Mucosal Immunology最新文献

The transcriptomic signatures that shape responses of innate lymphoid cells (ILCs) have been well characterised, however post-transcriptional mechanisms which regulate their development and activity remain poorly understood. We demonstrate that ILC groups of the intestinal lamina propria express mature forms of microRNA-142 (miR-142), an evolutionarily conserved microRNA family with several non-redundant regulatory roles within the immune system. Germline Mir142 deletion alters intestinal ILC compositions, resulting in the absence of T-bet⁺ populations and significant defects in the cellularity and phenotypes of ILC3 subsets including CCR6⁺ LTi-like ILC3s. These effects were associated with decreased pathology in an innate-immune cell driven model of colitis. Furthermore, Mir142^-/- mice demonstrate defective development of gut-associated lymphoid tissues, including a complete absence of mature Peyer's patches. Conditional deletion of Mir142 in ILC3s (Rorc^ΔMir142) supported cell-intrinsic roles for these microRNAs in establishing or maintaining cellularity and functions of LTi-like ILC3s in intestinal associated tissues. RNAseq analysis revealed several target genes and biological pathways potentially regulated by miR-142 microRNAs in these cells. Finally, lack of Mir142 in ILC3 led to elevated IL-17A production. These data broaden our understanding of immune system roles of miR-142 microRNAs, identifying these molecules as critical post-transcriptional regulators of ILC3s and intestinal mucosal immunity.

The impact of dietary fiber on intestinal T cell development is poorly understood. Here we show that a low fiber diet reduces MHC-II antigen presentation by small intestinal epithelial cells (IECs) and consequently impairs development of CD4⁺CD8αα⁺ intraepithelial lymphocytes (DP IELs) through changes to the microbiota. Dietary fiber supports colonization by Segmented Filamentous Bacteria (SFB), which induces the secretion of IFNγ by type 1 innate lymphoid cells (ILC1s) that lead to MHC-II upregulation on IECs. IEC MHC-II expression caused either by SFB colonization or exogenous IFNγ administration induced differentiation of DP IELs. Finally, we show that a low fiber diet promotes overgrowth of Bifidobacterium pseudolongum, and that oral administration of B. pseudolongum reduces SFB abundance in the small intestine. Collectively we highlight the importance of dietary fiber in maintaining the balance among microbiota members that allow IEC MHC-II antigen presentation and define a mechanism of microbiota-ILC-IEC interactions participating in the development of intestinal intraepithelial T cells.

Acute respiratory distress syndrome (ARDS) is a life-threatening condition characterized by severe inflammation and pulmonary dysfunction. Despite advancements in critical care, effective pharmacological interventions for ARDS remain elusive. While Janus kinase 2 (JAK2) inhibitors have emerged as an innovative treatment for numerous autoinflammatory diseases, their therapeutic potential in ARDS remains unexplored. In this study, we investigated the contribution of JAK2 and its underlying mechanisms in ARDS utilizing myeloid-specific JAK2 knockout murine models alongside a pharmacological JAK2 inhibitor. Notably, myeloid-specific JAK2 knockout led to a notable attenuation of ARDS induced by intratracheal administration of LPS, accompanied by reduced levels of neutrophils and inflammatory cytokines in bronchoalveolar lavage fluid (BALF) and lung tissue. Intriguingly, the ameliorative effects were abolished upon the depletion of monocyte-derived alveolar macrophages (Mo-AMs) rather than tissue-resident alveolar macrophages (TR-AMs). JAK2 deficiency markedly reversed LPS-induced activation of STAT5 in macrophages. Remarkably, pharmacological JAK2 inhibition using baricitinib failed to substantially alleviate neutrophils infiltration, implying that specific inhibition of JAK2 in Mo-AMs is imperative for ARDS amelioration. Collectively, our data suggest that JAK2 may mitigate ARDS progression through the JAK2 pathway in Mo-AMs, underscoring JAK2 in alveolar macrophages, particularly Mo-AMs, as a promising therapeutic target for ARDS treatment.

PLX5622 is a small molecular inhibitor of the CSF1 receptor (CSF1R) and is widely used to deplete macrophages within the central nervous system (CNS). We investigated the impact of PLX5622 treatment in wild-type C57BL/6 mice and discovered that one-week treatment with PLX5622 was sufficient to deplete interstitial macrophages in the lung and brain-infiltrating Ly6C^low patrolling monocytes, in addition to CNS-resident macrophages. These cell types were previously indicated to act as infection reservoirs for the pathogenic fungus Cryptococcus neoformans. We found that PLX5622-treated mice had significantly reduced fungal lung infection and reduced extrapulmonary dissemination to the CNS but not to the spleen or liver. Fungal lung infection mapped to MHCII^hi interstitial lung macrophages, which underwent significant expansion during infection following monocyte replenishment and not local division. Although PLX5622 depleted CNS infiltrating patrolling monocytes, these cells did not accumulate in the fungal-infected CNS following pulmonary infection. In addition, Nr4a1-deficient mice, which lack patrolling monocytes, had similar control and dissemination of C. neoformans infection to wild-type controls. PLX5622 did not directly affect CD4 T-cell responses, or significantly affect production of antibody in the lung during infection. However, we found that mice lacking lymphocytes had reduced numbers of MHCII^hi interstitial macrophages in the lung, which correlated with reduced infection load. Accordingly, PLX5622 treatment did not alter fungal burdens in the lungs of lymphocyte-deficient mice. Our data demonstrate that PLX5622 may help reduce lung burden of pathogenic fungi that utilise CSF1R-dependent myeloid cells as infection reservoirs, an effect which is dependent on the presence of lymphocytes.

The helper-like ILC contains various functional subsets, such as ILC1, ILC2, ILC3 and LTi cells, mediating the immune responses against viruses, parasites, and extracellular bacteria, respectively. Among them, LTi cells are also crucial for the formation of peripheral lymphoid tissues, such as lymph nodes. Our research, along with others', indicates a high proportion of LTi cells in the fetal ILC pool, which significantly decreases after birth. Conversely, the proportion of non-LTi ILCs increases postnatally, corresponding to the need for LTi cells to mediate lymphoid tissue formation during fetal stages and other ILC subsets to combat diverse pathogen infections postnatally. However, the regulatory mechanism for this transition remains unclear. In this study, we observed a preference for fetal ILC progenitors to differentiate into LTi cells, while postnatal bone marrow ILC progenitors preferentially differentiate into non-LTi ILCs. Particularly, this differentiation shift occurs within the first week after birth in mice. Further analysis revealed that adult ILC progenitors exhibit stronger activation of the Notch signaling pathway compared to fetal counterparts, accompanied by elevated Gata3 expression and decreased Rorc expression, leading to a transition from fetal LTi cell-dominant states to adult non-LTi ILC-dominant states. This study suggests that the body can regulate ILC development by modulating the activation level of the Notch signaling pathway, thereby acquiring different ILC subsets to accommodate the varying demands within the body at different developmental stages.

Peyer's patches (PPs) are B cell-rich sites of intestinal immune induction, yet PP-associated B cell signaling, activation, and differentiation are poorly defined. Single-cell and spatial transcriptomics were completed to study B cells from porcine jejunum and ileum containing PPs. Intestinal locations had distinct immune landscapes, including more follicular B cells in ileum and increased MHC-II-encoding gene expression in jejunal B cells. Despite distinct landscapes, conserved B cell dynamics were detected across intestinal locations, including B cell signaling to CD4⁺ macrophages that are putative phagocytic, cytotoxic, effector cells and deduced routes of B cell activation/differentiation, including resting B cells migrating into follicles to replicate/divide or differentiate into antibody-secreting cells residing in intestinal crypts. A six-biomarker panel recapitulated transcriptomics findings of B cell phenotypes, frequencies, and spatial locations via ex vivo and in situ staining. Findings convey conserved B cell dynamics across intestinal locations containing PPs, despite location-specific immune environments. Results establish a benchmark of B cell dynamics for understanding intestinal immune induction important to promoting gut/overall health.

Itaconate was initially identified as an antimicrobial compound produced by myeloid cells. Beyond its antimicrobial role, itaconate may also serve as a crucial metabolic and immune modulator. We therefore examined the roles of aconitate decarboxylase 1 (Acod1) and itaconate in house dust mite (HDM)-sensitized and -challenged mice, a model of T helper 2 (Th2)-driven allergic airways disease. HDM treatment induced lung Acod1 mRNA expression and bronchoalveolar lavage (BAL) itaconate levels in wild-type C57BL/6 mice. Acod1 knockout mice (Acod1-KO) with negligible BAL itaconate showed heightened HDM-induced type 2 cytokine expression, increased serum IgE, and enhanced recruitment of Th2 cells in the lung, indicating a shift towards a more pronounced Th2 immune response. Acod1-KO mice also showed increased eosinophilic airway inflammation and hyperresponsiveness. Experiments in chimeric mice demonstrated that bone marrow from Acod1-KO mice is sufficient to increase type 2 cytokine expression in wild-type mice, and that restitution of bone marrow from wild type mice attenuates mRNA expression of Th2 cytokines in Acod1-KO mice. Specific deletion of Acod1 in lysozyme-secreting macrophages (LysM-cre⁺Acod1^flox/flox) recapitulated the exaggerated phenotype observed in whole-body Acod1-KO mice. Adoptive transfer of Acod1-KO bone marrow-derived macrophages also increased lung mRNA expression of Th2 cytokines. In addition, treatment of Th2-polarized CD4 cells with itaconate impeded Th2 cell differentiation, as shown by reduced expression of Gata3 and decreased release of IL-5 and IL-13. Finally, public datasets of human samples show lower Acod1 expression in subjects with allergic asthma, consistent with a protective role of itaconate in asthma pathogenesis. Together, these data suggest that itaconate plays a protective, immunomodulatory role in limiting airway type 2 inflammation after allergen challenge by attenuating T cell responses.

Conventional dendritic cells (cDC) are central to maintaining the balance between protective immune responses and tolerance to harmless antigens, especially in the intestine. Short chain fatty acids (SCFAs) such as butyrate play critical roles in regulating intestinal immunity, but the underlying mechanisms remain unclear. Here we demonstrate that microbiota-derived butyrate alters intestinal cDC populations in vivo resulting in decreased numbers of the cDC2 lineage. By establishing a novel in vitro culture model, we show that butyrate has a direct and selective ability to repress the development of cDC2 from cDC precursors, an effect that is independent of G-protein coupled receptors (GPCRs) and is due to inhibition of histone deacetylase 3. Finally, cDC derived from pre-cDC in the presence of butyrate in vitro express lower levels of costimulatory molecules and have a decreased ability to prime naïve T cells. Together, our data show that butyrate affects the developmental trajectory of cDC, selectively repressing the cDC2 lineage and reducing their ability to stimulate T cells. These properties may help explain the ability of butyrate to maintain homeostasis in the intestine.

Intestinal intraepithelial T lymphocytes (IEL) constitutively express high amounts of the cytotoxic proteases Granzymes (Gzm) A and B and are therefore thought to protect the intestinal epithelium against infection by killing infected epithelial cells. However, the role of IEL granzymes in a protective immune response has yet to be demonstrated. We show that GzmA and GzmB are required to protect mice against oral, but not intravenous, infection with Salmonella enterica serovar Typhimurium, consistent with an intestine-specific role. IEL-intrinsic granzymes mediate the protective effects by controlling intracellular bacterial growth and aiding in cell-intrinsic pyroptotic cell death of epithelial cells. Surprisingly, we found that both granzymes play non-redundant roles. GzmB^-/- mice carried significantly lower burdens of Salmonella, as predominant GzmA-mediated cell death effectively reduced bacterial translocation across the intestinal barrier. Conversely, in GzmA^-/- mice, GzmB-driven apoptosis favored luminal Salmonella growth by providing nutrients, while still reducing translocation across the epithelial barrier. Together, the concerted actions of both GzmA and GzmB balance cell death mechanisms at the intestinal epithelium to provide optimal control that Salmonella cannot subvert.

Group 3 innate lymphoid cells (ILC3s) are abundant in the developing or healthy intestine to critically support tissue homeostasis in response to microbial colonization. However, intestinal ILC3s are reduced during chronic infections, colorectal cancer, or inflammatory bowel disease (IBD), and the mechanisms driving these alterations remain poorly understood. Here we employed RNA sequencing of ILC3s from IBD patients and observed a significant upregulation of RIPK3, the central regulator of necroptosis, during intestinal inflammation. This was modeled in mice where we found that intestinal ILC3s express RIPK3, with conventional (c)ILC3s exhibiting high RIPK3 and low levels of pro-survival genes relative to lymphoid tissue inducer (LTi)-like ILC3s. ILC3-specific RIPK3 is promoted by gut microbiota, further upregulated following enteric infection, and dependent upon IL-23R and STAT3 signaling. However, lineage-specific deletion of RIPK3 revealed a redundant role in ILC3 survival, due to a blockade of RIPK3-mediated necroptosis by caspase 8, which was also activated in response to enteric infection. In contrast, lineage-specific deletion of caspase 8 resulted in loss of cILC3s from the healthy intestine and all ILC3 subsets during enteric infection, which increased pathogen burdens and gut inflammation. This function of caspase 8 required catalytic activity induced by TNF or TL1A and was dispensable if RIPK3 was simultaneously deleted. Caspase 8 activation and cell death were associated with increased Fas on ILC3s, and the Fas-FasL pathway was upregulated by cILC3s during enteric infection, which could restrain the abundance of intestinal ILC3s. Collectively, these data reveal that interpretation of key cytokine signals controls ILC3 survival following microbial challenge, and that an imbalance of these pathways, such as in IBD or across ILC3 subsets, provokes depletion of tissue-protective ILC3s from the inflamed intestine.