Maria G. Mytilinaiou

Twin studies in autoimmune disease: Genetics, gender and environment

Twin studies are powerful tools to discriminate whether a complex disease is due to genetic or environmental factors. High concordance rates among monozygotic (MZ) twins support genetic factors being predominantly involved, whilst low rates are suggestive of environmental factors. Twin studies have often been utilised in the study of systemic and organ specific autoimmune diseases. As an example, type I diabetes mellitus has been investigated to establish that that disease is largely affected by genetic factors, compared to rheumatoid arthritis or scleroderma, which have a weaker genetic association. However, large twin studies are scarce or virtually non-existent in other autoimmune diseases which have been limited to few sets of twins and individual case reports. In addition to the study of the genetic and environmental contributions to disease, it is likely that twin studies will also provide data in regards to the clinical course of disease, as well as risk for development in related individuals. More importantly, genome-wide association studies have thus far reported genomic variants that only account for a minority of autoimmunity cases, and cannot explain disease discordance in MZ twins. Future research is therefore encouraged not only in the analysis of twins with autoimmune disease, but also in regards to epigenetic factors or rare variants that may be discovered with next-generation sequencing. This review will examine the literature surrounding twin studies in autoimmune disease including discussions of genetics and gender.

New ELISA for Detecting Primary Biliary Cirrhosis–Specific Antimitochondrial Antibodies

BACKGROUND Antimitochondrial antibodies specific for primary biliary cirrhosis (PBC) target the E2 subunits of 2-oxo acid dehydrogenase complexes, in particular the pyruvate dehydrogenase complex (PDC)-E2. Their antigen-specific detection relies on conventional ELISA using purified PDC. More recent assays have employed a hybrid containing the 3 E2-subunits (MIT3). Some PBC sera react with one or the other preparation, suggesting the presence of nonoverlapping epitopes. METHODS We have developed an ELISA (anti-M2-3E) using a mixture of purified PDC and MIT3 as antigenic targets. We compared this assay to anti-MIT3 alone, conventional anti-PDC, and indirect immunofluorescence using 173 PBC and 247 disease controls. RESULTS The anti-M2-3E ELISA showed a 93.6% diagnostic sensitivity compared with 91.3%, 83.8%, and 87.3% for MIT3, purified PDC, or indirect immunofluorescence, respectively, when all specificities are set to 98.8%. By immunoblotting, anti-M2-3E-positive sera unreactive to purified PDC recognized recombinant E2-subunits of the other 2 complexes, whereas those with no reactivity to MIT3 immunofixed PDC subunits E1alpha or E1beta. CONCLUSIONS The diagnostic accuracy of the anti-M2-3E ELISA for detection of antibodies to 2-oxo acid dehydrogenase complexes exceeds that of conventional ELISA and IFL; its novelty derives from the combination of the MIT3 hybrid and purified PDC.

Asialoglycoprotein receptor (ASGPR) as target autoantigen in liver autoimmunity: lost and found.

Asialoglycoprotein receptor (ASGPR) has attracted the attention of liver immunologists for many years. This liver-specific lectin was found to be a major B and T cell autoantigenic target in patients with autoimmune liver diseases, and in particular in autoimmune hepatitis (AIH). This review discusses the biological significance of ASGPR and its relevance to the pathogenesis of autoimmune and virus-triggered liver diseases. We also discuss emerging data on the diagnostic and clinical relevance of anti-ASGPR antibodies in light of recent reports based on commercially available anti-ASGPR enzyme-linked immunosorbent assays. Finally, we critically revisit the data reporting on disease-specific cellular immune responses against ASGPR and their relevance in relation to the pathogenesis of AIH.

Helicobacter pylori and autoimmune disease: Cause or bystander

Helicobacter pylori (H. pylori) is the main cause of chronic gastritis and a major risk factor for gastric cancer. This pathogen has also been considered a potential trigger of gastric autoimmunity, and in particular of autoimmune gastritis. However, a considerable number of reports have attempted to link H. pylori infection with the development of extra-gastrointestinal autoimmune disorders, affecting organs not immediately relevant to the stomach. This review discusses the current evidence in support or against the role of H. pylori as a potential trigger of autoimmune rheumatic and skin diseases, as well as organ specific autoimmune diseases. We discuss epidemiological, serological, immunological and experimental evidence associating this pathogen with autoimmune diseases. Although over one hundred autoimmune diseases have been investigated in relation to H. pylori, we discuss a select number of papers with a larger literature base, and include Sjögrens syndrome, rheumatoid arthritis, systemic lupus erythematosus, vasculitides, autoimmune skin conditions, idiopathic thrombocytopenic purpura, autoimmune thyroid disease, multiple sclerosis, neuromyelitis optica and autoimmune liver diseases. Specific mention is given to those studies reporting an association of anti-H. pylori antibodies with the presence of autoimmune disease-specific clinical parameters, as well as those failing to find such associations. We also provide helpful hints for future research.

Antimitochondrial antibodies of immunoglobulin G3 subclass are associated with a more severe disease course in primary biliary cirrhosis

Background/Aims: Primary biliary cirrhosis (PBC) is characterised by the presence of immunoglobulin (Ig) G antimitochondrial antibodies (AMA), which are routinely detected by indirect immunofluorescence (IFL) using composite rodent tissue substrate. The IgG subclass distribution and clinical significance of IFL‐detected AMA in patients with PBC have not been previously studied in detail.

Ileal Inflammation May Trigger the Development of GP2-Specific Pancreatic Autoantibodies in Patients with Crohn’s Disease

Why zymogen glycoprotein 2 (GP2), the Crohns disease (CD)-specific pancreatic autoantigen, is the major target of humoral autoimmunity in inflammatory bowel diseases (IBD) is uknown. Recent evidence demonstrates that GP2 is also present on the apical surface of microfold (M) intestinal cells. As the colon lacks GP2-rich M cells, we assumed that patients with colonic CD are seronegative for anti-GP2. Anti-GP2 antibodies were tested in 225 CDs, including 45 patients with colonic location (L2), 45 with terminal ileum (L1) and 135 with ileocolonic involvement; 225 patients with ulcerative colitis (UC) were also tested. Anti-GP2 reactivity was detected in 59 (26.2%) CDs and 15 (6.7%) UCs (P < 0.001). Only 5 CDs with L2 had anti-GP2 antibodies, compared to 54/180 (30.0%, P = 0.0128) of the CDs with L1 and L3. Anti-GP2 antibody positive CD patients had higher ASCA titres compared to seronegative cases. Amongst the 128 CD patients with previous surgical intervention, 45 (35.0%) were anti-GP2 antibody positive compared to 14/97 (14.0%) without surgical (P < 0.001). Our data support the assumption that ileal inflammation is required for the development of anti-GP2 antibodies in CD, and suggest that the intestine rather than the pancreatic juice is the antigenic source required for the initiation of anti-GP2 antibodies.

Diagnostic and clinical utility of antibodies against the nuclear body promyelocytic leukaemia and Sp100 antigens in patients with primary biliary cirrhosis.

BACKGROUND The lack of an immunoassay that detects antibodies to promyelocytic leukaemia (PML) protein, the primary biliary cirrhosis (PBC)-specific multiple nuclear dot (MND) antigen, has prompted us to develop a line immunoassay (LIA) for the simultaneous detection of PML and Sp100 MND-specific autoantibodies. METHODS PML and Sp100 were expressed in Escherichia coli, and analysed by SDS-PAGE and immunoblotting using a monoclonal antibody and MALDI-ToF fingerprinting. A quantitative PML and Sp100 LIA were developed and testing was performed in 150 anti-mitochondrial antibody (AMA) positive, 20 AMA-PBCs and 130 controls. RESULTS Thirty-five (23%) of 150 AMA+ PBCs (18 anti-MND+) were anti-PML+ (12%) or anti-Sp100+ (20%), 10 being anti-PML+/Sp100+, 5 single anti-PML+ and 20 single anti-Sp100+. Six (30%, 5 anti-MND+) AMA-PBCs were anti-PML+ or Sp100+. Only 2 (1.7%) pathological controls were anti-PML+ and/or anti-Sp100+. Levels of anti-PML correlated with those of anti-Sp100 (R=0.64, p<0.0001). The autoantibody profile largely remained unchanged over a 10year-follow up (52 patients, 352 samples). Anti-PML, Sp100 or MND-reactive PBCs were younger and had longer disease duration than the seronegative (p=0.06, for both). Anti-Sp100 levels correlated with the Mayo risk score (r=0.63, p=0.01). Anti-PML+/Sp100+ patients had more advanced disease compared to patients negative for anti-PML/Sp100 (p=0.04). CONCLUSION The new line immunoassay offers a robust and accurate method for the detection of clinically-relevant PBC-specific anti-MND antibodies.

Primary Biliary Cirrhosis Associated with Systemic Sclerosis: Diagnostic and Clinical Challenges

Patients with primary biliary cirrhosis (PBC) often have concurrent limited systemic sclerosis (SSc). Conversely, up to one-fourth of SSc patients are positive for PBC-specific antimitochondrial antibodies (AMA). The mechanisms responsible for the co-occurrence of these diseases are largely unknown. Genetic, epigenetic, environmental, and infectious factors appear to be important for the pathogenesis of the disease, but the hierarchy of events are not well defined. Patients with SSc and PBC have an increased morbidity and mortality compared with the general population, but whether the presence of both diseases in an affected individual worsens the prognosis and/or outcome of either disease is not clear. Some case reports suggested that the presence of SSc in PBC patents is associated with a more favorable prognosis of the liver disease, whereas others report an increased mortality in patients with PBC and SSc compared to patients with PBC alone. This paper discusses the features of patients with PBC-associated SSc. Our aims are to clarify some of the pathogenetic, diagnostic, and clinical challenges that are currently faced in the routine management of these patients. We also intend to provide some practical hints for practitioners that will assist in the early identification of patients with PBC-associated SSc.

Anti-Helicobacter pylori antibody responses specific for VacA do not trigger primary biliary cirrhosis-specific antimitochondrial antibodies

Andreas Koutsoumpas, Maria Mytilinaiou, Dimitrios Polymeros, George N. Dalekos and Dimitrios Petrou Bogdanos, Liver Immunopathology, Institute of Liver Studies, King’s College London School of Medicine, King’s College Hospital, London, UK, 2nd Department of Medicine, Hepatogastroenterology Unit, Attikon University General Hospital, Athens, Department of Medicine, Academic Liver Unit and Research Laboratory of Internal Medicine, Medical School, University of Thessaly and Research Group of Investigational Medicine, Institute of Biomedical Research and Technology, Centre for Research and Technology – Thessaly (CE.RE.TE.TH), Larissa, Greece

Asialoglycoprotein receptor (ASGPR): a peculiar target of liver-specific autoimmunity

Asialoglycoprotein receptor (ASGPR) autoantibodies have been considered specific markers of autoimmune hepatitis (AIH). The exact mechanisms responsible for the development of these autoantibodies and leading to autoimmunity to this peculiar liver receptor remain elusive. Furthermore, loss of T cell tolerance to ASGPR has been demonstrated in patients with AIH, but it is poorly understood whether such liver-specific T cell responses bear a pathogenic potential and/or participate in the precipitation of AIH. Newly developed enzyme-linked immunosorbent assays have led to the investigation of the sensitivity and specificity of anti-ASGPR antibodies for AIH. The present review provides an overview of the diagnostic and clinical relevance of anti-ASGPR antibodies. A thorough investigation of the autoreactivity against ASGPR may assist efforts to understand liver autoimmunity in susceptible individuals.