Multicenter prospective study of the humoral autoimmune response in bullous pemphigoid

Bullous pemphigoid (BP) is an autoimmune bullous disease, associated with autoantibodies directed against the hemidesmosomal components BP180 and BP230. In this study for the first time different laboratories have analyzed the autoantibody profile in the same group of 49 prospectively recruited BP patients. The results show that: 1) disease severity and activity correlated with levels of IgG against the BP180-NC16A domain, but also against a COOH-terminal epitope of BP180, 2) distinct epitopes of the BP180 ectodomain other than BP180-NC16A were recognized by 96% of the BP sera; and 3) the combined use of BP180 and BP230 ELISA led to the detection of IgG autoantibodies in all the BP sera. These results demonstrate the usefulness of the combined ELISAs based on various BP180 and BP230 fragments in establishing the diagnosis of BP and support the concept that BP180 is the major autoantigen of BP.     

IgE recognition of bullous pemphigoid (BP)180 and BP230 in BP patients and elderly individuals with pruritic dermatoses

Bullous pemphigoid (BP) is the most common autoimmune bullous disease of the elderly and is associated with IgG and IgE autoantibodies against the hemidesmosomal proteins, BP180 and BP230. The purpose of this study was to characterize the epitope specificity of IgE against defined regions of BP180 and BP230 in 32 BP patients and 21 elderly patients with pruritic disorders who did not yet fulfill all the criteria of BP by immunoblot (IB), ELISA and indirect immunofluorescence microscopy. Our findings show that IgE from BP sera preferentially targets the COOH-terminus of BP230 (IB: 16/32, ELISA: 12/32) and, to a lesser extent, the BP180-NC16A domain (IB: 11/32, ELISA: 9/32). Noteworthy, a subgroup of elderly patients with pruritic dermatoses also showed IgE recognition of BP180-NC16A (IB: 1/21, ELISA: 4/21) and less frequently of BP230 (IB: 2/21, ELISA: 2/21). Thus, IgE recognition of the BP autoantigens is presumably an early pathogenetic event in BP.     

IgE Antibodies in Sera from Patients with Bullous Pemphigoid Are Autoantibodies Preferentially Directed Against the 230-kDa Epidermal Antigen (BP230)

Bullous pemphigoid (BP) is unique among autoimmune skin diseases in which a high serum IgE level has been detected. We sought to determine the antigenic specificity of these IgE antibodies in 39 BP sera by immunofluorescence microscopy, immunoblot, and ELISA. The patient's sera contained IgG antibodies to 230-kDa (BP230) (n = 20), 180-kDa (BP180) (n = 9), and both BP230 and BP180 (n = 10) antigens. Serum IgE levels varied from 29 to 5000 kIU/L (mean ± SD, 856 ± 1426 kIU/L), among which sera containing IgG antibodies to BP230 had an IgE level on average 4.3 times higher than anti-BP180 sera. IgE antibodies in 18 sera were found to be autoantibodies reactive either with an epidermal component of basement membrane zone by immunofluorescence microscopy on 1 M NaCl-split skin or with a 230-kDa antigen by immunoblots of cultured human keratinocytes.⁷ The 230-kDa epidermal antigen recognized by IgE antibodies comigrated with the BP230 as labeled by a specific human monoclonal antibody. IgE anti-BP230 antibodies in patients' sera were always associated with IgG autoantibodies. No sera contained IgE antibodies to BP180 or to any other epidermal or dermal antigens as verified by immunoblot and ELISA. A good correlation was found between the presence of IgE circulating autoantibodies and the level of serum IgE (P < 0.004). IgE antibodies to BP230, like IgG autoantibodies, were mapped primarily to the C-terminal end of the protein, as they labeled rBP55, a BP230 recombinant protein encoded by a cDNA for the C-terminal end of BP230.     

Patients with bullous pemphigoid and linear IgA disease show a dual IgA and IgG autoimmune response to BP180

Bullous pemphigoid (BP) and linear IgA disease (LAD) are autoimmune subepidermal blistering skin diseases associated with autoantibodies against the transmembrane hemidesmosomal protein BP180/type XVII collagen. It has been demonstrated previously that BP is characterized predominantly by IgG autoantibodies, while autoantibodies in LAD mainly belong to the IgA isotype. The aim of the present study was to investigate the hypothesis that there is a significant overlap in the autoantibody isotype profiles associated with these two diseases. Several new recombinant forms of BP180 were generated in the baculovirus expression system, including the full-length protein. IgG autoantibodies to BP 180 were detectable in 39 of 40 (98%) of BP sera; interestingly, 88% of BP sera also contained IgA anti-BP180 autoantibodies. Similarly, anti-BP180 reactivity in LAD sera (n=22) was also attributed to both an IgA (68%) and an IgG (76%) autoantibody response. IgA and IgG autoantibodies to the intracellular portion of BP180 were found in 14% and 28% of BP sera, respectively, and in 8% of LAD sera (same percentage for both isotypes). Our findings clearly demonstrate that both BP and LAD patients have a dual IgA and IgG autoimmune response to BP180 which is directed not only to the ectodomain, but also to the intracellular portion of this protein.     

Anti-soluble liver antigen (SLA) antibodies in chronic HCV infection

Hepatitis C infection is associated with autoimmune disorders, such as the production of autoantibodies. Anti-LKM1 and anti-LC1, immunomarkers of type 2 autoimmune hepatitis, have been previously associated with a HCV infection. Anti-Soluble-Liver-Antigen autoantibodies (SLA) are specifically associated with type 1 and type 2 autoimmune hepatitis and more closely related to patients who relapse after steroid therapy. The recent molecular cloning of the soluble liver antigen provides the opportunity to develop more specific tests for the detection of antibodies against it. The aim of this work is to characterize anti-soluble-liver autoantibodies in sera from patients chronically infected by HCV. A recombinant cDNA from activated Jurkat cells coding for the full length tRNP(Ser)Sec/SLA antigen was obtained. ELISA, Western Blot and immunoprecipitation tests were developed and used to search for linear and conformational epitopes recognized by anti-SLA antibodies in sera from patients chronically infected by HCV. Anti-soluble liver antigen antibodies were found in sera from 10.4% of HCV-infected patients. The prevalence was significantly increased to 27% when anti-LKM1 was also present. Most anti-SLA reactivity was directed against conformational epitopes on the antigen. The means titers by ELISA were lower than those obtained in type 2 AIH. The result of autoantibody isotyping showed a subclass restriction to IgG1 and also IgG4. This study shows the presence of anti-SLA antibodies in approximately 10% of HCV infected patients. The prevalence of SLA autoantibodies in HCV infected patients increases when LKM1 autoantibodies are also present. The relationship between the prevalence of this characteristic autoimmune hepatitis autoantibody and the implication of an autoimmune phenomenon in the liver injury of patients chronically infected by HCV needs further investigation.     

Autoantibody detection in bullous pemphigoid: clinical evaluation of the EUROPLUS™ Dermatology Mosaic

Bullous pemphigoid (BP) is an autoimmune blistering skin disease. Autoantibodies to BP180 and BP230 can be detected by indirect immunofluorescence (IIF) on different substrates (oesophagus, salt-split-skin, BP180-antigen dots, BP230-transfected cells) and ELISA. Here, we compared test characteristics of these test systems. We analysed sera from BP patients (n=60) in whom the clinical diagnosis had been confirmed histopathologically. The control cohort comprised sera from patients with other autoimmune-associated (n=22) or inflammatory (n=35) skin diseases. All samples were tested by IIF (EUROIMMUN? Dermatology Mosaic) and ELISA (EUROIMMUN and MBL). Anti-BP180 is best detected with BP180-antigen dots by IIF (sensitivity: 88%; specificity: 97%). As compared to IIF, the differences with both BP180 ELISA techniques are small though. Likelihood ratios (LRs) for positive and negative test results are >10 and between 0.1 and 0.2, respectively, for all test systems. Detection of anti-BP230 is highly variable (sensitivity range 38-60%; specificity range 83-98%). Only the IIF test reveals a LR for positive test results >10. Since the LRs for a negative test are all ~0.5, negative test results for anti-BP230 antibodies do not help to exclude BP. In conclusion, the multi-parameter IIF test reveals a good diagnostic performance in BP. Since this test simultaneously allows for the detection of anti-Dsg1 and anti-Dsg3 antibodies, involved in pemphigus foliaceus and vulgaris, a single test-incubation may be sufficient to differentiate between the most frequent autoimmune blistering diseases.     

IgG antibodies against immunodominant C-terminal epitopes of BP230 do not induce skin blistering in mice

Bullous pemphigoid, the most common autoimmune blistering disease in Western Europe and the USA is characterized by the presence of circulating and tissue-bound autoantibodies against the hemidesmosomal proteins BP230 and BP180/collagen XVII. After binding to their target antigens at the basement membrane of the dermal–epidermal junction these autoantibodies are thought to trigger an inflammatory cascade comprising complement- and granulocyte-dependent reactions that result in tissue damage. Whereas the role of anti-BP180 antibodies has been extensively characterized, few and conflicting data is available on the contribution of anti-BP230 antibodies to bullous pemphigoid pathogenesis. Therefore, we addressed in the present study the role of autoantibodies to BP230 in experimental bullous pemphigoid. Rabbit polyclonal antibodies generated against epitopes of the C-terminal fragment of murine BP230 bound to the basement membrane and activated the complement system ex vivo. Affinity-purified antibodies were subsequently subcutaneously transferred into neonatal and adult BALB/c mice. In vivo, we observed a dose-dependent binding of transferred antibodies in the murine skin; however, there was no complement activation and these mice showed no clinical or histological signs of inflammatory disease, in contrast to mice receiving anti-BP180 antibodies. We further conducted ex vivo experiments and demonstrated that rabbit IgG anti-BP230-specific antibodies, in contrast to antibodies from bullous pemphigoid patients or rabbit IgG anti-BP180 antibodies used as positive controls, did not activate human granulocytes to induce dermal–epidermal separation in skin cryosections. Our present findings demonstrate that antibodies against BP230 are non-pathogenic in experimental models of bullous pemphigoid and suggest that proper activation of the complement and granulocytes represent prerequisites for conferring bullous pemphigoid autoantibodies their tissue destructive potential.     

Anti-Soluble Liver Antigen (SLA) Antibodies in Chronic HCV Infection

Hepatitis C infection is associated with autoimmune disorders, such as the production of autoantibodies. Anti-LKM1 and anti-LC1, immunomarkers of type 2 autoimmune hepatitis, have been previously associated with a HCV infection. Anti-Soluble-Liver-Antigen autoantibodies (SLA) are specifically associated with type 1 and type 2 autoimmune hepatitis and more closely related to patients who relapse after steroid therapy. The recent molecular cloning of the soluble liver antigen provides the opportunity to develop more specific tests for the detection of antibodies against it. The aim of this work is to characterize anti-soluble-liver autoantibodies in sera from patients chronically infected by HCV. A recombinant cDNA from activated Jurkat cells coding for the full length tRNP^(Ser)Sec/SLA antigen was obtained. ELISA, Western Blot and immunoprecipitation tests were developed and used to search for linear and conformational epitopes recognized by anti-SLA antibodies in sera from patients chronically infected by HCV. Anti-soluble liver antigen antibodies were found in sera from 10.4% of HCV-infected patients. The prevalence was significantly increased to 27% when anti-LKM1 was also present. Most anti-SLA reactivity was directed against conformational epitopes on the antigen. The means titers by ELISA were lower than those obtained in type 2 AIH. The result of autoantibody isotyping showed a subclass restriction to IgG1 and also IgG4. This study shows the presence of anti-SLA antibodies in approximately 10% of HCV infected patients. The prevalence of SLA autoantibodies in HCV infected patients increases when LKM1 autoantibodies are also present. The relationship between the prevalence of this characteristic autoimmune hepatitis autoantibody and the implication of an autoimmune phenomenon in the liver injury of patients chronically infected by HCV needs further investigation.     

Epidermal adhesion molecules and basement membrane components as target structures of autoimmunity

 Intraepidermal and dermal-epidermal cohesion are of paramount importance for the integrity of the skin. Some constituent molecules of keratinocyte adhesion complexes and basement membrane-associated structures are the targets of antibody-mediated autoimmune reactions that give rise to various (muco-)cutaneous blistering diseases. The current state of our knowledge about these molecules – along with the main clinical, histological, and immunohistochemical features of the corresponding autoimmune diseases and their pathogenetic mechanisms – comprise the subjects surveyed in this review. Among the desmosomal cadherins (desmogleins and desmocollins) that mediate epidermal cell–cell adhesion, it has been demonstrated that desmoglein 1 and desmoglein 3 are the autoantigens of pemphigus foliaceus and pemphigus vulgaris, respectively, both diseases that result in intraepidermal blistering. Further, desmocollin autoantibodies may be involved in IgA pemphigus. Paraneoplastic pemphigus is associated with autoantibodies directed against the desmosomal plaque protein, desmoplakin. Of the constituents of hemidesmosomes, the plaque protein, BP230 (BPAG1), and the collagen-like transmembrane protein, BP180 (BPAG2), are the autoantigens of bullous pemphigoid and pemphigoid gestationis, the manifestations of both of which include subepidermal blistering. Several diseases arise from autoimmune reactions against certain proteins associated with the basement membrane located beneath hemidesmosomes, for example laminin 5 (cicatricial pemphigoid), ladinin (LAD-1; linear IgA disease), uncein, and collagen VII (epidermolysis bullosa acquisita), the last of which is the constituent protein of the anchoring fibrils. Such recent advances in the elucidation of the molecular nature of autoantigens may serve as the basis for the development of novel molecule-based therapeutic strategies. Received: 12 September1997 / Accepted: 27 October 1997     

Oral pemphigoid autoantibodies preferentially target BP180 ectodomain

Mucous membrane pemphigoid (MMP) comprises a heterogenous group of autoimmune subepithelial bullous diseases very frequently having oral involvement. Very few studies have investigated the immunological status of a subset of MMP, termed oral pemphigoid (OP), presenting with exclusive oral lesions. In this study we show that 75% of 20 OP patients without scarring phenotype possessed circulating autoantibodies against the BP180 molecule, indicating a prominent role of this protein as a target antigen in OP. Of note, the frequency of reactivity against BP180 ectodomain epitopes in OP was similar to that previously reported for MMP with cicatricial phenotype, while the lack of significant recognition of BP180 intracellular domain appears to characterize OP with respect to other diseases of the pemphigoid group. Finally, the combined use of sensitive techniques allowed the detection of circulating autoantibodies in 90% of OP patients, supporting the usefulness of this approach in the diagnosis of MMP disease.     

The Pathophysiology of Bullous Pemphigoid

Bullous pemphigoid (BP) is a blistering skin disease characterized by an autoimmune response to 2 hemidesmosomal proteins within the dermal–epidermal junction, designated BP180 and BP230. While BP230 localizes intracellularly and associates with the hemidesmosomal plaque, BP180 is a transmembrane glycoprotein with an extracellular domain. Most BP patients have autoantibodies binding to an immunodominant region of BP180, the noncollagenous 16A domain (NC16A), which is located extracellularly close to the transmembrane domain of the protein. Autoreactive T and B cell responses to BP180 have been found in patients with BP. Passive transfer of antibodies to the murine BP180 ectodomain triggers a blistering skin disease in mice that closely mimics human BP. Lesion formation in this animal model depends upon complement activation, mast cell degranulation and accumulation of neutrophils and eosinophils. Patients’ autoantibodies to BP180 induce dermal–epidermal separation in cryosections of human skin when co-incubated with leukocytes. The loss of cell-matrix adhesion is mediated by proteinases released by granulocytes. The increased knowledge of the pathophysiology of BP should facilitate the development of novel therapeutic strategies for this disease.     

Autoantibody detection in type 2 autoimmune hepatitis using a chimera recombinant protein

Autoantibodies against cytochrome P450 2D6 (CYP2D6), known as anti-liver/kidney microsome type 1 (LKM1) and/or anti-human formiminotransferase cyclodeaminase, formally known as anti-liver cytosol type 1 (LC1) define type 2 autoimmune hepatitis (AIH). The aims of this work are to develop a sensitive and specific test to detect anti-LKM1 and/or anti-LC1 autoantibodies and to establish the prevalence of anti-LC1. Sera from children with type 2 AIH (n=48) and those from a control group (n=100) were evaluated for anti-LKM1 and anti-LC1 by Enzyme-Linked Immunosorbent Assay (ELISA) and Western blotting. Each serum sample was assayed for reactivity against formiminotransferase cyclodeaminase and CYP2D6 alone or as part of a recombinant chimera protein. By ELISA with recombinant chimera protein, 50 serum samples were positive, 48 from patients with type 2 AIH and 2 from patients with chronic hepatitis C. Twenty-five of 48 (52%) patients studied were positive for both CYP2D6 and LC1 autoantibodies. Anti-LC1, either as the only marker or associated with anti-LKM1, was positive in 34/48 (71%). By Western blotting, anti-LC1 was found in 27/48 (56%) patients. This ELISA technique has proven to be antigen-specific and more sensitive than Western blot for the detection of anti-LC1 and anti-LKM1 autoantibodies. The prevalence of anti-LC1 (71%) confirms it as an important immunomarker in type 2 AIH.     

IgE-mediated mechanisms in bullous pemphigoid and other autoimmune bullous diseases

Autoimmune bullous diseases (AIBDs) are characterized by autoantibodies against structural proteins of the dermal–epidermal junction (in pemphigoid diseases) and the epidermal/ epithelial desmosomes (in pemphigus diseases). By far, the most common AIBD is bullous pemphigoid, which is immunopathologically characterized by autoantibodies against BP180 (type XVII collagen) and BP230. IgG and, to a lesser extent, IgA autoantibodies are the major autoantibody isotypes in these disorders. IgE autoantibodies are increasingly reported in particular in bullous pemphigoid. The development of specific and sensitive anti-BP180 IgE ELISA systems, the report of two experimental murine models employing IgE autoantibodies against BP180, and the successful treatment of bullous pemphigoid with the anti-IgE antibody omalizumab have raised interest in the role of IgE autoantibodies and the modulation of their production in AIBDs. Here, the relevance of IgE autoantibodies in the diagnosis, pathophysiology, and treatment decisions of AIBDs, with a focus on bullous pemphigoid, is reviewed.     

Granulocyte-derived elastase and gelatinase B are required for dermal-epidermal separation induced by autoantibodies from patients with epidermolysis bullosa acquisita and bullous pemphigoid

Epidermolysis bullosa acquisita (EBA) and bullous pemphigoid (BP) are two clinically and immunologically distinct autoimmune subepidermal blistering skin diseases associated with IgG autoantibodies against the dermal-epidermal junction. BP antibodies are directed against the hemidesmosomal antigens BP180 and BP230, and those in patients with EBA target type VII collagen, a major component of anchoring fibrils. While the pathogenetic mechanisms of subepidermal blistering in BP have been previously studied using a passive transfer mouse model, the effector pathways of blister formation in EBA are largely unknown. Autoantibodies to type VII collagen and BP180 have recently been shown to induce leucocyte-mediated subepidermal cleavage in cryosections of human skin. The aim of the present study was to identify human leucocyte protease(s) instrumental in dermal-epidermal separation induced by autoantibodies to type VII collagen and BP180. When incubated with cryosections of human skin pretreated with IgG from patients with EBA or BP but not from patients with anti-laminin 5 mucous membrane pemphigoid or healthy controls, granulocytes were recruited to the dermal-epidermal junction and induced subepidermal splits. A combination of broad-range protease inhibitors as well as inhibitors of serine and matrix metalloproteases completely abolished dermal-epidermal separation induced by EBA or BP autoantibodies. When characterizing the proteases involved more specifically, selective inhibition of human leucocyte elastase or gelatinase B/MMP-9 was also found to result in suppression of blistering. These findings strongly suggest that elastase and gelatinase B are essential for granulocyte-mediated proteolysis resulting in dermal-epidermal separation in EBA and BP patients' skin.     

Biological predictors shared by dementia and bullous pemphigoid patients point out a cross-antigenicity between BP180/BP230 brain and skin isoforms

Bullous pemphigoid (BP) following dementia diagnosis has been reported in the elderly. Skin and brain tissues express BP180 and BP230 isoforms. Dementia has been associated with rs6265 (Val66Met) polymorphism of the brain-derived neurotrophic factor (BDNF) gene and low serum BDNF. Here we investigated a possible cross-antigenicity between BP180/BP230 brain and skin isoforms. We assessed antibodies against BP180/BP230 and BDNF levels by ELISA and BDNF Val66Met SNP by PCR in three groups: 50 BP patients, 50 patients with dementia, and 50 elderly controls. Heatmap hierarchical clustering and data mining decision tree were used to analyze the patients’ demographic and laboratorial data as predictors of dementia-BP association. Sixteen percent of BP patients with the lowest serological BDNF presented dementia-BP clinical association. Anti-BP180/230 positivity was unexpected observed among dementia patients (10%, 10%) and controls (14%, 1%). Indirect immunofluorescence using healthy human skin showed a BP pattern in two of 10 samples containing antibodies against BP180/BP230 obtained from dementia group but not in the control samples. Neither allelic nor genotypic BDNF Val66Met SNP was associated with dementia or with BP (associated or not with clinical manifestation of dementia). Heatmap analysis was able to differentiate the three studied groups and confirmed the ELISA results. The comprehensive data mining analysis revealed that BP patients and dementia patients shared biological predictors that justified the dementia-BP association. Autoantibodies against the BP180/BP230 brain isoforms produced by dementia patients could cross-react with the BP180/BP230 skin isoforms, which could justify cases of dementia preceding the BP disease.     

Autoimmune responses in patients with linear IgA bullous dermatosis: both autoantibodies and T lymphocytes recognize the NC16A domain of the BP180 molecule

Linear IgA bullous disease (LABD) is an autoimmune skin disease characterized by subepidermal blisters and IgA autoantibodies directed against the epidermal basement membrane zone (BMZ) of the skin. Various antigens have been identified as targets of IgA autoantibodies including BP180, a type II glycoprotein that spans the BMZ and lamina lucida. Previously, we have identified a subset of LABD patients whose sera contained IgA antibodies against the 16th noncollagenous (NC16A) domain of BP180. NC16A was previously shown to harbor epitopes that are recognized by both autoantibodies and T cells from patients with bullous pemphigoid and herpes gestationis and is thought to be associated with the development of these immunobullous diseases. The aim of this study was to determine whether T lymphocytes from LABD patients with anti-NC16A IgA autoantibodies respond to epitopes in the same region of the BP180 protein. Indeed, of the four LABD patients in our study, all had T cells that specifically proliferated in response to NC16A. Moreover, two subfragments of NC16A were identified as the predominant targets of LABD T cells. Further analysis of T cell lines and clones derived from these patients revealed that these cells express a CD4 memory T cell phenotype and secrete a Th1/Th2 mixed-cytokine profile, characteristics similar to those of T cells in bullous pemphigoid patients. Our data suggest that the BP180 protein, typically the NC16A region, is the common target of both cellular and humoral immune responses in some LABD patients. This information helps to further elucidate the autoimmune mechanisms in this disease.     

Detection of anti-PL-12 autoantibodies by ELISA using a recombinant antigen; study of the immunoreactive region

Autoantibodies to aminoacyl-tRNA synthetases are highly associated with myositis and detection is important in clinical diagnosis; however, current methods of screening limit its clinical utility. In the present study, alanyl-tRNA synthetase (PL-12) recombinant protein was obtained by immunological screening of a HeLa expression library and used in an ELISA with 22 anti-PL-12 sera, 200 autoimmune sera negative for PL-12 and 100 healthy individual sera. Sensitivity of the method was 95% (21/22) and specificity 100%. Mapping of the immunoreactive region was carried out using three anti-PL-12 sera and different recombinant protein-derived peptides. Results show that the same conformational epitope located within amino acids 730–951 of the PL-12 antigen outside the catalytic region was recognized by the three anti-PL-12 sera tested. We conclude that ELISA using recombinant protein is an effective and useful method for routine screening for anti-PL-12 autoantibodies.     

Cortactin autoantibodies in myasthenia gravis

Myasthenia gravis (MG) is an autoimmune disease characterized by muscle weakness, fatigability, and autoantibodies against protein antigens of the muscle endplate. Antibodies against acetylcholine receptor (AChR), and less frequently against muscle-Specific Kinase (MuSK) or lipoprotein related protein 4 (LRP4) occur in patients with seropositive MG (SPMG). However, about 10% of patients do not have detectable autoantibodies despite evidence suggesting that the disorder is immune mediated; this disorder is known as seronegative MG (SNMG). Using a protein array approach we identified cortactin (a protein that acts downstream from agrin/MuSK promoting AChR clustering) as potential new target antigen in SNMG. We set up an ELISA assay and screened sera from patients with SPMG, SNMG, other autoimmune diseases and controls. Results were validated by immunoblot. We found that 19.7% of patients with SNMG had antibodies against cortactin whereas only 4.8% of patients with SPMG were positive. Cortactin antibodies were also found in 12.5% of patients with other autoimmune disorders but only in 5.2% of healthy controls. We conclude that the finding of cortactin antibodies in patients with SNMG, suggests an underlying autoimmune mechanism, supporting the use of immune therapy.     

IgG4 autoantibodies are inhibitory in the autoimmune disease bullous pemphigoid

The IgG4 subclass of antibodies exhibits unique characteristics that suggest it may function in an immunoregulatory capacity. The inhibitory function of IgG4 has been well documented in allergic disease by the demonstration of IgG4 blocking antibodies, but similar functions have not been explored in autoimmune disease. Bullous pemphigoid (BP) is a subepidermal autoimmune blistering disease characterized by autoantibodies directed against BP180 and an inflammatory infiltrate including eosinophils and neutrophils. Animal models have revealed that the NC16A region within BP180 harbors the critical epitopes necessary for autoantibody mediated disease induction. BP180 NC16A-specific IgG belong to the IgG1, IgG3, and IgG4 subclasses. The purpose of this study was to determine effector functions of different IgG subclasses of NC16A-specific autoantibodies in BP. We find that IgG4 anti-NC16A autoantibodies inhibit the binding of IgG1 and IgG3 autoantibodies to the NC16A region. Moreover, IgG4 anti-NC16A blocks IgG1 and IgG3 induced complement fixation, neutrophil infiltration, and blister formation clinically and histologically in a dose-dependent manner following passive transfer to humanized BP180-NC16A mice. These findings highlight the inhibitory role of IgG4 in autoimmune disease and have important implications for the treatment of BP as well as other antibody mediated inflammatory and autoimmune diseases.     

Differential diagnosis of hepatitis: development of new laboratory tests for autoimmune hepatitis and progress in pathophysiology

Liver dysfunction has been found in 8.1% of postpartum women in the general population. This dysfunction was speculated to be developed by postpartum aggravation of subclinical autoimmune hepatitis. Therefore, we developed two methods for detection of autoantibodies to liver-specific antigens: an ELISA for anti-liver-specific arginase antibodies, and a highly sensitive radioligand assay for anti-CYP2D6 antibodies. Basic examinations of dilution curve, inhibition study and reproducibility were satisfactory for clinical application in both assays. Anti-arginase antibodies and anti-CYP2D6 antibodies were found in 28.6% and 42.6% of patients with autoimmune hepatitis, respectively. There was no correlation between the two autoantibodies and thus, combined use of these antibodies detects 55.3% of autoimmune hepatitis. Autoimmune hepatitis exists frequently when we include mild cases.