Mucosal Immunology

{gamma}{delta} T cells provide mucosal defense against infection while also contributing to tissue repair. However, data regarding the effect of the human lung environment on {gamma}{delta} T cell functionality remains limited. To address whether lung inflammation impacts {gamma}{delta} T cell functionality, we analyzed lung and matched hilar lymph node (LN) tissue from deceased donors and patients with interstitial lung disease (ILD). We performed high-parameter spectral flow cytometry to examine the expression pattern of phenotypic biomarkers and assess ex vivo function. We identified lung-specific enrichment of {gamma}{delta} T cells with an effector memory phenotype relative to matched regional LN. We then used an ex vivo stimulation approach to interrogate the capacity to protect against infection (granzyme B [GzmB], interferon-{gamma} [IFN{gamma}] and tumor necrosis factor [TNF]) and promote epithelial cell proliferation (amphiregulin [AREG]). We found that {gamma}{delta} T cells in lung and LN from deceased donors had similar functional properties. While {gamma}{delta} T cell populations from ILD lungs largely maintained cytokine production capacity, expression was diminished relative to LN counterparts. Importantly, lung {gamma}{delta} T cells maintained polyfunctional GzmB, IFN{gamma} and TNF expression across cohorts. Overall, we report human lung {gamma}{delta} T cells are regionally distinct with conserved functionality in a fibrotic environment.

BackgroundMalnutrition compromises mucosal immunity, especially in the respiratory tract, increasing susceptibility to pathogens like Streptococcus pneumoniae. This study assessed whether nasal administration of Lacticaseibacillus rhamnosus CRL1505 or its peptidoglycan could promote the recovery of nasopharynx-associated lymphoid tissue (NALT) structure and functionality, thereby enhancing resistance to S. pneumoniae infection in protein-malnourished mice. MethodsMale Swiss albino mice were fed to a protein-free diet to induce malnutrition, followed by nutritional repletion with or without nasal supplementation of CRL1505 or its peptidoglycan. Resistance to S. pneumoniae infection, NALT architecture, immune cell composition in NALT and regional lymph nodes, and nasal cytokine production were evaluated. ResultsProtein deficiency caused marked NALT atrophy, immune cell depletion, and heightened susceptibility to S. pneumoniae. Nutritional repletion alone partially reversed these effects. In contrast, nasal supplementation with CRL1505 or its postbiotic fully restored NALT structure and cellularity, normalized lymphoid and myeloid populations, and reduced pathogen burden. Both treatments increased B and T lymphocytes, immature B cells, dendritic cells, and macrophages. The postbiotic also enhanced MHCII expression and balanced neutrophil-like Gr-1 cells. Notably, immune enhancement was evident even before infection, indicating a mucosal priming effect. Cytokine levels in nasal fluids remained largely unchanged. ConclusionsNasal delivery of L. rhamnosus CRL1505 or its postbiotic effectively reestablished NALT integrity and mucosal immunity in malnourished mice, providing significant protection against respiratory pathogens. These findings support the development of nasal immunobiotic formulations as non-invasive interventions to bolster respiratory defenses in immunocompromised hosts.

Polymorphonuclear neutrophils (PMNs) serve as frontline defenders against injury and infection, eliminating pathogens and initiating mucosal tissue repair. However, excessive PMN transepithelial migration (TEpM) contributes to chronic mucosal inflammatory disorders, including inflammatory bowel disease. PMN pro-inflammatory and pro-repair functions are regulated by incompletely defined signaling cascades involving kinases and phosphatases. Here, we determined how the protein tyrosine phosphatase CD45/PTPRC regulates PMN trafficking and effector functions in the gut. Pharmacologic inhibition of CD45 significantly reduced PMN colonic TEpM in vitro and in vivo and decreased intestinal PMN trafficking was observed in transgenic mice with PMN-specific deletion of CD45 (MRP8-Cre;Cd45fl/fl). Beyond limiting TEpM, CD45 depletion impaired key antimicrobial functions, including degranulation and phagocytosis, indicating broader effects on PMN effector activity. Importantly, recovery from dextran sodium sulfate (DSS)-induced colitis and biopsy-induced colonic wounding was delayed in MRP8-Cre;Cd45fl/fl mice, linking altered PMN function to defective mucosal healing. Mechanistically, CD45 depletion reduced surface expression of the {beta}2 integrin CD11b/CD18 and inactivated the Src family kinase member Lyn. Together, data highlight a novel CD45-CD11b-Lyn signaling axis that regulates PMN trafficking and effector functions in the intestine and identify CD45 as a promising target for modulating PMN function to promote mucosal tissue repair.

T cell development in the thymus requires tightly coordinated transcriptional programs that regulate lineage commitment, proliferation and differentiation. While key transcription factors controlling these processes have been extensively characterized, the contribution of the low expressed nuclear receptor Liver Receptor Homolog 1 (LRH-1, Nr5a2) in T cell development remains unexplored. Here, we investigated the role of LRH-1 in thymocyte maturation using an inducible ex vivo deletion system and in vivo Lck-Cre- and CD4-Cre-mediated LRH-1 knockout mouse models. We demonstrate that inducible LRH-1 deletion impairs early thymocyte development, identifying LRH-1 as a critical regulator of the double negative (DN)2/DN3 to DN4 transition. Early Lck-Cre-mediated deletion of LRH-1, but not CD4-Cre-mediated deletion at the double positive stage, resulted in markedly reduced thymic size and cellularity, indicating a stage-specific requirement for LRH-1 during thymopoiesis. Lck-Cre-mediated LRH-1 deletion led to a decreased frequency of mature CD4 T cells in peripheral lymphoid organs, while the remaining mature T cells were predominantly Cre reporter-negative and therefore escaped LRH-1 deletion. CD4 T cells that escaped Cre-mediated LRH-1 deletion exhibited impaired T cell activation marker expression and cytokine secretion. In vivo, these defects resulted in attenuated T cell effector function and compromised regulatory T cell-mediated protection in a T cell transfer model of colitis, indicating impaired effector and regulatory T cell function under (patho)physiological conditions. Collectively, our findings identify LRH-1 as a critical, previously unrecognized regulator of early thymocyte development, and establish its essential role in shaping functional peripheral CD4 T cell-mediated immune responses.

Mounting evidence indicates that T cells can operate in an innate-like mode challenging the classical description of T cells as strictly adaptive immune effectors. T cells can engage innate pattern recognition receptors to mount rapid but antigen-nonspecific responses to infection or cellular stress. This study observed that CD8+ T cells, and to a lesser extent also CD4+ T cells, responded to viral proteins in the mouse lung quickly in an innate-like fashion. We employed intravital lung microscopy to visualize infiltration of CD8+ T cells into the lung following intratracheal instillation of the SARS-CoV-2 envelope (E)-protein. Here, we demonstrate acute recruitment of CD8+ from the pulmonary microcirculation into the lung as early as 4 and 24 hours after (E)-protein instillation. The acute infiltration of CD8+ T cells was not observed in Tlr2-/- mice. Immunohistochemistry analysis of mouse lungs revealed T cell accumulation in nodular inflammatory foci (NIF) of the lung at perivascular regions and around large airways. Stimulating spleen-derived CD8+ T cells from wild-type mice with (E)-protein ex vivo in combination with cytokines or TCR agonists significantly upregulated CD69 and activated secretion of interferon (IFN){gamma} which was not observed with CD8+ T cells isolated from Tlr2-/- mice. These findings indicate rapid bystander activation of CD8+ T cells by the SARS-CoV-2 envelope (E)-protein that depends on (E)-protein sensing by TLR2. This innate-like CD8+ T cell response to SARS-CoV-2 (E)-protein may offer novel opportunities for diagnostic and therapeutic development, warranting further investigation.

Type I interferons (IFN-Is) play a critical role in innate immunity, modulating the host response. While dysregulated IFN-I signaling has been implicated in autoimmune and infectious disorders, its role in inflammatory bowel disease (IBD) remains unclear. In this study, we extensively assessed the function of IFN-I signaling in human IBD and murine models of colitis. Expression of IFN-I signature genes was elevated in patients with active ulcerative colitis as well as multiple murine models of colitis. Single cell RNA sequencing revealed that upregulated IFN-I signature genes were enriched in myeloid cells, which exhibited increased expression of IFN receptors during mucosal inflammation. Mice carrying gain-of-function alleles of Ifnar1, a subunit of IFN-I receptor, showed heightened IFN-I signaling and altered colonic immune homeostasis at baseline, and were more susceptible to experimental colitis. In contrast, postnatal inhibition of IFNAR1, using either an inducible transgenic mouse model or an anti-IFNAR1 blocking antibody, protected against experimental colitis. Taken together, our findings reveal a previously under-recognized pathogenic role of IFN-I in IBD and provide a rationale for therapeutic intervention targeting this pathway.

T-helper (Th)-17 lymphocytes are central mediators of adaptive type 17 immunity. Decreased type-17 signaling increases severity of infections in humans and mice. However, detrimental effects of excessive type 17 responses in autoimmune and other inflammatory diseases highlight a need for type-17 immune calibration to support beneficial host defense requirements. Mechanisms of type 17 calibration are poorly understood. A gut-lung axis has been proposed to coordinate homeostatic protection and acute host defense. Factors that acutely alter the gut microbiome are heterogeneous and include acute intestinal infections, non-infectious colitis, and medical treatments such as antibiotics. How changes in the gut microbiome affect lung immune tone during homeostasis and acute pulmonary infections are also poorly understood. Prior studies have shown that antibiotics reduce expression of IL-17-mediated host defense in the gut. Since gut microbial homeostasis influences Th17 cell numbers in both the intestine and remote tissues, we postulated that antibiotic treatment would result in gut dysbiosis and weakened type-17 host defense in the lungs. We found that amoxicillin induces significant dysbiosis that is long-lasting and that there is a long-term decrease in type-17 tone in the lungs. We also found that in mice lacking the gut mucin, Muc2, Th17 cells increased in the lungs following inflammatory challenge. These findings suggest that antibiotic-induced dysbiosis can decrease lung immune defenses for long periods of time after cessation of antibiotic treatment.

Respiratory viruses can induce excessive bronchoconstriction in both asthmatic and healthy airways. Airway mucins such as Muc5ac form the first line of defense against inhaled pathogens. However, when produced in excess, they can also contribute to airway narrowing and mucus plug formation in asthma. In this study, we investigated the role of airway mucins in host defense against parainfluenza virus and in virus-induced airway hyperresponsiveness using Muc5ac-deficient (Muc5ac-/-) C57BL/6 mice. Parainfluenza virus infection induced airway hyperresponsiveness to inhaled methacholine in wild-type mice, an effect that was abolished in Muc5ac-/- mice. Parainfluenza virus-induced airway hyperresponsiveness was reversed by vagotomy, demonstrating it is mediated by parasympathetic nerve dysfunction. Muc5ac-/- mice exhibited higher viral titers, increased bronchoalveolar lavage cellularity, and elevated antiviral cytokine levels, but did not develop airway hyperresponsiveness. We did not see mucus plugging in any of our animals. Together, these findings indicate that Muc5ac is important for host defense against parainfluenza virus but paradoxically is also required for virus-induced airway hyperresponsiveness.

There is growing evidence that neonates harbor innate-like CD8a+ T cell subsets that contribute to both protection and hyper-inflammatory states. It remains unclear, however, where these innate-like features are found among the many conventional and unconventional T cell populations that can upregulate the CD8 receptor. Further delineation of these unique populations and functions, with a focus on CD8ab co-expression, will enable studies that seek to understand the unique immune features in conventional T cell populations that are present during fetal and early postnatal life. We used cord blood from infants across the full viable gestational age range to examine phenotypic and transcriptional heterogeneity, with a particular focus on the naive T cell pool. We report a set of fetally-derived and innate-like naive CD8{beta}+ T cells ( FITs) that are marked by their KLRG1+CD161+ phenotype, unique transcriptomic features and which are sparsely detected in adult peripheral blood. Additionally, using T cell receptor repertoire profiling, we can distinguish FITs from well-described and semi-invariant unconventional T cell populations such as mucosa-associated invariant T cells. Our delineation of FITs unique features will enable future investigation into their ontogeny and tissue distribution, and ultimately their role in immune-related outcomes in preterm infants.

Resident dermal macrophages (DMs) play essential roles in maintaining skin homeostasis and initiating inflammatory responses during tissue injury and against infectious agents. However, studies of their cellular mechanisms have been limited by their low abundance in steady-state skin and by technical challenges in isolating resident DMs. Here, we describe the generation and characterization of a novel DM cell line, termed SB89. F4/80+ skin-resident DMs were sorted and immortalized using J2 retroviral transduction. SB89 cells display a stable, homogeneous macrophage phenotype and distinct surface markers compared with Langerhans cells and alveolar macrophages. Functionally, SB89 cells efficiently phagocytose methicillin-resistant Staphylococcus aureus (MRSA), Escherichia coli, zymosan particles, and apoptotic cells, and effectively kill MRSA. Importantly, SB89 cells respond to LPS, as evidenced by production of IL-6, TNF, and IL-10, and by MRSA-induced production of inflammatory cytokines, chemokines, and eicosanoids. RNA-seq and gene ontology analyses revealed that SB89 cells elicit stronger responses in innate immunity, cell signaling, and epigenetic regulation than immortalized bone marrow-derived macrophages. SB89 cells are genetically tractable, amenable to gene silencing via RNAi and gene introduction via plasmid transfection. Overall, SB89 cells provide a renewable, dermis-imprinted macrophage model that preserves key functional and transcriptional features of resident DMs while reducing reliance on primary cells and animal models. This cell line represents a powerful platform for mechanistic, genetic, and translational studies in skin immunobiology.

BackgroundT helper 2 (Th2) lymphocytes orchestrate type-2 immunity and drive allergic diseases that disproportionately affect females. Sexual dimorphism in Th2 responses is well-documented, yet current models attribute sex differences exclusively to circulating gonadal hormones and sex chromosomes. Whether cell-intrinsic steroidogenesis, mediated by the enzyme Cyp11a1, contributes to female-biased Th2 differentiation and function remains unknown. MethodsTranscriptomes of in vitro generated Th2 cells from male and female T cell-specific Cyp11a1-knockout (Cyp11a1fl/fl;Cd4Cre) and control (Cyp11a1fl/fl) mice were compared. Differential expression, hallmark pathway analysis, transcription factor activity scoring, and functional assays were performed across sexes and genotypes. Cyp11a1-dependent differentially expressed genes were integrated with sex-stratified human Th2 transcriptomes obtained from the type-2 inflammatory skin disease atopic dermatitis. ResultsCyp11a1 deletion markedly reduced the transcriptional signature distinguishing female from male Th2 cells. Female Cyp11a1-knockout Th2 cells underwent extensive transcriptomic reprogramming converging toward the male profile, while male cells were largely unaffected. Female-specific pathway changes included reduced inflammatory signatures and enhanced cell-cycle programmes. Functionally, female Cyp11a1-deficient Th2 cells exhibited significantly increased proliferation and elevated IL-13 production; male knockout cells showed no comparable changes. These effects were developmentally stage-specific, emerging during Th2 differentiation but not in naive precursors. Cross-species analysis identified a conserved gene module shared between Cyp11a1-deficient female mouse Th2 cells and female-biased human Th2 cells in atopic dermatitis. ConclusionsCyp11a1-mediated steroidogenesis is a cell-intrinsic regulator of the female-biased Th2 transcriptional and functional state, identifying de novo steroidogenesis as a mechanism of immunological sexual dimorphism with direct relevance for female-predominant allergic disease.

Naive CD4+ T cells differentiation into T-helper type 2 (TH2) cells requires Interleukin 2 (IL-2) and IL-4-dependent signaling as well as presentation of allergens by dendritic cells (DCs). The role of IL-2 and IL-4 in TH2 differentiation has been mostly studied in vitro, however, these models do not account for the heterogeneity of TH responses and bypass the DC-derived signals that are necessary in vivo. We used cytokine-blocking antibodies and IL-4RKO/IL-4RWT mixed bone marrow chimeras to show that IL-4 signaling was not required for initial upregulation of GATA3 by CD4+ T cells after intradermal immunization, but was necessary for later TH2 cell expansion and further GATA3 upregulation. Single-cell transcriptomics and computational analyses confirmed that IL-4 signaling was not necessary for TH2 identity but promoted TH2 proliferation and expression of a pathogenic signature. Early IL-2 blockade prevented GATA3 upregulation without affecting TH2 proliferation or the differentiation of TH1 and TFH subsets after immunization. Adoptive transfer experiments showed that reduced competition for IL-4 in vivo drove extensive T cell proliferation and preferential expansion of the GATA3hi population. Overall, our results suggest temporally and functionally distinct roles of IL-2 and IL-4 during TH2 differentiation: IL-2 is necessary for GATA3 upregulation, while IL-4 drives subsequent TH2 proliferation and licensing to effector activity. Therefore, IL-2 and IL-4 act in a co-ordinated manner to respectively promote TH2 differentiation, expansion, and effector commitment in the LN.

Inflammatory bowel disease (IBD), comprising Ulcerative colitis (UC) and Crohns Disease, is a chronic relapsing immune-mediated inflammatory disorder of the gut. The intestinal mucus layer is a protective barrier that safeguards direct exposure of epithelium to luminal microbes and antigens. A prolonged disruption of the mucus layer may contribute to the development of IBD. Loss of mucin-producing goblet cells is a hallmark of UC. The underlying molecular mechanism controlling goblet regulation remains poorly understood. In the current work, we show a key role for NCoR1 (Nuclear corepressor 1) in goblet cell regulation. A specific downregulation of NCoR1 in intestinal crypts and goblet cells was observed in human UC and mice models. While NCoR1 was upregulated during goblet cell differentiation, inflammatory cues downregulated its expression. Experimental loss of NCoR1 resulted in exacerbated disease in a murine model of colitis, whereas its upregulation via Vitamin D led to a rescue. ChIP-seq led to the identification of KLF-16, a transcription factor, as a target of NCoR1. NCoR1 -KLF16 regulatory axis regulated key goblet cell proteins, including MUC2. Mechanistically, the regulation of MUC2 is modulated by the NCoR1-KLF16 axis, via mTOR signalling. In conclusion, this work shows a critical involvement of NCoR1-KLF16 in governing goblet cell function and intestinal homeostasis.

Aspergillus fumigatus is a ubiquitous environmental mould and a leading cause of chronic fungal-associated respiratory disease, yet the mechanisms by which persistent airway colonisation drives immune adaptation and lung pathology remain poorly understood. Progress in this area has been limited by the lack of in vivo models that recapitulate stable, non-invasive fungal persistence without immunosuppression. Here, we developed and optimised a murine model of chronic airway colonisation using agar bead-embedded A. fumigatus conidia delivered intratracheally. Embedding did not impair fungal germination or hyphal growth, and the agar matrix was immunologically inert, supporting its use as a neutral scaffold. This approach established stable fungal persistence in the airways for at least three weeks in immunocompetent mice without inducing invasive disease or systemic morbidity. Colonisation elicited a transient, airway-restricted innate immune response characterised by early neutrophil and monocyte recruitment and increased CXCL1, MIP-1, MIP-1{beta}, and TNF production, which resolved over time. Histopathological analysis revealed a progressive sequence of disease-relevant features, including initial immune containment, followed by mucus hypersecretion, and airway remodelling. At the adaptive level, persistent colonisation induced a dynamic T cell response that transitioned from an early polyfunctional profile to a sustained Th17-dominant phenotype. Importantly, application of this model in CFTR-deficient mice uncovered enhanced collagen deposition and fibrotic remodelling without altered fungal burden, demonstrating its utility in modelling disease-relevant outcomes in susceptible hosts. Together, this study establishes a robust and physiologically relevant platform for investigating host-fungal interactions during chronic airway colonisation. This model provides new opportunities to dissect mechanisms of immune adaptation, fungal persistence, and tissue remodelling, and to identify therapeutic strategies targeting chronic Aspergillus-associated lung disease.

Inflammatory bowel disease (IBD) is a chronic inflammatory disorder of the gastrointestinal tract that encompasses ulcerative colitis and Crohns disease. Here we identify the cystine/glutamate antiporter xCT as being markedly upregulated in the inflamed intestinal epithelium of patients with IBD. To clarify its functional contribution to disease pathogenesis, we performed genetic loss-of-function study and found that inhibition of xCT confers robust protection against dextran sulfate sodium (DSS)-induced colitis in mice. Intestinal epithelial cell (IEC)-specific deletion of xCT markedly attenuated colitis severity, demonstrating that epithelial xCT upregulation acts as a disease-exacerbating factor in IBD. Mechanistically, xCT deficiency preserved intracellular glutamate levels and protein polyglutamylation, thereby maintaining epithelial barrier integrity and protecting IECs from inflammatory injury. Consistently, pharmacological inhibition of glutamine synthetase, which increases intracellular glutamate, exerted a potent anti-inflammatory effect on the DSS-induced colitis. These findings identify intracellular glutamate retention in IECs as a previously unrecognized mechanism of epithelial protection and highlight both inhibition of xCT-dependent glutamate efflux and suppression of glutamine synthetase as potential therapeutic strategies for IBD.

Circadian rhythms, 24-hour repeating oscillations in daily physiology, are implicated in maintaining intestinal homeostasis. These rhythms are driven by the circadian clock, a molecular timekeeper found throughout cells of the body, including those of the intestinal epithelium. Loss of clock function has been found to worsen colitis; however, it is not clear how the clock impacts regeneration which enables a tissue to return to its homeostatic set point following an injury. To investigate these questions, we used a conditional knockout of the core clock gene, Bmal1, in mouse colon epithelial cells. Our data show that prior to injury Bmal1 promotes colon mucus production, which increases in thickness and within goblet cells when mice are active and begin feeding. Bmal1 loss lowers mucus production but does not drive an apparent tissue phenotype until the system is injured and regenerates itself. In this context, Bmal1 epithelial loss drives a male-specific colitis phenotype and a delay in the ability of colon epithelial cells of both male and female mice to resolve injury to return to their homeostatic set point. Our data suggest that epithelial sex-specific clock rhythms are needed for optimal colon barrier homeostasis.

Coeliac Disease (CeD) is a chronic gastrointestinal inflammatory disease initiated by dietary gluten in genetically predisposed individuals. While the inflammatory processes which drive tissue destruction in the coeliac duodenum have been extensively characterised, an increased oxidative stress (OS) response has also been suggested to contribute to CeD pathogenesis. However, the precise mechanisms which regulate OS in the coeliac mucosa and whether they impact inflammation remain ill defined. The master anti-oxidant transcriptional regulator Nuclear factor erythroid 2-related factor 2 (Nrf2), and its inhibitor, Kelch like ECH-associated protein 1 (Keap1) have been implicated in chronic gastrointestinal inflammatory diseases, such as ulcerative colitis but have been largely unexplored in the context of CeD. To investigate redox balance in the CeD duodenum, we utilised single cell transcriptomics to assess overall OS and cytoprotective Nrf2 activation across cell subsets in duodenal biopsies from CeD patients. OS induced gene expression was broadly increased across multiple cell subsets in the CeD mucosa. Simultaneously, specific markers of Nrf2 activation were decreased in cell subtypes central to pathogenesis of CeD, including activated CD4+ T cells and intraepithelial T lymphocytes, indicating a distinct redox imbalance in these cells. Furthermore, pharmacological activation of Nrf2 significantly decreased gliadin induced IFNG expression in CeD duodenal biopsies. Taken together, our findings demonstrate that redox imbalance represents a therapeutic opportunity for the modulation of proinflammatory responses that drive the pathogenesis of CeD.

Although early-life immunity was once considered immature, the human fetal immune system is dynamic and compartmentalized by the second trimester. By 21 weeks of gestation, T lymphocytes become a major immune population in the fetal small intestine (SI), yet their functional roles within this tissue remain largely undefined. To explore their unique contributions to intestinal development, we established an ex vivo co-culture system in which mucosal T cells isolated from fetal, neonatal, or adult SI donors were cultured with tissue-derived 3D SI organoids derived from various ages. Homeostatic early-life (fetal and neonatal) SI T cells uniquely promoted organoid generation, a metric of stem cell renewal, by upregulating cell cycle-associated gene programs. These early-life T cells also directed intestinal stem cell differentiation toward the secretory lineage in both growth and differentiation phase, highlighting that T cells poise stem cells to adopt secretory fates. T cells from infants with necrotizing enterocolitis (NEC), an inflammatory intestinal disease affecting predominantly preterm infants, failed to activate these same programs, suggesting a pathologic role for T cells in NEC. T cells from the adult SI similarly failed to support organoid growth or differentiation, revealing developmentally specialized, nonimmune functions for early-life T cells in the intestine. Similarly, T cells derived from cord blood did not enhance organoid generation, indicating that this function is not necessarily a generalized feature of early-life T cells but rather is restricted to mucosal T cells. Organoids derived from adults or NEC, however, could re-enter regenerative states when co-cultured with fetal T cells, indicating that fetal T cells can restore stem cell self-renewal across developmentally and disease-imposed states. We further identified that T cell-derived soluble factors alone were insufficient to modulate intestinal stem cell fate, implying the need for physical interactions. Concordant with this finding, we report that T cells heavily localize to the stem cell niche during prenatal development, where they express factors involved in Notch, Wnt, and growth factor signaling to support fetal stem cell function. Collectively, these findings reveal a coordinated developmental program in which fetal SI T cells balance stem cell self-renewal and differentiation, identifying a developmental immune-epithelial axis that can be harnessed to restore intestinal regeneration.

Type 2 high asthma is driven by coordinated GATA3 dependent programs in CD4+ T cells and group 2 innate lymphoid cells (ILC2). Although biologics targeting IL4, IL5, or IL13 benefit subsets of patients, many remain symptomatic, suggesting that upstream regulatory mechanisms may sustain type 2 inflammation. We investigated whether HuR (ELAVL1), an RNA-binding protein that stabilizes GATA3 and Th2 cytokines mRNA, regulates type 2 inflammatory programs in allergic asthma. Using a house dust mite (HDM) model in vivo, HuR inhibition with the small molecule KH3 reduced lung inflammation, suppressed Th2 cytokine expression, accelerated Gata3 mRNA decay in lung CD4+ T cells, and attenuated airway hyperresponsiveness toward control levels. In ex vivo activated human lung CD4+ T cells, KH3 accelerated GATA3 mRNA decay with minimal effects on RORC or TBX21 and selectively reduced Th2 cytokine secretion, while IL10 and IL2 were unchanged. Similarly, ILC2s isolated from peripheral blood mononuclear cells (PBMCs) of type 2 high asthmatic donors showed reduced GATA3 mRNA stability and diminished Th2 cytokine production following KH3 treatment. Single-cell transcriptomic analysis of bronchoalveolar lavage fluid after allergen challenge demonstrated co-enrichment of ELAVL1 and GATA3 within Th2 clusters in human airways. Together, these findings identify HuR as a post-transcriptional regulator of GATA3 driven type 2 inflammation in allergic asthma.

ProblemThe anti-microbial protein granulysin is present in vaginal secretions during the follicular phase of the menstrual cycle but nearly disappears during the luteal phase. The reason for this change is unknown. Method of studyParticipants (n = 23) with regular menstrual cycles collected daily vaginal swabs for granulysin ELISAs. Endocervical cytobrushes, ectocervical biopsies, vaginal biopsies, and PBMC were collected across the cycle to enumerate granulysin-expressing cells by flow cytometry. Cycle phase was determined by daily urinary luteinizing hormone testing and confirmed by serum progesterone levels. ResultsGranulysin levels in secretions were up to 10,000 times higher during menstruation than during the luteal phase (menstruation, median 3,924 pg/mL [IQR 400-17,280]; luteal, median and IQR undetectable [<7.81 pg/mL]). In the endocervical canal, granulysin-expressing cells were much more abundant during menstruation than during the mid-follicular or mid-luteal phases. In contrast, the number of granulysin-expressing cells in the ectocervix and vagina remained stable during the cycle. The most abundant granulysin-expressing cell types in the mucosa were CD8 T cells and NK cells. In a minority of participants, granulysin was consistently detected in luteal-phase swabs; this phenomenon was associated with parity. ConclusionsGranulysin in vaginal secretions is associated with menstruation, which also drives a spike in granulysin-expressing cells in the endocervical canal. This result explains the much higher granulysin levels in secretions during the follicular than the luteal phase. In contrast, immune cells from ectocervical and vaginal biopsies express granulysin independently of the menstrual cycle, indicating their continuous ability to respond to microbial infection.