In drug-induced, immune-mediated hepatitis, interleukin-33 reduces hepatitis and improves survival independently and as a consequence of FoxP3+ T-cell activity

Immune-mediated, drug-induced hepatitis is a rare complication of halogenated volatile anesthetic administration. IL-4-regulated Th2-polarized reactions initiate this type and other types of hepatitis, while the mechanisms that regulate the severity remain elusive. IL-33 is an innate, IL-4-inducing, Th2-polarizing cytokine that has been detected in patients with liver failure and has been associated with upregulated ST2+Foxp3+CD4+CD25+ T cells; however, roles for IL-33 in drug-induced hepatitis are unclear. We investigated IL-33 in an anesthetic, immune-mediated hepatitis modeled in BALB/c, IL-33-/- and ST2-/- mice, as well as in patients with anesthetic hepatitis. The hepatic IL-33 and ST2 levels were elevated in BALB/c mice (p < 0.05) with hepatitis, and anti-IL-33 diminished hepatitis (p < 0.05) without reducing IL-33 levels. The complete absence of IL-33 reduced IL-10 (p < 0.05) and ST2+Foxp3+CD4+CD25+ T cells (p < 0.05), as well as reduced the overall survival (p < 0.05), suggesting suppressive roles for IL-33 in anesthetic, immune-mediated hepatitis. All of the mice demonstrated similar levels of CD4+ T-cell proliferation following direct T-cell receptor stimulation, but we detected splenic IL-33 and ST2-negative Foxp3+CD4+CD25+ T cells in ST2-/- mice that developed less hepatitis than BALB/c mice (p < 0.05), suggesting that ST2-negative Foxp3+CD4+CD25+ T cells reduced hepatitis. In patients, serum IL-33 and IPEX levels were correlated in controls (r² = 0.5, p < 0.05), similar to the levels in mice, but not in anesthetic hepatitis patients (r² = 0.01), who had elevated IL-33 (p < 0.001) and decreased IPEX (p < 0.01). Our results suggest that, in anesthetic, immune-mediated hepatitis, IL-33 does not regulate the CD4+ T-cell proliferation that initiates hepatitis, but IL-33, likely independent of ST2, reduces hepatitis via upregulation of Foxp3+CD4+CD25+ T cells. Further studies are needed to translate the role of IL-33 to human liver disease.

Chemokine (C-X-C motif) ligand 13 promotes intrahepatic chemokine (C-X-C motif) receptor 5+ lymphocyte homing and aberrant B-cell immune responses in primary biliary cirrhosis

The serological hallmark of primary biliary cirrhosis (PBC) is the presence of high titer and specific antimitochondrial antibodies (AMAs). Although there is no global immune defect in patients with PBC, there is widespread dysregulated B-cell function, including increased sera levels of immunoglobulin M and enhanced B-cell responses to cytosine-phosphate-guanine stimulation. The mechanisms involved in this B-cell dysfunction have remained unknown. To address this issue, we focused on identifying the frequencies of B-cell subsets in patients with PBC and the mechanisms that lead to B-cell dysregulation, including the relationships with chemokine (C-X-C motif) receptor 5 (CXCR5)(+) CD4(+) T cells. Herein, we report that elevations of both serum and intrahepatic interleukin-21 (IL-21) were found in patients with PBC and, in particular, promoted B-cell proliferation, signal transducer and activator of transcription 3 phosphorylation and AMA production in vitro. More important, upon stimulation with recombinant E2 subunit of pyruvate dehydrogenase complex, CXCR5(+) CD4(+) T cells in PBC produced higher levels of IL-21 than healthy controls. Additionally, sorted CXCR5(+) CD4(+) T cells increased production of AMAs by autologous CD19(+) B cells. Indeed, elevated expression of intrahepatic chemokine (C-X-C motif) ligand 13 (CXCL13), a key chemokine of CXCR5(+) cells, was uniquely found within the portal tracts in PBC, accompanied by infiltrates of CD4(+) , CXCR5(+) , CD19(+) , and CD38(+) cells.

CONCLUSION

CXCL13 promotes aggregation of CD19(+) B cells and CXCR5(+) CD4(+) T cells, which directs the aberrant AMA response by IL-21. These data have implications for potential immunotherapy and also reflect the unique lymphoid biology in liver of PBC.

Ongoing activation of autoantigen-specific B cells in primary biliary cirrhosis

The serologic hallmark of primary biliary cirrhosis (PBC), the antimitochondrial response to the E2 component of the pyruvate dehydrogenase complex (PDC-E2), has unique features, including continuous high titers of immunoglobulin M (IgM) and IgG reactivity throughout all stages of disease, capable not only of target enzyme inhibition, but also crossreactive with chemical xenobiotics that share molecular homology with the inner lipoyl domain of PDC-E2; such chemicals have been proposed as potential etiological agents. We used flow cytometry and enzyme-linked immunospot assay (ELISPOT) to examine B-cell subsets in 59 subjects, including 28 with PBC, 13 with primary sclerosing cholangitis (PSC), and 18 healthy controls. Strikingly, in PBC, although there were no significant differences in B-cell phenotype subpopulations, 10% of the total IgG and IgA plasmablast population and 23% of the IgM plasmablast population were uniquely reactive with PDC-E2, detected in the CXCR7+ CCR10low plasmablast population. In contrast, plasmablast reactivity to a control antigen, tetanus toxoid, was minimal and similar in all groups. Additionally, we isolated plasmablast-derived polyclonal antibodies and compared reactivity with plasma-derived antibodies and noted a distinct noncirculating tissue source of xenobiotic crossreacting antibodies. The high levels of autoantigen specific peripheral plasmablasts indicate recent activation of naive or memory B cells and a continuous and robust activation. The presence of CXCR7+ CCR10low PDC-E2-specific ASCs suggests a mechanistic basis for the migration of circulating antigen specific plasmablasts to the mucosal epithelial ligands CXCL12 and CCL28.

CONCLUSION

Our findings suggest a sustained rigorous B-cell response in PBC, likely activated and perpetuated by cognate autoantigen.

Fashioning the immunological self: the biological individuality of F. Macfarlane Burnet

During the 1940s and 1950s, the Australian microbiologist F. Macfarlane Burnet sought a biologically plausible explanation of antibody production. In this essay, we seek to recover the conceptual pathways that Burnet followed in his immunological theorizing. In so doing, we emphasize the influence of speculations on individuality, especially those of philosopher Alfred North Whitehead; the impact of cybernetics and information theory; and the contributions of clinical research into autoimmune disease that took place in Melbourne. We point to the influence of local experimental and intellectual currents on Burnet's work. Accordingly, this essay describes an arc distinct from most other tracings of Burnet's conceptual development, which focus on his early bacteriophage research, his fascination with the work of Julian Huxley and other biologists in the 1920s, and his interest in North Atlantic experimental investigations in the life sciences. No doubt these too were potent influences, but they seem insufficient to explain, for example, Burnet's sudden enthusiasm in the 1940s for immunological definitions of self and not-self. We want to demonstrate here how Burnet's deep involvement in philosophical biology - along with attention to local clinical research - provided him with additional theoretic tools and conceptual equipment, with which to explain immune function.

Bilateral deep inferior epigastric perforator flaps based on unilateral perforators

This report highlights the case of an unusual bilateral breast reconstruction using bilateral Deep Inferior Epigastric Perforator flaps based solely upon unilateral perforators. The usual lower paramedian perforating vessels were absent on one side and subsequently the main abdominal flap was split obliquely (rather than midline) to base both individual flaps on perforators arising from the same side. The operation was a success with no flap complications post-operatively.

Epitope-specific anti-nuclear antibodies are expressed in a mouse model of primary biliary cirrhosis and are cytokine-dependent

Although the hallmark of primary biliary cirrhosis (PBC) is the presence of anti-mitochondrial antibodies (AMA), a significant number of patients have anti-nuclear antibodies (ANA) directed primarily against two nuclear proteins, gp210 and sp100. In PBC, there are considerable data on the specificity of these anti-nuclear antibodies as well as suggestive evidence that antibodies to gp210 predict a poor outcome. However, a further understanding of the significance of these autoantibodies has been hampered by limitations in accessing human subjects in a preclinical or early asymptomatic stage. To overcome this limitation, we have taken advantage of transgenic mice with abrogated transforming growth factor-β signalling in T cells (dnTGF-βRII) that develop histological features of PBC as well as the same AMA specificity. We studied these mice for serum ANA, including specific autoantibodies against gp210 and sp100. We further examined sera from dnTGF-βRII mice with concurrent deletions of the genes encoding interleukin (IL)-12p35, IL-12p40, IL-23p19, IL-17, IL-6, interferon (IFN)-γ or tumour necrosis factor (TNF)-α. Sera from all the dnTGF-βRII mouse lines contained antibodies against gp210 and sp100. Of significance, mice with germline deletions of the genes encoding IL-12p40, IL-23p19, IL-17, IL-6 and TNF-α had significantly lower titres of anti-gp210 antibodies. These results provide a platform to dissect the mechanisms of gp210 and sp100 autoantibody production in dnTGF-βRII mice as well as to study the possible role of ANA in the pathophysiology of PBC.

BAFF/BLyS inhibitors: A new prospect for treatment of systemic lupus erythematosus

In November 2009, Human Genome Sciences and Glaxo-Smith Kline [HGS (Rockville, Maryland) and GSK, respectively] announced that Belimumab, a neutralizing antibody to the tumour necrosis factor (TNF)-like ligand, B-cell activating factor (BAFF belonging to the TNF family, also named BLyS), met the primary endpoints in two phase III clinical trials in systemic lupus erythematosus (SLE, lupus). In March 2011, Belimumab was approved by the US Federal Drug Agency for treatment of SLE patients; this was followed in May with approval by the European Medicines Agency for use in the European Union. This is an exciting development as it is the first successful late-stage clinical trial in SLE in over 40 years. In the light of this breakthrough, we review the key data and research outcomes and examine how blocking BAFF in patients with SLE significantly improves clinical outcomes.

Stiff-person syndrome (SPS) and anti-GAD-related CNS degenerations: protean additions to the autoimmune central neuropathies

Stiff Person Syndrome (SPS) is a rare autoimmune neurological disease attributable to autoantibodies to glutamic acid decarboxylase (anti-GAD) more usually associated with the islet beta cell destruction of autoimmune type 1 diabetes (T1D). SPS is characterized by interference in neurons with the synthesis/activity of the inhibitory neurotransmitter gamma amino butyric acid (GABA) resulting in the prototypic progressive spasmodic muscular rigidity of SPS, or diverse neurological syndromes, cerebellar ataxia, intractable epilepsy, myoclonus and several others. Remarkably, a single autoantibody, anti-GAD, can be common to widely different disease expressions, i.e. T1D and SPS. One explanation for these data is the differences in epitope engagement between the anti-GAD reactivity in SPS and T1D: in both diseases, anti-GAD antibody reactivity is predominantly to a conformational epitope region in the PLP- and C-terminal domains of the 65 kDa isoform but, additionally in SPS, there is reactivity to conformational epitope(s) on GAD67, and short linear epitopes in the C-terminal region and at the N-terminus of GAD65. Another explanation for disease expressions in SPS includes ready access of anti-GAD to antigen sites due to immune responsiveness within the CNS itself according to intrathecal anti-GAD-specific B cells and autoantibody. Closer study of the mysterious stiff-person syndrome should enhance the understanding of this disease itself, and autoimmunity in general.

Inflammatory bowel disease: beyond the boundaries of the bowel

Dysregulated inflammation in the gut, designated clinically as inflammatory bowel disease (IBD), is manifested by the prototypic phenotypes of an Arthus-like reaction restricted to the mucosa of the colon, as in ulcerative colitis, or a transmural granulomatous reaction, as in Crohn's disease, or an indeterminate form of the two polar types. That the inflammation of IBD can trespass the boundaries of the bowel has long been known, with articular, ophthalmologic, cutaneous, hepatobiliary or other complications/associations - some autoimmune and others not - affecting significant numbers of patients with IBD. Also notable is the frequency of diagnosis of IBD-type diseases on a background of systemic, (mostly myelo-hematological) disorders, associated with alterations of either (or both) innate or adaptive arms of the immune response. Finally, cases of IBD are reported to occur as an adverse effect of TNF inhibitors. Bone marrow transplant has been proven to be the only curative measure for some of the above cases. Thus, in effect, the IBDs should now be regarded as a systemic, rather than bowel-localized, disease. Genome-wide association studies have been informative in consolidating the view of three phenotypes of IBD (ulcerative colitis, Crohn's disease and mixed) and, notably, are revealing that the onset of IBD can be linked to polymorphisms in regulatory miRNAs, or to nucleotide sequences coding for regulatory lymphokines and/or their receptors. At the effector level, we emphasize the major role of the Th17/IL-23 axis in dictating the perpetuation of intestinal inflammation, augmented by a failure of physiological control by regulatory T-cells. In conclusion, there is a central genesis of the defects underlying IBD, which therefore, in our opinion, is best accommodated by the concept of IBD as more of a syndrome than an autonomous disease. This altered mindset should upgrade our knowledge of IBD, influence its medical care and provide a platform for further advances.

The Scottish-Finnish-Swedish PARTNER study of taprostene versus placebo treatment in patients with critical limb ischemia

AIM

Atherosclerotic peripheral arterial disease is a major health problem in the western world, often manifested as intermittent claudication, affecting 10-20% males above 60 years. Ischemic complications can lead to rest pain, ulceration and gangrene. The treatment of choice for critical limb ischemia (CLI) is vascular reconstruction or endovascular interventions. Medical management with vasodilator antiplatelet prostaglandins, could be considered in patients unsuitable for surgery. Long term follow-up on previous prostaglandin studies has been insufficient to evaluate amputation rates. Hence this study evaluated safety and longer term efficacy of taprostene sodium, a prostacyclin (PGI2) analogue in CLI. The aim of this study was to determine whether Taprostene sodium, a PGI2 analogue, was a safe and effective treatment for CLI.

METHODS

This paper reports the data from the Scottish-Finnish-Swedish PARTNER Study Group which consisted of a double-blind placebo controlled multi-centre study evaluating Taprostene compared to placebo. The primary endpoints were pain relief and early ulcer healing response at the end of the four week infusion phase and amputation at six months follow-up. The patients were randomly allocated to receive taprostene or placebo in a two to one randomization of active versus placebo. A total of 111 patients with CLI were recruited. Taprostene was given twice a day over two 2 hour periods for four weeks. The early response was evaluated at the end of the four week infusion phase. In patients with rest pain without ulceration, a positive response was complete pain relief without any requirement for analgesic therapy. However in patients with ulceration, a positive response was defined as a decrease in the ulcer size by >30%. Amputation scores were compared at the end of the 6 months follow-up period for all participants.

RESULTS

Seventy-four patients received taprostene and 37 placebo. Overall, 61 male patients were enrolled in the study along with 50 females with 11% more women in the taprostene (active) group. For both patients with and without ulcers there was no statistically significant difference noted in the early response between those receiving taprostene and those receiving placebo infusion. The percentage of patients without any amputations was 43% in the taprostene group compared to 38% in the control group at the end of six months; however, these results were not statistically significant.

CONCLUSION

Although a reasonable number of patients enrolled in the study it has not been possible to demonstrate any statistically significant benefit of taprostene over placebo. This may be due to more patients with risk factors for peripheral artery disease (PAD) such as hypertension, diabetes mellitus and cigarette smoking in the actively treated group and also due the increased number of women in the active group who are known to generally respond less favourably to antiplatelet agents.

A 50-year experience with autoimmune hepatitis: and where are we now?

BACKGROUND

Autoimmune hepatitis (AIH) as chronic active hepatitis became recognized in the 1940s as a progressive hyperglobulinemic disease affecting younger women attributed to persisting virus infection of the liver: autoimmunity then was barely on the horizon.

EARLY OBSERVATIONS

The lupus erythematosus (LE) cell reported in 1948 signified the presence of antinuclear autoantibodies, promoting perceptions of autoimmunity in certain chronic diseases. Recognition of LE cells in chronic hepatitis led to the designation of 'lupoid hepatitis', with autoimmunity further substantiated by anti-cytoplasmic autoantibodies detected by complement fixation. Next a serum reactant with smooth muscle of rodent stomach was found to have a wider distribution and became identified as an autoantibody to filamentous (F) actin. Therapy with corticosteroids proved effective, particularly combined with azathioprine. Various trials showed greatly improved survival and established modern therapy of AIH. An HLA-based predisposition (B8, DR3) was the first pointer to a genetic etiology.

RECENT ADVANCES

Recombinant or purified autoantigenic substrates have led to automated assays, which, together with improved immunofluorescence procedures, allow serological confidence in diagnosis and institution of effective immunosuppressive therapies. The liver-kidney 'microsomal' autoantigen reactive with cytochrome P450 2D6 distinguishes two serological types of AIH that appear pathogenetically distinct. Molecular characterization of antigens and epitopes remains wanting in type 1 AIH.

FUTURE PROSPECTS

The challenge remains with both types of AIH to elucidate in molecular terms the genetic and environmental basis of pathogenesis from initiation to ultimate progression and cirrhosis (when inadequately treated). Advancing technologies are bringing this goal closer to being attainable.

Autoantibody heritability in thyroiditis: IgG subclass contributions

Using a simple screening technique called regression of offspring on mid-parent (ROMP) to examine the role of IgG subclasses in affected and unaffected siblings of children and adolescents with autoimmune thyroid disease and their parents, both total-restricted and subclass-restricted autoantibodies to thyroglobulin (Tg) were assayed quantitatively for each of the IgG subclasses. There was a significant correlation of anti-Tg titer of probands with parental titers in thyrotoxicosis (TT), (R(2) = 0.569, p = 0.001), but not in chronic lymphocytic thyroiditis. The most striking correlation was in TT patients of African-American ancestry, (R(2) = 0.9863, p = 0.0007). Additional insight is provided by examining the contributions of the IgG subclasses individually, particularly those whose concentrations appear not to have direct influence on the total IgG titers. Thus, using small numbers of patients, and assaying the IgG subclass distributions, as well as any other immunoglobulin isotypes that are significantly altered in autoantibody assays, ROMP can be performed rapidly to ascertain which quantifiable parameters may be usefully extended to predict disease onset and progression.

What's in a name? Experimental encephalomyelitis: 'allergic' or 'autoimmune'

New linguistic coinage can signify new practices and fresh perceptions in science: descriptors therefore are not trivial. Here, we consider the shifting valence of 'allergic' and 'autoimmune' in conceptions of experimental encephalomyelitis (EE). Ehrlich's dismissal of the relevance to disease of autoimmunity resulted in its 'long struggle for recognition' notwithstanding the convincing attribution in 1904 of the hemolysis of paroxysmal cold hemoglobinuria. Yet allergy did take hold because of its assumption that harmful effects could be ascribed to an extrinsic agent against which immune responses were supposed to be directed, in line with contemporary microbiological research. In 1885 the history of EE began with Pasteur's anti-rabies vaccine, dried virus-infected rabbit spinal cord, with use occasionally inducing a post-vaccinal encephalomyelitis (PVE). From 1933 to 1935, PVE was investigated by Rivers who reported that some monkeys immunized with normal rabbit CNS extracts developed an inflammatory demyelinating EE and anti-brain antibodies: no cause was attributed. In the 1940s Freund developed an adjuvant that greatly potentiated immunization and in 1947 this was applied to animals immunized for EE: induction was accelerated and the disease was called 'E allergic E', initiating the EAE acronym. As recorded, 'the study of autoimmune disease leapt from nothing in 1945 to a vigorous field in the 1950s'. Yet researchers sedulously retained allergic in the EAE acronym until the1980s, long after 'autoimmune' had become available to them. Eventually practitioners for whom autoimmunity had meaning influenced the transition to 'E autoimmune E' as the laboratory analogue of human autoimmune multiple sclerosis.

CX3CL1 (fractalkine): a signpost for biliary inflammation in primary biliary cirrhosis

Improvements in the treatment of primary biliary cirrhosis (PBC) may depend upon dissection of mechanisms that determine recruitment of mononuclear cells to intralobular bile ducts, including the role of the chemokine-adhesion molecule CX3CL1 (fractalkine). We submit that there are unique interactions between intrahepatic biliary epithelial cells (BECs), endothelial cells (ECs), liver sinusoidal endothelial cells (LSECs), and liver-infiltrating mononuclear cells (LMCs), and that such interactions will in part dictate the biliary-specific inflammatory response. To address this, we studied fresh explanted livers from pretransplantation patients with PBC and with inflammatory liver disease due to viral infection (disease controls) and biopsy material from patients with a discrete liver tumor (normal controls). Using this clinical material, we isolated and stimulated BECs, ECs, LSECs, and LMCs with a panel of Toll-like receptor ligands. We also studied the interactions of these cell populations with LMCs with respect to adhesion capability and production of tumor necrosis factor alpha (TNF-alpha). Finally, we used fresh biopsy samples to evaluate mononuclear cells around intrahepatic biliary ductules using monoclonal antibodies specific to CD68 or CD154, markers for monocytes/macrophages, and activated T cells, respectively.

CONCLUSION

There are common properties of ECs, LSECs, and BECs, whether derived from PBC or viral hepatitis, but there are also significant differences, particularly in the potential in PBC for LMCs to adhere to ECs and BECs and to produce TNF-alpha; such properties were associated with augmented CX3CL1 production by BEC from PBC liver. The processes defined herein suggest potential novel biotherapies for biliary specific inflammation.

B-cell depletion with anti-CD20 ameliorates autoimmune cholangitis but exacerbates colitis in transforming growth factor-beta receptor II dominant negative mice

The treatment of primary biliary cirrhosis (PBC) with conventional immunosuppressive drugs has been relatively disappointing and there have been few efforts in defining a role for the newer biological agents useful in rheumatoid arthritis and other systemic autoimmune diseases. In this study we took advantage of transforming growth factor-beta (TGF-beta) receptor II dominant negative (dnTGF-betaRII) mice, a mouse model of autoimmune cholangitis, to address the therapeutic efficacy of B-cell depletion using anti-CD20. Mice were treated at either 4-6 weeks of age or beginning at 20-22 weeks of age with intraperitoneal injections of anti-CD20 every 2 weeks. We quantitated B-cell levels in all mice as well as antimitochondrial antibodies (AMA), serum and hepatic levels of proinflammatory cytokines, and histopathology of liver and colon. In mice whose treatment was initiated at 4-6 weeks of age, anti-CD20 therapy demonstrated a significantly lower incidence of liver inflammation associated with reduced numbers of activated hepatic CD8(+) T cells. However, colon inflammation was exacerbated. In contrast, in mice treated at 20-22 weeks of age, anti-CD20 therapy had relatively little effect on either liver or colon disease. As expected, all treated animals had reduced levels of B cells, absence of AMA, and increased levels in sera of tumor necrosis factor alpha (TNF-alpha), interleukin 6 (IL-6), and chemokine (C-C motif) ligand (CCL2) (monocyte chemoattractant protein 1 [MCP-1]).

CONCLUSION

These data suggest potential usage of anti-CD20 in early PBC resistant to other modalities, but raise a cautionary note regarding the use of anti-CD20 in inflammatory bowel disease.

Deletion of interleukin-12p40 suppresses autoimmune cholangitis in dominant negative transforming growth factor beta receptor type II mice

Our laboratory has reported that mice that express a dominant negative form of transforming growth factor beta receptor restricted to T cells (dnTGFbetaRII) develop an inflammatory biliary ductular disease with elevated serum levels of interleukin (IL)-12p40 and other proinflammatory cytokines and antimitochondrial autoantibodies (AMAs) closely resembling human primary biliary cirrhosis (PBC). We have used this mouse model to address the potential mechanisms of immunomodulation of liver disease by creating two unique genetic strains: IL-12p40 knockout (KO)-dnTGFbetaRII mice and IFN-gamma KO-dnTGFbetaRII mice. The two colonies of genetically modified mice-and, for purposes of controls, the dnTGFbetaRII mice-were monitored for liver immunopathology, AMAs, and intrahepatic cytokine production. Disease expression in the IFN-gamma KO-dnTGFbetaRII mice, including liver immunopathology, were similar to those of dnTGFbetaRII mice, whereas the IL-12p40 KO-dnTGFbetaRII mice had a dramatic reduction in histological autoimmune cholangitis and significant decreases in levels of intrahepatic proinflammatory cytokines, but similar levels of AMAs compared with dnTGFbetaRII controls.

CONCLUSION

These data indicate that in this mouse model of PBC, signaling by way of IL-12p40 is an essential requirement for the development of autoimmune cholangitis. The results of these studies will play an important role in identifying pathways and reagents that will selectively inhibit IL-12 signaling for the outlining of future therapeutic strategies for human PBC.

Travels and travails of autoimmunity: a historical journey from discovery to rediscovery

Consideration on autoimmunity began, as did immunology itself, around year 1900, first with Ehrlich's doctrine of 'horror autotoxicus', then interpreted as 'autoimmunity cannot happen'. Yet by 1904 the antibody nature of the autohemolysin responsible for cold hemoglobinuria was described, and soon confirmed, but without generating any durable concept on autoimmunization as a cause of disease. Reasons included Ehrlich's doctrine, the particular directions that immunology was to take after the initial advances, and a greater preoccupation with bodily responses to extrinsic rather than autologous substances. So, during 1915-1945, autoimmunity underwent a long eclipse despite, during this time, some potentially telling studies relating to brain, kidney and other diseases. The 'awakening' dates from 1945 when a general theoretical concept did appear feasible. Knowledge accrued from applications of several research undertakings mostly for purposes quite unrelated to the proof of autoimmunization: the use of adjuvants; the Coombes anti-globulin reaction; the Waaler-Rose rheumatoid factor; Hargraves' LE cell; the Witebsky-Rose experimental induction of thyroiditis with autologous thyroid gland, and others. By the early 1960s resistance to the idea of autoimmunization had weakened, perhaps hastened by a monograph on autoimmune disease published in 1963, and surely by the consensus reached at a large international conference published as proceedings in 1965. This present conspectus arbitrarily concludes at year 1965, recognizing that the history of autoimmunity even now is far from over.

Autoimmune Gastritis: Historical Antecedents, Outstanding Discoveries, and Unresolved Problems

The earliest recorded history of autoimmune gastritis can be traced to 1849 in London, when Thomas Addison described "a very remarkable form of anemia" later called pernicious (fatal) anemia (PA). This was followed by the recognition of a gastric mucosal defect suspected to have a nutritional basis, the discovery of the megaloblast that characterized the anemia, the insufficiency of a dietary extrinsic factor characterized as vitamin B12 (cobalamin), and a gastric-secreted intrinsic factor. Treatment with vitamin B12 proved curative. The link between PA and gastritis and atrophy was first confirmed histologically after immediate fixation of the stomach postmortem and later, in the 1940s, by peroral tube biopsy. The causes of gastritis remained enigmatic until the era of autoimmunity, when autoantibodies were detected first to gastric intrinsic factor and then to gastric parietal cells. Hints of a dichotomy in pathogenesis of gastritis were crystallized by the description in 1973 of Type A (Autoimmune) and Type B (later, Bacterial) gastritis. Clarification was enhanced by identification in Type A gastritis of the autoantigen of the parietal cell antibody, by the alpha and beta subunits of gastric H+/K+ ATPase, and by the highly informative experimental murine model of postneonatal thymectomy autoimmune gastritis, and in Type B of the causative role of gastric infection with Helicobacter pylori (H. pylori). A denouement will require a full understanding of (1) the origin and pathogenetic contribution of antibody to intrinsic factor; (2) the connection, if any, between H. pylori infection and Type A autoimmune gastritis; and (3) the genetic contributions to gastritis, whether due to autoimmunity or to H. pylori infection.

Heritability of levels of autoantibodies using the method of plotting regression of offspring on midparent (ROMP)

The genetic control of the levels of autoantibodies has rarely been examined. We examined the heritability of autoantibodies to glutamic acid decarboxylase (GAD65) in type 1 diabetes, and to thyroglobulin (Tg) in chronic lymphocytic thyroiditis and thyrotoxicosis, using regression of offspring on midparent (ROMP) methods. Levels of autoantibodies in patients and their parents were significantly correlated in thyrotoxicosis (R2 = 0.569, p = 0.001), consistent with the reported Gm association, but not in chronic lymphocytic thyroiditis or type 1 diabetes. Extension of the procedure to other autoantibody disorders could be informative.

Apotopes and the biliary specificity of primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is characterized by antimitochondrial antibodies (AMAs), directed to the E2 component of the pyruvate dehydrogenase complex (PDC-E2). Notwithstanding the presence of mitochondria in virtually all nucleated cells, the destruction in PBC is limited to small intrahepatic bile ducts. The reasons for this tissue specificity remain unknown, although biliary epithelial cells (BECs) uniquely preserve the PDC-E2 epitope following apoptosis. Notably, PBC recurs in an allogeneic transplanted liver, suggesting generic rather than host PBC-specific susceptibility of BEC. We used cultured human intrahepatic BECs (HIBECs) and other well-characterized cell lines, including, HeLa, CaCo-2 cells, and nontransformed human keratinocytes and bronchial epithelial cells, to determine the integrity and specific localization of PDC-E2 during induced apoptosis. All cell lines, both before and after apoptosis, were tested with sera from patients with PBC (n = 30), other autoimmune liver and rheumatic diseases (n = 20), and healthy individuals (n = 20) as well as with a mouse monoclonal antibody against PDC-E2 and AMA with an immunoglobulin A isotype. PDC-E2 was found to localize unmodified within apoptotic blebs of HIBECs, but not within blebs of various other cell lineages studied. The fact that AMA-containing sera reacted with PDC-E2 on apoptotic BECs without a requirement for permeabilization suggests that the autoantigen is accessible to the immune system during apoptosis.

CONCLUSION

Our data indicate that the tissue (cholangiocyte) specificity of the autoimmune injury in PBC is a consequence of the unique characteristics of HIBECs during apoptosis and can be explained by exposure to the immune system of intact immunoreactive PDC-E2 within apoptotic blebs.

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.

Induction of autoimmune cholangitis in non-obese diabetic (NOD).1101 mice following a chemical xenobiotic immunization

Our laboratory has suggested that loss of tolerance to pyruvate dehydrogenase (PDC-E2) leads to an anti-mitochondrial antibody response and autoimmune cholangitis, similar to human primary biliary cirrhosis (PBC). We have suggested that this loss of tolerance can be induced either via chemical xenobiotic immunization or exposure to select bacteria. Our work has also highlighted the importance of genetic susceptibility. Using the non-obese diabetic (NOD) congenic strain 1101 (hereafter referred to as NOD.1101 mice), which has chromosome 3 regions from B6 introgressed onto a NOD background, we exposed animals to 2-octynoic acid (2OA) coupled to bovine serum albumin (BSA). 2OA has been demonstrated previously by a quantitative structural activity relationship to react as well as or better than lipoic acid to anti-mitochondrial antibodies. We demonstrate herein that NOD.1101 mice immunized with 2OA-BSA, but not with BSA alone, develop high titre anti-mitochondrial antibodies and histological features, including portal infiltrates enriched in CD8(+) cells and liver granulomas, similar to human PBC. We believe this model will allow the rigorous dissection of early immunogenetic cause of biliary damage.

Chronic complications and mortality in community-based patients with latent autoimmune diabetes in adults: the Fremantle Diabetes Study

AIMS

To compare (i) the prevalence and incidence of chronic complications and (ii) cardiac and all-cause mortality in community-based patients with latent autoimmune diabetes in adults (LADA) with those in Type 2 diabetic patients without antibodies to glutamic acid decarboxylase (GAD).

METHODS

Of the 1294 patients with clinically-defined Type 2 diabetes recruited to the longitudinal, observational Fremantle Diabetes Study between 1993 and 1996, 1255 (97%) had GAD antibodies measured at baseline. Complications were ascertained using standard criteria in patients returning for annual assessments until November 2001. Data on hospital admissions and mortality were available to the end of June 2006. Cox proportional hazards modelling was used to determine independent predictors of first occurrence of complications and cardiac and all-cause mortality.

RESULTS

Forty-five (3.6%) subjects had LADA. Compared with the GAD antibody-negative patients, they had a similar prevalence and incidence of coronary heart (P = 0.48 and 0.80, respectively) and cerebrovascular (P = 0.64 and 0.29) disease and cardiac and all-cause mortality (P = 0.62 and 0.81, respectively). There was also a similar prevalence and incidence of retinopathy (P = 0.22 and 0.64, respectively) and neuropathy (P = 0.25 and 0.95), but microalbuminuria was less frequent both at baseline and during follow-up in the LADA subgroup in unadjusted models (P = 0.046) and after adjustment for other risk factors (P = 0.014 and 0.013).

CONCLUSIONS

Except for a lower prevalence and incidence of nephropathy, LADA patients have a similar risk of complications and death to patients with clinically-diagnosed Type 2 diabetes without GAD antibodies. Cardiovascular risk factor management in LADA should, therefore, be as intensive as that for GAD antibody-negative patients.

Loss of tolerance in C57BL/6 mice to the autoantigen E2 subunit of pyruvate dehydrogenase by a xenobiotic with ensuing biliary ductular disease

There have been important advances in defining effector mechanisms for several human autoimmune diseases. However, for most human autoimmune diseases, the induction stage is less well defined and there are very few clues on etiology. Our laboratory has focused on defining the molecular basis of autoantibody recognition and epitope modification in primary biliary cirrhosis (PBC). Our work has demonstrated that antibodies to mitochondria, the hallmark of disease, are directed against a very conserved site of pyruvate dehydrogenase, the E2 subunit of pyruvate dehydrogenase (PDC-E2). We have also demonstrated that several chemical xenobiotics, chosen based on quantitative structural activity relationship analysis and rigorous epitope analysis, when coupled to the lysine residue that normally binds the lipoic acid cofactor of PDC-E2, reacts as well or better to PBC sera than native autoantigen. In the present studies, we immunized C57BL/6 mice with one such xenobiotic, 2-octynoic acid, coupled to bovine serum albumin and we followed the mice for 24 weeks. Animals were studied for appearance of histologic lesions as well as appearance of antibodies to PDC-E2, serum levels of tumor necrosis factor-alpha and interferon-gamma, and splenic and liver lymphoid phenotyping by flow cytometry. Mice immunized with 2-octynoic acid manifest autoimmune cholangitis, typical mitochondrial autoantibodies, increased liver lymphoid cell numbers, an increase in CD8(+) liver infiltrating cells, particularly CD8(+) T cells that coexpress CD44, and finally an elevation of serum tumor necrosis factor-alpha and interferon-gamma.

CONCLUSION

these data provide a persuasive argument in favor of an environmental origin for human PBC.

CD4 T-cell autoreactivity to the mitochondrial autoantigen PDC-E2 in AMA-negative primary biliary cirrhosis

Approximately 5% of patients with primary biliary cirrhosis (PBC) lack characteristic anti-mitochondrial antibodies (AMA). Yet clinically AMA+ and AMA- patients are similar. Using both AMA+ and AMA- patients, we quantitated the frequency of autoreactive T cells that respond to the major CD4 T-cell epitope, PDC-E2 163-176, using limiting dilution assays and quantitation of IFN-gamma, IL-10 and IL-4. Further, based on data that both PBC patients and healthy subjects have CD4+ T cells that recognize PDC-E2 163-176 but with differing costimulation requirements, assays were performed using two different antigen-presenting cell (APC) systems: either autologous peripheral blood mononuclear cells (PBMC) or HLA DR53 transfected mouse fibroblast cell lines (L-DR53). When costimulation-incompetent L-DR53 were used as APCs, the PDC-E2 CD4 T-cell frequency and capacity for IFN-gamma production were equivalent in both AMA+ and AMA- patients but the frequencies of such cells were significantly lower in normals, with IL-10 production similar in all three groups. Thus, in PBC there is 'universal' autoreactive CD4+ T-cell immune responsiveness to the critical autoantigen, PDC-E2. These observations emphasize that the mitochondrial autoreactivity in PBC is a multi-lineage response and hence, AMA-negative PBC may be an anachronism that refers only to sera autoantibodies.

Binding properties of radiolabeled basic protein of myelin: reassessment in relation to diagnostic immunoassays

The binding of radioiodinated basic protein of myelin ([125I]BPM) to a sheep lymphocyte cell pellet, sheep erythrocytes, and cell-free tubes used in the assay was investigated as a possible diagnostic procedure in multiple sclerosis. [125I]BPM apparently bound to 5 x 10(6) sheep lymphocytes incrementally with no plateau, up to 300 ng, and also to sheep erythrocytes; when cells were transferred to fresh tubes, over 90% of the radioactivity remained on the original tube, regardless of the tube surface. Various substances, including BPM and unrelated basic proteins, competitively inhibited the binding of basic protein of myelin to sheep cells and assay tubes. Binding was inhibited by sera from patients with multiple sclerosis, but equally so by normal sera. The large capacity of BPM to bind nonspecifically could limit its use in the above type of binding assay and would need to be allowed for in conventional radioimmunoassays.

Autoimmune liver diseases

The liver was one of the earliest recognized sites among autoimmune diseases yet autoimmune hepatitis, primary biliary cirrhosis, primary sclerosing cholangitis, and their overlap forms, are still problematic in diagnosis and causation. The contributions herein comprise 'pairs of articles' on clinical characteristics, and concepts of etiopathogenesis, for each of the above diseases, together with childhood autoimmune liver disease, overlaps, interpretations of diagnostic serology, and liver transplantation. This issue is timely, since we are witnessing an ever increasing applicability of immunology to a wide variety of chronic diseases, hepatic and non-hepatic, in both developed and developing countries. The 11 invited expert review articles capture the changing features over recent years of the autoimmune liver diseases, the underlying immunomolecular mechanisms of development, the potent albeit still unexplained genetic influences, the expanding repertoire of immunoserological diagnostic markers, and the increasingly effective therapeutic possibilities.

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.

Historical reflections on autoimmune hepatitis

Autoimmune hepatitis (AIH), initially known as chronic active or active chronic hepatitis (and by various other names), first came under clinical notice in the late 1940s. However, quite likely, chronic active hepatitis (CAH) had been observed prior to this and was attributed to a persistently destructive virus infection of the liver. An earlier (and controversial) designation in 1956 as lupoid hepatitis was derived from associated L.E. cell test positivity and emphasized accompanying multisystem features and immunological aberrations. Young women featured prominently in early descriptions of CAH. AIH was first applied in 1965 as a descriptive term. Disease-characteristic autoantibodies were defined from the early 1960s, notably antinuclear antibody (ANA), smooth muscle antibody (SMA) and liver-kidney microsomal (LKM) antibody. These are still widely used diagnostically but their relationship to pathogenesis is still not evident. A liver and disease specific autoantigen has long been searched for but unsuccessfully. Prolonged immunosuppressive therapy with predisolone and azathioprine in the 1960s proved beneficial and remains standard therapy today. AIH like many other autoimmune diseases is associated with particular HLA alleles especially with the "ancestral" B8, DR3 haplotype, and also with DR4. Looking forwards, AIH is one of the several enigmatic autoimmune diseases that, despite being (relatively) organ specific, are marked by autoimmune reactivities with non-organ-specific autoantigens. New paradigms are needed to explain the occurrence, expressions and pathogenesis of such diseases.

Autoimmune liver serology: Current diagnostic and clinical challenges

Liver-related autoantibodies are crucial for the correct diagnosis and classification of autoimmune liver diseases (AiLD), namely autoimmune hepatitis types 1 and 2 (AIH-1 and 2), primary biliary cirrhosis (PBC), and the sclerosing cholangitis variants in adults and children. AIH-1 is specified by anti-nuclear antibody (ANA) and smooth muscle antibody (SMA). AIH-2 is specified by antibody to liver kidney microsomal antigen type-1 (anti-LKM1) and anti-liver cytosol type 1 (anti-LC1). SMA, ANA and anti-LKM antibodies can be present in de-novo AIH following liver transplantation. PBC is specified by antimitochondrial antibodies (AMA) reacting with enzymes of the 2-oxo-acid dehydrogenase complexes (chiefly pyruvate dehydrogenase complex E2 subunit) and disease-specific ANA mainly reacting with nuclear pore gp210 and nuclear body sp100. Sclerosing cholangitis presents as at least two variants, first the classical primary sclerosing cholangitis (PSC) mostly affecting adult men wherein the only (and non-specific) reactivity is an atypical perinuclear antineutrophil cytoplasmic antibody (p-ANCA), also termed perinuclear anti-neutrophil nuclear antibodies (p-ANNA) and second the childhood disease called autoimmune sclerosing cholangitis (ASC) with serological features resembling those of type 1 AIH. Liver diagnostic serology is a fast-expanding area of investigation as new purified and recombinant autoantigens, and automated technologies such as ELISAs and bead assays, become available to complement (or even compete with) traditional immunofluorescence procedures. We survey for the first time global trends in quality assurance impacting as it does on (1) manufacturers/purveyors of kits and reagents, (2) diagnostic service laboratories that fulfill clinicians’ requirements, and (3) the end-user, the physician providing patient care, who must properly interpret test results in the overall clinical context.

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.

COOH-terminal clustering of autoantibody and T-cell determinants on the structure of GAD65 provide insights into the molecular basis of autoreactivity

OBJECTIVE

To gain structural insights into the autoantigenic properties of GAD65 in type 1 diabetes, we analyzed experimental epitope mapping data in the context of the recently determined crystal structures of GAD65 and GAD67, to allow "molecular positioning" of epitope sites for B- and T-cell reactivity.

RESEARCH DESIGN AND METHODS

Data were assembled from analysis of reported effects of mutagenesis of GAD65 on its reactivity with a panel of 11 human monoclonal antibodies (mAbs), supplemented by use of recombinant Fab to cross-inhibit reactivity with GAD65 by radioimmunoprecipitation of the same mAbs.

RESULTS

The COOH-terminal region on GAD65 was the major autoantigenic site. B-cell epitopes were distributed within two separate clusters around different faces of the COOH-terminal domain. Inclusion of epitope sites in the pyridoxal phosphate-and NH(2)-terminal domains was attributed to the juxtaposition of all three domains in the crystal structure. Epitope preferences of different mAbs to GAD65 aligned with different clinical expressions of type 1 diabetes. Epitopes for four of five known reactive T-cell sequences restricted by HLA DRB1*0401 were aligned to solvent-exposed regions of the GAD65 structure and colocalized within the two B-cell epitope clusters. The continuous COOH-terminal epitope region of GAD65 was structurally highly flexible and therefore differed markedly from the equivalent region of GAD67.

CONCLUSIONS

Structural features could explain the differing antigenicity, and perhaps immunogenicity, of GAD65 versus GAD67. The proximity of B- and T-cell epitopes within the GAD65 structure suggests that antigen-antibody complexes may influence antigen processing by accessory cells and thereby T-cell reactivity.

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.

Cell damage and autoimmunity: a critical appraisal

In April 2007, an international Colloquium bridging scientific and clinical disciplines was held to discuss the role of cellular and tissue damage in the initiation, development and persistence of autoimmune disease. Five potential etiologic and pathophysiologic processes fundamental to autoimmune disease (i.e. inflammation, infection, apoptosis, environmental exposure and genetics) were the focus of the presentations and integrative discussions at the Colloquium. The information presented on these topics is condensed in this review. Inflammation has close clinico-pathologic associations with autoimmunity, but future analyses will require better definition and metrics of inflammation, particularly for the earliest cellular and molecular components dependent on recruitment of elements of innate immunity. Although infection may be associated with increased levels of autoantibodies, most infections and virtually all vaccinations in humans lack well-established links to autoimmune diseases. Further application of well-designed, long-term epidemiologic and population-based studies is urgently needed to relate antecedent exposures with later occurring stigmata of autoimmunity with a goal of discerning potentially susceptible individuals or subpopulations. Suspect infections requiring closer interrogation include EB virus (SLE and other diseases), HCV (autoimmune hepatitis), beta hemolytic streptococci (rheumatic carditis) and Helicobacter pylori (autoimmune gastritis) among others. And even if a micro-organism was to be incriminated, mechanisms of initiation/perpetuation of autoimmunity continue to challenge investigators. Plausible mechanisms include potentiation and diversion of innate immunity; exposure or spillage of intracellular autoantigens; or provision of autoantigenic mimics. Integrity of apoptosis as a critical safeguard against autoimmunity was discussed in the contexts of over-reactivity causing autoantigens to gain enhanced exposure to the immune system, or under-reactivity producing insufficient elimination of autoreactive clones of lymphocytes. Although environmental agents are widely believed to serve as necessary "triggers" of autoimmune disease in genetically predisposed individuals, only a few such agents (mainly drugs and some nutrients) have been clearly identified and their mechanism of action defined. Finally an essential genetic foundation underlies all these hazards for autoimmunity in the form of risk-associated polymorphisms in immunoregulatory genes. They may be predictive of future or impending disease.

Regulatory T cells in the prevention of mucosal inflammatory diseases: patrolling the border

Regulatory T (Treg) cells are important contributors to the maintenance of immune tolerance in the periphery, and deficiency of Tregs is associated with various immunopathic diseases. Murine models of autoimmune and autoinflammatory disorders have helped to elucidate how Tregs are involved in these diseases. A feature in common between human and mice that lack one or another of the key Treg subsets is the occurrence of mucosal inflammation. The relatively fragile mucosal surface represents a complex system that is normally well equipped to ward off harmful pathogens yet at the same time is inhibitory to destructive inflammatory responses to biologically needed (probiotic) microorganisms, or other common environmental antigens e.g. nutrients. We here discuss the importance of Tregs in maintaining tolerance at mucosal surfaces and the outcomes of deficiency of Treg function. The intestinal tract and its inflammatory diseases provide the "point of departure" for discussion, but similar considerations could apply to other mucosal linings exposed to the environment such as other members of the digestive system. However, the lungs, bile ducts, urogenital tract and other mucosal surfaces are susceptible to poorly understood inflammatory states that possibly depend on dysfunction of Treg cells. Finally there are now potential therapies predicated on reconstitution of effective function of Treg cells.

GAD autoantibodies and epitope reactivities persist after diagnosis in latent autoimmune diabetes in adults but do not predict disease progression: UKPDS 77

AIMS/HYPOTHESIS

Latent autoimmune diabetes in adults (LADA) is a slowly progressive form of autoimmune diabetes, with autoantibodies to islet proteins developing in older patients who have no immediate requirement for insulin therapy. Markers of its clinical course are uncharacterised. The aim of this study was to determine whether persistence of, or changes in, GAD65 autoantibodies (GADAs) in the LADA patients who participated in the United Kingdom Prospective Diabetes Study (UKPDS) were associated with disease progression or insulin requirement.

METHODS

GADA levels and their relative epitope reactivities to N-terminal, middle and C-terminal regions of human GAD65 were determined in 242 UKPDS patients who were GADA-positive at diagnosis; samples taken after 0.5, 3 and 6 years of follow-up were tested using a radiobinding assay. Comparisons were made of GADA status with clinical details and disease progression assessed by the requirement for intensified glucose-lowering therapy.

RESULTS

GADA levels fluctuated between 0.5 and 6 years but persisted in 225 of 242 patients. No association of GADA levels with disease progression or insulin requirement was observed. Antibody reactivity was directed to C-terminal and middle epitopes of GAD65 in >70% patients, and the N-terminal in <9%. There were no changes in epitope reactivity pattern over the 6 year follow-up period, nor any association between epitope reactivity and insulin requirement.

CONCLUSIONS/INTERPRETATION

GADAs persist for 6 years after diagnosis of LADA, but levels and reactivity to different GAD65 epitopes are not associated with disease progression.