Serum inflammatory cytokines, complement components, and soluble interleukin 2 receptor in primary biliary cirrhosis

Soluble chemokine receptor CXCR4 is present in human sera

A soluble form of the chemokine receptor CXCR4 was detected in human sera by isoelectric focusing and Western blotting. Sera of patients and normal subjects were analyzed using a panel of specific antibodies. Compared with controls, high levels of serum CXCR4 were found in patients with inflammatory bowel diseases. Serum CXCR4 levels in the majority of HIV patients were similar to those in healthy controls. A sensitive polyclonal antibody was developed in rabbit immunized with a maltose binding protein (MBP) construct expressing the full-length CXCR4. Using anti-MBPCXCR4 antibody, the level of CXCR4 in sera of a majority of patients with fibrosis was very low. The potential of serum CXCR4 as a new diagnostic biomarker warrants further investigation.

Immune-mediated bile duct injury: The case of primary biliary cirrhosis

Autoimmune cholangitis would be the appropriate name to define the immune-mediated bile duct injury following the breakdown of tolerance to mitochondrial proteins and the appearance of serum autoantibodies and autoreactive T cells. Nevertheless, the condition is universally named primary biliary cirrhosis (PBC). The disease etiology and pathogenesis remain largely unknown despite the proposed lines of evidence. One twin study and numerous epidemiology reports suggest that both a susceptible genetic background and environmental factors determine disease onset while a recent genome-wide association study proposed highly significant associations with several common genetic polymorphisms in subgroups of patients. Specific infectious agents and chemicals may contribute to the disease onset and perpetuation in a genetically susceptible host, possibly through molecular mimicry. Importantly, several murine models have been proposed and include strains in which PBC is genetically determined or induced by immunization with chemicals and bacteria. From a pathogenetic standpoint, new exciting data have demonstrated the unique apoptotic features of bile duct cells that allow the mitochondrial autoantigens to be taken up in their intact form within apoptotic blebs. We are convinced that the application of the most recent molecular techniques will soon provide developments in PBC etiology and pathogenesis with likely implications in diagnostics and therapeutics.

The spectrum of autoantibodies in IPEX syndrome is broad and includes anti-mitochondrial autoantibodies

IPEX syndrome is a congenital disorder of immune regulation caused by mutations in the FOXP3 gene, which is required for the suppressive function of naturally arising CD4 + CD25 + regulatory T cells. In this case series we evaluated serum samples from 12 patients with IPEX syndrome for the presence of common autoantibodies associated with a broad range of autoimmune disorders. We note that 75% of patients (9/12) had 1 or more autoantibodies, an incidence far above the cumulative rate observed in the general population. The range of autoantibodies differed between patients and there was no predominant autoantibody or pattern of autoantibodies present in this cohort. Surprisingly, one patient had high-titer anti-mitochondrial antibodies (AMA) typically associated with primary biliary cirrhosis (PBC) although the patient had no signs of cholestasis. PBC is a well-characterized autoimmune disease that occurs primarily in women and includes the serological hallmarks of serum AMA and elevated IgM which were both present in this patient. PBC is virtually absent in children with the exception of one reported child with interleukin 2 receptor α (CD25) deficiency which is associated with an IPEX-like regulatory T cell dysfunction. Based on the present data and the available literature we suggest a direct role for CD4 + CD25 + regulatory T cells in restraining B cell autoantibody production and that defects in regulatory T cells may be crucial to the development of PBC.

Deletion of interleukin-6 in mice with the dominant negative form of transforming growth factor beta receptor II improves colitis but exacerbates autoimmune cholangitis

The role of interleukin-6 (IL-6) in autoimmunity attracts attention because of the clinical usage of monoclonal antibodies to IL-6 receptor (IL-6R), designed to block IL-6 pathways. In autoimmune liver disease, activation of the hepatocyte IL-6/STAT3 (signal transducer and activator of transcription 3) pathway is associated with modulating pathology in acute liver failure, in liver regeneration, and in the murine model of concanavalin A-induced liver inflammation. We have reported that mice expressing a dominant negative form of transforming growth factor beta receptor II (dnTGFbetaRII) under control of the CD4 promoter develop both colitis and autoimmune cholangitis with elevated serum levels of IL-6. Based on this observation, we generated IL-6-deficient mice on a dnTGF-betaRII background (dnTGFbetaRII IL-6(-/-)) and examined for the presence of antimitochondrial antibodies, levels of cytokines, histopathology, and immunohistochemistry of liver and colon tissues. As expected, based on reports of the use of anti-IL-6R in inflammatory bowel disease, dnTGFbetaRII IL-6(-/-) mice manifest a dramatic improvement in their inflammatory bowel disease, including reduced diarrhea and significant reduction in intestinal lymphocytic infiltrates. Importantly, however, autoimmune cholangitis in dnTGFbetaRII IL-6(-/-) mice was significantly exacerbated, including elevated inflammatory cytokines, increased numbers of activated T cells, and worsening hepatic pathology.

CONCLUSION

The data from these observations emphasize that there are distinct mechanisms involved in inducing pathology in inflammatory bowel disease compared to autoimmune cholangitis. These data also suggest that patients with inflammatory bowel disease may not be the best candidates for treatment with anti-IL-6R if they have accompanying autoimmune liver disease and emphasize caution for therapeutic use of anti-IL-6R antibody.

Update on primary biliary cirrhosis

Primary biliary cirrhosis is an autoimmune chronic liver disease characterized by progressive bile duct destruction eventually leading to cirrhosis, liver failure, and death. The autoimmune pathogenesis is supported by a plethora of experimental and clinical data, such as the presence of autoreactive T cells and serum autoantibodies. The aetiology remains unknown, although evidence suggests a role for both genetic susceptibility and environmental factors that remain to be determined. In fact, a number of chemicals and infectious agents have been proposed to induce the disease in predisposed individuals. The recent availability of several murine models will significantly help in understanding pathophysiology mechanisms. In this review, we critically summarize the most recent data on the aetiopathogenesis of primary biliary cirrhosis, discuss the latest theories and developments, and suggest directions for future research.

Long-term bacterial exposure can trigger nonsuppurative destructive cholangitis associated with multifocal epithelial inflammation

Bacterial infection has become a focus of attention in the pathogenesis of primary biliary cirrhosis (PBC). We earlier reported that the bacterial lipoteichoic acid was detected at the sites of inflammation around damaged bile ducts in the livers of PBC, and PBC patients' sera showed high titers against streptococcal histone-like protein. Here, we investigated whether chronic bacterial exposure could trigger PBC-like epithelial cell damage in normal mouse. BALB/c mice were repeatedly inoculated with various bacteria for 8 weeks. At 1 week (Group 1) and 3, 4, or 20 months (long term; Group 2) after the final inoculation, mice were killed to obtain samples. In the livers of the Streptococcus intermedius (S.i.)-inoculated mice in Group 1, cellular infiltration was predominantly observed around the bile ducts over the hepatic parenchyma. In the S.i.-inoculated mice in Group 2, portal but not parenchymal inflammation was observed in the livers, and periductal cellular infiltrates were detected in the salivary glands. Both S.i.-inoculated Groups 1 and 2 BALB/c mice sera had antibodies against HuCCT1 biliary epithelial cells, anti-nuclear antibodies, and anti-gp210 antibodies, but not anti-mitochondrial antibodies. Immunoreactivity to histone-like DNA-binding protein of S.i. (S.i.-HLP) was detectable around the sites of chronic nonsuppurative destructive cholangitis in the portal area in the livers of both S.i.-inoculated Groups 1 and 2 BALB/c mice. Furthermore, anti-S.i.-HLP antibody bound to synthetic gp210 peptide, as well. Bacteria triggered PBC-like cholangitis, multifocal epithelial inflammation, and autoantibody production. Bacteria are likely involved in the pathogenesis of PBC and of associated multifocal epithelial inflammation.