Senga Whittingham

The peculiar autoimmunity of primary biliary cirrhosis.

Summary: Autoantibodies to mitochondria (AMA, anti‐M2) are a serologic hallmark of primary biliary cirrhosis (PBC). These react with three structurally and functionally related multienzymic complexes, the 2‐oxoacid dehydrogenase complexes, but chiefly with the E2 subunit of pyruvate dehydrogenase complex (PDC‐E2). Their very close (95%) and specific association with PBC underpins the autoimmune concept of pathogenesis of that disease, notwithstanding several non‐congruent features. Detailed studies, including structural analysis of epitopes, do not disclose how these autoantibodies originate. Their ubiquity in PBC has overshadowed the existence of a second set of relatively PBC‐specific autoantibodies to nuclear antigens for which reactants have been cloned and characterized. These include centromeric proteins; proteins of the nuclear pore complex; nuclear dot proteins, which include Sp‐100 and the promyelocytic leukemia antigen; and a recently identified autoantigen, SOX13. Certain of these reactants are DNA‐binding proteins with transcriptional regulatory activity. Thus serum from individuals with the same clinical syndrome can have autoimmune reactivity to disparate mitochondrial and nuclear constituents in different cellular compartments. Antibody probing of phage displayed random peptide libraries, together with epitope scanning using overlapping sequential octameric peptides from the PDC‐E2 sequence, showed that the discontinuous motifs MH, FV(E) and SYP contributed to a predicted conformational antibody epitope in the inner lipoyl domain of PDC‐E2.

An arthritogenic monoclonal antibody to type II collagen, CII-C1, impairs cartilage formation by cultured chondrocytes.

Antibodies to type II collagen (CII) cause articular damage in collagen‐induced arthritis (CIA) in mice as judged by passive transfer to naive animals of mAb to CII. We tested the hypothesis that mAb degrade cartilage structure by reacting with functionally important regions of the collagen molecule by examining the effects of an arthritogenic mAb to CII, CII‐C1, on cultured bovine chondrocytes at high density, at days 7 and 14. The effects were compared of CII‐C1, an isotype‐matched control mAb, or medium alone, on chondrocyte proliferation and viability, cell morphology, matrix structure by light and electron microscopy, and matrix synthesis by metabolic labelling with 3H‐proline for collagen or 35SO4 for proteoglycans. Chondrocytes in culture remained viable, proliferated, and produced an extracellular matrix in which CII was the major collagen. The addition of CII‐C1, but not a control mAb, increased the synthesis of CII and proteoglycan, and caused disorganization of the extracellular matrix and thin collagen fibrils ultrastructurally. Moreover, using a cell‐free assay, CII‐C1 inhibited the normal self‐assembly of collagen fibrils from CII in solution. The finding that the mAb to CII, CII‐C1 has striking degradative effects in vitro on cartilage synthesis suggests that antibodies to collagen perpetuate the chronic phase of CIA and that, in mice at least, such antibodies are an important component of pathogenesis.

A tribute to an outstanding immunologist – Ian Reay Mackay

The 11th Australasian Autoimmunity Workshop was held in Melbourne, Australia from July 6-8, 2007 organized by the Monash University Autoimmunity Network. The workshops, founded by the late Kevin Lafferty, are a chance for Australasians interested in research into autoimmune disease to present and discuss their work. This workshop also was a chance to acknowledge Ian Mackay, a pioneer clinician-scientist who has made major contributions to our understanding of autoimmune diseases. Friends, colleagues and former students attended the Workshop and acknowledged Ians expertise and mentorship. This edition of the Journal of Autoimmunity pays tribute to Ian Mackay. It features articles from attendees at the workshop, and contributions from some of Ians past students and past and current collaborators.

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 α and β 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 dénouement 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.

Autoantibodies associated with presymptomatic insulin‐dependent diabetes mellitus in women

Presymptomatic autoantibody markers of insulin‐dependent (Type 1) diabetes mellitus (IDDM) are less well characterized in adults than in children. We quantitated anti‐GAD, anti‐ICA512 and ICA by titration to endpoint and compared frequencies and levels in 139 Finnish women from whom 390 serum samples had been archived during antecedent pregnancies for 10 years before and up to 1 year after diagnosis of diabetes. Also, we compared the autoantibody status in adults with IDDM with that of children with newly diagnosed IDDM. Of the 35 women seropositive for 1 or more autoantibodies, 77u2009% developed IDDM, 11u2009% non‐insulin‐dependent (Type 2) diabetes mellitus (NIDDM), 9u2009% gestational diabetes mellitus requiring insulin (GDM‐ins) and 3u2009% GDM controlled by diet. The frequency of antibodies during the 10‐year presymptomatic period was 83u2009% for anti‐glutamic acid decarboxylase (GAD), 52u2009% for anti‐ICA512 and 41u2009% for islet cell antibodies (ICA) for those who developed IDDM, 25u2009%, 17u2009%, and 0u2009% for NIDDM, 12u2009%, 4u2009%, and 8u2009% for GDM‐ins and 1u2009%, 0u2009%, and 1u2009% for GDM‐diet. Anti‐GAD was found most consistently in early samples; 13 of 15 with a single autoantibody at their first test had anti‐GAD. Among those who developed IDDM, the frequency of anti‐GAD was constant, anti‐ICA512 increased threefold, and ICA increased slightly before diagnosis. Levels of the autoantibodies varied between subjects, but were relatively stable in individual subjects. Comparison of tests on the women, and children after diagnosis of IDDM, showed the frequencies and levels to be the same for anti‐GAD but lower for anti‐ICA512 and ICA in adults.

Autoimmune cholangitis syndrome with a bias towards primary biliary cirrhosis

&NA; The apparent coexistence of primary biliary cirrhosis (PBC) and autoimmune hepatitis in the same patient raises unresolved problems for nosology and therapy. These are exemplified by a 45‐year‐old Japanese woman with overlapping clinical, serological and histological features of autoimmune cholangitis and autoimmune hepatitis. The classical serological test for PBC, antimitochondrial antibody (AMA) by immunofluorescence, was atypical. By immunoblotting there was reactivity with one of the enzymes of the 2‐oxo‐acid dehydrogenase complex (2‐OADC) family, now recognized as autoantigens responsible for AMA reactivity. Also there was reactivity by immunofluorescence for antinuclear antibodies (ANA), one showing the typical speckled pattern of anti‐Sp‐100 and the other the peripheral pattern of antinuclear membrane antibody, both with titres > 106. There was also a positive result to the lupus erythematosus (LE) cell test. Treatment with ursodeoxycholic acid was beneficial. Thus while the clinical presentation suggested the overlapping syndrome of autoimmune hepatitis and PBC, PBC eventually proved to be the likely diagnosis. We suggest that apparent cases of overlapping PBC‐autoimmune cholangitis‐hepatitis syndromes, after detailed testing, will mostly align with PBC.

Autoantibodies to M2 mitochondrial autoantigens in normal human sera by immunofluorescence and novel assays

Primary biliary cirrhosis (PBC) is characterized by the presence of antimitochondrial antibodies (anti‐M2), directed against the E2 subunits of the 2‐oxo‐acid dehydrogenase complexes (2‐OADC), chiefly pyruvate dehydrogenase complex (PDC‐E2). We present here a detailed study, based on a large panel of normal sera, of the specificity of tests for anti‐M2 by immunofluorescence and for anti‐PDC by other assays for the diagnosis of PBC. The assays for anti‐PDC included immunoblotting with bovine heart mitochondria, ELISA using recombinant PDC‐E2 and an enzyme inhibition assay using purified porcine PDC. The positivity rates for normal sera were 0 (0/170), 2 (4/201), 1.5 (3/198) and 0% (0/186) for immunofluorescence, immunoblotting, ELISA and the enzyme inhibition assay, respectively. The seven positive reactions detected either by immunoblotting (n= 4) or ELISA (n= 3) were negative by the other three assays and in no instance did biochemical indices give any indication of chronic liver disease. Thus, as judged by reactivity with normal sera, the specificity of a positive test for the antibody to the major M2 autoantigen (PDC‐E2) is 100% for immunofluorescence and the enzyme inhibition assay, 98% for immunoblotting and 98.5% for ELISA.

Type II collagen–specific antibodies induce cartilage damage in mice independent of inflammation

OBJECTIVEnMurine collagen antibody-induced arthritis (CAIA), like collagen-induced arthritis, has clinical and immunopathologic features that parallel those in human rheumatoid arthritis (RA). This study was undertaken to examine the effects of autoantibodies to type II collagen (CII) on articular cartilage in the paws of mice, under conditions in which other factors that may influence joint pathology could be excluded.nnnMETHODSnMice of 2 different strains, B10.QC5δ and the parental strain B10.Q, were injected intravenously with either saline or arthritogenic monoclonal antibodies (mAb) to CII. B10.QC5δ mice lack complement factor C5 and do not develop CAIA when injected with arthritogenic mAb, whereas B10.Q mice have C5 and develop CAIA when administered the mAb and a subsequent injection of lipopolysaccharide. Three days after injection the paws of the mice were examined by standard histologic methods to assess morphologic appearance and proteoglycan loss, and by synchrotron-enhanced Fourier transform infrared microspectroscopy to assess chemical evidence of structural change.nnnRESULTSnNo macroscopic or microscopic signs of inflammation were evident in the mice. However, in contrast to the saline-injected controls, all mAb-injected mice exhibited cartilage damage in all joints, with loss of proteoglycans and collagen, chondrocyte hyperplasia and/or loss, and surface damage in the interphalangeal joints.nnnCONCLUSIONnThe implication of these findings is that an autoimmune response to CII can disrupt articular cartilage, particularly that of the small joints, and the subsequent integrity of the cartilage depends on a balance between breakdown and repair. This has relevance with regard to RA, in which such autoantibodies occur but the inflammatory response may dominate clinically and mask underlying features of the autoimmune response.

Smooth Muscle Autoantibodies

Publisher Summary nThis chapter discusses the pathogenetic role, methods of detection, and clinical use of smooth muscle autoantibodies (SMA). These autoantibodies were first observed by immunofluorescence on unfixed sections of rat stomach in the sera of patients with chronic active hepatitis. SMA is the standard diagnostic marker of autoimmune hepatitis, the classical expression of which includes an insidious onset of lethargy, malaise, loss of appetite, arthralgiamyalgia, amenorrhea, signs of hepatosplenomegaly, jaundice, and an acneiform skin rash. Immunofluorescence on monolayers of acetone-fixed fibroblasts, whereby “stress” fibers are stained as actin cables show that SMA has specificity for F-actin.

Gastritis and Pernicious Anemia

Publisher Summary Autoimmune gastritis is an asymptomatic and innocuous autoimmune disease. Pernicious anemia and gastric atrophy are terminal events in a protracted chronic autoimmune gastritis that affects the fundus and body of the stomach. The vitamin B12 deficiency and ensuing megaloblastic anemia are the result of gastric parietal cell loss with failure of production of intrinsic factor, an obligatory factor for absorption of the vitamin from the terminal ileum. Autoimmune gastritis fulfills the criteria for an organ-specific autoimmune disease: autoantibodies to gastric antigens, infiltration of mononuclear cells into the target organ with evidence of destruction, a regenerative response of the affected tissue to corticosteroid drugs, familial predisposition, and association with other autoimmune diseases, mostly the autoimmune endocrinopathies. The molecular target of parietal cell autoantibodies is the gastric H+/K+ ATPase located on secretory membranes of gastric parietal cells and autoantibodies to gastric intrinsic factor. The chapter also discusses animal models that have provided insights into the pathogenesis of autoimmune gastritis.