Liver infiltrating mononuclear cells in children with type 1 autoimmune hepatitis

Autoimmune Hepatitis: Pathophysiology

Genome-wide association analyses suggest that HLA genes including HLA-DRB*0301, HLA-DRB*0401, and HLA-B*3501 as well as non-HLA genes including CD28/CTLA4/ICOS and SYNPR increased AIH susceptibility. The destruction of hepatocytes is the result of the imbalance between proinflammatory cells and immunosuppressive cells, especially the imbalance between Tregs and Th17 cells. The microbiome in patients with AIH is decreased in diversity with a specific decline in Bifidobacterium and enrichment in Veillonella and Faecalibacterium. Recent evidence has demonstrated the pathogenic role of E. gallinarum and L.reuteri in inducing autoimmunity in the liver.

In vivo study of subacute oral toxicity of kelulut honey

Kelulut honey is favoured for its tremendous nutritional benefits. However, the lack of systematic safety studies leads to it having no quality control or safety guarantee for the consumers. Consequently, the present work was designed to assess the effect of daily kelulut honey consumption. Subacute oral toxicity study was conducted following the Organization for Economic Co-operation and Development (OECD) test guideline 407. Sprague Dawley rats were administered with kelulut honey at the concentrations of 500, 1,000, and 2,000 mg/kg for four weeks, and observed for any changes or toxicity signs following daily consumption. The rats were physically and biochemically analysed, and the serum of highest honey concentration (2,000 mg/kg) consumption underwent metabolite analysis. Histopathology observations on the kidney and liver were also performed. The highest concentration of kelulut honey did not show any mortality or toxicity. Overall, there were no significant differences in all parameters, physically and biochemically, as compared to the control (distilled water), thus indicating the absence of toxicity of kelulut honey daily consumption. It was found that kelulut honey consumption demonstrated generally good health effects, such as in controlling food intake, weight gain, and increasing immune function. The honey’s lethal medium dose surpassed 2,000 mg/kg, thus classified in category 5 according to the Globally Harmonized System of Classification and Labelling of Chemicals, which means that it is safe to consume at a high dose.

Celastrol Alleviates Autoimmune Hepatitis Through the PI3K/AKT Signaling Pathway Based on Network Pharmacology and Experiments

Objective: This work aims to explore the potential targets and underlying therapeutic mechanisms of celastrol in autoimmune hepatitis (AIH) through network pharmacology and experiments on Laboratory Animals.

Methods: A drug-target interaction network was constructed to predict the possible targets of celastrol and their potential relationship with the drug; docking studies were also performed for validation. This study used both acute and chronic rodent models of autoimmune hepatitis. Gross appearance of liver and spleen were obtained from murine models, hematoxylin-eosin staining and Sirius red staining were performed to examine hepatic inflammation and fibrosis respectively. By combining molecular docking and enrichment analysis results, the most prominent signaling pathway was selected and further confirmed by Western blot in AIH models administered with celastrol.

Results: In total, 82 common targets of celastrol and AIH were obtained from databases, identified by network pharmacology, and adequately enriched. Among them, PIK3R1, SRC, MAPK1, AKT1, and HRAS were selected as the top 5 closely related targets to celastrol. They all performed effectively in molecular docking, with AKT1 and PIK3R1 exhibiting more-prominent binding energy. Subsequently, celastrol administration significantly ameliorated hepatitis and liver fibrosis by reducing AKT1 and PI3K phosphorylation in both acute liver injury and chronic models of autoimmune hepatitis.

Conclusion: In summary, celastrol significantly attenuates autoimmune hepatitis by suppressing the PI3K/AKT signaling pathway, confirmed by validated animal models. These findings may help identify the mechanism involved in the anti-inflammatory action of celastrol in autoimmune hepatitis and provide ideas for future comprehensive studies.

Concanavalin A-induced autoimmune hepatitis model in mice: Mechanisms and future outlook

The concanavalin A (Con A)-induced liver injury mouse model is a typical animal model focusing on T cell-dependent hepatic damage in the field of autoimmune hepatitis (AIH). However, the underlying mechanism of hepatic dysfunction due to cell activation or signaling pathways triggered by Con A has not been fully clarified. Therefore, the controversy on this model remains in the academic community. In this article, we first summarized the merit and demerit of this contentious model from the perspectives of cell dysfunction, microcirculation disturbance, involved signaling pathways, as well as the properties of Con A. Then, we summed up the scientific implications of the model in elucidating the pathogenesis of AIH, and the shortcomings of this model were also summarized to elucidate the pathogenesis and application prospect of this classical liver injury mouse model in the study of AIH.

Cellular and Molecular Mechanisms of Autoimmune Hepatitis

Autoimmune hepatitis is an uncommon idiopathic syndrome of immune-mediated destruction of hepatocytes, typically associated with autoantibodies. The disease etiology is incompletely understood but includes a clear association with human leukocyte antigen (HLA) variants and other non-HLA gene variants, female sex, and the environment. Pathologically, there is a CD4+ T cell-rich lymphocytic inflammatory infiltrate with variable hepatocyte necrosis and subsequent hepatic fibrosis. Attempts to understand pathogenesis are informed by several monogenetic syndromes that may include autoimmune liver injury, by several drug and environmental agents that have been identified as triggers in a minority of cases, by human studies that point toward a central role for CD4+ effector and regulatory T cells, and by animal models of the disease. Nonspecific immunosuppression is the current standard therapy. Further understanding of the disease's cellular and molecular mechanisms may assist in the design of better-targeted therapies, aid the limitation of adverse effects from therapy, and inform individualized risk assessment and prognostication.

Novel Diagnostic and Therapeutic Strategies in Juvenile Autoimmune Hepatitis

Juvenile autoimmune hepatitis (JAIH) is a rare, chronic, inflammatory disease of the liver characterized by a complex interaction between genetic, immunological, and environmental factors leading to loss of immunotolerance to hepatic antigens. It affects both children and adolescents, most commonly females, and its clinical manifestations are quite variable. JAIH is progressive in nature and if left untreated may lead to cirrhosis and terminal liver failure. Although JAIH was first described almost 50 years ago, there have been few significant advances in the clinical management of these patients, both in terms of available diagnostic tools and therapeutic options. Aminotransferase activity, class G immunoglobulins and autoantibodies are the biomarkers used to diagnose AIH and monitor treatment response alongside clinical and histological findings. Despite their utility and cost-effectiveness, these biomarkers are neither an accurate expression of AIH pathogenic mechanism nor a precise measure of treatment response. Current standard of care is mainly based on the administration of steroids and azathioprine. This combination of drugs has been proven effective in inducing remission of disease in the majority of patients dramatically improving their survival; however, it not only fails to restore tolerance to hepatic autoantigens, but it also does not halt disease progression in some patients, it is often needed life-long and finally, it has deleterious side-effects. The ideal therapy should be enough selective to contrast immune-mediated live damage while preserving or potentiating the ability to develop permanent tolerance vs. pathogenic autoantigens. By reviewing the state of the art literature, this article highlights novel diagnostic and therapeutic strategies for managing pediatric AIH with a special focus on new strategies of immunotherapy. These promising tools could improve the diagnostic algorithm, more accurately predict disease prognosis, and provide targeted, individualized treatment.

Autoimmune Hepatitis in Brazilian Children: IgE and Genetic Polymorphisms in Associated Genes

Pediatric autoimmune hepatitis (AIH) patients present hypergammaglobulinemia, periportal CD8(+) cytotoxic T cell infiltration, and cirrhosis. Autoantibody profile defines AIH types 1 and 2 in addition to strong association with HLA-DRB1. We previously detected increased IgE serum levels and sought to compare clinical and histological features according to IgE levels in AIH (n = 74, ages 1-14 years) patients. Additionally, we typed 117 patients and 227 controls for functional polymorphisms of IL4, IL13, IL5, and IL4RA genes involved in IgE switching and eosinophil maturation that might contribute to overall genetic susceptibility to AIH. Serum IgE levels were high in 55% of AIH-1, but only in 12% of AIH-2 (P = 0.003) patients. Liver IgE was present in 91.3% of AIH-1 patients. The A alleles at both IL13 rs20541 and IL4RA rs1805011 were associated with AIH-1 (P = 0.024, OR = 1.55 and P < 0.0001, OR = 2.15, resp.). Furthermore, individuals presenting homozygosis for the A allele at IL4RA rs1805011 and HLA-DRB1(∗)03 and/or (∗)13 allele had sixfold greater risk to develop the disease (OR = 14.00, P < 0.001). The novel association suggests an additional role for IgE-linked immune response genes in the pathogenesis of AIH.

Immunity, tolerance and autoimmunity in the liver: A comprehensive review

The hepatic immune system is constantly exposed to a massive load of harmless dietary and commensal antigens, to which it must remain tolerant. Immune tolerance in the liver is mediated by a number of specialized antigen-presenting cells, including dendritic cells, Kupffer cells, liver sinusoidal endothelial cells and hepatic stellate cells. These cells are capable of presenting antigens to T cells leading to T cell apoptosis, anergy, or differentiation into regulatory T cells. However, the hepatic immune system must also be able to respond to pathogens and tumours and therefore must be equipped with mechanisms to override immune tolerance. The liver is a site of accumulation of a number of innate lymphocyte populations, including natural killer cells, CD56(+) T cells, natural killer T cells, γδ T cells, and mucosal-associated invariant T cells. Innate lymphocytes recognize conserved metabolites derived from microorganisms and host cells and respond by killing target cells or promoting the differentiation and/or activation of other cells of the immune system. Innate lymphocytes can promote the maturation of antigen-presenting cells from their precursors and thereby contribute to the generation of immunogenic T cell responses. These cells may be responsible for overriding hepatic immune tolerance to autoantigens, resulting in the induction and maintenance of autoreactive T cells that mediate liver injury causing autoimmune liver disease. Some innate lymphocyte populations can also directly mediate liver injury by killing hepatocytes or bile duct cells in murine models of hepatitis, whilst other populations may protect against liver disease. It is likely that innate lymphocyte populations can promote or protect against autoimmune liver disease in humans and that these cells can be targeted therapeutically. Here I review the cellular mechanisms by which hepatic antigen-presenting cells and innate lymphocytes control the balance between immunity, tolerance and autoimmunity in the liver.

The role of innate cells is coupled to a Th1-polarized immune response in pediatric nonalcoholic steatohepatitis

BACKGROUND

Nonalcoholic steatohepatitis (NASH) is a chronic inflammatory liver disease influenced by risk factors for the metabolic syndrome. In adult patients, NASH is associated with an altered phenotype and functionality of peripheral immune cells, the recruitment of leukocytes and intrahepatic activation, and an exacerbated production of reactive oxygen species (ROS) and cytokines. It remains unclear if the previously described differences between pediatric and adult nonalcoholic fatty liver diseases also reflect differences in their pathogenesis.

AIMS

We aimed to investigate the phenotype and functionality of circulating immune cells and the potential contribution of liver infiltrating leukocytes to the immunological imbalance in pediatric NASH.

RESULTS

By a real-time PCR-based analysis of cytokines and immunohistochemical staining of liver biopsies, we demonstrated that the hepatic microenvironment is dominated by interferon-gamma (IFN-γ) but not interleukin-4 and is infiltrated by a higher number of CD8(+) cells in pediatric NASH. The number of infiltrating neutrophils positively correlated with ROS generation by peripheral polymorphonuclear cells. By a flow cytometric analysis of peripheral blood lymphocytes, a distinctive increase in CD8(+) CD45RO and CD8(+) CD45RA subpopulations and an increased production of IFN-γ by CD4(+) and CD8(+) cells were shown. The production of ROS following PMA stimulation was augmented in circulating neutrophils but not in monocytes.

CONCLUSION

In sum, the distinctive phenotype and functionality of infiltrating and circulating cells suggest that the role of innate cells is coupled to a Th1-polarized immune response in pediatric NASH.

Antitumor immunity produced by the liver Kupffer cells, NK cells, NKT cells, and CD8 CD122 T cells

Mouse and human livers contain innate immune leukocytes, NK cells, NKT cells, and macrophage-lineage Kupffer cells. Various bacterial components, including Toll-like receptor (TLR) ligands and an NKT cell ligand (α-galactocylceramide), activate liver Kupffer cells, which produce IL-1, IL-6, IL-12, and TNF. IL-12 activates hepatic NK cells and NKT cells to produce IFN-γ, which further activates hepatic T cells, in turn activating phagocytosis and cytokine production by Kupffer cells in a positive feedback loop. These immunological events are essentially evoked to protect the host from bacterial and viral infections; however, these events also contribute to antitumor and antimetastatic immunity in the liver by activated liver NK cells and NKT cells. Bystander CD8⁺CD122⁺ T cells, and tumor-specific memory CD8⁺T cells, are also induced in the liver by α-galactocylceramide. Furthermore, adoptive transfer experiments have revealed that activated liver lymphocytes may migrate to other organs to inhibit tumor growth, such as the lungs and kidneys. The immunological mechanism underlying the development of hepatocellular carcinoma in cirrhotic livers in hepatitis C patients and liver innate immunity as a double-edged sword (hepatocyte injury/regeneration, septic shock, autoimmune disease, etc.) are also discussed.

Autoimmune hepatitis, HLA and extended haplotypes

Autoimmune hepatitis (AIH) is a chronic inflammatory liver disease. Characteristic liver-infiltrating immune cells in portal and periportal areas, hypergammaglobulinemia and typical autoantibodies indicate an ongoing autoimmune reaction against liver self antigens, which lead to irreversible cellular damage and ultimately to severe hepatic failure. A significant part of adult, but not pediatric AIH patients, exhibit concurrent autoimmune diseases, further strengthening the immunological etiology of the disease. Genetic susceptibility to autoimmune hepatitis is strongly associated with HLA-DRB1 alleles. In Caucasian European and North American patients, AIH-1 is associated with the presence of DRB1*0301, DRB3*0101 and DRB1*0401 alleles, while AIH-2 is associated with DRB1*0301 or DRB1*07. In Brazil, the primary susceptibility allele for AIH-1 is DRB1*1301, but a secondary association with DRB1*0301 has also been identified. We looked for additional susceptibility factors in the extended MHC region. We genotyped 107 AIH-1 children and up to 326 healthy subjects for TNFA G-308A, TNFA G-238A, LTA A+252G, LTA A+80C, NFKBIL1 T-63A, BAT1 C-348T, BAT1 G-22C, MICA, and HLA-B polymorphisms. The TNFA-308 A allele was significantly increased in AIH-1 when compared with healthy controls, confirming data from other studies. Linkage disequilibrium analysis was carried out. The ancestral haplotype comprising TNFA-308A, TNFA-238G, LTA+252G, LTA+80C, NFKBIL1-63A, BAT1-348C, BAT1-22C, HLA-B*08, MICA*08 was more common in DRB1*03 positive patients than in controls (40% vs. 14%), showing a seven-fold increased risk for the disease [OR=7.8 (95%CI 2.04-29.9.2, p=0.0021). In contrast, the remaining patients carrying DRB1*03 exhibited varied haplotypes. Finally, a variety of class III haplotypes was also present in HLA-DRB1*13 patients, without a predominant pattern. The most common of the 98 haplotypes present in patients were completely absent in controls. The extended haplotype analysis in this sample of AIH-1 patients highlights not only the genetic diversity present in the Brazilian population, but is also in accordance with the previously documented microdiversity within the MHC region. The present knowledge of AIH suggests that the same or a very similar disease can be induced by yet unknown, but different, triggers followed by presentation on different HLA-DR molecules of the epitopes derived from the corresponding autoantigens, characterizing a much more complex disease than previously thought.

Identification and characterization of IgG4-associated autoimmune hepatitis

BACKGROUND

Autoimmune hepatitis (AIH) and autoimmune pancreatitis (AIP) share clinical and pathological features such as high serum levels of immunoglobulin (Ig) G and autoantibodies, and lymphoplasmacytic infiltration, suggesting the presence of common immunological abnormalities. However, little is known about the possible involvement of IgG4, a hallmark of AIP, in AIH.

AIMS

In this study, we examined whether the IgG4 response contributes to the histopathological and clinical findings in AIH.

METHODS

Liver sections from 26 patients with AIH, 10 patients with primary biliary cirrhosis (PBC), three patients with primary sclerosing cholangitis (PSC) and 20 chronic hepatitis patients with hepatitis C virus (HCV) infection were immunostained for IgG4. We investigated the relationship among the histopathology, the responses to steroid therapy and the IgG4 staining.

RESULTS

Nine of the 26 liver specimens from patients with AIH showed positive staining for IgG4 whereas none of the 10 samples from patients with PBC, the three samples from patients with PSC or the 20 samples from patients with HCV hepatitis were positive. Patients with IgG4-positive AIH also showed increased serum levels of IgG. The numbers of T cells, B cells and plasma cells were significantly increased in the livers of patients with IgG4-positive AIH as compared with those patients with IgG4-negative AIH. Patients with IgG4-positive AIH also showed a marked response to prednisolone therapy.

CONCLUSIONS

AIH may be classified into either an IgG4-associated type or an IgG4 non-associated type with the former showing a marked response to prednisolone treatment.

Autoimmune hepatitis in Brazil: an overview

Autoimmune hepatitis is an immune cell-mediated chronic liver disease of unknown cause that leads, when untreated, to cirrhosis and liver failure. Importantly, this disease affects not only adults but children as well. Genetic susceptibility is clearly important and the major susceptibility factor identified up to now is the HLA-DRB1 locus, but other genes may play a role as well. HLA-DRB1 alleles present in South American patients differ from those found in patients in other parts of the world. In addition, we have recently identified two chromosomal regions where additional susceptibility factors may be found in Brazilian patients, namely, the class III MHC region and the 5q31 region where the IL-4 and IL-13 genes are located. This review discusses the current knowledge of the pathogenesis of this autoimmune disease occurring in the setting of an immune-privileged organ, the liver, and compares the data on gene polymorphisms studied in Brazil and in other parts of the world.

Autoimmune liver disease

PURPOSE OF REVIEW

The aim of this article is to review studies that improve the diagnosis and treatment of autoimmune hepatitis and suggest new drug and molecular interventions.

RECENT FINDINGS

Elderly patients have an indolent but aggressive disease that responds well to corticosteroid therapy. Variant syndromes are artificial designations that reflect uncertainties regarding the diagnostic limits of classical disease. Antibodies to cyclic citrullinated proteins and complex assays for antibodies to actin and alpha-actinin may have prognostic value. Defects in the number and function of T regulatory cells may enhance cell-mediated cytotoxicity. HLA DRB113 may be a risk factor in some North American patients, and disease outcome may be influenced by the 'dose' of alleles encoding critical residues. Screening for thiopurine methyltransferase deficiency does not predict azathioprine intolerance. Treatment until normalization of the laboratory and histological features reduces the risk of relapse by 30-50%. Adverse outcomes in pregnancy are associated with antibodies to soluble liver antigen/liver pancreas and Ro/SSA.

SUMMARY

Novel serological tests may have prognostic value. Defects in the suppressor activity of regulatory T cells may promote liver injury. Genetic predispositions strongly influence disease occurrence and outcome. Laboratory and histological features should be normal prior to drug withdrawal. Azathioprine toxicities cannot be predicted.