILC3s,9 thereby reinforcing a feedback circuit between tuft cells and ILC3s. This finding uncovered a previously unrecognized regulatory axis in which ILC3s play a role in tuft cell development and establish a self-reinforcing circuit that coordinates epithelial differentiation with antihelminth immunity. During helminth infection, epithelial tuft cells and ILC2s form a well-established communication circuit that amplifies type 2 immunity. In this pathway, the presence of parasites, such as Nippostrongylus brasiliensis (N. brasiliensis) and Heligmosomoides polygyrus (H. polygyrus), stimulates tuft cells to produce IL-25 which activates ILC2s.1, 12 In turn, activated ILC2s secrete IL-13 to promote tuft cell differentiation, thereby reinforcing the feedback circuit during infection.1, 12 While this circuit is well characterized in antiparasitic immunity, Liao et al.13 (2025) revealed a nutrient-driven pathway that promotes tuft cell expansion via ILC2 activation under homeostatic conditions (Figure 1). In this pathway, food-derived nutrients sensed by enteroendocrine cells led to the secretion of glucagon-like peptide 2 (GLP2), which acted on GLP2 receptor-expressing subepithelial fibroblasts to drive production of thymic stromal lymphopoietin (TSLP).13 TSLP activated intestinal ILC2s, which in turn drove tuft cell hyperplasia in an IL-13-dependent manner.13 This finding demonstrated that epithelial nutrient sensing integrates with the tuft cell-ILC2 circuit to enable readiness for rapid type 2 immune responses. Despite the well-defined IL-25-mediated tuft cell-ILC2 circuit, the role of IL-25 in intestinal immunity remains controversial. At steady-state, IL-25 treatment induces elevated expression of type 2 cytokines (IL-4, IL-5 and IL-13) and pathological changes in the lung and digestive tract.14 These pathologies are characterized by increased mucus production, goblet cell hypertrophy and tuft cell hyperplasia.14-16 During parasitic infections, however, potent inflammatory responses induced by IL-25, including type 2 cytokine production and mucus secretion, contribute to the “weep and sweep” response (increased mucus production and smooth muscle contraction) which facilitates helminth expulsion.17 Currently, the IL-25-mediated tuft cell-ILC2 circuit is thought to be a critical regulator orchestrating intestinal inflammation and antihelminth immunity.16 Nevertheless, the mechanism underpinning IL-25-regulated intestinal homeostasis is not clear. Recently, Feng et al.18 (2025) and Cortez et al.19 (2025) threw light on the mechanisms governing intestinal homeostasis after prolonged IL-25 treatment. In the first study, Feng et al.18 (2025) investigated how succinate and helminth infection induce IL-25 and activate the tuft cell-ILC2 circuit in the small intestine (Figure 1). They found that IL-25 bioavailability is a key regulator of this pathway. Succinate is known to drive small intestinal remodeling through tuft cell-IL-25 signaling and calcium-dependent mechanisms.15, 20 Building on earlier work, the authors showed that succinate activates tuft cells by triggering cytosolic calcium signaling via the inositol 1,4,5-trisphosphate receptor type 2 (IP3R2). Short-term IL-25 exposure activated ILC2s, increasing their proliferation, IL-13 secretion and expression of IL-17RB (IL-25 receptor) and killer cell lecti-nlike receptor subfamily G member 1 (KLRG1). In contrast, chronic exposure to IL-25, induced by succinate treatment or helminth infection (H. polygyrus), drove ILC2 into a hypo-proliferative state and impaired ILC2 activation. Prolonged IL-25 signaling also occurred in tuft cells lacking IL-17RB. This deficiency increased IL-25 bioavailability in the small intestine at steady-state and resulted in prolonged activation of the tuft cell-ILC2 circuit. This chronic activation resulted in ILC2 hypo-proliferation, impairing succinate-induced activation of ILC2s. This hypo-proliferation could be overcome by the activation of the nuclear factor of activated T cells (NFAT) pathway. Overall, this study showed that cell-intrinsic IL-17RB expression by tuft cells controls IL-25 bioavailability and thereby regulates ILC2 activation under both physiological and pathological conditions, contributing to intestinal homeostasis. In the second study, Cortez et al.19 (2025) showed that repeated high-dose IL-25 treatment caused long-lasting intestinal remodeling characterized by gut lengthening and the expansion of tuft and goblet cells (Figure 1). Unlike ILC2 hypo-proliferation seen in chronic IL-25 exposure,18 the authors revealed that repeated IL-25 treatment enhanced ILC2-mediated protection against barrier pathogens across multiple tissues. It was shown that after repeated IL-25 dosing, intestinal ILC2s proliferated, produced higher levels of IL-5 and IL-13, and showed distinct transcriptomic and epigenetic features compared with steady-state ILC2s. These cells were termed “effector-memory” ILC2s. They were distributed broadly across tissues, including the lung, and supported long-lasting intestinal remodeling while protecting the host from multiple mucosal pathogens such as Salmonella and SARS-CoV-2. Although IL-25 has been reported to mediate the tuft cell-ILC2 circuit,12 this form of intestinal remodeling occurred independently of tuft cells or leucine-rich repeat-containing G-protein-coupled receptor 5 (LGR5)+ intestinal stem cells, and could be maintained without ongoing IL-25 or IL-33 signaling. Instead, IL-4-IL-4Ra signaling, another key regulator of the tuft cell-ILC2 circuit,12, 15 was essential for IL-25-induced intestinal remodeling. In contrast to the repeated IL-25 dosing, acute IL-25 exposure did not protect the host from intestinal or airway infection, possibly due to potential epithelial vulnerability after IL-25 treatment. Protection emerged only after a rest period following repeated IL-25 exposure, enabling tissues to adapt and stabilize. Overall, this study identified a previously unrecognized population of IL-25-induced effector-memory ILC2s that promote durable mucosal immunity and highlighted the critical role of a recovery phase or “rest” in establishing IL-25-induced intestinal remodeling and protection. Together, these studies illuminate the increasingly complex network of interactions between intestinal ILCs and epithelial cells (Figure 1). ILC3-derived IL-22-OSM signaling demonstrates that ILC3s actively tune epithelial sensitivity to inflammatory cues, priming epithelial responses to inflammation and cancer. In parallel, prostaglandin induces RANKL expression on ILC3s, which regulates intestinal stem cell responsiveness to IL-13, thereby shaping tuft cell differentiation and influencing ILC2-mediated antihelminth immunity. Finally, ILC2s integrate nutrient-derived signals and cytokine history to calibrate type 2 immune responses. In particular, the dose, duration and recovery time of IL-25 exposure shape ILC2 memory, epithelial adaptation and mucosal protection. Although these studies reveal promising potential ILC-targetable pathways, future studies will be needed to further dissect how IL-25 exposure and epithelial cues shape ILC2 effector and memory programs and determine how these pathways might be leveraged to balance protective immunity with prevention of pathological inflammation. Huiyang Yu: Conceptualization; visualization; writing – original draft; writing – review and editing. Evelyn Chen: Conceptualization; writing – original draft; writing – review and editing; visualization. Gabrielle T Belz: Conceptualization; writing – review and editing; funding acquisition; supervision. The authors declare no conflicts of interest.