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).

Clonal hematopoiesis of indeterminate potential (CHIP) arises from aging-associated acquired mutations in hematopoietic progenitors, which display clonal expansion and produce phenotypically altered leukocytes. We associated CHIP-DNMT3A mutations with a higher prevalence of periodontitis and gingival inflammation among 4,946 community-dwelling adults. To model DNMT3A-driven CHIP, we used mice with the heterozygous loss-of-function mutation R878H, equivalent to the human hotspot mutation R882H. Partial transplantation with Dnmt3aR878H/+ bone marrow (BM) cells resulted in clonal expansion of mutant cells into both myeloid and lymphoid lineages and an elevated abundance of osteoclast precursors in the BM and osteoclastogenic macrophages in the periphery. DNMT3A-driven clonal hematopoiesis in recipient mice promoted naturally occurring periodontitis and aggravated experimentally induced periodontitis and arthritis, associated with enhanced osteoclastogenesis, IL-17-dependent inflammation and neutrophil responses, and impaired regulatory T cell immunosuppressive activity. DNMT3A-driven clonal hematopoiesis and, subsequently, periodontitis were suppressed by rapamycin treatment. DNMT3A-driven CHIP represents a treatable state of maladaptive hematopoiesis promoting inflammatory bone loss.
Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.

Butyrate-a metabolite produced by commensal bacteria-has been extensively studied for its immunomodulatory effects on immune cells, including regulatory T cells, macrophages and dendritic cells. However, the development of butyrate as a drug has been hindered by butyrate's poor oral bioavailability, owing to its rapid metabolism in the gut, its low potency (hence, necessitating high dosing), and its foul smell and taste. Here we report that the oral bioavailability of butyrate can be increased by esterifying it to serine, an amino acid transporter that aids the escape of the resulting odourless and tasteless prodrug (O-butyryl-L-serine, which we named SerBut) from the gut, enhancing its systemic uptake. In mice with collagen-antibody-induced arthritis (a model of rheumatoid arthritis) and with experimental autoimmune encephalomyelitis (a model of multiple sclerosis), we show that SerBut substantially ameliorated disease severity, modulated key immune cell populations systemically and in disease-associated tissues, and reduced inflammatory responses without compromising the global immune response to vaccination. SerBut may become a promising therapeutic for autoimmune and inflammatory diseases.
© 2024. The Author(s).

Rationale Bronchopulmonary dysplasia (BPD) is the most common morbidity affecting very preterm infants. Gut microbial communities contribute to multiple lung diseases and gut microbiome alterations may be a factor in BPD pathogenesis. Objective To determine if features of the multikingdom gut microbiome predict the development of BPD in very low birthweight newborns. Methods We performed a prospective, observational cohort study comparing the multikingdom fecal microbiota of 147 preterm infants with BPD or post-prematurity respiratory disease (PPRD) by sequencing the bacterial 16S and fungal ITS2 ribosomal RNA gene. To address the potential causative relationship between gut dysbiosis and BPD, we used fecal microbiota transplant in an antibiotic-pseudohumanized mouse model. Comparisons were made using RNA sequencing, confocal microscopy, lung morphometry, and oscillometry. Measurements and Main Results We analyzed 100 fecal microbiome samples collected during the second week of life. Infants who later developed BPD showed an obvious fungal dysbiosis as compared to infants with PPRD ( P = 0.0209). Instead of fungal communities dominated by Candida and Saccharomyces , the microbiota of infants who developed BPD were characterized by the abundance of Aureobasidium and a greater diversity of rarer fungi in less interconnected community architectures. On successful colonization, the gut microbiota from infants with BPD augmented lung injury in the offspring of recipient animals. We identified alterations in the murine lung and intestinal microbiomes and transcriptional alterations associated with augmented lung injury. Conclusions The gut fungal microbiome of infants who will develop BPD is dysbiotic and may contribute to disease pathogenesis. Trial Registration NCT03229967.

Natural IL-17-producing γδ T cells (γδT17 cells) are unconventional innate-like T cells that undergo functional programming in the fetal thymus. However, the intrinsic metabolic mechanisms of γδT17 cell development remain undefined. Here, we demonstrate that mTORC2, not mTORC1, selectively controls the functional fate commitment of γδT17 cells through regulating transcription factor c-Maf expression. scRNA-seq data suggest that fetal and adult γδT17 cells predominately utilize mitochondrial metabolism. mTORC2 deficiency results in impaired Drp1-mediated mitochondrial fission and mitochondrial dysfunction characterized by mitochondrial membrane potential (ΔΨm) loss, reduced oxidative phosphorylation (OXPHOS), and subsequent ATP depletion. Treatment with the Drp1 inhibitor Mdivi-1 alleviates imiquimod-induced skin inflammation. Reconstitution of intracellular ATP levels by ATP-encapsulated liposome completely rescues γδT17 defect caused by mTORC2 deficiency, revealing the fundamental role of metabolite ATP in γδT17 development. These results provide an in-depth insight into the intrinsic link between the mitochondrial OXPHOS pathway and γδT17 thymic programming and functional acquisition.
© 2023 The Author(s).