Inflammatory type 2 conventional dendritic cells contribute to murine and human cholangitis

The C5a/C5aR1 Axis Promotes Migration of Tolerogenic Dendritic Cells to Lymph Nodes, Impairing the Anticancer Immune Response

The precise mechanisms by which the complement system contributes to the establishment of an immunosuppressive tumor microenvironment and promotes tumor progression remain unclear. In this study, we investigated the expression and function of complement C5a receptor 1 (C5aR1) in human and mouse cancer-associated dendritic cells (DC). First, we observed an overexpression of C5aR1 in tumor-infiltrating DCs, compared with DCs from the blood or spleen. C5aR1 expression was restricted to type 2 conventional DCs and monocyte-derived DCs, which displayed a tolerogenic phenotype capable of inhibiting T-cell activation and promoting tumor growth. C5aR1 engagement in DCs drove their migration from tumors to tumor-draining lymph nodes, where C5a levels were higher. We used this knowledge to optimize an anticancer therapy aimed at enhancing DC activity. In three syngeneic tumor models, C5aR1 inhibition significantly enhanced the efficacy of poly I:C, a Toll-like receptor 3 agonist, in combination with PD-1/PD-L1 blockade. The contribution of C5aR1 inhibition to the antitumor activity of the combination treatment relied on type 1 conventional DCs and antigen-specific CD8+ T cells, required lymphocyte egress from secondary lymphoid organs, and was associated with an increase in IFNγ signaling. In conclusion, our study highlights the importance of the C5a/C5aR1 axis in the biology of cancer-associated DCs and provides compelling evidence for the therapeutic potential of modulating the complement system to enhance DC-mediated immune responses against tumors.

Liver transcriptome analysis reveals PSC-attributed gene set associated with fibrosis progression

Background & Aims

Primary sclerosing cholangitis (PSC) is a chronic heterogenous cholangiopathy with unknown etiology where chronic inflammation of the bile ducts leads to multifocal biliary strictures and biliary fibrosis with consecutive cirrhosis development. We here aimed to identify a PSC-specific gene signature associated with biliary fibrosis development.

Methods

We performed RNA-sequencing of 47 liver biopsies from people with PSC (n = 16), primary biliary cholangitis (PBC, n = 15), and metabolic dysfunction-associated steatotic liver disease (MASLD, n = 16) with different fibrosis stages to identify a PSC-specific gene signature associated with biliary fibrosis progression. For validation, we compared an external transcriptome data set of liver biopsies from people with PSC (n = 73) with different fibrosis stages (baseline samples from NCT01672853).

Results

Differential gene expression analysis of the liver transcriptome from patients with PSC with advanced vs. early fibrosis revealed 431 genes associated with fibrosis development. Of those, 367 were identified as PSC-associated when compared with PBC or MASLD. Validation against an external data set of 73 liver biopsies from patients with PSC with different fibrosis stages led to a condensed set of 150 (out of 367) differentially expressed genes. Cell type specificity assignment of those genes by using published single-cell RNA-Seq data revealed genetic disease drivers expressed by cholangiocytes (e.g. CXCL1, SPP1), fibroblasts, innate, and adaptive immune cells while deconvolution along fibrosis progression of the PSC, PBC, and MASLD samples highlighted an early involvement of macrophage- and neutrophil-associated genes in PSC fibrosis.

Conclusions

We reveal a PSC-attributed gene signature associated with biliary fibrosis development that may enable the identification of potential new biomarkers and therapeutic targets in PSC-related fibrogenesis.

Impact and implications

Primary sclerosing cholangitis (PSC) is an inflammatory liver disease that is characterized by multifocal inflammation of bile ducts and subsequent biliary fibrosis. Herein, we identify a PSC-specific gene set of biliary fibrosis progression attributing to a uniquely complex milieu of different cell types, including innate and adaptive immune cells while neutrophils and macrophages showed an earlier involvement in fibrosis initiation in PSC in contrast to PBC and metabolic dysfunction-associated steatotic liver disease. Thus, our unbiased approach lays an important groundwork for further mechanistic studies for research into PSC-specific fibrosis.

FcγRI plays a pro-inflammatory role in the immune response to Chlamydia respiratory infection by upregulating dendritic cell-related genes

BACKGROUND

FcγRI, a pivotal cell surface receptor, is implicated in diverse immune responses and is ubiquitously expressed on numerous immune cells. However, its role in intracellular bacterial infections remains understudied.

METHODS

Wild-type (WT) and FcγRI knockout (FcγRI-KO) mice were inoculated intranasally with a specific dose of C. muridarum. Lung tissues were harvested for transcriptome sequencing, and flow cytometry was employed to validate bioinformatics immune infiltration analysis. Differentially expressed DC-associated genes were subjected to Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses to elucidate their functions during infection. A PPI network was constructed to pinpoint crucial genes, and qPCR was utilized to confirm their expression changes. Additionally, we compared body weight, lung Chlamydia load, and pathological alterations between WT and FcγRI-KO mice post-infection to assess the effect of FcγRI on inflammation via gene regulation. Lastly, an mRNA-miRNA-lncRNA network was formulated to further probe the molecular mechanisms of FcγRI in C. muridarum infection.

RESULTS

Post-C. muridarum infection, FcγRI-KO mice exhibited a notable decrease in DC infiltration and maturation, along with downregulated co-stimulatory molecules (CD40, CD80, CD86) in lung tissues. Differential gene analysis identified 26 differentially expressed DC-related genes implicated in DC proliferation, migration, and inflammatory responses. KEGG analysis revealed their close association with key immune pathways. The PPI network delineated two modules, with the top six genes in the pivotal cluster 1 (Ccl4, Il6, Ccl3, Ptgs2, Il 1α, Il7) being significantly downregulated in FcγRI-KO mice. A ceRNA network encompassing 12 miRNAs and 37 lncRNAs regulating four key genes (Ptgs2, Il1α, Il6, Il7) was also constructed.

CONCLUSIONS

In C. muridarum respiratory infections, FcγRI facilitates DC infiltration and maturation, upregulates six pro-inflammatory genes (Ccl4, Il6, Ccl3, Ptgs2, Il1α, Il7), and exhibits a pro-inflammatory role. A key ceRNA network was formulated to unravel the underlying molecular mechanisms.

Elucidating the immunomodulatory effects of phytoestrogens and their groundbreaking applications in transplantation medicine

Phytoestrogens are natural compounds found in plants and plant-based foods. When ingested, they can affect the human body in the same way as estrogen produced by the body. Phytoestrogens affect the regulation, differentiation, and production of immune cells. People who consume polyphenol and flavonoid-rich foods have lower incidences of inflammation, autoimmune diseases, and cancer. In organ transplantation, immune rejection is a lifelong problem for patients. In clinical practice, acute rejection is treated with hormonal shock or immunosuppressive drugs. However, effective reversal measures for chronic rejection, specifically for prevention, are still lacking. Recipients are also prone to post-transplant complications such as new tumors, diabetes, hyperlipidemia, hyperuricemia, and cardiovascular and cerebrovascular diseases, owing to the long-term use of immunosuppressive drugs. Phytoestrogens play a promising role in immune regulation and exert curative effects on cardiovascular diseases and cancer. In this study, we reviewed the use of phytoestrogens in the fields of immune regulation and organ transplantation.

Immune cell traits and causal relationships with cholecystitis: a mendelian randomization analysis

Cholecystitis, characterized by inflammation of the gallbladder, is intricately linked to immune cells and the cytokines they produce. Despite this association, the specific contributions of immune cells to the onset and progression of cholecystitis remain to be fully understood. To delineate this relationship, we utilized the Mendelian randomization (MR) method to scrutinize the causal connections between 731 immune cell phenotypes and cholecystitis. By conducting MR analysis on 731 immune cell markers from public datasets, this study seeks to understand their potential impact on the risk of cholecystitis. It aims to elucidate the interactions between immune phenotypes and the disease, aiming to lay the groundwork for advancing precision medicine and developing effective treatment strategies for cholecystitis. Taking immune cell phenotypes as the exposure factor and cholecystitis as the outcome event, this study used single nucleotide polymorphisms (SNPs) closely associated with both immune cell phenotypes and cholecystitis as genetic instrumental variables. We conducted a two-sample MR analysis on genome-wide association studies (GWAS) data. Our research thoroughly examined 731 immune cell markers, to determine potential causal relationships with susceptibility to cholecystitis. Sensitivity analyses were performed to ensure the robustness of our findings, excluding the potential impacts of heterogeneity and pleiotropy. To avoid reverse causality, we conducted reverse MR analyses with cholecystitis as the exposure factor and immune cell phenotypes as the outcome event. Among the 731 immune phenotypes, our study identified 21 phenotypes with a causal relationship to cholecystitis (P < 0.05). Of these, eight immune phenotypes exhibited a protective effect against cholecystitis (odds ratio (OR) < 1), while the other 13 immune phenotypes were associated with an increased risk of developing cholecystitis (OR > 1). Additionally, employing the false discovery rate (FDR) method at a significance level of 0.2, no significant causal relationship was found between cholecystitis and immune phenotypes. Our research has uncovered a significant causal relationship between immune cell phenotypes and cholecystitis. This discovery not only enhances our understanding of the role of immune cells in the onset and progression of cholecystitis but also establishes a foundation for developing more precise biomarkers and targeted therapeutic strategies. It provides a scientific basis for more effective and personalized treatments in the future. These findings are expected to substantially improve the quality of life for patients with cholecystitis and mitigate the impact of the disease on patients and their families.

Central role for cholangiocyte pathobiology in cholestatic liver diseases

Cholangiopathies comprise a spectrum of chronic intrahepatic and extrahepatic biliary tract disorders culminating in progressive cholestatic liver injury, fibrosis, and often cirrhosis and its sequela. Treatment for these diseases is limited, and collectively, they are one of the therapeutic "black boxes" in clinical hepatology. The etiopathogenesis of the cholangiopathies likely includes disease-specific mediators but also common cellular and molecular events driving disease progression (eg, cholestatic fibrogenesis, inflammation, and duct damage). The common pathways involve cholangiocytes, the epithelial cells lining the intrahepatic and extrahepatic bile ducts, which are central to the pathogenesis of these disorders. Current information suggests that cholangiocytes function as a signaling "hub" in biliary tract-associated injury. Herein, we review the pivotal role of cholangiocytes in cholestatic fibrogenesis, focusing on the crosstalk between cholangiocytes and portal fibroblasts and HSCs. The proclivity of these cells to undergo a senescence-associated secretory phenotype, which is proinflammatory and profibrogenic, and the intrinsic intracellular activation pathways resulting in the secretion of cytokines and chemokines are reviewed. The crosstalk between cholangiocytes and cells of the innate (neutrophils and macrophages) and adaptive (T cells and B cells) immune systems is also examined in detail. The information will help consolidate information on this topic and guide further research and potential therapeutic strategies for these diseases.

Regulatory T cells: masterminds of immune equilibrium and future therapeutic innovations

Regulatory T cells (Tregs), a subset of CD4+T cells marked by the expression of the transcription factor forkhead box protein 3 (Foxp3), are pivotal in maintaining immune equilibrium and preventing autoimmunity. In our review, we addressed the functional distinctions between Foxp3+Tregs and other T cells, highlighting their roles in autoimmune diseases and cancer. We uncovered the dual nature of Tregs: they prevented autoimmune diseases by maintaining self-tolerance while contributing to tumor evasion by suppressing anti-tumor immunity. This study underscored the potential for targeted therapeutic strategies, such as enhancing Treg activity to restore balance in autoimmune diseases or depleting Foxp3+Tregs to augment anti-tumor immune responses in cancer. These insights laid the groundwork for future research and clinical applications, emphasizing the critical role of Foxp3+Tregs in immune regulation and the advancement of next-generation immunotherapies.

Immunobiology of primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC) is a chronic inflammatory progressive cholestatic liver disease. Genetic risk factors, the presence of autoantibodies, the strong clinical link with inflammatory bowel disease, and associations with other autoimmune disorders all suggest a pivotal role for the immune system in PSC pathogenesis. In this review, we provide a comprehensive overview of recent immunobiology insights in PSC. A particular emphasis is given to immunological concepts such as tissue residency and knowledge gained from novel technologies, including single-cell RNA sequencing and spatial transcriptomics. This review of the immunobiological landscape of PSC covers major immune cell types known to be enriched in PSC-diseased livers as well as recently described cell types whose biliary localization and contribution to PSC immunopathogenesis remain incompletely described. Finally, we emphasize the importance of time and space in relation to PSC heterogeneity as a key consideration for future studies interrogating the role of the immune system in PSC.

Single-cell, single-nucleus, and spatial transcriptomics characterization of the immunological landscape in the healthy and PSC human liver

BACKGROUND & AIMS

Primary sclerosing cholangitis (PSC) is an immune-mediated cholestatic liver disease for which there is an unmet need to understand the cellular composition of the affected liver and how it underlies disease pathogenesis. We aimed to generate a comprehensive atlas of the PSC liver using multi-omic modalities and protein-based functional validation.

METHODS

We employed single-cell and single-nucleus RNA sequencing (47,156 cells and 23,000 nuclei) and spatial transcriptomics (one sample by 10x Visium and five samples with Nanostring GeoMx DSP) to profile the cellular ecosystem in 10 PSC livers. Transcriptomic profiles were compared to 24 neurologically deceased donor livers (107,542 cells) and spatial transcriptomics controls, as well as 18,240 cells and 20,202 nuclei from three PBC livers. Flow cytometry was performed to validate PSC-specific differences in immune cell phenotype and function.

RESULTS

PSC explants with parenchymal cirrhosis and prominent periductal fibrosis contained a population of cholangiocyte-like hepatocytes that were surrounded by diverse immune cell populations. PSC-associated biliary, mesenchymal, and endothelial populations expressed chemokine and cytokine transcripts involved in immune cell recruitment. Additionally, expanded CD4+ T cells and recruited myeloid populations in the PSC liver expressed the corresponding receptors to these chemokines and cytokines, suggesting potential recruitment. Tissue-resident macrophages, by contrast, were reduced in number and exhibited a dysfunctional and downregulated inflammatory response to lipopolysaccharide and interferon-γ stimulation.

CONCLUSIONS

We present a comprehensive atlas of the PSC liver and demonstrate an exhaustion-like phenotype of myeloid cells and markers of chronic cytokine expression in late-stage PSC lesions. This atlas expands our understanding of the cellular complexity of PSC and has potential to guide the development of novel treatments.

IMPACT AND IMPLICATIONS

Primary sclerosing cholangitis (PSC) is a rare liver disease characterized by chronic inflammation and irreparable damage to the bile ducts, which eventually results in liver failure. Due to a limited understanding of the underlying pathogenesis of disease, treatment options are limited. To address this, we sequenced healthy and diseased livers to compare the activity, interactions, and localization of immune and non-immune cells. This revealed that hepatocytes lining PSC scar regions co-express cholangiocyte markers, whereas immune cells infiltrate the scar lesions. Of these cells, macrophages, which typically contribute to tissue repair, were enriched in immunoregulatory genes and demonstrated a lack of responsiveness to stimulation. These cells may be involved in maintaining hepatic inflammation and could be a target for novel therapies.

Monocyte differentiation within tissues: a renewed outlook

When recruited to mammalian tissues, monocytes differentiate into macrophages or dendritic cells (DCs). In the past few years, the existence of monocyte-derived DCs (moDCs) was questioned by the discovery of new DC populations with overlapping phenotypes. Here, we critically review the evidence for monocyte differentiation into DCs in tissues and highlight their specific functions. Recent studies have shown that monocyte-derived macrophages (moMacs) with distinct life cycles coexist in tissues, both at steady state and upon inflammation. Integrating studies in mice and humans, we highlight specific features of moMacs during inflammation and tissue repair. We also discuss the notion of monocyte differentiation occurring via a binary fate decision. Deciphering monocyte-derived cell properties is essential for understanding their role in nonresolving inflammation and how they might be targeted for therapies.

Integrative bioinformatics analysis and experimental validation of key biomarkers for risk stratification in primary biliary cholangitis

BACKGROUND

Primary biliary cholangitis (PBC) is an autoimmune liver disease, whose etiology is yet to be fully elucidated. Currently, ursodeoxycholic acid (UDCA) is the only first-line drug. However, 40% of PBC patients respond poorly to it and carry a potential risk of disease progression. So, in this study, we aimed to explore new biomarkers for risk stratification in PBC patients to enhance treatment.

METHODS

We first downloaded the clinical characteristics and microarray datasets of PBC patients from the Gene Expression Omnibus (GEO) database. Differentially expressed genes (DEGs) were identified and subjected to enrichment analysis. Hub genes were further validated in multiple public datasets and PBC mouse model. Furthermore, we also verified the expression of the hub genes and developed a predictive model in our clinical specimens.

RESULTS

A total of 166 DEGs were identified in the GSE79850 dataset, including 95 upregulated and 71 downregulated genes. Enrichment analysis indicated that DEGs were significantly enriched in inflammatory or immune-related process. Among these DEGs, 15 risk-related genes were recognized and further validated in the GSE119600 cohort. Then, TXNIP, CD44, ENTPD1, and PDGFRB were identified as candidate hub genes. Finally, we proceeded to the next screening with these four genes in our serum samples and developed a three-gene panel. The gene panel could effectively identify those patients at risk of disease progression, yielding an AUC of 0.777 (95% CI, 0.657-0.870).

CONCLUSIONS

In summary, combining bioinformatics analysis and experiment validation, we identified TXNIP, CD44, and ENTPD1 as promising biomarkers for risk stratification in PBC patients.

Autoantigen-selected B cells are bystanders in spontaneous T cell-driven experimental autoimmune hepatitis

Autoreactive B cells are considered pathogenic drivers in many autoimmune diseases; however, it is not clear whether autoimmune B cells are invariably pathogenic or whether they can also arise as bystanders of T cell-driven autoimmune pathology. Here, we studied the B cell response in an autoantigen- and CD4+ T cell-driven model of autoimmune hepatitis (AIH), the Alb-iGP_Smarta mouse in which expression of a viral model antigen (GP) in hepatocytes and its recognition by GP-specific CD4+ T cells causes spontaneous AIH-like disease. T cell-driven AIH in Alb-iGP_Smarta mice was marked by autoantibodies and hepatic infiltration of plasma cells and B cells, particularly of isotype-switched memory B cells, indicating antigen-driven selection and activation. Immunosequencing of B cell receptor repertoires confirmed B cell expansion selectively in the liver, which was most likely driven by the hepatic GP model antigen, as indicated by branched networks of connected sequences and elevated levels of IgG antibodies to GP. However, intrahepatic B cells did not produce increased levels of cytokines and their depletion with anti-CD20 antibody did not alter the CD4+ T cell response in Alb-iGP_Smarta mice. Moreover, B cell depletion did not prevent spontaneous liver inflammation and AIH-like disease in Alb-iGP_Smarta mice. In conclusion, selection and isotype-switch of liver-infiltrating B cells was dependent on the presence of CD4+ T cells recognizing liver antigen. However, recognition of hepatic antigen by CD4+ T cells and CD4+ T cell-mediated hepatitis was not dependent on B cells. Thus, autoreactive B cells can be bystanders and need not be drivers of liver inflammation in AIH.