Early immune dynamics during the initiation of fatal tularemia caused by Francisella tularensis infection remain unknown. Unto that end, we generated a transcriptomic map at single-cell resolution of the innate-like lymphocyte responses to F. tularensis live vaccine strain (LVS) infection of mice. We found that both interferon-γ (IFN-γ)-producing type 1 and interleukin-17 (IL-17)-producing type 3 innate-like lymphocytes expanded in the infected lungs. Natural killer (NK) and NKT cells drove the type 1 response, whereas mucosal-associated invariant T (MAIT) and γδ T cells drove the type 3 response. Furthermore, tularemia-like disease resistant NKT cell-deficient, Cd1d -/- mice accumulated more MAIT1 cells, MAIT17 cells, and cells with a hybrid phenotype between MAIT1 and MAIT17 cells than wild-type mice. Critically, adoptive transfer of LVS-activated MAIT cells from Cd1d -/- mice, which were enriched in MAIT17 cells, was sufficient to protect LVS-susceptible, immunodeficient RAG2 -/- mice from severe LVS infection-inflicted pathology. Collectively, our findings position MAIT cells as potential mediators of IL-17-dependent protection from pulmonary tularemia-like disease.
© 2025 The Author(s).

Pediatric ulcerative colitis (UC) is an inflammatory bowel disease characterized by dysregulated immune responses and intestinal inflammation, often more severe than adult-onset UC. Th17 cells play a crucial role in UC pathogenesis but the mechanisms regulating their differentiation and recruitment in pediatric UC remain incompletely understood.
Transcriptomic analysis of pediatric UC patients and weighted gene co-expression network analysis (WGCNA) were performed to identify key dysregulated genes. The functional role of the candidate gene ITGAX was investigated using in vitro Th17 differentiation assays with siRNA knockdown and an in vivo dextran sodium sulfate (DSS)-induced UC mouse model with intrarectal siRNA administration.
WGCNA identified ITGAX, SOCS3, CXCL1, CASP1, and CXCL11 as core upregulated genes in pediatric UC, with ITGAX being a novel candidate regulator of Th17 cells. ITGAX knockdown in naive CD4+ T cells impaired Th17 differentiation and IL-17A production in vitro. In the DSS-induced UC mouse model, intrarectal ITGAX siRNA ameliorated colonic inflammation and ulceration, suppressed IL-17A levels, and selectively reduced the expansion of IFNγ-IL-17+ Th17 cells in the colon.
ITGAX is a key promoter of Th17-cell differentiation and expansion, contributing to the pathogenesis of pediatric UC. Targeting ITGAX may represent a potential therapeutic strategy for pediatric UC by modulating aberrant Th17 responses.
©The Author(s) 2025. Open Access. This article is licensed under a Creative Commons CC-BY International License.

Tertiary lymphoid structures (TLSs) are de novo ectopic lymphoid aggregates that regulate immunity in chronically inflamed tissues, including tumours. Although TLSs form due to inflammation-triggered activation of the lymphotoxin (LT)-LTβ receptor (LTβR) pathway1, the inflammatory signals and cells that induce TLSs remain incompletely identified. Here we show that interleukin-33 (IL-33), the alarmin released by inflamed tissues2, induces TLSs. In mice, Il33 deficiency severely attenuates inflammation- and LTβR-activation-induced TLSs in models of colitis and pancreatic ductal adenocarcinoma (PDAC). In PDAC, the alarmin domain of IL-33 activates group 2 innate lymphoid cells (ILC2s) expressing LT that engage putative LTβR+ myeloid organizer cells to initiate tertiary lymphoneogenesis. Notably, lymphoneogenic ILC2s migrate to PDACs from the gut, can be mobilized to PDACs in different tissues and are modulated by gut microbiota. Furthermore, we detect putative lymphoneogenic ILC2s and IL-33-expressing cells within TLSs in human PDAC that correlate with improved prognosis. To harness this lymphoneogenic pathway for immunotherapy, we engineer a recombinant human IL-33 protein that expands intratumoural lymphoneogenic ILC2s and TLSs and demonstrates enhanced anti-tumour activity in PDAC mice. In summary, we identify the molecules and cells of a druggable pathway that induces inflammation-triggered TLSs. More broadly, we reveal a lymphoneogenic function for alarmins and ILC2s.
© 2025. The Author(s).

Ascariasis (roundworm) is the most prevalent parasitic nematode infection worldwide, impacting approximately 500 million people predominantly in low- and middle-income countries (LMICs). While people of all ages are infected with Ascaris , infection intensity (defined by worm burden) paradoxically peaks in pre-school and school aged children but then declines with age. The cause of age-dependent Ascaris worm intensity is not well understood but may be dependent on cellular changes in mucosal barrier sites. We have previously found that the gastric mucosa is a critical barrier site for Ascaris infection. Following oral ingestion of Ascaris eggs, larvae use AMCase secreted by gastric chief cells and acid secreted by gastric parietal cells to hatch. Once hatched, larvae translocate across the gastric mucosa to initiate the larval migratory cycle. However, inducing mucosal injury with administration of Tamoxifen induces mucosa cellular changes that impairs Ascaris hatching and reduces larval translocation across the gastric mucosa. In this study we established a repeated Ascaris suum challenge mouse model and evaluated if repeated Ascaris challenge also lead to cellular changes in the gastric mucosal barrier. We found that repeated Ascaris challenge caused cellular changes in the gastric mucosa which reduced worm intensity in the liver independent of the adaptive immune response. Thus, in endemic regions, where individuals experience recurrent infection throughout their lives, gastric cellular changes may be a key mechanism leading to the observed age-dependent Ascaris worm intensity changes from childhood to adulthood.

The immune system has emerged as an important target of thyroid hormones (THs); however, the role of TH in T cells has so far remained elusive. In this study, we assessed the effect of TH receptor α (TRα) signaling on activation and function of T cells. Our findings show that lack of canonical TRα action not only increased the frequency of regulatory T cells (Treg) but propelled an activated and migratory Treg phenotype and nuclear factor κB (NF-κB) activation in Treg. Conversely, canonical TRα action reduced activation of the NF-κB pathway previously shown to play a pivotal role in Treg differentiation and function. Taken together, our findings demonstrate that TRα impacts T cell differentiation and phenotype. Given the well-known interaction of inflammation, immune responses, and TH axis in e.g., severe illness, altered TH-TRα signaling may have an important role in regulating T cell responses during disease.
© 2024 The Author(s).