Desmoglein-1 is a minor autoantigen in dogs with pemphigus foliaceus

The majority of human patients with pemphigus foliaceus (PF) have circulating IgG autoantibodies that target conformational epitopes on the desmosomal cadherin desmoglein-1 (dsg1). Limited studies using immunoblot techniques suggested that the principal autoantigen in dogs with PF might also be dsg1. It was the objective of this study to test this hypothesis. A comprehensive survey of canine PF sera was conducted using a novel screening strategy that detects conformational epitopes. This method consists of the ectopic expression of canine dsg1 at the surface of human 293T epithelial kidney cells and their live screening, i.e. prior to fixation. Out of seven control human PF sera that bound to canine epidermis, three (57%) contained IgG autoantibodies that recognized ectopically expressed canine dsg1 with a membrane and punctate pattern. Out of 83 canine PF sera only five (6%) contained IgG that recognized canine dsg1. Consistent with findings for human PF sera obtained in this study, autoantibody binding was conformation- and glycosylation-dependent as demonstrated by calcium chelation with EDTA and tunicamycin or wheat germ agglutinin treatment, respectively. In conclusion, these studies establish canine dsg1 as a minor autoantigen for canine PF. Antigenic epitopes appear to be conformation- and glycosylation-dependent.

Treatment of thrombotic thrombocytopenic purpura

Thrombotic thrombocytopenic purpura (TTP), characterized by thrombocytopenia and microangiopathic haemolytic anaemia, was almost universally fatal until the introduction of plasma exchange (PE) therapy in the 1970s. Based on clinical studies, daily PE has become the first-choice therapy since 1991. Recent findings may explain its effectiveness, which may include, in particular, the removal of anti-ADAMTS13 autoantibodies and unusually large von Willebrand factor multimers and/or supply of ADAMTS13 in acquired idiopathic or congenital TTP. Based on currently available data, the favoured PE regimen is daily PE [involving replacement of 1-1.5 times the patient's plasma volume with fresh-frozen plasma (FFP)] until remission. Adverse events of treatment are mainly related to central venous catheters. The potential reduction of plasma related side-effects, such as transfusion-related acute lung injury (TRALI) or febrile transfusion reactions by use of solvent-detergent treated (S/D) plasma instead of FFP is not established by controlled clinical studies. Uncontrolled clinical observations and the hypothesis of an autoimmune process in a significant part of the patients with acquired idiopathic TTP suggest a beneficial effect of adjunctive therapy with corticosteroids. Other immunosuppressive treatments are not tested in controlled trials and should be reserved for refractory or relapsing disease. There is no convincing evidence for the use of antiplatelet agents. Supportive treatment with transfusion of red blood cells or platelets has to be evaluated on a clinical basis, but the transfusion trigger for platelets should be very restrictive. Further controlled, prospective studies should consider the different pathophysiological features of thrombotic microangiopathies, address the prognostic significance of ADAMTS13 and explore alternative exchange fluids to FFP, the role of immunosuppressive therapies and of new plasma saving approaches as recombinant ADAMTS13 and protein A immunoadsorption.

Current management of thrombotic thrombocytopenic purpura

PURPOSE OF REVIEW: New treatment modalities have become increasingly popular for the treatment of acute thrombotic thrombocytopenic purpura. Widespread availability of ADAMTS13 assays resulted in the increased recognition of patients with hereditary thrombotic thrombocytopenic purpura and specific issues related to acquired ADAMTS13 deficiency. These new aspects with implications on management of thrombotic thrombocytopenic purpura patients are reviewed here. RECENT FINDINGS: Today, plasma exchange with the replacement of fresh frozen plasma is still the treatment of choice in acute thrombotic thrombocytopenic purpura. The finding of circulating anti-ADAMTS13 autoantibodies in the majority of patients constitutes the rationale for the concomitant administration of immunosuppressive drugs. Rituximab seems to have a favorable benefit-risk ratio in plasma-refractory and relapsing thrombotic thrombocytopenic purpura; however, long-term follow-up data are not yet available. Constitutively lacking ADAMTS13 in hereditary thrombotic thrombocytopenic purpura can be supplemented by simple plasma infusions. Severe acquired ADAMTS13 deficiency either at presentation or in remission identifies patients at a particularly high risk of relapse. SUMMARY: Despite progress in understanding the pathophysiology of thrombotic thrombocytopenic purpura, acute bouts as well as relapses still represent serious health threats to patients and rapid initiation of plasma exchange is mandatory. Large randomized clinical trials, however, need to determine whether new treatment modalities are superior to standard plasma exchange.

Rituximab immunotherapy in pemphigus: therapeutic effects beyond B-cell depletion

The anti-CD20 mAb rituximab, first approved for use in B-cell malignancies, is increasingly used to treat a variety of autoimmune diseases. Two studies in this issue investigate the effects of rituximab in pemphigus. Rituximab induces not only a depletion of all B cells and a decline of antidesmoglein autoantibodies but also a decrease in desmoglein-specific T cells. Furthermore, B-cell populations recovered after treatment were modified. These novel aspects may contribute to the clinical responses observed in patients.

Evidence that anti-muscarinic antibodies in Sjögren's syndrome recognise both M3R and M1R

Inhibitory anti-muscarinic receptor type 3 (M3R) antibodies may contribute to the pathogenesis of Sjögren's syndrome (SS), and putative anti-M3R blocking antibodies in intravenous immunoglobulin (IVIg) have been suggested as a rationale for treatment with IVIg. We investigated the presence of subtype-specific anti-MR autoantibodies in healthy donor and SS sera using MR-transfected whole-cell binding assays as well as M1R and M3R peptide ELISAs. Control antibodies against the second extracellular loop of the M3R, a suggested target epitope, were induced in rabbits and found to be cross-reactive on the peptides M3R and M1R. The rabbit antibodies had neither an agonistic nor an antagonistic effect on M3R-dependent ERK1/2 signalling. Only one primary SS (out of 5 primary SS, 2 secondary SS and 5 control sera) reacted strongly with M3R transfected cells. The same SS serum also reacted strongly with M1R and M2R transfectants, as well as M1R and two different M3R peptides. Strong binding to M1R and low-level activities against M3R peptides were observed both in SS and control sera. IVIg showed a strong reactivity against all three peptides, especially M1R. Our results indicate that certain SS individuals may have antibodies against M1R, M2R and M3R. Our results also suggest that neither the linear M3R peptide nor M3R transfectants represent suitable tools for discrimination of pathogenic from natural autoantibodies in SS.

[Diagnostics of autoimmune diseases]

Autoantibodies play a key role in diagnostic laboratories as markers of autoimmune diseases. In addition to their role as markers they mediate diverse effects in vivo. Autoantibodies with protective effect have been described. Natural protective IgM autoantibodies against tumour-antigens of malignant cells or their precursors may contribute to increased survival rates of carcinoma patients. In a mouse model of systemic lupus erythematosus it has been shown that anti-dsDNA IgM autoantibodies protect from glomerular damage. In contrast, a direct pathogenic role of autoantibodies has been well established e.g. in myasthenia gravis or in Goodpasture syndrome. Similarly autoantibodies against SSA Ro52 are detrimental in neonatal lupus erythematosus with congenital heart block. Moreover, putatively protective autoantibodies may become pathogenic during the course of the disease such as the onconeuronal autoantibodies whose pathogenicity depends on their compartmentalisation. In patients with paraneoplastic syndromes tumour cells express proteins that are also naturally present in the brain. Anti-tumour autoantibodies which temporarily suppress tumour growth can provoke an autoimmune attack on neurons once having crossed the blood-brain barrier and cause specific neurological symptoms. Only a restricted number of autoantibodies are useful follow-up markers for the effectiveness of treatment in autoimmune diseases. Certain autoantibodies hold prognostic value and appear years or even decades before the diagnosis of disease such as the antimitochondrial antibodies in primary biliary cirrhosis or anti-citrullinated protein (CCP)-antibodies in rheumatoid arthritis. It is crucial to know whether the autoantibodies in question recognise linear or conformational epitopes in order to choose the appropriate detection methods. Indirect immunofluorescence microscopy remains a very useful tool for confirmation of results of commercially available immunoassays and for detection of special and rare autoantibodies that otherwise often remain undetected. Standardisation of autoimmune diagnostics is still underway and requires joint efforts by laboratories, clinicians and industry.

[Cerebral vasculitis]

Cerebral vasculitis is a rare disease with a potentially harmful or even fatal outcome that often affects young adults. Primary autoimmune mediated disease can be distinguished from secondary vasculitis associated to infectious disorders, connective tissue diseases, malignancies or toxic drug effects. Pathomechanisms lead to destruction of the vessel wall and consecutive hemorrhagic or ischemic brain lesions. Beyond these mechanisms direct autoimmune mediated neurotoxicity is postulated. Clinical presentation is highly variable with potentially fluctuating signs and symptoms. Besides multifocal deficits from disseminated CNS involvement, diffuse encephalopathy or psychosis may result from diffuse CNS affection. For systemic vasculitis with CNS involvement, affection of joints, skin and organs may facilitate the diagnostic evaluation. CNS affection in systemic diseases is highly variable and may even precede systemic manifestation. The diagnostic work-up includes clinical evaluation, analysis of autoantibodies, MRI, digital subtraction angiography and biopsy of the affected tissue in doubtful cases. Standard therapy are corticosteroids often combined with immunosuppressants such as azathioprine, methotrexate or mycophenolate mofetil in chronic disease or cyclophosphamid in acute disorder. When therapy can be initiated timely, prognosis of cerebral vasculitis is usually favourable.

[Systemic ANCA-associated vasculitis--diagnosis and therapy]

ANCA-associated vasculitis represents a group of small-vessel vasculitides, including Wegener's granulomatosis, microscopic polyangiitis and the Churg-Strauss-syndrome. These diseases affect mainly small arteries, venules and capillaries, showing a lack of immunocomplex formation on immunohistology, the so-called "pauci-immune" vasculitis. Nevertheless, Anti-Neutrophil Cytoplasmatic Autoantibodies (ANCA's) are pathogenic for this type of disease. In spite of important advances in technical diagnostic tools, careful medical history and clinical examinations often give the clues for the correct diagnosis. Recent collaborative therapeutic studies have lead to therapeutic schemas that are much more adapted to the individual disease state. Besides the acute and sometimes life-threatening form of ANCA-vasculitis, chronic disease and relapses become more important in clinical practice. Thus, therapeutic efficacy must be outweighed against long-term toxicity to make the right choice for therapeutic intervention in ANCA-associated vasculitis.

Incidence of bullous pemphigoid and pemphigus in Switzerland: a 2-year prospective study

BACKGROUND: Bullous pemphigoid (BP), pemphigus vulgaris (PV) and pemphigus foliaceus (PF) are autoimmune bullous diseases characterized by the presence of tissue-bound and circulating autoantibodies directed against disease-specific target antigens of the skin. Although rare, these diseases run a chronic course and are associated with significant morbidity and mortality. There are few prospective data on gender- and age-specific incidence of these disorders. OBJECTIVES: Our aims were: (i) to evaluate the incidence of BP and PV/PF in Swiss patients, as the primary endpoint; and (ii) to assess the profile of the patients, particularly for comorbidities and medications, as the secondary endpoint. METHODS: The protocol of the study was distributed to all dermatology clinics, immunopathology laboratories and practising dermatologists in Switzerland. All newly diagnosed cases of BP and pemphigus occurring between 1 January 2001 and 31 December 2002 were collected. In total, 168 patients (73 men and 95 women) with these autoimmune bullous diseases, with a diagnosis based on clinical, histological and immunopathological criteria, were finally included. RESULTS: BP showed a mean incidence of 12.1 new cases per million people per year. Its incidence increased significantly after the age of 70 years, with a maximal value after the age of 90 years. The female/male ratio was 1.3. The age-standardized incidence of BP using the European population as reference was, however, lower, with 6.8 new cases per million people per year, reflecting the ageing of the Swiss population. In contrast, both PV and PF were less frequent. Their combined mean incidence was 0.6 new cases per million people per year. CONCLUSIONS; This is the first comprehensive prospective study analysing the incidence of autoimmune bullous diseases in an entire country. Our patient cohort is large enough to establish BP as the most frequent autoimmune bullous disease. Its incidence rate appears higher compared with other previous studies, most likely because of the demographic characteristics of the Swiss population. Nevertheless, based on its potentially misleading presentations, it is possible that the real incidence rate of BP is still underestimated. Based on its significant incidence in the elderly population, BP should deserve more public health concern.

Prednisolone treatment induces tolerogenic dendritic cells and a regulatory milieu in myasthenia gravis patients

FOXP3-expressing naturally occurring CD4(+)CD25(high) T regulatory cells (Treg) are relevant in the control of autoimmunity, and a defect in this cell population has been observed in several human autoimmune diseases. We hypothesized that altered functions of peripheral Treg cells might play a role in the immunopathogenesis of myasthenia gravis, a T cell-dependent autoimmune disease characterized by the presence of pathogenic autoantibodies specific for the nicotinic acetylcholine receptor. We report in this study a significant decrease in the in vitro suppressive function of peripheral Treg cells isolated from myasthenia patients in comparison to those from healthy donors. Interestingly, Treg cells from prednisolone-treated myasthenia gravis patients showed an improved suppressive function compared with untreated patients, suggesting that prednisolone may play a role in the control of the peripheral regulatory network. Indeed, prednisolone treatment prevents LPS-induced maturation of monocyte-derived dendritic cells by hampering the up-regulation of costimulatory molecules and by limiting secretion of IL-12 and IL-23, and enhancing IL-10. In addition, CD4(+) T cells cultured in the presence of such tolerogenic dendritic cells are hyporesponsive and can suppress autologous CD4(+) T cell proliferation. The results shown in this study indicate that prednisolone treatment promotes an environment that favors immune regulation rather than inflammation.

Immunosuppressive treatment for acquired haemophilia: current practice and future directions in Germany, Austria and Switzerland

Acquired haemophilia is an autoimmune disorder characterised by autoantibody formation against coagulation factor VIII. Immunosuppressive treatments including steroids, cytotoxic drugs, rituximab or combinations thereof have been used to eradicate autoantibodies. Very few prospective studies exist evaluating the use of these treatments. Here, we performed a survey among 73 physicians from 57 haemophilia treatment centres in order to describe current practice patterns and critical issues for future research in acquired haemophilia. The results demonstrate a high diversity of first- and second-line treatments. Factors influencing treatment decision were underlying disorder, severity of bleeding and inhibitor titre. Frequently used first-line treatments were steroids plus cyclophosphamide (44%) and steroids alone (11%). Second-line treatment was most often rituximab (30%), with or without steroids and/or cyclophosphamide. Most participants indicated to change from first- to second-line treatment after 4 weeks in case of failure to obtain partial remission (31%), continued bleeding (40%) or continued severe bleeding requiring bypass treatment (59%). Immunoadsorption was preferred for first- and second-line treatment by 10% and 9% of participants, respectively. These results highlight critical issues in the field. Open questions and directions for future research are discussed.

IgG subclass distribution of anti-ADAMTS13 antibodies in patients with acquired thrombotic thrombocytopenic purpura

BACKGROUND: ADAMTS13-neutralizing IgG autoantibodies are the major cause of acquired thrombotic thrombocytopenic purpura (TTP). OBJECTIVE: To analyze the IgG subclass distribution of anti-ADAMTS13 antibodies and a potential relationship between subclass distribution and disease prognosis. METHODOLOGY: An enzyme-linked immunosorbent assay-based method was used to quantify the relative amounts of IgG subclasses of anti-ADAMTS13 antibodies in acquired TTP plasma. RESULTS: IgG(4) (52/58, 90%) was the most prevalent IgG subclass in patients with acquired TTP, followed by IgG(1) (52%), IgG(2) (50%), and IgG(3) (33%). IgG(4) was found either alone (17/52) or with other IgG subclasses (35/52). IgG(4) was not detected in 10% of the patients. There was an inverse correlation between the frequency and abundance of IgG(4) and IgG(1) antibodies (P < 0.01). Patients with high IgG(4) levels and undetectable IgG(1) are more prone to relapse than patients with low IgG(4) levels and detectable IgG(1). CONCLUSIONS: All IgG subclasses of anti-ADAMTS13 antibodies were detected in patients with acquired TTP, with IgG(4), followed by IgG(1), antibodies dominating the anti-ADAMTS13 immune response. Levels of IgG(4) could be useful for the identification of patients at risk of disease recurrence.

VH1-69 germline encoded antibodies directed towards ADAMTS13 in patients with acquired thrombotic thrombocytopenic purpura

BACKGROUND: Autoantibodies directed towards ADAMTS13 are present in the majority of patients with acquired thrombotic thrombocytopenic purpura (TTP). Analysis of a set of antibodies derived from two patients with acquired TTP revealed frequent use of the VH1-69 heavy chain gene segment for the assembly of anti-ADAMTS13 antibodies. OBJECTIVE: We explored the ability of two VH1-69 germline gene-encoded antibodies to inhibit the von Willebrand factor (VWF)-processing activity of ADAMTS13 under different experimental conditions. Furthermore, the presence of VH1-69 encoded anti-ADAMTS13 antibodies in 40 patients with acquired TTP was monitored using monoclonal antibody G8, which specifically reacts with an idiotype expressed on VH1-69 encoded antibodies. METHODS AND RESULTS: Binding of the two VH1-69 encoded monoclonal antibodies was dependent on the presence of the spacer domain. Both antibodies inhibited ADAMTS13 activity under static conditions, as measured by cleavage of FRETS-VWF73 substrate and cleavage of VWF multimers. The recombinant antibodies were also capable of inhibiting the processing of UL-VWF strings on the surface of endothelial cells. G8-reactive antibodies directed towards ADAMTS13 were present in plasma of all patients containing anti ADAMTS13 antibodies. CONCLUSIONS: These results suggest that VH1-69 derived antibodies directed towards ADAMTS13 develop in the majority of patients with acquired TTP.

Influence of age and genetic risk on anti-tissue transglutaminase IgA titers

OBJECTIVES: False-positive results of anti-tissue-transglutaminase (tTG) IgA autoantibodies have been reported in subjects with a genetic risk for celiac disease (CD). The aims of this retrospective study were to assess the prevalence of false-positive tTG titers in patients at risk of CD compared with symptomatic children and to evaluate the influence of age and indication for testing on tTG titers. PATIENTS AND METHODS: All tTG results measured in our institution during a 33-month period were evaluated. Patients with known CD were excluded. Indications for testing were either symptoms suggestive of CD (group 1) or history of being at risk for CD (group 2). Duodenal biopsies were recommended if titers were positive (> or =10 U/mL) and offered if borderline (> or =4 to <10 U/mL). RESULTS: The final analysis included 2056 patients, 1707 belonged to group 1, and 349 to group 2. All 65 patients with positive tTG results underwent biopsy (group 1: 57, group 2: 8). Celiac disease was confirmed in 61 subjects (median titer: 107.8 U/mL, range 12.0-1748 mL, NS between group 1 and 2), whereas 4 had normal histology (10.2-25.2 U/mL). Three out of 16 patients with borderline results underwent biopsy and had normal histology. Borderline titers were more common in group 2 patients (2.6% vs 0.4%, P<0.001). Multiple regression analysis in patients with negative tTG results (n=1975) revealed that titers were independently related to age (P<0.05) and indication for testing (P<0.001). CONCLUSIONS: The influence of age and genetic predisposition/risk has to be taken into account when interpreting tTG results.

Novel autoantigens immunogenic in COPD patients

Background Chronic obstructive pulmonary disease (COPD) is a respiratory inflammatory condition with autoimmune features including IgG autoantibodies. In this study we analyze the complexity of the autoantibody response and reveal the nature of the antigens that are recognized by autoantibodies in COPD patients. Methods An array of 1827 gridded immunogenic peptide clones was established and screened with 17 sera of COPD patients and 60 healthy controls. Protein arrays were evaluated both by visual inspection and a recently developed computer aided image analysis technique. By this computer aided image analysis technique we computed the intensity values for each peptide clone and each serum and calculated the area under the receiver operator characteristics curve (AUC) for each clone and the separation COPD sera versus control sera. Results By visual evaluation we detected 381 peptide clones that reacted with autoantibodies of COPD patients including 17 clones that reacted with more than 60% of the COPD sera and seven clones that reacted with more than 90% of the COPD sera. The comparison of COPD sera and controls by the automated image analysis system identified 212 peptide clones with informative AUC values. By in silico sequence analysis we found an enrichment of sequence motives previously associated with immunogenicity. Conclusion The identification of a rather complex humoral immune response in COPD patients supports the idea of COPD as a disease with strong autoimmune features. The identification of novel immunogenic antigens is a first step towards a better understanding of the autoimmune component of COPD.