Identification of HLA-A2-restricted CD8(+) cytotoxic T cell responses in primary biliary cirrhosis: T cell activation is augmented by immune complexes cross-presented by dendritic cells

In liver fibrosis, dendritic cells govern hepatic inflammation in mice via TNF-alpha

Hepatic fibrosis occurs during most chronic liver diseases and is driven by inflammatory responses to injured tissue. Because DCs are central to modulating liver immunity, we postulated that altered DC function contributes to immunologic changes in hepatic fibrosis and affects the pathologic inflammatory milieu within the fibrotic liver. Using mouse models, we determined the contribution of DCs to altered hepatic immunity in fibrosis and investigated the role of DCs in modulating the inflammatory environment within the fibrotic liver. We found that DC depletion completely abrogated the elevated levels of many inflammatory mediators that are produced in the fibrotic liver. DCs represented approximately 25% of the fibrotic hepatic leukocytes and showed an elevated CD11b+CD8- fraction, a lower B220+ plasmacytoid fraction, and increased expression of MHC II and CD40. Moreover, after liver injury, DCs gained a marked capacity to induce hepatic stellate cells, NK cells, and T cells to mediate inflammation, proliferation, and production of potent immune responses. The proinflammatory and immunogenic effects of fibrotic DCs were contingent on their production of TNF-alpha. Therefore, modulating DC function may be an attractive approach to experimental therapeutics in fibro-inflammatory liver disease.

Beta-glucosylceramide ameliorates liver inflammation in murine autoimmune cholangitis

We have demonstrated spontaneous development of autoimmune cholangitis, similar to human primary biliary cirrhosis, in mice expressing a dominant negative form of the transforming growth factor-beta receptor (dnTGF-betaRII) restricted to T cells. The autoimmune cholangitis appears to be mediated by autoreactive CD8(+) T lymphocytes that home to the portal tracts and biliary system. Because the liver pathology is primarily secondary to CD8(+) T cells, we have determined herein whether administration of beta-glucosylceramide (GC), a naturally occurring plant glycosphingolipid, alters the natural history of disease in this model. We chose GC because previous work has demonstrated its ability to alter CD8(+) T cell responses and to down-regulate tissue inflammation. Accordingly, dnTGF-betaRII mice were treated with either GC or control for a period of 18 weeks beginning at 6 weeks of age. Importantly, in mice that received GC, there was a significant decrease in the frequency and absolute number of autoreactive liver-infiltrating CD8(+) T cells, accompanied by a significant decrease in activated CD44(high) CD8(+) T cell populations. Further, there was a significant reduction in portal inflammation in GC-treated mice. Interestingly, there were no changes in anti-mitochondrial antibodies, CD4(+) T cells, CD19(+) B cells or natural killer (NK) T cell populations, indicating further that the beneficial effects of GC on liver inflammation were targeted specifically to liver-infiltrating CD8(+) T cells. These data suggest that further work on GC in models of CD8(+) T-mediated inflammation are needed and point to a new therapeutic venue for potentially treating and/or modulating autoimmune disease.

The role of environmental factors in primary biliary cirrhosis

The etiology of primary biliary cirrhosis (PBC) is enigmatic, although it is clearly related to a combination of genetic predisposition and environmental stimulation. PBC is a chronic autoimmune cholestatic liver disease that occurs throughout the world with a reported latitudinal gradient in prevalence and incidence. PBC is also characterized by a 60% concordance in monozygotic twins and is considered a model autoimmune disease because of several features common to other conditions and the relatively homogeneous serological and biochemical features. Several risk factors have been suggested to be associated with PBC, including exposure to infectious agents and chemical xenobiotics. This review will attempt to place such factors in perspective.

Induction of tumor immunity following allogeneic stem cell transplantation

The curative potential of allogeneic hematopoietic stem cell transplantation (allo-HSCT) for many hematologic malignancies derives in large part from reconstitution of normal donor immunity and the development of a potent graft-versus-leukemia (GVL) immune response capable of rejecting tumor cell in vivo. Elucidation of the mechanisms of GVL by studies of animal models and analysis of clinical data has yielded important insights into how clinically effective tumor immunity is generated following allo-HSCT. These studies have identified NK cells and B cells as well as T cells as important mediators of the GVL response. A variety of antigenic targets of the GVL response have also been identified, and include tumor-associated antigens as well as minor histocompatibility antigens. The principles of effective GVL can now be applied to the development of novel therapies that enhance the therapeutic benefit of allogeneic HSCT while minimizing the toxicities associated with treatment. Moreover, many components of this approach that result in elimination of tumor cells following allogeneic HSCT can potentially be adapted to enhance the effectiveness of tumor immunity in the autologous setting.

SNP analysis of genes implicated in T cell proliferation in primary biliary cirrhosis

Previous studies on primary biliary cirrhosis (PBC) have focused on the role of T lymphocytes as potential effectors of tissue injury. We hypothesized that single nucleotide polymorphisms (SNPs) of genes involved in lymphocyte proliferation would be responsible for uncontrolled expansion of T cells and autoreactivity. To address this, we genotyped DNA from 154 patients with PBC and 166 ethnically matched healthy controls for SNPs of five candidate genes (60G/A CTLA-4, 1858 C/T LYP, -IVS9 C/T foxp3, p1323 C/G ICOS and -9606 T/C CD25) using a TaqMan assay.

We report herein a statistically significant decrease in homozygosity rate for the 60A⋆CTLA-4 allele in patients with PBC compared to controls (p = 0.0411). Moreover, we found a significant association of the same allele and of the LYP⋆T allele with anti-mitochondrial antibody (AMA) serum negativity (p = 0.0304 and 0.0094, respectively). No association between any of the other studied SNPs and PBC susceptibility, progression, or AMA status was observed. In conclusion, given the high prevalence of SNPs in CTLA-4 detected in numerous autoimmune diseases, we encourage a more detailed genetic analysis of this candidate gene. Further, although obtained from a limited number of AMA-negative subjects, our data suggest a potential genetic heterogeneity for this specific subgroup of patients with PBC.

Bacteria and primary biliary cirrhosis

Infectious agents have been postulated to play a pathogenic role in the loss of immunological tolerance and the induction of primary biliary cirrhosis, an immune-mediated cholestatic liver disease characterized by progressive destruction of the small intrahepatic bile ducts and subsequent cirrhosis and liver failure. This review discusses emerging issues implicating infectious agents such as Escherichia coli, mycobacteria, chlamydia, helicobacter species, lactobacilli, Novosphingobium aromaticivorans, and betaretroviruses in the pathogenesis of primary biliary cirrhosis. We also review the immunopathological mechanisms responsible for the induction of the disease with special emphasis on the role of molecular mimicry and microbial/self immunological cross-reactivity.

B cells suppress the inflammatory response in a mouse model of primary biliary cirrhosis

BACKGROUND & AIMS

Mice that express a dominant-negative form of transforming growth factor-beta receptor restricted to T cells (dnTGF-betaRII) develop antimitochondrial antibodies and liver inflammation similar to human primary biliary cirrhosis.

METHODS

To address the role of B cells in this model of primary biliary cirrhosis, we bred B cell-deficient mice (Igmu(-/-)) with dnTGF-betaRII mice, creating Igmu(-/-)dnTGF-betaRII mice, and compared the resulting disease phenotype with that of dnTGF-betaRII mice (controls). We also performed adoptive transfer of dnTGF-betaRII CD8(+) splenocytes, with or without B cells, to 8-week-old female Rag-1(-/-) mice to assess the role of B cells in the inflammatory response.

RESULTS

The B cell-deficient Igmu(-/-)dnTGF-betaRII mice unexpectedly developed a more severe form of cholangitis than controls (dnTGF-betaRII mice) and had a significantly greater frequency of activated CD4(+) and CD8(+) T cells in the liver. They also had reduced frequency of Foxp3(+) regulatory T cells in the hepatic CD4(+) T-cell population and natural killer (NK) T cells (NK1.1(+) CD3(+)) in hepatic inflammatory cell infiltrates. The Igmu(-/-)dnTGF-betaRII mice had increased levels of proinflammatory cytokines (tumor necrosis factor-alpha and interleukin-6) and developed a more severe form of colitis than controls. Adoptive transfer of CD8(+) splenocytes from dnTGF-betaRII mice and peritoneal cavity-derived, but not spleen-derived, CD19(+) B cells into Rag-1(-/-) mice resulted in decreased amounts of liver inflammation and bile duct damage, compared with Rag-1(-/-) mice in which only CD8(+) splenocytes were transferred.

CONCLUSION

B cells have a suppressive effect on the inflammatory response in the dnTGF-betaRII model of primary biliary cirrhosis.

The good, the bad and the ugly: how altered peptide ligands modulate immunity

BACKGROUND

The basis of T cell immune responses is the specific recognition of an immunogenic peptide epitope by a T cell receptor. Peptide alterations of such T cell epitopes with single or few amino acid variations can have drastic effects on the outcome of this recognition. These altered peptide ligands can act as modulators of immune responses as they are capable of downregulating or upregulating responses.

OBJECTIVE/METHODS

We review how altered peptide ligands can have 'good' 'bad' and 'ugly' outcomes in treating diseases.

RESULTS/CONCLUSION

Altered peptide ligands have been used as immunotherapeutics in autoimmune (and allergic) diseases, infectious diseases and cancer. In the next five years we anticipate seeing a number of altered peptide ligands in clinical trials, progressing from contradictory classifications of good, bad or ugly, to the exciting outcome of 'useful'.

Deficiency in regulatory T cells results in development of antimitochondrial antibodies and autoimmune cholangitis

There have been several descriptions of mouse models that manifest select immunological and clinical features of autoimmune cholangitis with similarities to primary biliary cirrhosis in humans. Some of these models require immunization with complete Freund's adjuvant, whereas others suggest that a decreased frequency of T regulatory cells (Tregs) facilitates spontaneous disease. We hypothesized that antimitochondrial antibodies (AMAs) and development of autoimmune cholangitis would be found in mice genetically deficient in components essential for the development and homeostasis of forkhead box 3 (Foxp3)(+) Tregs. Therefore, we examined Scurfy (Sf) mice, animals that have a mutation in the gene encoding the Foxp3 transcription factor that results in a complete abolition of Foxp3(+) Tregs. At 3 to 4 weeks of age, 100% of animals exhibit high-titer serum AMA of all isotypes. Furthermore, mice have moderate to severe lymphocytic infiltrates surrounding portal areas with evidence of biliary duct damage, and dramatic elevation of cytokines in serum and messenger RNAs encoding cytokines in liver tissue, including tumor necrosis factor alpha, interferon-gamma, interleukin (IL)-6, IL-12, and IL-23.

CONCLUSION

The lack of functional Foxp3 is a major predisposing feature for loss of tolerance that leads to autoimmune cholangitis. These findings reflect on the importance of regulatory T cells in other murine models as well as in patients with primary biliary cirrhosis.

Altered B-cell homeostasis and excess BAFF in human chronic graft-versus-host disease

Chronic graft-versus-host disease (cGVHD) causes significant morbidity and mortality in patients otherwise cured of malignancy after hematopoietic stem cell transplantation (HSCT). The presence of alloantibodies and high plasma B cell-activating factor (BAFF) levels in patients with cGVHD suggest that B cells play a role in disease pathogenesis. We performed detailed phenotypic and functional analyses of peripheral B cells in 82 patients after HSCT. Patients with cGVHD had significantly higher BAFF/B-cell ratios compared with patients without cGVHD or healthy donors. In cGVHD, increasing BAFF concentrations correlated with increased numbers of circulating pre-germinal center (GC) B cells and post-GC "plasmablast-like" cells, suggesting in vivo BAFF dependence of these 2 CD27(+) B-cell subsets. Circulating CD27(+) B cells in cGVHD comprised in vivo activated B cells capable of IgG production without requiring additional antigen stimulation. Serial studies revealed that patients who subsequently developed cGVHD had delayed reconstitution of naive B cells despite persistent BAFF elevation as well as proportional increase in CD27(+) B cells in the first year after HSCT. These studies delineate specific abnormalities of B-cell homeostasis in patients with cGVHD and suggest that BAFF targeting agents may be useful in this disease.

Differential mechanisms in the pathogenesis of autoimmune cholangitis versus inflammatory bowel disease in interleukin-2Ralpha(-/-) mice

Interleukin-2 (IL-2) receptor alpha knockout (IL-2Ralpha(-/-)) mice have a deficiency of CD25 and a corresponding functional defect in T regulatory cells (Tregs). These mice spontaneously develop portal inflammation with biliary ductular damage and colitis with features similar to human inflammatory bowel disease with T cell infiltrates in both the liver and colon. In humans, inflammatory bowel disease may be accompanied by primary sclerosing cholangitis (PSC), but seldom primary biliary cirrhosis (PBC). We hypothesized that the effector mechanism responsible for T cell infiltrates would differ for colon versus liver. To address this thesis, we developed three colonies of double-knockout mice including IL-2Ralpha(-/-) CD4(-/-), IL-2Ralpha(-/-) CD8(-/-), and IL-2Ralpha(-/-) T cell receptor (TCR)-beta(-/-). Tissue immunopathology, body weight, and serum levels of cytokines, immunoglobulins, and anti-mitochondrial antibodies (AMA) were assayed at 3 months of age. Relative to IL-2Ralpha(-/-) mice, IL-2Ralpha(-/-) CD4(-/-) mice had increased biliary ductular damage but reduced inflammation in the colon. In contrast, IL-2Ralpha(-/-) CD8(-/-) mice had increased colon inflammation but markedly attenuated biliary ductular damage. Both IL-2Ralpha(-/-) CD4(-/-) and IL-2Ralpha(-/-) CD8(-/-) mice demonstrated elevated serum levels of tumor necrosis factor alpha (TNF-alpha), interferon gamma (IFN-gamma), interleukin-12p40 (IL-12p40), and interleukin-2 (IL-2) compared with C57BL/6J controls, but only IL-2Ralpha(-/-) CD8(-/-) mice had increased serum levels of immunoglobulin A (IgA), AMA and interleukin-17 (IL-17). Finally, and of importance, IL-2Ralpha(-/-) TCR-beta(-/-) mice had abrogation of liver and colon pathological conditions and lacked AMA. In conclusion, on loss of Treg function in mice, CD8 T cells mediate biliary ductular damage whereas CD4 T cells mediate induction of colon-specific autoimmunity.

Mitochondrial depolarisation and oxidative stress in rheumatoid arthritis patients

OBJECTIVES

To investigate mitochondrial membrane integrity, lipid peroxidation and cytotoxicity in peripheral lymphocytes (PL) from rheumatoid arthritis (RA) patients.

DESIGN AND METHODS

South African black RA patients (HIV(-)) were recruited into the study. Mitochondrial membrane potential (Deltapsi(m)) was analysed in PL using the JC-1 dye distribution assay and flow cytometry. Correlations between Deltapsi(m) and clinical parameters were tested for statistical significance. Cytotoxicity (LDH) and lipid peroxidation (thiobarbituric acid reactive substances (TBARS)) was also determined.

RESULTS

Our findings show significantly elevated levels of cytotoxicity (p=0.0029) and lipid peroxidation (p=0.0030) in RA. A significantly higher percentage of circulating PL contained depolarised mitochondria (p=0.0003) which correlated with disease activity and C-reactive protein levels in patients. Collapse of Deltapsi(m) also negatively correlated to absolute lymphocyte counts (r=-0.4041; p=0.0197).

CONCLUSION

These findings suggest a possible role for mitochondrial membrane alterations in the pathology of RA.

Identification of annexin 1 as a novel autoantigen in acute exacerbation of idiopathic pulmonary fibrosis

Consistent with the hypothesis that pulmonary epithelial apoptosis is the key to the acute exacerbation of idiopathic pulmonary fibrosis (IPF), we conducted serological identification of Ags by recombinant expression cloning (SEREX) analysis using type II alveolar cell carcinoma (A549) cell lines to identify disease-related Abs. In a survey of Abs to the recombinant autoantigens identified by SEREX analysis, five Abs were identified as novel candidates for the acute exacerbation of IPF. Abs to annexin 1 were detected in 47 and 53% of the sera and bronchoalveolar lavage materials from patients with acute exacerbation of IPF. Some identical TCR Vbeta genes were identified in sequential materials obtained at 1-3 mo in all 10 acute exacerbation IPF cases, suggesting that some infiltrating CD4-positive T cells sharing limited epitopes expand by Ag-driven stimulation during disease extension. The CDR3 region of these identical TCR Vbeta genes showed high homology with the N-terminal portion of annexin 1, including in the HLA-DR ligand epitopes predicted by TEPITOPE analysis. By Western blotting analysis and observation of the CD4-positive T cell responses in bronchoalveolar lavage samples, the N-terminal portion of annexin 1 was cleaved and found to induce marked proliferative responses of CD4-positive T cells in three patients. Our study demonstrates that annexin 1 is an autoantigen that raises both Ab production and T cell response in patients with acute exacerbation of IPF, and that the N-terminal portion of annexin 1 plays some role in the pathogenesis of acute exacerbation in IPF patients.

Etiopathogenesis of primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is an autoimmune disease of the liver characterized by progressive bile duct destruction eventually leading to cirrhosis and liver failure. The serological hallmark of the disease is the presence of circulating antimitochondrial antibodies (AMA). These reflect the presence of autoreactive T and B cells to the culprit antigens, the E2 subunits of mitochondrial 2-oxo-acid dehydrogenase enzymes, chiefly pyruvate dehydrogenase (PDC-E2). The disease results from a combination of genetic and environmental risk factors. Genetic predisposition is indicated by the higher familial incidence of the disease particularly among siblings and the high concordance rate among monozygotic twins. Environmental triggering events appear crucial to disrupt a pre-existing unstable immune tolerance of genetic origin allowing, after a long latency, the emergence of clinical disease. Initiating mimotopes of the vulnerable epitope of the PDC-E2 autoantigen can be derived from microbes that utilize the PDC enzyme or, alternatively, environmental xenobiotics/chemical compounds that modify the structure of native proteins to make them immunogenic. A further alternative as a source of antigen is PDC-E2 derived from apoptotic cells. In the effector phase the biliary ductular cell, by reason of its proclivity to express the antigen PDC-E2 in the course of apoptosis, undergoes a multilineage immune attack comprised of CD4⁺ and CD8⁺ T cells and antibody. In this article, we critically review the available evidence on etiopathogenesis of PBC and present interpretations of complex data, new developments and theories, and nominate directions for future research.

Adoptive transfer of CD8(+) T cells from transforming growth factor beta receptor type II (dominant negative form) induces autoimmune cholangitis in mice

We recently reported that mice with a T cell-restricted expression of a dominant negative form of transforming growth factor beta receptor type II (dnTGFbetaRII) spontaneously develop autoimmune cholangitis that resembles human primary biliary cirrhosis (PBC), including antimitochondrial antibodies (AMAs) and extensive portal CD4(+) and CD8(+) lymphocytic infiltrates. On the basis of these data, we performed a series of experiments to determine whether the pathology was secondary to direct dnTGFbetaRII disruption of the liver and/or alternatively the appearance of autoreactive T cells. First, using dnTGFbetaRIIRag1(-/-) mice, we noted a normal hepatic and biliary structure. Hence, we performed a rigorous series of adoptive transfer studies, transferring Ly5.1(+) unfractionated spleen cell CD4(+) or CD8(+) T cells from dnTGFbetaRII mice into B6/Rag(-/-) (Ly 5.2) recipients. In unmanipulated dnTGFbetaRII mice, there was a marked increase in CD4(+) and CD8(+) T cell biliary infiltrates with AMA. Indeed, B6/Rag(-/-) recipients of dnTGFbetaRII unfractionated cells develop features of liver disease similar to PBC, suggesting that splenic loss of self-tolerance alone is sufficient to cause disease in this model and therefore that there is no specific abnormality in the biliary targets required for appearance of disease. More importantly, adoptive transfer of CD8(+) but not CD4(+) T cells into B6/Rag(-/-) mice led to liver histopathology remarkably similar to PBC, emphasizing a prominent role for CD8 T cell-mediated pathogenesis. In contrast, B6/Rag(-/-) recipients of CD4(+) T cells from dnTGFbetaRII mice predominantly developed inflammatory bowel disease associated with higher levels of serum interferon gamma and tumor necrosis factor alpha.

CONCLUSION

These data suggest that in this model of PBC, autoreactive CD8(+) cells destroy bile ducts.

Pathogenesis of primary biliary cirrhosis

Autoimmune phenomena have been recognized in primary biliary cirrhosis (PBC) for more than 50 years and the specificity of the characteristic responses directed at highly conserved mitochondrial antigens determined in detail over the past 20. Effecter autoreactive immune responses are characterized and potential mechanisms of breakdown of tolerance to self proposed. Elements of the clinical pattern of PBC, including the recurrence of the disease across HLA boundaries after liver transplantation, remain difficult to reconcile with a simple autoimmune model. Alternative (but not necessary mutually exclusive) pathogenetic models have been outlined, including a potential role for retroviral pathogens and directly cytopathic effects.

Intrahepatic status of regulatory T cells in autoimmune liver diseases and chronic viral hepatitis

AIM

Regulatory T cells (Tregs) maintain immunological tolerance and suppress autoreactive immune responses. We evaluated the intrahepatic status of Tregs in patients with autoimmune hepatitis (AIH), primary biliary cirrhosis (PBC), chronic hepatitis C (CH-C), or chronic hepatitis B (CH-B).

METHODS

We analyzed 85 patients (20 AIH, 22 PBC, 27 CH-C, and 16 CH-B) and 14 controls. Using liver tissue samples obtained by needle biopsy or from marginal parts of resected metastatic liver tumors in the controls, immunohistochemical analyses of forkhead box P3(+), which is a specific marker for Tregs, CD4(+), and CD8(+) cells were performed.

RESULTS

Intrahepatic Tregs were significantly more infiltrated in patients with liver diseases than in the controls. There were significantly fewer intrahepatic Tregs in the AIH patients than in the PBC patients (P = 0.037). Patients with alow frequency of intrahepatic Tregs were detected significantly more in the AIH and CH-B groups than in the PBC and CH-C groups (P < 0.05). In addition, the frequency of Tregs decreased in the liver of PBC patients as the pathological stage of the disease advanced. We found significantly less infiltration of CD4(+) T cells in AIH than in other diseases (P < 0.05). Liver-infiltrating CD8(+) T cells were detected more frequently in the CH-B group than in other groups (P < 0.003).

CONCLUSION

Intrahepatic Tregs were increased in both patients with autoimmune liver diseases and those with viral hepatitis. In autoimmune liver diseases, intrahepatic Tregs were fewer in the AIH patients than in the PBC patients.

The causes of primary biliary cirrhosis: Convenient and inconvenient truths

The most difficult issue in autoimmunity remains etiology. Although data exist on effector mechanisms in many autoimmune diseases, the underlying cause or causes are still generically ascribed to genetics and environmental influences. Primary biliary cirrhosis (PBC) is considered a model autoimmune disease because of its signature antimitochondrial autoantibody (AMA), the homogeneity of clinical characteristics, and the specificity of biliary epithelial cell (BEC) pathology. Twenty years ago, we reported the cloning and identification of the E2 component of pyruvate dehydrogenase (PDC-E2) as the immunodominant autoantigen of PBC, allowing for vigorous dissection of T and B lymphocyte responses against PDC-E2 and development of several valid experimental models. There has also been considerable study of the biology of BECs, which has included the unique properties of apoptosis in which there is exposure of PDC-E2 to the effector processes of the immune system. In this review, we present these data in the context of our proposal that the proximal cause of PBC is autoimmunity directed against well-identified mitochondrially located autoantigens in individuals with inherited deficits of immune tolerance. We present these data under the umbrella of convenient truths that support this thesis as well as some inconvenient truths that are not readily accommodated by current theory.

CONCLUSION

We emphasize that the potential initiator of PBC includes inter alia particular environmental xenobiotics; pathogenesis is aided and abetted by genetic weaknesses in mechanisms of immune regulation; and subsequent multilineage immunopathology impacts upon uniquely susceptible BECs to culminate clinically in the chronic autoimmune cholangiolitis of PBC.

Natural killer T cells exacerbate liver injury in a transforming growth factor beta receptor II dominant-negative mouse model of primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is an organ-specific autoimmune liver disease characterized by the presence of antimitochondrial antibodies and the destruction of small intrahepatic bile ducts with portal inflammation. In previous studies, we reported that both CD1d expression and the frequency of CD1d-restricted natural killer T (NKT) cells were increased in the livers of patients with PBC. To define a specific role of CD1d-restricted NKT cells in the pathogenesis of PBC, particularly early events, we investigated the function of hepatic CD1d-restricted NKT cells in our transforming growth factor beta (TGF-beta) receptor II dominant-negative (dnTGFbetaRII) mouse model of PBC. We generated CD1d(-/-) and CD1d(+/-) dnTGFbetaRII mice and performed a comparative study of liver immunopathology. We report herein that these dnTGFbetaRII mice demonstrate a massive increase of hyperactive CD1d-restricted NKT cells within the hepatic tissues. CD1d(-/-)dnTGFbetaRII mice, which lack CD1d-restricted CD1d-restricted NKT cells, exhibit significantly decreased hepatic lymphoid cell infiltrates and milder cholangitis compared with CD1d(+/-)dnTGFbetaRII mice. Interestingly, there was a significant increase in the production of interferon-gamma in hepatic CD1d-restricted NKT cells activated by alpha-galactosylceramide in young but not older dnTGFbetaRII mice, suggesting an age-dependent role of CD1d-restricted NKT cells.

CONCLUSION

These data demonstrate that CD1d-restricted NKT cells in dnTGFbetaRII mice are a critical factor in liver injury.

Primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is a chronic and slowly progressive cholestatic liver disease of autoimmune etiology characterized by injury of the intrahepatic bile ducts that may eventually lead to liver failure. Affected individuals are usually in their fifth to seventh decades of life at time of diagnosis, and 90% are women. Annual incidence is estimated between 0.7 and 49 cases per million-population and prevalence between 6.7 and 940 cases per million-population (depending on age and sex). The majority of patients are asymptomatic at diagnosis, however, some patients present with symptoms of fatigue and/or pruritus. Patients may even present with ascites, hepatic encephalopathy and/or esophageal variceal hemorrhage. PBC is associated with other autoimmune diseases such as Sjogren's syndrome, scleroderma, Raynaud's phenomenon and CREST syndrome and is regarded as an organ specific autoimmune disease. Genetic susceptibility as a predisposing factor for PBC has been suggested. Environmental factors may have potential causative role (infection, chemicals, smoking). Diagnosis is based on a combination of clinical features, abnormal liver biochemical pattern in a cholestatic picture persisting for more than six months and presence of detectable antimitochondrial antibodies (AMA) in serum. All AMA negative patients with cholestatic liver disease should be carefully evaluated with cholangiography and liver biopsy. Ursodeoxycholic acid (UDCA) is the only currently known medication that can slow the disease progression. Patients, particularly those who start UDCA treatment at early-stage disease and who respond in terms of improvement of the liver biochemistry, have a good prognosis. Liver transplantation is usually an option for patients with liver failure and the outcome is 70% survival at 7 years. Recently, animal models have been discovered that may provide a new insight into the pathogenesis of this disease and facilitate appreciation for novel treatment in PBC.

Peripheral tolerance and the qualitative characteristics of autoreactive T cell clones in primary biliary cirrhosis

Primary biliary cirrhosis is characterized by autoreactive T cells specific for the mitochondrial Ag PDC-E2(163-176). We studied the ability of eight T cell clones (TCC) specific for PDC-E2(163-176) to proliferate or become anergic in the presence of costimulation signals. TCC were stimulated with either human PDC-E2(163-176), an Escherichia coli 2-oxoglutarate dehydrogenase mimic (OGDC-E2(34-47)), or analogs with amino acid substitutions using HLA-matched allogeneic PBMC or mouse L-DR53 fibroblasts as APC. Based on their differential responses to these peptides (human PDC-E2(163-176), E. coli OGDC-E2(34-47)) in the different APC systems, TCC were classified as costimulation dependent or independent. Only costimulation-dependent TCC could become anergic. TCC with costimulation-dependent responses to OGDC-E2 become anergic to PDC-E2 when preincubated with mimic, even if costimulation is independent for PDC-E2(163-176). Anergic TCC produced IL-10. One selected TCC could not become anergic after preincubation with PDC-E2(163-176)-pulsed L-DR53 but became anergic using L-DR53 pulsed with PDC-E2 peptide analogs with a substitution at a critical TCR binding site. TCC that only respond to peptide-pulsed PBMC, but not L-DR53, proliferate with peptide-pulsed CD80/CD86-transfected L-DR53; however, anergy was not induced with peptide-pulsed L-DR53 transfected with only CD80 or CD86. These data highlight that costimulation plays a dominant role in maintaining peripheral tolerance to PBC-specific Ags. They further suggest that, under specific circumstances, molecular mimicry of an autoantigen may restore rather than break peripheral tolerance.

Induction of primary biliary cirrhosis in guinea pigs following chemical xenobiotic immunization

Although significant advances have been made in dissecting the effector mechanisms in autoimmunity, the major stumbling block remains defining the etiological events that precede disease. Primary biliary cirrhosis (PBC) illustrates this paradigm because of its high degree of heritability, its female predominance, and its extraordinarily specific and defined immune response and target destruction. In PBC, the major autoantigens belong to E2 components of the 2-oxo-acid dehydrogenase family of mitochondrially located enzymes that share a lipoylated peptide sequence that is the immunodominant target. Our previous work has demonstrated that synthetic mimics of the lipoate molecule such as 6-bromohexoanate demonstrate a high degree of reactivity with PBC sera prompted us to immunize groups of guinea pigs with 6-bromohexanoate conjugated to BSA. In this study, we provide serologic and immunohistochemical evidence that such immunized guinea pigs not only develop antimitochondrial autoantibody responses similar to human PBC, but also develop autoimmune cholangitis after 18 mo. Xenobiotic-immunized guinea pigs are the first induced model of PBC and suggest an etiology that has implications for the causation of other human autoimmune diseases. The data also reflect the likelihood that, in PBC, the multilineage antimitochondrial response is a pathogenic mechanism and that loss of tolerance and subsequent development of biliary lesions depends on either modification of the host mitochondrial Ag or a similar breakdown due to molecular mimicry.

Autoreactive CD8-specific T-cell response in primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is an autoimmune liver disease of unknown etiology. Autoimmune attack in PBC is predominantly organ-specific, despite the presence of mitochondrial autoantigens, the major targets of autoimmunity in PBC, in all nucleated cells. Cytotoxic T lymphocytes are thought to be directly involved in the tissue injury in PBC. The major histocompatibility complex (MHC) class I-restricted epitope for E2 components of pyruvate dehydrogenase complexes, namely amino acid 159-167, a region very close to the epitoperecognized by MHC class II-restricted CD4 cells and by antibody, has been characterized. In addition, there was a 10-fold increase in the frequency of autoreactive cytotoxic T lymphocytes in the liver as compared to the blood in PBC patients using tetramer technology.

Murine models of primary biliary cirrhosis: Comparisons and contrasts

The absence of suitable mouse models has represented a major drawback in our understanding of early events leading to the development of primary biliary cirrhosis (PBC). The recent report of not one, but three mouse models, each with distinctive features resembling PBC, represents a major advance in PBC research and generates novel experimental perspectives. The dnTGFbetaRII mouse, the IL-2Ralpha(-/-) mouse and the NOD.c3c4 mouse are all characterized by different genetic backgrounds and modifications, nonetheless all develop characteristic lymphocytic biliary infiltrates and specific antimitochondrial antibody response. Each model reflects characteristics of PBC in association with unique phenotypic differences. These three distinct models will allow a better understanding of the specific genetics involved in breaking of tolerance and progression of disease, in association with the possible definition of novel therapeutic approaches.

Oxidative stress-induced apoptosis of bile duct cells in primary biliary cirrhosis

There has been a relative paucity of effort at defining effector mechanisms of biliary damage in PBC. We hypothesize that biliary cells are destroyed secondary to the immunologic relationships of inflammation and biliary epithelial apoptosis and, in particular, that biliary damage is a result of reduced levels of glutathione-S-transferase (GST), the production of hypochlorous acid (HOCl) and its association with eosinophil peroxidase (EPO). To address this issue, we examined the expression of EPO and GST in PBC and control livers and demonstrated an increase of EPO within the portal areas of PBC. We also demonstrated that macrophages have evidence of phagocytosed EPO. Furthermore, we studied the influence of HOCl on apoptosis in cultured human biliary epithelial cells (BEC) as well as the associated activity of Bcl-2, Bax, p-JNK, JNK, p53, Fas and caspase-3. HOC1-induced apoptosis in BEC in a dose-dependent fashion increased the activity of caspase-3 and the expression of p53 and p-JNK. Pretreatment with l-buthionine-(S,R)-sulfoximine, a glutathione (GSH) inhibitor, potentiated the sensitivity of BEC to HOCl-induced apoptosis. We conclude that intracellular GSH reduction leads directly to BEC apoptosis. Modulation of these events will be critical to reduce immune-mediated destruction.

Regulation by Src Homology 2 Domain-Containing Protein Tyrosine Phosphatase Substrate-1 of α-Galactosylceramide-Induced Antimetastatic Activity and Th1 and Th2 Responses of NKT Cells

Interaction of alpha-galactosylceramide (alpha-GalCer) presented by CD1d on dendritic cells (DCs) with the invariant TCR of NKT cells activates NKT cells. We have now investigated the role of Src homology 2 domain-containing protein tyrosine phosphatase substrate-1 (SHPS-1), a transmembrane protein abundantly expressed on DCs, in regulation of NKT cells with the use of mice that express a mutant form of SHPS-1. The suppression by alpha-GalCer of experimental lung metastasis was markedly attenuated in SHPS-1 mutant mice compared with that apparent in wild-type (WT) mice. The antimetastatic effect induced by adoptive transfer of alpha-GalCer-pulsed DCs from SHPS-1 mutant mice was also reduced compared with that apparent with WT DCs. Both the production of IFN-gamma and IL-4 as well as cell proliferation in response to alpha-GalCer in vitro were greatly attenuated in splenocytes or hepatic mononuclear cells from SHPS-1 mutant mice compared with the responses of WT cells. Moreover, CD4+ mononuclear cells incubated with alpha-GalCer and CD11c+ DCs from SHPS-1 mutant mice produced markedly smaller amounts of IFN-gamma and IL-4 than did those incubated with alpha-GalCer and CD11c+ DCs from WT mice. SHPS-1 on DCs thus appears to be essential for alpha-GalCer-induced antimetastatic activity and Th1 and Th2 responses of NKT cells. Moreover, our recent findings suggest that SHPS-1 on DCs is also essential for the priming of CD4+ T cells by DCs.

Antibody-enhanced cross-presentation of self antigen breaks T cell tolerance

We have developed a model of autoimmunity to investigate autoantibody-mediated cross-presentation of self antigen. RIP-mOVA mice, expressing OVA in pancreatic beta cells, develop severe autoimmune diabetes when given OT-I cells (OVA-specific CD8(+) T cells) and anti-OVA IgG but not when given T cells alone. Anti-OVA IgG is not directly injurious to the islets but rather enhances cross-presentation of apoptotic islet antigen to the OT-I cells, leading to their differentiation into potent effector cells. Antibody-driven effector T cell activation is dependent on the presence of activating Fc receptors for IgG (FcgammaRs) and cross-priming DCs. As a consequence, diabetes incidence and severity was reduced in mice lacking activating FcgammaRs. An intact complement pathway was also required for disease development, as C3 deficiency was also partially protective. C3-deficient animals exhibited augmented T cell priming overall, indicating a proinflammatory role for complement activation after the T cell priming phase. Thus, we show that autoreactive antibody can potently enhance the activation of effector T cells in response to cross-presented self antigen, thereby contributing to T cell-mediated autoimmunity.

Primary biliary cirrhosis: what we know and what we want to know about human PBC and spontaneous PBC mouse models

Human autoimmune cholangiopathy comprises several intractable liver diseases that ultimately lead to hepatic failure. Primary biliary cirrhosis (PBC), allograft rejection, graft versus host diseases, and, possibly, primary sclerosing cholangitis are representative of immune-mediated cholangiopathies. Among them, PBC is the best-investigated human autoimmune cholangiopathy. The immunological approach to PBC has provided much critical information regarding its pathogenesis. The breakdown of self-tolerance in both B cells and T cells toward E2 components of the pyruvate dehydrogenase complex is evident. However, a number of questions regarding its etiology are unclear, in particular, the mechanisms involved in the selectivity of cholangiocyte destruction. In this brief review, we discuss what we know and we do not know regarding the pathogenesis of PBC.

AMA production in primary biliary cirrhosis is promoted by the TLR9 ligand CpG and suppressed by potassium channel blockers

We previously reported that peripheral blood mononuclear cells (PBMCs) from patients with primary biliary cirrhosis (PBC) produce significantly higher levels of polyclonal IgM than controls after exposure to CpG. Furthermore, the prevalence and unusually high levels of antimitochondrial antibodies (AMAs) in patients with PBC suggest a profound loss ofB cell tolerance. We have addressed the issue of whether CpG will promote the production ofAMAs and whether new experimental agents that inhibit the lymphocyte potassium channels Kv1.3 and KCa3.1 can suppress CpG-mediated B cell activation and AMA production. PBMCs were stimulated with and without CpG and were subsequently analyzed for phenotype, including expression of TLR9, CD86, and KCa3.1 concurrent with measurements of AMA and responses to a control antigen, tetanus toxoid, in supernatants. Additionally, K+ channel expression on B cells from PBC patients and controls was studied using whole-cell patch-clamp technology. In patients with PBC, CpG induces secretion of AMAs in PBMCs andalso up-regulates B cell expression of TLR9, CD86, and KCa3.1. Additionally, K+ channel blockers suppress secretion of AMA without a reduction of CpG-B-enhanced IgM production. Furthermore, there is diminished up-regulation of TLR9 and CD86 without affecting proliferation of B cells, B cell apoptosis, or viability.

CONCLUSION

These data suggest that the hyperresponsiveness of B cells in PBC accelerates B cell-mediated autoimmunity.

DEC-205 receptor on dendritic cells mediates presentation of HIV gag protein to CD8+ T cells in a spectrum of human MHC I haplotypes

Optimal HIV vaccines should elicit CD8+ T cells specific for HIV proteins presented on MHC class I products, because these T cells contribute to host resistance to viruses. We had previously found that the targeting of antigen to dendritic cells (DCs) in mice efficiently induces CD8+ T cell responses. To extend this finding to humans, we introduced the HIV p24 gag protein into a mAb that targets DEC-205/CD205, an endocytic receptor of DCs. We then assessed cross-presentation, which is the processing of nonreplicating internalized antigen onto MHC class I for recognition by CD8+ T cells. Low doses of alphaDEC-gag, but not control Ig-gag, stimulated proliferation and IFN-gamma production by CD8+ T cells isolated from the blood of HIV-infected donors. alphaCD205 fusion mAb was more effective for cross-presentation than alphaCD209/DC-SIGN, another abundant DC uptake receptor. Presentation was diverse, because we identified eight different gag peptides that were recognized via DEC-205 in 11 individuals studied consecutively. Our results, based on humans with highly polymorphic MHC products, reveal that DCs and DEC-205 can cross-present several different peptides from a single protein. Because of the consistency in eliciting CD8+ T cell responses, these data support the testing of alphaDEC-205 fusion mAb as a protein-based vaccine.

T cell targeting and phagocytosis of apoptotic biliary epithelial cells in primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is characterized by loss of tolerance against ubiquitously expressed mitochondrial autoantigens followed by biliary and salivary gland epithelial cell (BEC and SGEC) destruction by autoreactive T cells. It is unclear why BECs and SGECs are targeted. Previous work demonstrated that the reduced form of the major PBC autoantigen predominated in apoptotic BECs and SGECs as opposed to an oxidized form in other apoptotic cells. This led to the hypothesis that presentation of novel self-peptides from phagocytosed apoptotic BECs might contribute to BEC targeting by autoreactive T cells. The effect of autoantigen redox status on self-peptide formation was examined along with the phagocytic ability of BECs. Oxidation of PBC autoantigens first was shown to be due to protein S-glutathionylation of lipoyllysine residues. Absence of protein S-glutathionylation generated novel self-peptides and affected T cell recognition of a lipoyllysine containing peptide. Liver biopsy staining revealed BEC phagocytosis of apoptotic BECs (3.74+/-2.90% of BEC) was present in PBC (7 of 7 cases) but not in normal livers (0 of 3). BECs have the ability to present novel mitochondrial self-peptides derived from phagocytosed apoptotic BECs. Apoptotic cell phagocytosis by non-professional phagocytes may influence the tissue specificity of autoimmune diseases.

Novel conformation of histidyl–transfer RNA synthetase in the lung

OBJECTIVE

We previously proposed that novel expression and/or conformation of autoantigens in the target tissue may play a role in generating phenotype-specific immune responses. The strong association of autoantibodies to histidyl-transfer RNA synthetase (HisRS, Jo-1) with interstitial lung disease in patients with myositis led us to study HisRS expression and conformation in the lung.

METHODS

Normal human tissue specimens were probed with a novel anti-HisRS antibody recognizing its granzyme B-cleavable conformation by immunoblotting and immunohistochemistry. The HisRS granzyme B site was mapped using site-directed mutagenesis, and its relationship to the antibody recognition domain was evaluated in tandem immunoprecipitation/granzyme B cleavage studies.

RESULTS

The HisRS alpha-helical coiled-coil N-terminal domain recognized by autoantibodies is bounded by a granzyme B cleavage site. In immunoprecipitation studies with patient sera, HisRS was found to exist in 2 conformations, defined by sensitivity to cleavage by granzyme B and modification by autoantibody binding. Despite similar global expression of HisRS in different tissue, expression of its granzyme B-cleavable form was enriched in the lung and localized to the alveolar epithelium.

CONCLUSION

A proteolytically sensitive conformation of HisRS exists in the lung, the target tissue associated with this autoantibody response. We thus propose that autoimmunity to HisRS is initiated and propagated in the lung.

Naturally-occurring regulatory T cells are increased in inflamed portal tracts with cholangiopathy in primary biliary cirrhosis

BACKGROUND

Primary biliary cirrhosis (PBC) is an autoimmune liver disease targeting the intrahepatic small bile ducts showing chronic non-suppurative destructive cholangitis (CNSDC). Recent studies suggest that naturally-occurring CD4+CD25high regulatory T cells (Tregs) expressing Forkhead box P3 (Foxp3) play an active role in immunological self-tolerance.

AIMS

To investigate whether Foxp3+Tregs are involved in the pathogenesis of PBC.

METHODS

Foxp3+Tregs was detected immunohistochemically in livers from patients with PBC (n = 27), chronic viral hepatitis (CVH) (n = 15), and normal subjects (n = 10). The distribution of Tregs in portal tracts was semi-quantitatively evaluated in each groups. Levels of Foxp3, IL-10, TGFbeta, IFNgamma and TNFalpha mRNA was evaluated in PBC (n = 15) and control livers (n = 21) using semi-quantitative reverse transcriptase-PCR.

RESULTS

In PBC and CVH livers, the amounts of infiltrating Foxp3+Tregs in portal tracts were in parallel with the degree of portal inflammation irrespective of disease. The infiltration of Foxp3+Tregs into portal tracts with CNSDC in PBC was foremost in comparison with inflamed portal tracts in CVH or those without CNSDC in PBC (p<0.05). Focally, Tregs infiltrated into the biliary epithelial layer at the site of CNSDC. The level of Foxp3, IL-10 and TGFbeta mRNA expression was high in PBC compared with normal livers (p<0.05). IFNgamma and TNFalpha mRNA was high in early PBC and CVH livers.

CONCLUSION

Results of this evaluation of Foxp3+Tregs do not suggest that the reduced regulatory function accounts for the development of CNSDC in PBC.

Novel model of antigen-specific induction of bile duct injury

BACKGROUND & AIMS

Biliary-directed inflammation is an important cause of acute and chronic liver disease. We developed and characterized a transgenic mouse model of immune-mediated hepatobiliary injury.

METHODS

Ovalbumin (OVA)-BIL mice were developed using 3.0 kilobase of the rat apical sodium-dependent bile acid transporter promoter to drive aberrant expression of a membrane form of ovalbumin (OVA) on biliary epithelium. Liver inflammation resulted from adoptive transfer of OVA-specific T cells. Liver immune cells were characterized to determine the mechanism of the response by assessing activation, proliferation, and intracellular cytokine expression.

RESULTS

OVA-BIL transgenic mice were tolerant to OVA, without evidence of liver disease. Adoptive transfer of OVA-specific CD4+ and CD8+ T cells into naïve OVA-BIL mice led to biliary-centered necroinflammatory damage in a dose-dependent manner. This inflammation absolutely required CD8+ T cells and was augmented by CD4+ T cells. Adoptively transferred OVA CD8+ cells homed to and proliferated in the liver but not the spleen. These activated, adoptively transferred cytotoxic T lymphocytes produced elevated levels of tumor necrosis factor alpha and interferon gamma.

CONCLUSIONS

T-cell recognition of antigen aberrantly expressed on bile duct epithelium induced an acute necroinflammatory response specific to the liver, with activation, proliferation, and cytokine production predominantly by the OVA-specific cytotoxic T cells. Thus, OVA BIL represents an antigen-specific animal model of inflammatory bile duct injury.

In vivo expansion of two distinct dendritic cells in mouse livers and its impact on liver immune regulation

Liver transplant tolerance in pigs, rats, and mice has been disclosed for decades, but the underlying mechanisms are not completely understood. Accumulating data indicate that residing dendritic cells (DC) are important in determining direction of immune responses in the liver. However, our knowledge remains very limited due to the difficulties in obtaining sufficient liver DC. Most of the previous studies were dependent on DC propagated in vitro with growth factors and cytokines. In this study, we adopted an approach to transfect genes into the mouse liver by tail vein injection of plasmid DNA. Transfection with plasmid granulocyte-macrophage colony-stimulating factor markedly expanded liver CD11c(+) DC mainly located in portal regions, while liver B220(+) DC were dramatically generated after injection with plasmid interleukin (IL)-3/CD40L largely present in the lobules. Although both were phenotypically mature and strong T-cell stimulators, CD11c(+)DC induced potent T-cell response while B220(+)DC induced T-cell hyporesponsiveness. Administration of CD11c(+)DC accelerated cardiac allograft rejection, while B220(+)DC significantly prolonged graft survival. This hyporesponsiveness is not due to inhibition of DC/T-cell interaction, but rather through an active process of stimulating T-cell apoptosis. Compared to B220(+) DC that expressed messenger RNA of (TLR) 1, 2, 6, 7, and 9, CD11c(+)DC expressed all TLR 1 to 9. TLR 9 ligation stimulated very high IL-12 in CD11c(+) DC, but high IL-10 and no IL-12 in B220(+) DC. In conclusion, through these mechanisms, liver DC may be actively involved in immune regulation in the liver.

Identification of Novel HLA-A*0201-restricted epitopes in recent-onset type 1 diabetic subjects and antibody-positive relatives

Cytotoxic T-lymphocytes (CTLs) are considered to be essential for beta-cell destruction in type 1 diabetes. However, few islet-associated peptides have been demonstrated to activate autoreactive CTLs from type 1 diabetic subjects. In an effort to identify novel epitopes, we used matrix-assisted algorithms to predict peptides of glial fibrillary acidic protein (GFAP), prepro-islet amyloid polypeptide (ppIAPP), and islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP) that likely bind to HLA-A*0201 with a strong affinity and contain a COOH-terminal proteasomal cleavage site. Seven peptides stabilized HLA-A*0201 expression in binding assays and were used to stimulate peripheral blood mononuclear cells and were evaluated for granzyme B secretion. We found that 5 of 13 type 1 diabetic subjects and 4 of 6 antibody-positive relatives exhibited greater numbers of granzyme B-secreting cells in response to at least one putative epitope compared with healthy control subjects. The most prevalent responses in antibody-positive and type 1 diabetic subjects were to ppIAPP(9-17). Other peptides recognized by type 1 diabetic or antibody-positive subjects included GFAP(143-151), IGRP(152-160), and GFAP(214-222). These data implicate peptides of ppIAPP, GFAP, and IGRP as CTL epitopes for a heterogenous CD8(+) T-cell response in type 1 subjects and antibody-positive relatives.

Differential epitope mapping of antibodies to PDC-E2 in patients with hematologic malignancies after allogeneic hematopoietic stem cell transplantation and primary biliary cirrhosis

A unique characteristic of the autoimmune liver disease primary biliary cirrhosis (PBC) is the presence of high-titer and extremely specific autoantibodies to the E2 component of the pyruvate dehydrogenase complex (PDC-E2). Autoantibodies to PDC-E2 antigen have only been detected in patients with disease or in those who subsequently develop PBC. One exception has been a subgroup of patients with multiple myeloma (MM) who underwent allogeneic hematopoietic stem cell transplantation (HSCT) and received donor lymphocyte infusions (DLIs) after transplantation. These patients developed high-titer antibodies to a variety of myeloma-associated antigens, including PDC-E2, coincident with rejection of myeloma cells in vivo. To examine the specificity of autoantibodies to PDC in these patients, we screened sera from patients with MM, chronic leukemias, monoclonal gammopathy of unknown significance (MGUS), PBC, and healthy donors. Three of 11 patients with MM (27%) and 2 of 6 patients with chronic leukemias (33%) developed anti-PDC-E2 antibodies in association with DLI response; 2 of 12 (17%) patients in the MGUS pretreatment control population also had detectable anti-PDC responses. Interestingly, the epitope specificity of these PDC-E2 autoantibodies was distinctive, suggesting that the mechanisms leading to loss of tolerance in the transplantation patients are distinct from PBC.

[Seropositivity for Chlamydia pneumoniae in patients with primary biliary cirrhosis]

INTRODUCTION

Primary biliary cirrhosis (PBC) is a chronic cholestatic liver disease characterized by inflammatory injury and bile duct destruction. Recent studies suggest that Chlamydia pneumoniae could be associated with the development of PBC. The aim of this study was to determine the seroprevalence of C. pneumoniae in a cohort of patients with PBC.

PATIENTS AND METHODS

The presence of IgG antibodies against C. pneumoniae was investigated in 46 patients with PBC and in 105 subjects without cirrhosis.

RESULTS

Twenty-one patients (46%) with PBC had antibodies against C. pneumoniae compared with 74 subjects (71%) in the control group (OR = 0.6; 95% CI, 0.3-1.2; p = NS). Subanalysis of the PBC group showed that patients with C. pneumoniae antibodies had a higher frequency of advanced Child-Pugh stages (24% A, 52% B and 24% C vs 64% A, 32% B and 4% C; p = 0.01), a higher score on the Mayo Clinic Prognostic Index (7.8 +/- 2.1 vs 5.6 +/- 1.2; p = 0.004), a higher frequency of ascites (29% vs 4%; OR = 9.6; 95% CI, 1-87; p = 0.02), higher total bilirubin levels (4.5 +/- 2.5 mg/dl vs 2.4 +/- 4.3 mg/dl, p = 0.001) and lower serum albumin levels (2.6 +/- 0.9 g/dl vs 3.3 +/- 0.6 g/dl, p = 0.02).

CONCLUSION

No association was found between C. pneumoniae infection and PBC in this study. An association was found between the severity of PBC and C. pneumoniae, which may suggest a deleterious effect of C. pneumoniae infection or a predisposition in advanced stages of PBC to acquire infection with this microorganism.

New insights to the immunopathology and autoimmune responses in primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is an autoimmune liver disease with profound changes in different compartments of the immune system, including those involved in innate, and adaptive immunity. New data from epidemiological studies of PBC have reinforced the thesis that the cause for this relatively uncommon disease is likely to be a combination of both environmental factors and a susceptible genetic predisposition. Recent findings of abnormalities of the innate immune system in PBC suggest that they may serve as links between the environmental factors and the early events in PBC development. Viral and bacterial infections as well as xenobiotics are some of the potential environmental factors that have been implicated in this complex process. Identification of the etiological factors for PBC will point to new preventive or therapeutic treatments.

Primary biliary cirrhosis: solving the enigma

Primary biliary cirrhosis (PBC) is a chronic cholestatic liver disease, most commonly affecting female patients between 40 and 60 years of age. Patient sera present autoantibodies against mitochondrial antigens (AMA) and elevated serum IgM. Histologic studies demonstrate progressive destruction of small- and medium-sized intrahepatic bile ducts and, ultimately, liver cirrhosis. The precise mechanisms leading to selective destruction of such biliary epithelial cells are still unknown, although a number of immunomediated pathways have been proposed. Genetic background is critical in determining susceptibility to the disease, although no clear association with haplotypes of the major histocompatibility complex has been identified. Molecular mimicry by either infectious agents or xenobiotics has been proposed as a means of breaking tolerance in genetically predisposed individuals, thus leading to the onset of PBC. In this review, available data and current theories regarding the immunomediated pathogenesis of PBC will be described.

Increased killing activity and decreased cytokine production in NK cells in patients with primary biliary cirrhosis

Although the pathogenesis of primary biliary cirrhosis (PBC) remains enigmatic, the immune system plays a key role in the initiation and subsequent development of pathology. Previous studies have indicated a critical role of the innate immune system. Importantly, natural killer (NK) cells are abundant in liver where they serve as sentinels of the immune system. In addition, NK cells have significant biologic activity based on their production of immunoregulatory cytokines. To address this issue, we have investigated several qualitative and quantitative activities of NK cells in patients with PBC as well as normal and liver diseased controls. We report herein a marked increase in the frequency and absolute number of blood and liver NK cells in PBC patients. Moreover, the cytotoxic activity and perforin expression by isolated NK cells were significantly increased in PBC patients associated with increased levels of plasma IL-8 and the expression of CD128a (IL-8 receptor) on NK cells. In contrast, the levels of IFN-gamma, IL-6 and IL-8 synthesized by NK cells were significantly decreased in PBC patients as compared to controls. In conclusion, data from this study provide compelling evidence supporting a biologic role of NK cells in the immunopathogenesis of PBC.

NOD.c3c4 congenic mice develop autoimmune biliary disease that serologically and pathogenetically models human primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is an autoimmune disease with a strong genetic component characterized by biliary ductular inflammation with eventual liver cirrhosis. The serologic hallmark of PBC is antimitochondrial antibodies that react with the pyruvate dehydrogenase complex, targeting the inner lipoyl domain of the E2 subunit (anti–PDC-E2). Herein we demonstrate that NOD.c3c4 mice congenically derived from the nonobese diabetic strain develop an autoimmune biliary disease (ABD) that models human PBC. NOD.c3c4 (at 9–10 wk, before significant biliary pathology) develop antibodies to PDC-E2 that are specific for the inner lipoyl domain. Affected areas of biliary epithelium are infiltrated with CD3⁺, CD4⁺, and CD8⁺ T cells, and treatment of NOD.c3c4 mice with monoclonal antibody to CD3 protects from ABD. Furthermore, NOD.c3c4-scid mice develop disease after adoptive transfer of splenocytes or CD4⁺ T cells, demonstrating a central role for T cells in pathogenesis. Histological analysis reveals destructive cholangitis, granuloma formation, and eosinophilic infiltration as seen in PBC, although, unlike PBC, the extrahepatic biliary ducts are also affected. Using a congenic mapping approach, we define the first ABD (Abd) locus, Abd1. These results identify the NOD.c3c4 mouse as the first spontaneous mouse model of PBC.

Pathogenesis of primary biliary cirrhosis: A unifying model

Primary biliary cirrhosis (PBC) is a disease of unknown etiology leading to progressive destruction of small intrahepatic bile ducts and eventually to liver cirrhosis and failure. It is characterised by female predominance and serum auto-antibodies to mitochondrial antigens targeting the E2 components of the 2-oxoacid dehydrogenase complex. Although they are associated with disease pathogenesis, no concrete evidence has been presented so far. Epidemiological data indicate that a geographical clustering of cases and possible environmental factors are implicated in pathogenesis. A number of genetic factors play a role in determining disease susceptibility or progression, although no definitive conclusion has been reached so far. A key factor to immune pathogenesis is considered to be the breakdown of immune tolerance, either through molecular mimicry or through the so called determinant density model. In this review, the available data regarding the pathogenesis of primary biliary cirrhosis are described and discussed. A new unifying hypothesis based on early endothelin overproduction in primary biliary cirrhosis (PBC) is presented and discussed.

Mitochondrial antigens as targets of cellular and humoral auto-immunity in primary biliary cirrhosis

Several factors point toward an auto-immune pathogenesis for primary biliary cirrhosis(PBC), mostly based on the presence of serum auto-antibodies to mitochondrial antigens(AMAs) and autoreactive T cells (both helper and cytotoxic). Interestingly, epitopes recognized by AMA and T-cell clones are located within overlapping areas of the antigens. Moreover,a role for an imbalance in cytokine pattern and for natural-killer lymphocytes has also been proposed. Despite several experimental reports, no clear evidence is available regarding the interaction of these factors leading to bile duct destruction. This article reviews the current reports regarding the auto-immune reaction against mitochondrial auto-antigens in PBC.

The enigma of primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is a chronic cholestatic disease characterized by a striking predominance in female patients (with most cases diagnosed between ages 40 and 60 yr) as well as serum auto-antibodies to mitochondrial antigens, elevated serum immunoglobulin M,progressive destruction of intrahepatic bile ducts, and, ultimately, liver cirrhosis and failure(1). The precise mechanisms leading to selective destruction of biliary epithelial cells lining intrahepatic bile ducts are still unknown, although numerous immunomediated pathways have been proposed. Genetic background appears to be important in determining susceptibility to the disease (2), but no clear association with alleles in the major histocompatibility complex has been identified. Molecular mimicry either by infections (3) or xenobiotics (4) has been proposed to be capable of breaking tolerance in genetically predisposed individuals, thus leading to onset of PBC. This article describes and discusses the available data regarding the immunomediated pathogenesis of PBC (with particular attention to auto-antibodies and autoreactive T-cells) and presents the recent evidence indicating a role for either xenobiotic chemicals or novel infectious agents in the induction of the disease.

Liver-targeted and peripheral blood alterations of regulatory T cells in primary biliary cirrhosis

CD4+CD25high regulatory T cells (Tregs) play a critical role in self-tolerance, as seen in murine autoimmunity. Studies on Tregs in human autoimmunity have focused primarily on peripheral blood samples. A study targeting diseased tissue should identify direct relationships between Tregs and autoimmunity. Peripheral blood samples were collected from 91 patients with primary biliary cirrhosis (PBC), 28 immediate relatives, and 41 healthy controls, and Treg frequencies were determined as a percentage of CD4+CD25high T cells in CD4+TCR-alphabeta+ T cells. A tissue-targeted determination of frequency and distribution of FoxP3+ Tregs was also performed on 90 different liver tissue specimens exhibiting PBC (n = 52), chronic hepatitis C (CHC) (n = 30), and autoimmune hepatitis (AIH) (n = 8). Treg suppression studies were performed on 50 PBC patients and 27 controls. Patients with PBC demonstrated a relative reduction of Tregs compared with controls (P < .0002). Interestingly, a deficiency in CD4+CD25+ Tregs was also found in the daughters and sisters of PBC patients compared with controls (P < .0007). However, functional studies did not reveal a global PBC Treg defect. The level of FoxP3-expressing Tregs was markedly lower in affected PBC portal tracts compared with CHC and AIH (P < .001). In addition, the CD8+T cell/FoxP3+ Treg ratio was significantly higher in livers of late-stage PBC compared with those of CHC (P < .001) and early-stage AIH (P < .001). In conclusion, these data provide support for a genetic modulation of Treg frequency and illustrate the role Tregs play in the loss of tolerance in PBC.

Hyperhomocysteinemia and hypercoagulability in primary biliary cirrhosis

AIM: To assess the hypercoagulability in PBC and its relationship with homocysteine (HCY) and various components of the haemostatic system.

METHODS: We investigated 51 PBC patients (43F/8M; mean age: 63 ± 13.9 yr ) and 102 healthy subjects (86 women/16 men; 63 ± 13 yr), and evaluated the haemostatic process in whole blood by the Sonoclot analysis and the platelet function by PFA-100 device. We then measured HCY (fasting and after methionine loading), tissue factor (TF), thrombin-antithrombin complexes (TAT), D-dimer (D-D), thrombomodulin (TM), folic acid, vitamin B6 and B12 plasma levels. C677T 5,10-methylenetetrahydrofolate reductase (MTHFR) polymorphism was analyzed.

RESULTS: Sonoclot RATE values of patients were significantly (P < 0.001) higher than those of controls. Sonoclot time to peak values and PFA-100 closure times were comparable in patients and controls. TAT, TF and HCY levels, both in the fasting and post-methionine loading, were significantly (P < 0.001) higher in patients than in controls. Vitamin deficiencies were detected in 45/51 patients (88.2%). The prevalence of the homozygous TT677 MTHFR genotype was significantly higher in patients (31.4%) than in controls (17.5%) (P < 0.05). Sonoclot RATE values correlated significantly with HCY levels and TF.

CONCLUSION: In PBC, hyper-HCY is related to hypovitaminosis and genetic predisposing factors. Increased TF and HCY levels and signs of endothelial activation are associated with hypercoagulability and may have an important role in blood clotting activation.