Background Kupffer cells and monocyte-derived macrophages (MoMs) are difficult to study in human primary biliary cholangitis (PBC) even though they reflect a dynamic hepatic immune population. Objective We aim to investigate the role of hepatic macrophage and its therapeutic potential in human PBC and murine autoimmune cholangitis. Design Phenotypic analysis of hepatic macrophages in patients with PBC and dnTGFβRII mice model was performed by single-cell RNA sequencing, flow cytometry and immunohistochemistry. Depletion of hepatic macrophages and inhibition of MoMs were performed in murine autoimmune cholangitis. Lyz2-Cre -mediated Atg5 knockout mice and co-culture experiments were applied to explore the role and mechanism of macrophage autophagy in autoimmune cholangitis. Therapeutic intervention was performed using nanoparticle-capsuled small interfering RNA against Atg5 . Results Kupffer cells from patients with PBC and dnTGFβRII mice upregulate genes associated with inflammatory responses and exhibit increased autophagy. Further, macrophage-specific knockout of Atg5 leads to reduction of inflammation and bile duct damage. We propose that the mechanism of this modulation is secondary to decreased activation of pathogenic CD8 + T cells. Indeed, Kupffer cells maintain CD8 + T cell tolerance through expression of inducible nitric oxide synthase (iNOS) and generation of NO. Increased autophagy resulted in degradation of iNOS in Kupffer cells and abrogated their suppressive activity against CD8 + T cells. Finally, we report that targeted downregulation of Kupffer cell autophagy in vivo using cationic lipid-assisted nanoparticles encapsulating siRNA against Atg5 leads to reduction of liver inflammation and bile duct damage. Conclusion Macrophage autophagy promotes autoimmune cholangitis and strongly supports this pathway as a potential therapeutic target.

The complexity and heterogeneity of autoimmune diseases are only partially captured by current analytic tools, even when deep learning techniques are employed to intercept patterns beyond existing dogma. Synthetic data offer a newer paradigm through machine-generated reconstructions of real-world data that faithfully attempt to recapitulate biological and clinical patterns without creating duplicates and maintaining the privacy of the original ones. Synthetic data act as a magnifying lens, allowing predictions otherwise not possible on disease classification, progression, and therapeutic response. This approach has several advantages and is currently underutilized. Firstly, it provides cohort enrichment and equilibrates group imbalances. Second, it generates synthetic arms for both in vitro studies and human clinical trials, relevant to disentangle the rarity and heterogeneity of autoimmune diseases. Third, the platform allows applications beyond tabular registries, including medical images, genomics, and flow cytometry data. Last, 'digital twins' act through dynamic bidirectional links with the biological/clinical system counterpart, lending themselves to transformative opportunities for precision medicine. Herein, we discuss the current status of this fast-moving novel component of artificial intelligence and its implications for autoimmune diseases.

The biliary tract is now recognized as an immune organ, and within the biliary tract, both bile and cholangiocytes play a key role in maintaining immune defense and homeostasis. First, immunoreactive proteins such as secretory IgA provide local antimicrobial effects. Second, bile acids (BAs) protect the biliary tree from immune-related injury through receptor signaling, mainly via the membrane-bound receptor TGR5 on cholangiocytes. Third, the biliary microbiota, similar to the intestinal microbiota, contributes to sustaining a stable physiobiological microenvironment. Fourth, cholangiocytes actively modulate the expression/release of adhesion molecules and cytokines/chemokines and are involved in antigen presentation; additionally, cholangiocyte senescence and apoptosis also influence immune responses. Conversely, aberrant bile composition, altered BA profiles, imbalances in the biliary microbiota, and cholangiocyte dysfunction are associated with immune-mediated cholangiopathies, including primary biliary cholangitis, primary sclerosing cholangitis, and biliary atresia. While current therapeutic agents that modulate BA homeostasis and receptor signaling have shown promise in preclinical and clinical studies, future research on biliary/intestinal microbiota and cholangiocyte function should focus on developing novel therapeutic strategies for treating cholangiopathies.

Background: Uncertainties persist regarding the optimal management of acute onset of autoimmune hepatitis, including the use of corticosteroids. This study aimed to compare the effectiveness and safety of rapid versus slow corticosteroid tapering in acute onset of AIH. Methods: A multicenter study involving patients with acute AIH was conducted. We defined acute AIH as an acute presentation (<30 days) with AIH and exhibiting no evidence of pre-existing liver diseases. Initially, corticosteroid treatment and overall outcomes were reported. Subsequently, the role of corticosteroid tapering rate in modifying outcomes across subgroups was investigated. For patients with an initial corticosteroid dose of 20 mg/ day or higher, we further classified patients into rapid tapering group (duration until dose of prednisone <20 mg/day <3 weeks) and slow tapering group (duration until dose of prednisone <20 mg/day >= 3 weeks). Adverse events were defined as any of the following events, progression (e.g., acute icteric AIH progression to AS-AIH or AIH-ALF, AS-AIH progression to AIH-ALF, non-cirrhotic progression to cirrhosis, compensated cirrhosis progression to decompensation), LT, and liver-related death. Results: This retrospective cohort study enrolled 237 patients, with 109 presenting acute icteric AIH, 97 with acute-severe AIH (AS-AIH), and 31 with AIH-acute liver failure (ALF). Among patients with acute icteric AIH, slow tapering significantly improved adverse outcome-free survival compared to rapid tapering (99 % vs. 71 %, P < 0.0001). Similarly, in AS-AIH patients, slow tapering resulted in notably higher adverse outcome-free survival rates compared to rapid tapering (92 % vs. 54 %, P < 0.001). Slow tapering independently predicted fewer adverse events (OR 0.144; 95 % CI 0.037-0.562; P = 0.005). However, in AIH-acute liver failure (ALF) patients, tapering rate did not significantly affect adverse outcome-free survival (38 % vs. 50 %, P = 0.590). Overall, there were no significant differences in osteoporosis or infection occurrence between tapering groups in the entire acute AIH cohort. Conclusion: A slow corticosteroid tapering reduced adverse outcomes in acute exacerbation of AIH patients, particularly in acute icteric AIH and AS-AIH.

The dogma of an impenetrable blood-brain barrier (BBB) has given way to the view that resident immune cells within the central nervous system respond to a variety of blood-borne soluble factors, particularly cytokines, and play an important functional role. In particular, microglia cells contribute to the regulation of neuroinflammation, with both protective and pathological roles. Specific microglia activation states variably influence the progression of neuroinflammatory and neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, multiple sclerosis, and amyotrophic lateral sclerosis. Significant evidence indicates that gut microbiota-derived products regulate microglial function across the lifespan and influence the BBB. Myeloperoxidase (MPO) catalyzes the conversion of hydrogen peroxide and chloride ions into hypochlorous acid, a potent oxidant implicated in oxidative tissue damage and modulation of inflammatory signaling. Elevated MPO levels in the central nervous system have been correlated with human disease and the dysregulation of MPO activity in microglia is particularly detrimental, as it amplifies the oxidative stress, disrupts the BBB integrity, and potentiates the neuroinflammatory cascades through the activation of transcription factors like NF-κB. Targeting MPO activity through selective inhibitors or antioxidant strategies may attenuate microglial activation and reduce neuroinflammation, highlighting its potential as a therapeutic target, but the regulatory mechanisms governing MPO expression in microglia and its interplay with other inflammatory mediators remain poorly understood. New research efforts into the relationship between gut microbiota, microglia, MPO, and neuroinflammation are essential to unravel the complexities of neuropathology in a variety of conditions beyond neurodegenerative diseases.

Background & Aims: In this study, we aimed to evaluate the incidence, predictors, and prognostic significance of recompensation in autoimmune hepatitis (AIH)-related decompensated cirrhosis following immunosuppressive therapy (IST). Methods: We retrospectively analyzed patients with AIH at first decompensation. Recompensation, defined using modified Baveno VII criteria, required clinical resolution (≥12 months without ascites, variceal bleeding, or hepatic encephalopathy, with liver function restored to Child-Pugh A) along with aetiological suppression (complete biochemical response under IST). Predictors of recompensation were identified using multivariate regression, and survival outcomes were compared among compensated, recompensated, and non-recompensated groups. Results: A total of 258 patients with AIH-related decompensated cirrhosis were included (median follow-up: 47 months, IQR 28-75). Clinical resolution was achieved by 124 patients (48.1%), while 68 patients (30.9% of 220 treated with IST) met criteria for recompensation. Predictors of recompensation included ascites as the only complication (hazard ratio [HR] 14.40, 95% CI 4.17-49.64, p <0.001), lower IgG levels (HR 0.90, 95% CI 0.89-0.96, p <0.001), higher bilirubin levels (HR 1.04, 95% CI 1.00-1.08, p = 0.030), and higher platelet counts (HR 1.01, 95% CI 1.00-1.01, p = 0.039). Patients achieving recompensation experienced a significantly reduced risk of liver transplantation or death (HR 0.07, 95% CI 0.01-0.50, p = 0.009), with survival outcomes comparable to those of compensated patients. Conclusions: Recompensation was achieved in approximately one-third of patients with AIH-related decompensated cirrhosis undergoing IST, leading to markedly improved transplant-free survival. Predictors of recompensation included having ascites as the sole complication, lower IgG levels, higher bilirubin levels, and higher platelet counts. Impact and implications: The predictors and long-term prognostic implications of recompensation in patients with autoimmune hepatitis (AIH)-related decompensated cirrhosis remain unclear. This study demonstrates that recompensation is achievable in patients with AIH-related decompensated cirrhosis and is associated with significant long-term benefits, including improved survival and reduced transplantation needs. We identified ascites (as the sole decompensating event), lower IgG levels, higher bilirubin levels and higher platelet counts as independent predictors of recompensation. These findings can be used by clinicians to identify the patients most likely to benefit from immunosuppressive therapy.

Primary Biliary Cholangitis (PBC) is a chronic autoimmune liver disease characterized by intrahepatic bile duct destruction, progressive cholestasis, and fibrosis, accompanied by elevated anti-mitochondrial antibodies (AMAs) and IgM. While multiple mouse models have been developed to study PBC pathogenesis, no single model fully recapitulates all aspects of human disease. Among these, the NOD.c3c4 mouse model, generated by incorporating B10 and B6 insulin-dependent diabetes (Idd) loci into NOD mice, uniquely develops PBC-like features without progressing to type-1 diabetes. NOD.c3c4 exhibit PDC-E2-reactive AMAs, elevated autoantibodies, biliary leukocyte infiltration, and progressive liver dysfunction. However, key pathogenic mechanisms, particularly the role of fibrosis, remain poorly understood. Here, we provide a comprehensive characterization of PBC development and progression in NOD.c3c4 mice, focusing on adaptive and innate immune contributions to disease pathology. Our study confirms that both T and B cells are central drivers, as their depletion significantly mitigates PBC pathology. Additionally, our findings highlight a previously underappreciated role of innate immunity in disease progression. Notably, NOD.c3c4 mice develop fibrosis, which advances with age, making them a valuable model for studying fibrotic events in PBC. Given their resemblance to human disease, NOD.c3c4 mice represent a powerful platform for investigating PBC pathogenesis and evaluating new immunotherapeutics.

Axial spondyloarthritis (axSpA) manifests with inflammatory back pain and is diagnosed predominantly in subjects carrying the human leucocyte antigen (HLA)-B27 allele. While not diagnostic for the disease or a predictive biomarker in the general population, there is convincing data on the pathogenic role of HLA-B27 in axSpA via different proinflammatory mechanisms. Similar to other chronic conditions, axSpA requires lifelong treatments, including biologics and small molecules, to treat inflammation and ultimately halt disease progression by achieving sustained disease remission. There is currently no cure for axSpA, but one fascinating thesis is that gene therapy may hold the potential to reverse the disease. We provide herein a comprehensive and critical review of the advances in gene therapy strategies, including gene-editing techniques, RNA interference, and viral vector-mediated delivery systems, with a focus on the possible future developments in HLA-B27-related mechanisms. Understanding these novel approaches may pave the way for more effective, personalized treatments capable of solving the HLA-B27-positive axSpA conundrum.

The immune response to SARS-CoV-2 has been implicated in the onset of multiple, seemingly unrelated, autoimmune diseases. The immune response to SARS-CoV-2 has also been implicated in the unmasking and/or production of multiple autoantibodies, even in the absence of clinical disease. Despite such data, it remains unclear whether antibodies targeting antiviral signaling proteins and mitochondrial antigens reflect bystander activation or alternatively contribute to de novo viral immune escape mechanisms. With these comments in mind, a variety of professional antibody presenting cells and including lung resident macrophages of COVID-19 infected patients are impacted and dependent on the uptake of antibody-opsonized virus by Fcγ receptors; yet infection is aborted via antibody-dependent effector mechanisms or pyroptosis, possibly leading to autoantibody production, and autoinflammatory manifestations, respectively. TRIM21/Ro52, a cytosolic E3-ubiquitin ligase with an Fc-gamma receptor domain, functions as an intracytoplasmic antibody receptor, directs immune complexes binding virions but also autoantigens to autophagy. During autophagy, Ig-virions-TRIM21/Ro52-autoantigens complexes bind directly to class II human leukocyte antigen in lysosomal compartment, leading to subsequent presentation on the cell surface. This process favors the development of a specific humoral immune response but has the potential to lead to loss of tolerance. Interestingly, TRIM21/Ro52 can also contribute to pyroptosis. We propose that TRIM21/Ro52 is well-placed at the crossroad between the inflammatory response and clinical autoimmunity.

Objectives: Antibodies to gp210 and sp100 are specific and unique anti-nuclear autoantibodies (ANAs) associated with primary biliary cholangitis (PBC). Importantly the presence of anti-gp210 and anti-sp100 responses is indicative of poor clinical outcomes. However, the utility of measuring titers of these antibodies remains unclear. Materials and methods: Using the in-house purified gp210 (HSA108-C18) and sp100 (amino acid position 296-386), we quantitatively measured serum autoantibodies to gp210 and sp100 using chemiluminescence immunoassay (CLIA) in a very large cohort of 390 patients with PBC, including 259 cases with no prior ursodesoxycholic acid (UDCA) treatment and 131 cases with UDCA treatment. We also analyzed serial changes in anti-gp210 and anti-sp100 levels in 245 sequential samples from 88 patients. Results: In our cross-sectional analysis, we detected anti-gp210 immunoglobulin G (IgG) and anti-sp100 IgG autoantibodies in 129 out of 390 (33.1%) and 80 out of 390 (20.5%) PBC patients, respectively. Multivariate analysis revealed that serum IgG (st.8 = 0.35, P = 0.003) and gamma-glutamyltransferase (GGT) (st.8 = 0.23, P = 0.042) levels at baseline were independently associated with anti-gp210 concentrations. In serial testing, we observed significant fluctuations in anti-gp210 antibody levels. These fluctuations reflected responsiveness to UDCA therapy, particularly in anti-gp210-positive patients with initially lower concentrations in the stages of disease.

Increasing evidence suggests that, in addition to a loss of tolerance, bile acid (BA) modulates the natural history of primary biliary cholangitis (PBC). We focused on the impacts of dietary changes on the immunopathology of PBC, along with alterations in BA composition and gut microbiota. In this study, we have taken advantage of our unique PBC model, a Cyp2c70/Cyp2a12 double knockout (DKO), which includes a human-like BA composition, and develops progressive cholangitis following immunization with the PDC-E2 mimic, 2-octynoic acid (2OA). We compared the effects of a ten-week high-fat diet (HFD) (60 % kcal from fat) and a normal diet (ND) on 2OAtreated DKO mice. Importantly, we report that 2OA-treated DKO mice fed HFD had significantly exacerbated cholangitis, leading to cirrhosis, with increased hepatic expression of Th1 cytokines/chemokines and hepatic fibrotic markers. Serum lithocholic acid (LCA) levels and the ratio of chenodeoxycholic acid (CDCA)-derived BAs to cholic acid-derived BAs were significantly increased by HFD. This was also associated with downregulated expression of key regulators of BA synthesis, including Cyp8b1, Cyp3a11, and Sult2a1. In addition, there were increases in the relative abundances of Acetatifactor and Lactococcus and decreases in Desulfovibrio and Lachnospiraceae_NK4A136_group, which corresponded to the abundances of CDCA and LCA. In conclusion, HFD and HFD-induced alterations in the gut microbiota modulate BA composition and nuclear receptor activation, leading to cirrhotic change in this murine PBC model. These findings have significant implications for understanding the progression of human PBC.

Patients with primary biliary cholangitis (PBC) commonly experience extrahepatic rheumatic diseases. However, the epidemiologic and genetic associations as well as causal relationship between PBC and these extrahepatic conditions remain undetermined. In this study, we first conducted systematic review and meta-analyses by analyzing 73 studies comprising 334,963 participants across 17 countries and found strong phenotypic associations between PBC and rheumatic diseases. Next, we utilized large-scale genome-wide association study summary data to define the shared genetic architecture between PBC and rheumatic diseases, including rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), systemic sclerosis (SSc) and Sjögren's syndrome (SS). We observed significant genetic correlations between PBC and each of the four rheumatic diseases. Pleiotropy and heritability enrichment analysis suggested the involvement of humoral immunity and interferon-associated processes for the comorbidity. Of note, we identified four variants shared between PBC and RA (rs80200208), SLE (rs9843053), and SSc (rs27524, rs3873182) using cross-trait meta-analysis. Additionally, several pleotropic loci for PBC and rheumatic diseases were found to share causal variants with gut microbes possessing immunoregulatory functions. Finally, Mendelian randomization revealed consistent evidence for a causal effect of PBC on RA, SLE, SSc, and SS, but no or inconsistent evidence for a causal effect of extrahepatic rheumatic diseases on PBC. Our study reveals a profound genetic overlap and causal relationships between PBC and extrahepatic rheumatic diseases, thus providing insights into shared biological mechanisms and novel therapeutic interventions.

Background and aimsHypercholesterolemia is frequently diagnosed in patients with primary biliary cholangitis (PBC). However, its association with the prognosis and lipid metabolism is unknown. In this study, we aimed to investigate the prognostic value of baseline total cholesterol (TC) levels in PBC and characterized the lipid metabolism.MethodsOf note, 531 patients with PBC without prior cirrhosis-related complications were randomly divided into the derivation and validation cohorts at a ratio of 7:3. Complete clinical data were obtained and analyzed. The endpoints were defined as liver-related death, liver transplantation (LT) and cirrhosis-related complications. Untargeted lipidomics was performed in 89 patients and 28 healthy controls (HC).ResultsBaseline TC was independently associated with poor clinical outcomes and adjusted C-statistics were 0.8035 (95% confidence interval [CI]: 0.7372–0.8470) and 0.8754 (95% CI: 0.7777–0.9067) in the derivation and validation cohorts, respectively. The predictive ability of TC for disease outcomes was stable over the years and comparable to the Globe score. The 5.2 mmol/L cut-off optimally divided patients into low- and high-risk groups. A combination of TC and Globe score provided a more accurate stratification of patients into risk subgroups. Untargeted lipidomics indicated an upregulation of lipid families in high-risk patients. Pathway analysis of 66 upregulated lipids revealed the dysregulation of glycerophospholipid and sphingolipid metabolism in high-risk patients, which were associated with poor clinical outcomes.ConclusionsOur results indicate that patients with PBC having baseline TC levels above 5.2 mmol/L have unique lipidome characteristics and are at a higher risk of poor clinical outcomes.

Osteoporosis is a major clinical problem in many autoimmune diseases, including primary biliary cholangitis (PBC), the most common autoimmune liver disease. Osteoporosis is a major cause of fracture and related mortality. However, it remains unclear whether PBC confers a causally risk-increasing effect on osteoporosis. Herein, we aimed to investigate the causal relationship between PBC and osteoporosis and whether the relationship is independent of potential confounders. We performed bidirectional Mendelian randomization (MR) analyses to investigate the association between PBC (8021 cases and 16,489 controls) and osteoporosis in Europeans (the UK Biobank and FinnGen Consortium: 12,787 cases and 726,996 controls). The direct effect of PBC on osteoporosis was estimated using multivariable MR analyses. An independent replication was conducted in East Asians (PBC: 2495 cases and 4283 controls; osteoporosis: 9794 cases and 168,932 controls). Trans-ethnic meta-analysis was performed by pooling the MR estimates of Europeans and East Asians. Inverse-variance weighted analyses revealed that genetic liability to PBC was associated with a higher risk of osteoporosis in Europeans (OR, 1.040; 95

AbstractThe specific mechanisms underlying effector pathways in autoimmune liver disease remain enigmatic and therefore constructing appropriate murine models to investigate disease pathogenesis becomes critical. A spontaneous severe murine model of autoimmune liver disease has been previously established in dnTGFβRII Aire−/− mice, exhibiting disease phenotypes that resemble both human primary biliary cholangitis (PBC) and autoimmune hepatitis (AIH). The data suggests that auto‐reactive liver‐specific CD8+ T cells are the primary pathogenic cells in liver injury. In this study, these data are advanced through the use of both single‐cell sequencing and extensive in vitro analysis. The results identify a specific expanded pathogenic subset of PD‐1+CD8+ T cells in the liver, exhibiting strong functional activity and cytotoxicity against target cells. Depletion of PD‐1+CD8+ T cells using CAR‐T cells effectively alleviates the disease. GSDMD‐mediated pyroptosis is found to be aberrantly activated in the livers of model mice, and treatment with a GSDMD‐specific inhibitor significantly inhibits disease progression. In vitro experiments reveal that PD‐1+CD8+ T cells can induce the pyroptosis of hepatocytes through elevated production of granzyme B and perforin‐1. These results provide a novel explanation for the cytotoxic activity of pathogenic liver PD‐1+CD8+ T cells in autoimmune liver diseases and offer potential therapeutic targets.

Background Primary biliary cholangitis (PBC) is a progressive autoimmune liver disease. An inadequate response to ursodeoxycholic acid (UDCA) poses a high risk of progression toward end-stage liver disease. Gut dysbiosis has been implicated in PBC. Here, we aimed to investigate microbial signatures that permit risk stratification and provide mechanistic insights into novel therapies for PBC. Methods We prospectively recruited UDCA treatment-naive patients with PBC and performed metagenomic sequencing and metabolomic profiling using stool and serum samples obtained before (n = 132) and after (n = 59) treatment. PBC microbiome subtypes were identified using unsupervised machine learning methods and validated in two independent cohorts. Findings PBC baseline metagenomes clustered into two community subtypes characterized by varying abundances of Clostridia taxa. Compared with Clostridialow microbiomes, Clostridiahigh microbiomes were more similar to healthy controls. Notably, patients in the Clostridialow subtype exhibited a 2-fold higher UDCA non-response rate compared to those in the Clostridiahigh subtype (41% vs. 20%, p = 0.015). Integrative analysis of metagenomic and metabolomic data revealed divergent functional modules and metabolic activities between the two metacommunities. In particular, anaerobic fermentation and the production of bioactive metabolites, including tryptophan derivatives and secondary bile acids, crucial for immune regulation and gut barrier maintenance, were markedly diminished in the Clostridialow subtype. Moreover, UDCA administration reconfigured the fecal microbial and metabolic profiles only in the Clostridiahigh group. Importantly, the microbiome subtypes and their associations with UDCA response were reproducible in two independent treatment-naive PBC cohorts. Conclusions Characterizing baseline microbiota patterns may enable the prediction of treatment outcomes in PBC and facilitate personalized treatment strategies. Funding This research was mainly supported by the National Natural Science Foundation of China.

Background & aims: Association studies have greatly refined the important role of the major histocompatibility complex (MHC) region in autoimmune hepatitis (AIH). However, the effects of human leucocyte antigen (HLA) polymorphisms on AIH are not well established. The aim of this study is to systematically characterise the association of MHC variants with AIH in our well-defined cohort of patients.Methods: We performed an imputation-based analysis on the extensive association observed within the MHC region using the Han-MHC reference panel, and tested the comprehensive associations of HLA polymorphisms with AIH in 1622 Chinese AIH type 1 patients and 10,466 population controls.Results: A total of 588 HLA variants were significantly associated with AIH, with HLA-B & lowast;35:01 (p = 8.17 x 10(-304); odds ratio [OR] = 7.32) contributing the strongest signal. Stepwise conditional analysis revealed additional independent signals at HLA-B & lowast;08:01 (p = 1.35 x 10(-33); OR = 4.26) and rs7765379 (p = 5.08 x 10(-18); OR = 1.66). A strong link between the lead HLA variant and clinical phenotypes of AIH was observed: patients with HLA-B & lowast;35:01 were less frequently positive for ANA and tended to have higher serum AST and ALT levels at diagnosis, but lower serum IgG levels.Conclusions: Our study reveals three novel and independent variants at HLA-B & lowast;35:01, HLA-B & lowast;08:01, and rs7765379 associated with AIH across the whole MHC region in the Han Chinese population. The findings illustrate the value of the MHC region in AIH and provide a new perspective for the immunogenetics of AIH.Impact and implications: This study revealed three novel and independent variants associated with autoimmune hepatitis across the whole major histocompatibility complex region in the Han Chinese population. These findings are significant in identifying autoantigens, providing insights into the activation of the autoimmune processes, and further advancing our understanding of the immunogenetic basis underlying autoimmune hepatitis.(c) 2023 The Authors. Published by Elsevier B.V. on behalf of European Association for the Study of the Liver (EASL). This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Background & AimsPrimary biliary cholangitis (PBC) is a progressive-cholestatic autoimmune liver disease. Dendritic cells (DC) are professional antigen-presenting cells and their prominent presence around damaged bile ducts of PBC patients are documented. cDC1 is a rare subset of DC known for its cross-presentation abilities and interleukin 12 production. Our aim was to assess the role of cDC1 in the pathogenesis of PBC.MethodsWe utilized an inducible murine model of PBC and took advantage of the DC reporter mice Zbtb46gfp and the Batf3-/- mice that specifically lack the cDC1 subset. cDC1 cells were sorted from blood of PBC patients and healthy individuals and subjected to Bulk-MARS-seq transcriptome analysis.ResultsHistopathology assessment demonstrated peri-portal inflammation in wild type (WT) mice, whereas only minor abnormalities were observed in Batf3-/- mice. Flow cytometry analysis revealed a two-fold reduction in hepatic CD8/CD4 T cells ratio in Batf3-/- mice, suggesting reduced intrahepatic CD8 T cells expansion. Histological evidence of portal fibrosis was detected only in the WT but not in Batf3-/- mice. This finding was supported by decreased expression levels of pro-fibrotic genes in the livers of Batf3-/- mice. Transcriptome analysis of human cDC1, revealed 78 differentially expressed genes between PBC patients and controls. Genes related to antigen presentation, TNF and IFN signalling and mitochondrial dysfunction were significantly increased in cDC1 isolated from PBC patients.ConclusionOur data illustrated the contribution the cDC1 subset in the pathogenesis of PBC and provides a novel direction for immune based cell-specific targeted therapeutic approach in PBC.

The detection of antimitochondrial antibodies (AMA) is the specific diagnostic marker for primary biliary cholangitis. Indeed, it is the most specific autoantibody in clinical autoimmunity, with a high titer directed response to the inner lipoyl domain of PDC-E2. The current international reference for AMA detection is based upon sera samples of PBC patients. In rheumatic diseases, i.e. rheumatoid arthritis, great efforts are placed at development of international standards. In this study, we report the development of a monoclonal chimeric IgG1 antibody as a reference for AMA testing. A monoclonal 4G6 antibody was constructed from a murine monoclonal antibody specific for the inner lipoyl domain (ILD) of PDC-E2, by combining the variable region with the constant region of human IgG1. The 4G6 antibody recognizes all AMA epitopes containing the ILD of PDC-E2, including the classical BPO recombinant antigen in all currently available diagnostic methods. The binding affinity of the 4G6 antibody to PDC-E2 and BPO antigen reaches KD value of 7.22 x 10-11 M and 4.55 x 10- 11 M, which is sufficient to use as a quantitative reference for all AMA tests. The unlimited availability of the 4G6 antibody makes it a promising candidate for use as an AMA reference or assay calibrator for the international community.