Biology subjects

Weaver, C. T.

Publications and source records attributed to Weaver, C. T..

7 recordsLinked to original sources

bioRxiv2026

Ileitis abolishes tolerogenic functions of the enterohepatic bile acid pool

Bile acids (BAs) regulate lipid uptake, epithelial integrity, and immune responses in the gut. Hepatocytes synthesize primary BAs, which microbiota metabolize into secondary metabolites. Together, these species form a composite pool that circulates enterohepatically between the liver and intestines. Here, we show that immunoregulatory outputs of the enterohepatic BA pools involve competition between multiple BA species for individual nuclear receptors and are dependent on intestinal health. In healthy mice, the primary BA, tauro {beta} muricholic acid (t{beta}MCA) antagonized ROR{gamma}t-mediated Th17 function in the presence of two secondary BAs (tDCA, tLCA) which activated ROR{gamma}t. Conversely, ileitis in Crohns disease patients and Tnf{delta}ARE mice depleted primary BAs by reducing the number and function of BA transporting enterocytes. In mice, ileitis driven t{beta}MCA depletion enhanced tDCA and tLCA mediated ROR{gamma}t activation and supported Th17 cell function. Replenishing t{beta}MCA in Tnf{delta}ARE mice reestablished BA dependent Th17 cell regulation. Thus, intra pool competition underpins BA immunoregulatory functions and reveals new opportunities for precision Crohns disease therapy.

immunology↗

bioRxiv2026

IL-23 Licenses Pathogenic Th17 Transdifferentiation via STAT4-dependent Upregulation of IL-12Rβ2

Th17 cells exhibit substantial developmental plasticity, transdifferentiating into pathogenic, interferon-{gamma} (IFN-{gamma})-producing Th1-like effectors during chronic autoimmune inflammation. While both IL-23 and IL-12 are implicated in this process, how these structurally related cytokines coordinate to drive transdifferentiation remains unresolved. Here, we show that IL-23 acts as a developmental licensor rather than a terminal trigger, priming Th17 cells for transdifferentiation upon subsequent IL-12 encounter. IL-23 signals through STAT4 to upregulate the IL-12-specific receptor subunit IL-12R{beta}2, lowering the signalling threshold for IL-12. This licensing can be conferred at both early and late stages of Th17 development and produces a temporal logic in which IL-23-mediated STAT4 signaling functionally arms Th17 cells to terminally transdifferentiate in response to IL-12. Using Stat4 conditional knockouts and a structure-based IL-23 mutein that selectively abolishes IL-23-driven STAT4 signaling while preserving STAT3-dependent lineage maintenance, we genetically establish the IL-23-STAT4-IL-12R{beta}2 axis as a discrete licensing module. Furthermore, using the adoptive Th17 transfer colitis model, we show that host-derived IL-23 and IL-12 are required for Th17-driven colitis, and the inflamed colonic environment reconstitutes transdifferentiation capacity in classically "non-pathogenic" Th17 cells. These findings reframe the pathogenic dichotomy of Th17 cells as one of cumulative cytokine exposure rather than fixed cellular fate, and reveal a stepwise architecture of Th17 plasticity in which IL-23 licensing and IL-12 triggering operate as functionally distinct events. Significance StatementTh17 cells protect mucosal barriers but can convert into pathogenic, IFN-{gamma}-producing effectors that drive inflammatory bowel disease (IBD). Although IL-23 is essential for this conversion, the underlying molecular mechanism remains elusive. We show that IL-23 does not directly trigger transdifferentiation but instead licenses Th17 cells for this conversion, during both early and late stages of their development. By signaling through STAT4, IL-23 upregulates the IL-12-specific receptor subunit IL-12R{beta}2 on Th17 cells, rendering them responsive to subsequent IL-12 exposure. Our findings reframe the classical "pathogenic" versus "non-pathogenic" Th17 distinction and provide a mechanistic basis for the clinical efficacy of IL-23-targeted therapies in IBD.

immunology↗

bioRxiv2026

Barrier Immune Memory is Promoted by Intestinal Epithelial Cell Presentation of Injected Bacterial Antigens

The contributions of antigen compartmentalization to recognition differences between CD4 and CD8 T cells have long been appreciated, but little is known of how subcellular localization of different antigens expressed by a single pathogen impacts T cell immunity. By tracking a clonal CD4 T cell response to its cognate epitope shuttled between different virulence proteins of the enteropathogenic bacterium, Citrobacter rodentium (Cr), we find a remarkable bias in the magnitude and quality of the response contingent on whether antigen remains bacterially associated or is introduced into intestinal epithelial cells colonized by the bacterium. Only proteins injected into the cytosol of colonocytes via the type 3 secretion system (T3SS) of Cr were found to recruit robust antigen-specific T cell responses to the infected mucosa and give rise to CD4 resident memory T (Trm) cells that populate the mucosal epithelium--and this required direct presentation of these antigens by infected epithelial cells. Single-cell transcriptomic analyses revealed that sustained, bidirectional epithelial-T cell communication was required both to elicit epithelial barrier-protective T cell help and to promote transcriptional networks that program a tissue-residency rather than central memory fate. These results establish a central role for antigen presentation by non-professional APCs in controlling memory fate decisions by CD4 T cells, with important implications for development of successful mucosal vaccines.

immunology↗

bioRxiv2025

Probiotic biogeography and sepsis prevention in the neonatal intestine

Neonatal infection is one of the leading causes of neonatal morbidity and mortality worldwide, particularly in those born prematurely or with low birth weight. Probiotic bacteria have been demonstrated to protect against the development of neonatal intestinal dysbiosis and are widely used in peri- and post-natal clinical settings. However, formulations and efficacy are highly variable, highlighting a critical gap in the current understanding of the mechanistic underpinnings of successful probiotic interventions in this population. Furthermore, current studies on probiotic efficacy largely rely on indirect or relative readouts of intestinal bacterial burden. Herein, we directly mapped the biogeography of intestinal colonization and quantify the probiotic effects of Escherichia coli Nissle 1917 (EcN) and Ligilactobacillus murinus strain V10 against Klebsiella pneumoniae dysbiosis across the span of the neonatal murine intestine. Despite substantial differences in biogeography within the intestine, both EcN and L. murinus V10 significantly reduced K. pneumoniae colonization and mortality from K. pneumoniae sepsis, with EcN doing so much more robustly. EcNs probiotic effect was partially dependent on its ability to respire oxygen. Contrary to the dominant paradigm and practice in the probiotic field, combining multiple probiotic strains did not necessarily increase efficacy. Simultaneous treatment with EcN and L. murinus V10 was less effective than EcN treatment alone at preventing death from sepsis. These results highlight important variables which must be taken into account in the design of effective future probiotic intervention strategies. IMPORTANCEIn this work we use a mouse model of late-onset neonatal sepsis (LOS) to rigorously test fundamental assumptions that underlie the current paradigm for understanding the impact of probiotics on intestinal disease. We demonstrate that two distantly related probiotic bacteria (Escherichia coli Nissle 1917 and Ligilactobacillus murinus V10) can each effectively reduce both intestinal colonization and death caused by the LOS pathobiont Klebsiella pneumoniae, acting by distinct ecological and molecular mechanisms. Our results provide new evidence that will be critical for designing and implementing safe and effective probiotic treatment regimens for LOS, a devastating and difficult to treat disease. More broadly, our results show that ecological principles are key to understanding how interventions that modulate the gut microbiome work, and that some of the assumptions underlying current interventions need to be reevaluated, especially when it comes to combining multiple probiotic strains and species.

microbiology↗

bioRxiv2023

Fixation Before Dissociation Using a Deep Eutectic Solvent Preserves In Vivo States and Phospho-Signaling in Single-Cell Sequencing

Single-cell RNA-sequencing (scRNA-seq) presents an opportunity to deconstruct cellular networks but is limited by the loss of biological information, including in vivo cellular states and phospho-signaling. Herein, we present fixation before dissociation using a deep eutectic solvent (DES), which preserves multiple domains of in vivo biological data, including morphology, RNA, proteins, and post-translational modifications. In scRNA-seq of viable versus DES bone marrow, dissociation induced global stress responses, immune and stromal cell activation, and loss of highly sensitive cell populations, which were prevented with DES. Further, we introduce a validated and flexible method for performing intracellular CITE-seq in DES-fixed cells. Leveraging this approach during Th17 T cell stimulation allowed the simultaneous quantification of transcriptomes and four phosphorylated proteins, leading to the identification of a hyperactivated state in p-ERK/p-FOS double positive cells, which we experimentally validated. We anticipate that DES-based fixatives will allow the accurate reconstruction of in vivo cellular networks and uncover cooperativity amongst intracellular pathways.

immunology↗

bioRxiv2021

A Non-redundant Role for T cell-derived IL-22 in Antibacterial Defense of Colonic Crypts

IL-22 is a key cytokine in immune defense against pathogens at barrier sites. In response to enteric attaching and effacing bacteria, IL-22 produced by type 3 innate lymphoid cells (ILC3s) is thought to be important early for induction of antimicrobial peptides (AMPs) that protect intestinal epithelial cells (IECs) in advance of T cell-derived IL-22 that arises later. Yet, the basis for a requirement for both innate and adaptive IL-22-producing immune cells in protecting the intestinal mucosa is unknown. Here, using novel mice that both report IL-22 expression and can be targeted for its lineage-specific deletion, we show that mice with deficiency of IL-22 targeted to innate immune cells, including ILC3s, have impaired STAT3 activation of surface colonic IECs colonized by bacteria early in infection. In contrast, mice with IL-22 deficiency limited to T cells have complete loss of STAT3 activation in IECs lining colonic crypts and fail to protect the crypts from bacterial invasion late despite ongoing production of IL-22 from ILC3s. T cell-derived IL-22 is required for upregulation of many host-protective genes by crypt IECs, including those encoding AMPs, neutrophil-recruiting chemokines, and mucins and mucin-related molecules, while also restricting pro-inflammatory genes downstream of IFN{gamma} and TNF signals. Thus, T cell-derived IL-22 is indispensable for antibacterial defense and damage control of intestinal crypts.

immunology↗

bioRxiv2020

Constitutive androstane receptor directs T cell adaptation to bile acids in the small intestine

Bile acids (BAs) are lipid emulsifying metabolites synthesized in hepatocytes and maintained in vivo through enterohepatic circulation between the liver and small intestine1. As detergents, BAs can cause toxicity and inflammation in enterohepatic tissues2. Nuclear receptors maintain BA homeostasis in hepatocytes and enterocytes3, but it is unclear how mucosal immune cells tolerate high BA concentrations in the small intestine lamina propria (siLP). We previously reported that CD4+ T effector (Teff) cells upregulate expression of the xenobiotic transporter MDR1/ABCB1 in the siLP to prevent BA toxicity and suppress Crohns disease-like small bowel inflammation4. Here, we identify the nuclear xenobiotic receptor, constitutive androstane receptor (CAR/NR1I3), as a regulator of MDR1 expression in T cells, and safeguard against BA toxicity and inflammation in the small intestine. CAR was activated and induced large-scale transcriptional reprograming in Teff cells infiltrating the siLP, but not the colon. CAR induced expression of detoxifying enzymes and transporters in siLP Teff cells, as in hepatocytes, but also the key anti-inflammatory cytokine, Il10. Accordingly, CAR-deficiency in T cells exacerbated, whereas pharmacologic CAR activation suppressed, BA-driven ileitis in T cell-reconstituted Rag-/- mice. These data suggest that CAR acts locally in small intestinal T cells to detoxify BAs and resolve inflammation. Activation of this program offers an unexpected strategy to treat small bowel Crohns disease, and provides evidence of lymphocyte sub-specialization within the small intestine.

immunology↗