Non-receptor tyrosine kinase c-Abl is critical for host defense against bacterial and viral infections, yet its role in antifungal immunity remains elusive. Here, we report that inhibition of c-Abl with flumatinib mesylate significantly impairs the survival rate and exacerbates fungal burden in mice infected with Candida albicans . Our findings reveal that c-Abl inhibition reduces production of TNF-α, IL-10, and IL-12 in bone marrow-derived dendritic cells (BMDCs) after stimulation with fungal β-glucan or α-mannan. Mechanistically, c-Abl inhibition significantly blocks p38 and extracellular signal-regulated kinases 1/2 (ERK1/2) activation in BMDCs after α-mannan stimulation in a c-Cbl dependent manner. Collectively, our study uncovers a c-Abl/c-Cbl/MAPK signaling axis in dendritic cells that governs antifungal innate immunity, highlighting c-Cbl as a critical downstream mediator linking c-Abl to host defense against C. albicans . Our findings provide a mechanistic basis for fungal risk assessment in cancer patients treated with c-Abl inhibitors.

Chronic airway inflammation is a central driver of asthma pathogenesis, in which macrophages play a pivotal role. While autophagy is known to regulate macrophage function, the specific molecular mechanisms linking autophagy to allergic airway inflammation remain unclear. Here, we identify macrophage sirtuin 6 (SIRT6) as a critical regulator of autophagy and allergic inflammation in asthma. SIRT6 expression was elevated in lung tissues and macrophages from asthmatic mice. Myeloid-specific Sirt6 deletion attenuated allergic airway inflammation in asthma murine model. Mechanistically, SIRT6 promoted proinflammatory cytokine expression via autophagy-related 3 (ATG3)-mediated autophagy in macrophages. We further demonstrated that SIRT6 directly bound to ATG3 and deacetylated it at lysine 77 (K77), a modification required for driving the proinflammatory response. Importantly, pharmacological inhibition of SIRT6 with OSS_128167 suppressed macrophage autophagy and alleviated allergic inflammation. Our findings establish SIRT6 as a key promoter of allergic airway inflammation through ATG3 deacetylation and enhanced autophagy in macrophages, highlighting SIRT6 inhibition as a potential novel therapeutic strategy for asthma.

BACKGROUND AND OBJECTIVE:Myeloid-derived suppressor cells (MDSCs) participate in the progression of many diseases including chronic lung diseases. However, whether MDSCs are accumulated in the lung and how MDSCs orchestrate the pulmonary microenvironment in bronchiectasis remains unknown. Here, we aim to test a hypothesis that PMN-MDSCs are accumulated in the lung and play a role in creating an airway immunosuppressive milieu, thereby relating to clinical outcomes in bronchiectasis. METHODS:Flow cytometry and immunofluorescence staining were performed for analysing the frequencies and presence of PMN-MDSCs, LOX-1+ neutrophils, and ARG-1+ PMN-MDSCs in PBMCs, sputum, and lung tissues. T-cell proliferation assays were established for evaluating the immunosuppressive activities of PMN-MDSCs. RNA sequencing was performed to investigate the underlying mechanism of PMN-MDSCs-mediated immunosuppression. The relationship of PMN-MDSCs with the time to next exacerbation and treatment response to antibiotic therapy was analysed. RESULTS:PMN-MDSCs are accumulated in the lung and blood in bronchiectasis patients compared to healthy individuals. The majority of neutrophils in the lung of bronchiectasis patients are LOX-1+ PMN-MDSCs. Mechanistically, PMN-MDSCs suppress T cell proliferation via secreting high levels of the enzyme arginase-1 (ARG-1). Notably, the frequencies of PMN-MDSCs in sputum negatively correlate with the time to next exacerbation in bronchiectasis patients. Additionally, antibiotic therapy dramatically decreases PMN-MDSCs frequencies in the airway of bronchiectasis patients. CONCLUSION:These findings suggest that PMN-MDSCs accumulate and establish an immunosuppressive microenvironment in the lung via ARG-1 in bronchiectasis, which is associated with clinical outcome and response to antibiotic treatment, highlighting a potential role of PMN-MDSCs in bronchiectasis progression.

Background:Elevated serum Aspergillus-specific immunoglobulin G (IgG) is a key diagnostic criterion for chronic pulmonary aspergillosis (CPA). This study evaluated the diagnostic performance of Aspergillus-specific IgG testing, comparing rapid immunochromatographic point-of-care test (ICT-POCT) with enzyme-linked immunosorbent assay (ELISA) for CPA and its subtypes, while identifying factors influencing test accuracy. Methods:We recruited 112 CPA patients and 61 non-CPA controls with pulmonary diseases from The First Affiliated Hospital of Guangzhou Medical University between December 2021 and November 2022. CPA diagnosis followed composite clinical, radiological, and microbiological criteria. Serum Aspergillus-specific antibodies were analyzed using quantitative ELISA (IgG) and ICT [IgG/immunoglobulin M (IgM)]. Bronchoalveolar lavage (BAL) Aspergillus galactomannan (GM) was tested where available. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated. Results:90% of CPA patients had elevated Aspergillus-specific IgG antibodies by ImmunoCAP. ICT assay demonstrated superior overall diagnostic performance (sensitivity: 88.4%; specificity: 95.1%) vs. ELISA [58.9% sensitivity, 82.0% specificity at 80 arbitrary units per milliliter (AU/mL) cut-off]. Combined testing achieved peak specificity (98.4%) but reduced sensitivity vs. individual tests. Among patients with a history of antifungal treatment, the sensitivity of ICT assay varied by subtypes: 78.6% for chronic cavitary pulmonary aspergillosis (CCPA), 57.1% for chronic fibrosing pulmonary aspergillosis (CFPA), 66.7% for simple aspergilloma (SA), 66.7% for subacute invasive aspergillosis (SAIA), and 50% for Aspergillus nodule(s) (AN). In addition, the sensitivity of the ICT assay differed in comorbidities: 76.5% in patients with chronic obstructive pulmonary disease (COPD), 97.3% in patients with bronchiectasis, and 96.7% in patients with cavitary pulmonary tuberculosis. Notably, prior antifungal and steroid therapy decreased the performance of both assays. Conclusions:The Aspergillus-specific IgG ICT assay shows significant diagnostic value for CPA, particularly in untreated patients and CCPA subtype. Its high specificity and rapid format position it as a valuable point-of-care tool for prompt CPA diagnosis in resource-limited settings.

BACKGROUND:Primary ciliary dyskinesia (PCD), a rare ciliopathy disorder, is caused by variants in multiple genes, with DNAH5 being one of the most frequently implicated. However, the precise relationship between variant type or location in the DNAH5 gene and the clinical heterogeneity remains elusive. The present systematic review aims to provide critical insights into the impact of the molecular nature of DNAH5 variants on PCD phenotypes. METHODS:We enrolled all reported cases of PCD with biallelic pathogenic variants in the DNAH5 gene to date, and evaluated genotype-phenotype correlations in these patients, employing truncating (TV) and missense (MV) variant-carrying as grouping criteria. RESULTS:A total of 323 PCD patients with the DNAH5 variants were included, with 14.55% of these patients were diagnosed as Kartagener syndrome. Pediatric and adult patients exhibited distinct clinical features, including varying incidences of bronchiectasis, infertility, neonatal respiratory distress (NRD), ciliary ultrastructural defects distributions, and lung function (all p < 0.05). With regard to mutational patterns, truncating variants in DNAH5 were clustered in the 1200-3200 amino acid region, and were more prevalent in children compared to adult (p < 0.0001). Most missense variants are clustering in the linker, AAA + ATPase and AAA-lid domains. The most frequently observed mutation, c.10815delT, was prevalent in Europe and America, whereas c.8030G > A was more common in China and Asia. In terms of genotype-phenotype correlations, individuals with the TV/TV genotype exhibited a higher proportion of NRD and earlier onset compared to those with MV-carrying genotypes, both in overall population and in pediatric patients (all p < 0.05). Patients with the TV/TV genotype exhibited worse lung function compared to those with MV-carrying genotypes. CONCLUSION:The study underscores the broad mutational spectrum and high phenotypic heterogenicity in DNAH5-related PCD patients. The presence of biallelic truncating variants may predispose patients to earlier disease onset and poorer lung function.

Myeloid-derived suppressor cells (MDSCs), a heterogeneous cell population that consists of mostly immature myeloid cells, are immunoregulatory cells mainly characterized by their suppressive functions. Emerging findings have revealed the involvement of MDSCs in multiple sclerosis (MS) and its animal model experimental autoimmune encephalomyelitis (EAE). MS is an autoimmune and degenerative disease of the central nervous system characterized by demyelination, axon loss, and inflammation. Studies have reported accumulation of MDSCs in inflamed tissues and lymphoid organs of MS patients and EAE mice, and these cells display dual functions in EAE. However, the contribution of MDSCs to MS/EAE pathogenesis remains unclear. This review aims to summarize our current understanding of MDSC subsets and their possible roles in MS/EAE pathogenesis. We also discuss the potential utility and associated obstacles in employing MDSCs as biomarkers and cell-based therapies for MS.

Background Microbial infection and colonization are frequently associated with disease progression and poor clinical outcomes in bronchiectasis. Identification of pathogen spectrum is crucial for precision treatment at exacerbation of bronchiectasis. Methods We conducted a prospective cohort study in patients with bronchiectasis exacerbation onset and stable state. Bronchoalveolar lavage fluid (BALF) was collected for conventional microbiological tests (CMTs) and metagenomic Next-Generation Sequencing (mNGS). Bronchiectasis patients were monitored for documenting the time to the next exacerbation during longitudinal follow-up. Results We recruited 168 eligible participants in the exacerbation cohorts, and 38 bronchiectasis patients at stable state at longitudinal follow-up. 141 bronchiectasis patients at exacerbation onset had definite or probable pathogens via combining CMTs with mNGS reports. We identified that Pseudomonas aeruginosa, non-tuberculous mycobacteria, Haemophilus influenzae, Nocardia spp, and Staphylococcus aureus were the top 5 pathogens with a higher detection rate in our cohorts via combination of CMTs and mNGS analysis. We also observed strong correlations of Pseudomonas aeruginosa, Haemophilus influenzae, non-tuberculous mycobacteria with disease severity, including the disease duration, Bronchiectasis Severity Index, and lung function. Moreover, the adjusted pathogenic index of potential pathogenic microorganism negatively correlated (r = -0.7280, p < 0.001) with the time to the next exacerbation in bronchiectasis. Conclusion We have revealed the pathogenic microbial spectrum in lower airways and the negative correlation of PPM colonization with the time to the next exacerbation in bronchiectasis. These results suggested that pathogens contribute to the progression of bronchiectasis.

Epithelial cells play a crucial role in asthma, contributing to chronic inflammation and airway hyperresponsiveness. m6A modification, which involves key proteins such as the demethylase fat mass and obesity-associated protein (FTO), is crucial in the regulation of various diseases, including asthma. However, the role of FTO in epithelial cells and the development of asthma remains unclear. In this study, we investigated the demethylase activity of FTO using a small-molecule inhibitor FB23 in epithelial cells and allergic inflammation in vivo and in vitro. We examined the FTO-regulated transcriptome-wide m6A profiling by methylated RNA immunoprecipitation sequencing (MeRIP-seq) and RNA-seq under FB23 treatment and allergic inflammation conditions. Immunofluorescence staining was performed to assess the tissue-specific expression of FTO in asthmatic bronchial mucosa. We demonstrated that FB23 alleviated allergic inflammation in IL-4/IL-13-treated epithelial cells and house dust mite (HDM)-induced allergic airway inflammation mouse model. The demethylase activity of FTO contributed to the regulation of TNF-α signaling via NF-κB and epithelial-mesenchymal transition-related pathways under allergic inflammation conditions in epithelial cells. FTO was expressed in epithelial, submucosal gland, and smooth muscle cells in human bronchial mucosa. In conclusion, FB23-induced inhibition of FTO alleviates allergic inflammation in epithelial cells and HDM-induced mice, potentially through diverse cellular processes and epithelial-mesenchymal transition signaling pathways, suggesting that FTO is a potential therapeutic target in asthma management.

AbstractGut microbiota is an intricate microbial community containing bacteria, fungi, viruses, archaea, and protozoa, and each of them contributes to diverse aspects of host health. Nevertheless, the influence of interaction among gut microbiota on host health remains uncovered. Here, we showed that the interaction between intestinal fungi and bacteria shaped lung inflammation during infection. Specifically, antifungal drug‐induced dysbiosis of gut mycobiota enhanced lung inflammation during infection. Dysbiosis of gut mycobiota led to gut Escherichia coli (E. coli) overgrowth and translocation to the lung during infection, which induced lung accumulation of the CD45+F4/80+Ly6G−Ly6C−CD11b+CD11c+ macrophages. Clearance of macrophages or deletion of TLR4 (Toll‐like receptor 4, recognition of LPS) rather than Dectin‐1 (recognition of beta‐1,3/1,6 glucans on fungi) blocked the antifungal drug‐induced aggravation of lung inflammation during infection. These findings suggest that the interaction between intestinal mycobiota and commensal bacteria affects host health through the gut–lung axis, offering a potential therapeutic target for ameliorating lung inflammation during infection.

BACKGROUND:Previous research demonstrated that a homozygous mutation of g.136372044G>A (S12N) in caspase recruitment domain family member 9 ( CARD9 ) is critical for producing Aspergillus fumigatus -induced ( Af -induced) T helper 2 (T H 2)-mediated responses in allergic bronchopulmonary aspergillosis (ABPA). However, it remains unclear whether the CARD9S12N mutation, especially the heterozygous occurrence, predisposes the host to ABPA. METHODS:A total of 61 ABPA patients and 264 controls (including 156 healthy controls and 108 asthma patients) were recruited for sequencing the CARD9 locus to clarify whether patients with this heterozygous single-nucleotide polymorphisms are predisposed to the development of ABPA. A series of in vivo and in vitro experiments, such as quantitative real-time polymerase chain reaction, flow cytometry, and RNA isolation and quantification, were used to illuminate the involved mechanism of the disease. RESULTS:The presence of the p.S12N mutation was associated with a significant risk of ABPA in ABPA patients when compared with healthy controls and asthma patients, regardless of Aspergillus sensitivity. Relative to healthy controls without relevant allergies, the mutation of p.S12N was associated with a significant risk of ABPA (OR: 2.69 and 4.17 for GA and AA genotypes, P = 0.003 and 0.029, respectively). Compared with patients with asthma, ABPA patients had a significantly higher heterozygous mutation (GA genotype), indicating that p.S12N might be a significant ABPA-susceptibility locus ( aspergillus sensitized asthma: OR: 3.02, P = 0.009; aspergillus unsensitized asthma: OR: 2.94, P = 0.005). The mutant allele was preferentially expressed in ABPA patients with heterozygous CARD9S12N , which contributes to its functional alterations to facilitate Af -induced T H 2-mediated ABPA development. In terms of mechanism, Card9 wild-type ( Card9WT ) expression levels decreased significantly due to Af -induced decay of its messenger RNA compared to the heterozygous Card9S12N . In addition, ABPA patients with heterozygous CARD9S12N had increased Af -induced interleukin-5 production. CONCLUSION:Our study provides the genetic evidence showing that the heterozygous mutation of CARD9S12N , followed by allele expression imbalance of CARD9S12N , facilitates the development of ABPA.

Aspergillus fumigatus (A. fumigatus), a ubiquitous pathogen and allergen, is involved in the pathogenesis of invasive aspergillosis, allergic bronchopulmonary aspergillosis (ABPA), etc. As it possesses pathogenicity and allergenicity, A. fumigatus exposure can induce either Th1/Th17 dominated anti-fungal immunity or Th2 dominated allergic inflammation, or both based on the situations.1, 2 However, some investigations show that type-2 immunity can suppress Th1 mediated immune-protection against fungal infection, which promote fungal persistence and disease progression.3 These data suggest that anti-fungal immunity and sensitization to fungal allergen are always in dynamic balance and overwhelming type-2 immune response may be detrimental for fungal elimination. Caspase recruitment domain-containing protein 9 (CARD9), a central adaptor protein mainly expressed in myeloid cells, relays downstream signalling of C-type lectin receptors (CLRs) via CARD9-Bcl10-Malt1 (CBM) complex, finally controlling canonical NF-κB activation and resultant pro-inflammatory cytokines production (TNF-α, IL-6, IL-12, etc.), which are critical for fungal clearance.1, 4 Accumulating clinical evidence have found that null or lose-of-function mutations in CARD9 gene increase the susceptibility to fungal infection.5 However, in these fungal infected patients carrying CARD9 mutations, higher serum IgE concentration and hyper-eosinophilia are always a common manifestation.6-8 In our previous work, we have identified CARD9 S12N mutation (c.35G > A, rs4077515) as a susceptible gene to ABPA.8 These investigations imply that CARD9 not only regulates host anti-fungal immunity but also involves in modulation of allergic inflammation. However, whether CARD9 tunes the balance between anti-fungal immunity and type-2 immune response remains unclear. To determine the role of CARD9 in modulation of anti-fungal immunity and allergic inflammation, wild type (WT) and CARD9 deficient mice were infected with A. fumigatus. The detailed data about fungal burden and anti-fungal immune parameters are available in the following repository (https://zenodo.org/record/7493754#.Y651P8hqilw). We observed that CARD9 deficient mice had lower survival and higher fungal burden in the lung after A. fumigatus infection. Consistently, PASM staining showed more fungal colonization in the lung from CARD9 deficient mice. Furthermore, CARD9 deficiency dramatically reduced the mRNA abundance of Tnf-α, Il-6 and Ifng, and decreased TNF-α and IL-6 production in the lung from mice after A. fumigatus infection. Moreover, we observed that neutrophil infiltration was significantly decreased in CARD9 deficient mice compared with those in WT mice. These data suggested that CARD9 deficiency impaired anti-fungal immune response after A. fumigatus exposure. However, we strikingly observed airway remodelling such as airway wall thickening and airway stenosis in the lung from CARD9 deficient mice compared with that in WT mice after A. fumigatus exposure (Figure 1A). Simultaneously, large amounts of eosinophils were scattered in the lung from CARD9 deficient mice (Figure 1A). These H&E staining data made us hypothesize that CARD9 deficiency may screw host anti-fungal immunity into allergic inflammation. To confirm this hypothesis, we first analysed the frequency of eosinophils in the lung both in WT and CARD9 deficient mice via flow cytometry. A higher frequency of eosinophils (Figure 1B) were accumulated in the lung from CARD9 deficient mice in comparison to those in WT mice after A. fumigatus challenge. Furthermore, we found that CARD9 deficiency dramatically elevated the expression of type-2 cytokines including Il-4, Il-5, Il-13 and Il-10 (Figure 1C) in the lung, and augmented serum IgE levels (Figure 1D) compared with those in WT mice. Collectively, these data suggested that CARD9 deficiency impaired anti-fungal immunity, but promoted A. fumigatus-induced airway allergic inflammation. Dectin-1 is a well-established receptor for A. fumigatus swollen conidia (SC). To determine whether Dectin-1 was involved in regulating pulmonary type-2 immunity in CARD9 deficient mice, we used α-Dectin-1 antibody to neutralize dectin-1 signalling. We found that α-Dectin-1 neutralization significantly blocked eosinophils accumulation (Figure 1E) in the lung from CARD9 deficient mice after A. fumigatus exposure. Consistently, α-Dectin-1 neutralization significantly decreased IL-4 and IL-5 concentration (Figure 1F) in the lung and serum IgE levels (Figure 1G) in comparison to those in IgG control mice. Together, CARD9 deficiency-mediated pulmonary type-2 immunity was dependent on Dectin-1 signalling after A. fumigatus exposure. Accumulating evidence have demonstrated that alveolar macrophages are involved in triggering allergic immune responses.8 To evaluate whether alveolar macrophages was essential for A. fumigatus-induced pulmonary type-2 immunity, we analysed the population of alveolar macrophages in the lung from WT and CARD9 deficient mice at day 2 after A. fumigatus exposure. We observed that alveolar macrophages were substantially depleted in WT mice, but not CARD9 deficient mice after A. fumigatus exposure (Figure 2A). To confirm the role of alveolar macrophages, we employed clodronate liposomes to deplete alveolar macrophages via intratracheal instillation. We found that depletion of alveolar macrophages in CARD9 deficient mice significantly abolished the pulmonary eosinophils infiltration in comparison to those in control mice after A. fumigatus exposure (Figure 2B). Further, depletion of alveolar macrophages significantly decreased IL-4 and IL-5 levels (Figure 2C) in the lung and serum IgE concentration (Figure 2D) in CARD9 deficient mice. Thus, these data indicated that alveolar macrophages functioned as primary initiators for A. fumigatus-induced pulmonary type-2 immunity in CARD9 deficient mice. Next, we sought to determine the underlying mechanism of how CARD9 modulated pulmonary type 2 immune responses after A. fumigatus infection. We firstly analysed phenotype and antigen presentation capability of alveolar macrophages in WT and CARD9 deficient mice with/without A. fumigatus exposure. The detailed data about the characteristics of alveolar macrophages are available in the following repository (https://zenodo.org/record/7493754#.Y651P8hqilw). We found that alveolar macrophages were marked by Siglec-H, Ly6C, CD64 and F4/80 both in WT and CARD9 deficient mice. Simultaneously, we found that the expression of CD80, CD86 and MHC-II were comparable between WT and CARD9 deficient mice with/without A. fumigatus exposure, hinting that CARD9 did not affect the antigen presentation capacity of alveolar macrophages. Next, we determined whether CARD9 deficiency could regulate canonical NF-κB and MAPK signalling pathways upon fungus stimulation. As expected, CARD9 deficiency dramatically blocked p65 and p50 nuclear translocation compared with those in WT BMDM after resting conidial (RC) and SC of A. fumigatus stimulation, but not candida albicans (C. albicans) yeast and LPS stimulation. Consistently, the protein levels of phosphorylated IκBα were decreased and total IκBα levels were increased after A. fumigatus stimulation (RC and SC), but not C. albicans. However, the protein levels of phosphorylated Syk and JNK were comparable between WT and CARD9 deficient BMDM after A. fumigatus and C. albicans stimulation. The detailed data about NF-κB and MAPK signalling are available in the following repository (https://zenodo.org/record/7493754#.Y651P8hqilw). Our previous work demonstrated that CARD9 S12N mutation induced non-canonical NF-κB activation, which regulated IL-5 production in alveolar macrophages after A. fumigatus challenge.8 Therefore, we sorted out alveolar macrophages from naïve WT and CARD9 deficient mice and then stimulated with A. fumigatus, and observed that A. fumigatus stimulation induced p65 (red) nuclear translocation in WT alveolar macrophages but not in CARD9 deficient alveolar macrophages. On the contrary, RelB (green) translocated into nuclear in CARD9 deficient, but not in WT alveolar macrophages after A. fumigatus stimulation. Moreover, we sorted out alveolar macrophages from WT and CARD9 deficient mice infected with/without A. fumigatus, and further confirmed that RelB activation only occurred in CARD9 deficient alveolar macrophages. Previous study have demonstrated Curdlan could regulate non-canonical NF-κB activation and Ccl17 expression, which can tune Th1 and Th2 balance.9 Thus, we challenged CARD9 deficient BMDMs with Curdlan, and found that CARD9 deficiency significantly increased the expression of Ccl17 and Ccl11. These data suggested that CARD9 promoted canonical NF-κB activation, but inhibited non-canonical NF-κB activation, which may modulate Ccl17 and Ccl11 expression in alveolar macrophages after A. fumigatus exposure. Generally, appropriate innate and adaptive immune responses are critical for fungal clearance, and impaired immune response will result in fungal infection. CARD9 functions as an adaptor protein, which integrates CLRs signalling after ligand engagement, finally orchestrating host innate and adaptive immunity against fungal infection.4 Consistently, we found that CARD9 deficient mice were susceptible to A. fumigatus infection. However, histological analysis and flow cytometry analysis showed large eosinophil accumulation in lungs from CARD9 deficient mice after A. fumigatus exposure. Elevated type 2 cytokines production in lung and serum IgE levels in CARD9 deficient mice further confirmed allergic airway inflammation after A. fumigatus challenge. These data suggested that CARD9 deficiency impaired host anti-fungal immunity, but boosted pulmonary type 2 immune responses after A. fumigatus exposure. In our previous study, we have provided direct evidence that revealed the correlation of CARD9 with pulmonary allergic inflammation, and identified CARD9 S12N as a susceptible gene to ABPA.8 Thus, combination with our previous work, we uncover an unidentified function of CARD9 that modulate the dynamic balance between A. fumigatus-induced anti-fungal immunity and allergic inflammation. Furthermore, our observation was also supported by some clinical studies or case reports of which these fungal infected-patients with CARD9 null mutations are also manifested by higher serum IgE concentration and hyper-eosinophilia in the peripheral blood.5-7 In summary, our data suggested that CARD9 deficiency impaired host anti-fungal immune response, but promoted A. fumigatus-induced type-2 dominant immunity via Dectin-1 signalling. Meanwhile, we also found that alveolar macrophages were essential for triggering allergic airway inflammation after A. fumigatus exposure. Our study uncovers the unrecognized function of CARD9 in modulating the balance between anti-fungal and allergic inflammation in response to A. fumigatus exposure. Jielin Duan, Fan Li, Ronghua Huang, Siyuan Wu and Xia Xu performed the experiments; Jielin Duan, Zhiwen Huang and Xia Xu performed statistics analysis; Xia Xu designed the study; Jielin Duan and Xia Xu wrote the paper. This work was supported by grants from the National Natural Science Foundation of China (81970036 to Xia Xu; 82201929 to Jielin Duan), and the Natural Science Foundation of Beijing (7202130 to Xia Xu), and China Postdoctoral Science Foundation (2022 M720906 to Jielin Duan). The authors declare that they have no conflicts of interest. The data that support the findings of this study are openly available in Additional information for methods and supplementary data-Cl at https://zenodo.org/record/7493754#.Y651P8hqilw, reference number https://doi.org/10.5281/zenodo.7493754.

Recent compelling results indicate possible links between neurotransmitters, intestinal mucosal IgA + B cell responses, and immunoglobulin A nephropathy (IgAN) pathogenesis. Here, we demonstrated that γ-amino butyric acid (GABA) transporter-2 (GAT-2) deficiency induces intestinal germinal center (GC) B cell differentiation and worsens the symptoms of IgAN in a mouse model. Mechanistically, GAT-2 deficiency enhances GC B cell differentiation through activation of GABA–mammalian target of rapamycin complex 1 (mTORC1) signaling. In addition, IgAN patients have lower GAT-2 expression but higher activation of mTORC1 in blood B cells, and both are correlated with kidney function in IgAN patients. Collectively, this study describes GABA signaling–mediated intestinal mucosal immunity as a previously unstudied pathogenesis mechanism of IgAN and challenges the current paradigms of IgAN.

Lactobacillus delbrueckii (LAB) has been demonstrated to exert versatile beneficial effects on modulating intestinal immunity, increasing gut microbial diversity, promoting growth performance, and even preventing disease onset in pigs. However, the underlying mechanism of LAB-mediated gut immunity regulation in piglets remains unclear. In this study, we found that supplementation of LAB significantly increases serum TNF-α, ileum IL-4, and IL-10 levels compared with the control group. Meanwhile, oral supplementation of LAB-modified gut microbial communities was evidenced by the increased abundance of the Lactobacillus genus in the colon. Mechanistically, LAB induced dendritic cell (DC) maturation and activation, which may be relevant to the activation of NF-κB and MAPK signaling pathways. Moreover, we found that oral administration of LAB during the suckling period shows long-lasting immunomodulatory impacts on intestinal immunity after weaning. Collectively, this study uncovers the mechanism of LAB in regulating the intestinal immunity of piglets, suggesting that LAB can be developed as an immunoenhancing biological agent during the suckling period.

Abstract Background Our previous study shows that Adipose tissue‐derived mesenchymal stem cells (ASCs) are a promising strategy for cell‐based therapy against pulmonary infection with Pseudomonas aeruginosa (P. aeruginosa), but the underlying mechanisms remain unclear. Methods cDNA microarray assay was performed to explore the transcriptome of ASCs primed by P. aeruginosa. Small interfering RNA (siRNA) was constructed to select the receptor candidates for P. aeruginosa recognition and granulocyte‐macrophage colony‐stimulating factor (GM‐CSF) production in ASCs. The soluble protein chimeras containing the extracellular domain of human CD69 fused to the Fc region of human immunoglobulin IgG1 were used as a probe to validate the recognition of P. aeruginosa. The association between CD69 and extracellular regulated protein kinases 1/2 (ERK1/2) was explored via co‐immunoprecipitation, siRNA, and inhibitor. The murine models of P. aeruginosa pneumonia treated with WT‐ASCs, GM‐CSF −/−‐ASCs Cd69 −/−‐ASCs or Erk1 −/−‐ASCs were used to determine the role of GM‐CSF, CD69, and ERK1 in ASCs against P. aeruginosa infection. Results We showed that C‐type lectin receptor CD69 mediated the protective effects of ASCs partly through GM‐CSF. CD69 could specifically recognize P. aeruginosa and regulate GM‐CSF secretion of ASCs. CD69 regulated the production of GM‐CSF via ERK1 in ASCs after P. aeruginosa infection. Moreover, the Administration of ASCs with deficiency of CD69 or ERK1 completely blocked its protective effects in a murine model of P. aeruginosa pneumonia. Conclusions CD69 recognizes P. aeruginosa and further facilitates ERK1 activation, which plays a crucial role in ASCs‐based therapy against P. aeruginosa pneumonia. CD69 may be a novel target molecule to improve ASCs‐based therapy against P. aeruginosa infection.

In the published article, the images for Actin in Figs. 4a, 5a, 6a, and 6c were incorrectly presented.

Intestinal fungi are critical for modulating host immune homeostasis and underlying mechanisms remain unclear. We show that dendritic cell (DC)-specific deficiency of casitas B-lineage lymphoma (c-Cbl) renders mice susceptible to dextran sodium sulfate (DSS)-induced colitis. Mechanistically, we identify that c-Cbl functions downstream of Dectin-2 and Dectin-3 to mediate the ubiquitination and degradation of noncanonical nuclear factor κB subunit RelB. Thus, c-Cbl deficiency in DCs promotes α-mannan-induced activation of RelB, which suppresses p65-mediated transcription of an anti-inflammatory cytokine gene, il10, thereby aggravating DSS-induced colitis. Moreover, suppressing fungal growth with fluconazole or inhibition of RelB activation in vivo attenuates colitis in mice with DC-specific deletion of c-Cbl. We also demonstrate an interaction between c-Cbl and c-Abl tyrosine kinase and find that treatment with DPH, a c-Abl agonist, synergistically increases fungi-induced c-Cbl activation to restrict colitis. Together, these findings unravel a previously unidentified fungi-induced c-Cbl/RelB axis that sustains intestinal homeostasis and protects against intestinal inflammation.

Accumulating evidence reveals a pivotal role of intestinal fungi in modulating host immune homeostasis. However, the mechanisms for regulating immunity to commensal gut fungi remain unknown. Here, we show that dendritic cell (DC)-specific deficiency of casitas B-lineage lymphoma (c-Cbl), an E3 ubiquitin ligase, confers mice susceptible to dextran sodium sulfate-induced colitis. Moreover, c-Cbl functions as a signal mediator downstream of α-mannan recognition receptor Dectin-2 and Dectin-3 by mediating the ubiquitination and degradation of non-canonical NF-κB subunit RelB. Thus, DC-specific deficiency of c-Cbl facilitates fungi-derived α-mannan-induced activation of RelB, which suppresses p65-mediated transcription of an anti-inflammatory cytokine gene il10. Consequently, suppressing fungal growth or inhibition of RelB activation in vivo significantly attenuates colitis in c-Cblf/fCD11cCre/+ mice whereas treatment of DPH, agonist of c-Abl, could synergistically increase the fungi-induced activation of c-Cbl to restrict colitis. These data unravel a role of c-Cbl/RelB axis in regulating intestinal inflammation for sustaining intestinal homeostasis, and a potential clinical utility of DPH for colitis treatment.

Glutamic acid (Glu) and aspartic acid (Asp) are acidic amino acids with regulatory roles in nutrition, energy metabolism, and oxidative stress. This study aimed to evaluate the effects of low-protein diets supplemented with Glu and Asp on the intestinal barrier function and energy metabolism in weaned piglets challenged with hydrogen peroxide (H2O2). Forty piglets were randomly divided into 5 groups: NC, PC, PGA, PG, and PA (n = 8 for each group). Pigs in the NC and PC groups were fed a low-protein diet, while pigs in the PGA, PG, or PA groups were fed the low-protein diet supplemented with 2.0% Glu +1.0% Asp, 2.0% Glu, or 1.0% Asp, respectively. On day 8 and 11, pigs in the NC group were intraperitoneally injected with saline (1 mL/kg BW), while pigs in the other groups were intraperitoneally administered 10% H2O2 (1 mL/kg BW). On day 14, all pigs were sacrificed to collect jejunum and ileum following the blood sample collection in the morning. Notably, low-protein diets supplemented with Glu or Asp ameliorated the intestinal oxidative stress response in H2O2-challenged piglets by decreasing intestinal expression of genes (P < 0.05) (e.g., manganese superoxide dismutase [MnSOD], glutathione peroxidase [Gpx]-1, and Gpx-4) encoding oxidative stress-associated proteins, reducing the serum concentration of diamine oxidase (P < 0.05), and inhibiting apoptosis of the intestinal epithelium. Glu and Asp supplementation attenuated the upregulated expression of energy metabolism-associated genes (such as hexokinase and carnitine palmitoyltransferase-1) and the H2O2-induced activation of acetyl-coenzyme A carboxylase (ACC) in the jejunum and adenosine monophosphate-activated protein kinase–acetyl-ACC signaling in the ileum. Dietary Glu and Asp also ameliorated intestinal barrier damage as indicated by restored intestinal histology and morphology. In conclusion, low-protein diets supplemented with Glu and Asp protected against oxidative stress-induced intestinal dysfunction in piglets, suggesting that this approach could be used as a nutritional regulatory protectant against oxidative stress.

The morphological switch between yeast and hyphae of Candida albicans is essential for its interaction with the host defense system. However, the lack of understanding of host–pathogen interactions during C. albicans infection greatly hampers the development of effective immunotherapies. Here, we found that priming with the C. albicans FLO8- deficient ( flo8 ) mutant, locked in yeast form, protected mice from subsequent lethal C. albicans infection. Deficiency of Dectin-2, a fungus-derived α-mannan recognition receptor, completely blocked flo8 mutant-induced protection. Mechanistically, the flo8 mutant-induced Dectin-2/CARD9-mediated IL-10 production in DCs and macrophages to block thymus atrophy by inhibiting the C. albicans -induced apoptosis of thymic T cells, which facilitated the continuous output of naive T cells from the thymus to the spleen. Continuous recruitment of naive T cells to the spleen enhanced Th1-biased antifungal immune responses. Consequently, depletion of CD4+ T cells or blockade of IL-10 receptor function using specific antibodies in mice completely blocked the protective effects of flo8 mutant priming against C. albicans infection. Moreover, mannans exposed on the surface of the flo8 mutant were responsible for eliciting protective immunity by inhibiting the C. albicans -induced apoptosis of thymic T cells to sustain the number of naive T cells in the spleen. Importantly, priming with the flo8 mutant extensively protected mice from polymicrobial infection caused by cecal ligation and puncture (CLP) by enhancing Th1-biased immune responses. Together, our findings imply that targeting FLO8 in C. albicans elicits protective immune responses against polymicrobial infections and that mannans extracted from the flo8 mutant are potential immunotherapeutic candidate(s) for controlling infectious diseases.