Usefulness of liver infiltrating CD86-positive mononuclear cells for diagnosis of autoimmune hepatitis

Pathogenesis of Autoimmune Hepatitis-Cellular and Molecular Mechanisms

Pediatric autoimmune liver disorders include autoimmune hepatitis (AIH), autoimmune sclerosing cholangitis (ASC), and de novo AIH after liver transplantation. AIH is an idiopathic disease characterized by immune-mediated hepatocyte injury associated with the destruction of liver cells, causing inflammation, liver failure, and fibrosis, typically associated with autoantibodies. The etiology of AIH is not entirely unraveled, but evidence supports an intricate interaction among genetic variants, environmental factors, and epigenetic modifications. The pathogenesis of AIH comprises the interaction between specific genetic traits and molecular mimicry for disease development, impaired immunoregulatory mechanisms, including CD4+ T cell population and Treg cells, alongside other contributory roles played by CD8+ cytotoxicity and autoantibody production by B cells. These findings delineate an intricate pathway that includes gene to gene and gene to environment interactions with various drugs, viral infections, and the complex microbiome. Epigenetics emphasizes gene expression through hereditary and reversible modifications of the chromatin architecture without interfering with the DNA sequence. These alterations comprise DNA methylation, histone transformations, and non-coding small (miRNA) and long (lncRNA) RNA transcriptions. The current first-line therapy comprises prednisolone plus azathioprine to induce clinical and biochemical remission. Further understanding of the cellular and molecular mechanisms encountered in AIH may depict their impact on clinical aspects, detect biomarkers, and guide toward novel, effective, and better-targeted therapies with fewer side effects.

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.

Autoimmune Hepatitis and Autoimmune Hepatitis Overlap With Sclerosing Cholangitis: Immunophenotype Markers in Children and Adolescents

OBJECTIVE

The pathophysiology of autoimmune hepatitis (AIH) may involve the activation of immune cells and changes in the expression of cellular markers. The aim of the present study was to characterize the immunophenotype markers of lymphocytes and monocytes in the peripheral blood of children and adolescents with type 1 AIH and AIH overlap with sclerosing cholangitis (overlap syndrome [OS]).

METHODS

This is a cross-sectional study of 20 children and adolescents diagnosed with type 1 AIH and 19 with OS. Fifteen healthy subjects were included as controls. Flow cytometric analysis was used to identify markers of inflammation and autoimmunity.

RESULTS

The total number of CD4 T cells was higher in the AIH patients compared with the controls. The number of CD4 T cells expressing CCR3 and CD28 was higher in the AIH group than in the control group. CD45RO was more highly expressed in the AIH group, whereas CD45RA was more highly expressed in the OS group. In regard to CD8 T lymphocytes, the CCR3 expression was higher in both groups of patients. Patients with OS had the highest expression of CD45RA and CD25. In monocytes, human leukocyte antigen DR (HLA-DR) was less expressed in both groups of patients.

CONCLUSIONS

Complex phenotype features may be involved in the pathophysiology of AIH, accounting for changes in immune system regulation mechanisms. In conclusion, even after good response to treatment, patients still have immune activity signals at the cellular level.

Targeting novel antigens in the arterial wall in thromboangiitis obliterans

Thromboangiitis obliterans is an inflammatory disease possibly resulting from cigarette smoking as a primary etiologic factor, perhaps as a delayed type of hypersensitivity or toxic angiitis. As little is known about the pathogenesis of the disease, we aimed to determine novel antigens that might be responsible from the local inflammatory reactions and structural changes observed in this disease. An indirect immunoperoxidase technique is used to examine the tissue samples obtained from the dorsalis pedis artery of affected individuals with twenty monoclonal antibodies. Among these several antigens which are not previously reported in TAO like CD34, CD44 and CD90 were determined in the tissue samples examined. On the other hand, many other antigens like cytokine/chemokine receptors, several enzymes and leukocyte/lymphocyte antigens were lacking giving some clues about the local pathological reactions. We briefly discussed our findings for several critical antigens those first described in the present work, possibly having roles in the development of the disease. Expression of the CD90/CD11c receptor/ligand pair seems to play an important role in mononuclear cell recruitment to the damage site. Vascular invasion of not only tunica intima but also the tunica media in affected vessels is clearly demonstrated using endothelial cell specific antigens.

Autoimmune hepatitis. Part A: pathogenesis

Autoimmune hepatitis is a consequence of a triggering antigen and genetic factors that favor the presentation of autoantigens, polymorphisms that affect immunocyte activation and durability, cytokine alterations that promote proliferation of liver-infiltrating cytotoxic T cells, and perturbations in the number and function of immune-regulatory cell populations, including T regulatory cells and natural killer T cells. The triggering epitope is probably a short sequence peptide that is common in multiple infectious or toxic agents. Homologies between this epitope and self-antigens (molecular mimicry) may stimulate humoral and cellular responses that are cross-reactive. Sensitized immunocytes extend and perpetuate the inflammation through imprecise targeting of self-antigens that resemble foreign antigens (promiscuous behavior). The occurrence and clinical phenotype of the disease may relate to genetic susceptibility factors that favor protracted exposure to indigenous etiological agents, and these genetic factors can vary in different geographical regions and ethnic groups. The clinical phenotype within a population can be modified further by genetic polymorphisms that are not disease specific and that affect immunocyte activation, differentiation, proliferation and programmed death (apoptosis). Autoimmune hepatitis is a model of autoreactivity that reflects multiple disturbances in the counter-regulatory mechanisms essential for immune homeostasis.

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.

Analysis of CD28 and bcl-2 Expression on Peripheral Blood and Liver-Infiltrating Mononuclear Cells in Patients with Autoimmune Hepatitis

Because the underlying mechanism of hepatocellular damages in autoimmune hepatitis (AIH) still remains unclear, analysis of CD28 and bcl-2 molecules, which are critical for T cell activation and survival, was performed in patients with AIH. The number of CD28(+)CD4(+) peripheral blood mononuclear cells (PBMC) in corticosteroid (CS)-treated patients was comparable to normal control individuals but decreased in untreated AIH patients. In contrast, the number of CD28(+)CD8(+) PBMC was decreased in both CS-treated and untreated AIH patients. Analysis of liver-infiltrating mononuclear cells (LIMC) showed that the number of CD28(+)CD4(+) and CD28(-)CD8(+) LIMC were positively correlated with the histology activity index score. Bcl-2(+)CD4(+) LIMC were observed in the portal area of the liver and the numbers fluctuated with disease activity during the time course after CS administration. By contrast, CD8(+) LIMC were shown not to express bcl-2. Taken collectively, these results suggest that bcl-2(+)CD28(+)CD4(+) and bcl-2(-)CD28(-)CD8(+) cells may play critical and distinct roles in hepatocellular damage in AIH.