Michael Hertl

Consensus statement on definitions of disease, end points, and therapeutic response for pemphigus

Our scientific knowledge of pemphigus has dramatically progressed in recent years. However, despite the availability of various therapeutic options for the treatment of inflammatory diseases, only a few multicenter controlled trials have helped to define effective therapies in pemphigus. A major obstacle in comparing therapeutic outcomes between centers is the lack of generally accepted definitions and measurements for the clinical evaluation of patients with pemphigus. Common terms and end points of pemphigus are needed so that experts in the field can accurately measure and assess disease extent, activity, severity, and therapeutic response, and thus facilitate and advance clinical trials. This consensus statement from the International Pemphigus Committee represents 2 years of collaborative efforts to attain mutually acceptable common definitions for pemphigus. These should assist in development of consistent reporting of outcomes in future studies.

Deficiency of PORCN, a regulator of Wnt signaling, is associated with focal dermal hypoplasia

Focal dermal hypoplasia (FDH) is an X-linked dominant multisystem birth defect affecting tissues of ectodermal and mesodermal origin. Using a stepwise approach of (i) genetic mapping of FDH, (ii) high-resolution comparative genome hybridization to seek deletions in candidate chromosome areas and (iii) point mutation analysis in candidate genes, we identified PORCN, encoding a putative O-acyltransferase and potentially crucial for cellular export of Wnt signaling proteins, as the gene mutated in FDH. The findings implicate FDH as a developmental disorder caused by a deficiency in PORCN.

Identification and characterization of autoreactive T cell responses to bullous pemphigoid antigen 2 in patients and healthy controls.

Antibodies against the extracellular domain of bullous pemphigoid antigen 2 (BPAG2) are thought to play a key role in the pathogenesis of bullous pemphigoid (BP), the most frequent autoimmune bullous disease of the skin. Autoreactive T cell responses to BPAG2 were investigated in 16 BP patients and 24 healthy controls by coculture of PBMC with two recombinant BPAG2 proteins (extracellular domain of BPAG2). Primary in vitro T cell responses to BPAG2 were observed in 10/12 BP patients expressing the BP-associated HLA-DQB1*0301 allele and 8/10 DQB1*0301 positive healthy individuals. DQB1*0301 also restricted three autoreactive T cell lines from two BP patients and a healthy donor. In contrast, PBMC from 14 normal patients carrying HLA class II alleles other than DQB1*0301 were not stimulated by BPAG2. Autoreactive BPAG2-specific CD4(+) T cell lines and clones from five BP patients produced both Th1 and Th2 cytokines, whereas three autoreactive T cell lines from three DQB1*0301 positive normal patients produced exclusively IFN-gamma. The absence of BPAG2-specific Th2 cells in healthy individuals strongly suggests that autoreactive Th2 responses to BPAG2 are restricted to BP patients and may thus be critical in the pathogenesis of BP.

T cell control in autoimmune bullous skin disorders

Autoimmune bullous disorders are a group of severe skin diseases characterized clinically by blisters and erosions of skin and/or mucous membranes. A hallmark of these disorders is the presence of IgG and occasionally IgA autoantibodies that target distinct adhesion structures of the epidermis, dermoepidermal basement membrane, and anchoring fibrils of the dermis. This Review focuses on the potential role of autoreactive T cells in the pathogenesis of these disorders. Pemphigus vulgaris (PV) and bullous pemphigoid (BP) are the best-characterized bullous disorders with regard to pathogenesis and T cell involvement. Activation of autoreactive T cells in PV and BP is restricted by distinct HLA class II alleles that are prevalent in individuals with these disorders. Autoreactive T cells are not only present in patients but can also be detected in healthy individuals. Recently, a subset of autoreactive T cells with remarkable regulatory function was identified in healthy individuals and to a much lesser extent in patients with PV, suggesting that the occurrence of autoimmune bullous disorders may be linked to a dysfunction of Tregs.

Type I Regulatory T Cells Specific for Desmoglein 3 Are More Frequently Detected in Healthy Individuals than in Patients with Pemphigus Vulgaris

Pemphigus vulgaris (PV) is a severe autoimmune bullous skin disorder and is primarily associated with circulating autoantibodies against desmoglein 3 (Dsg3) that are presumably regulated by Th cells. The aim of this study was to identify Dsg3-specific T regulatory (Tr) cells that may help to maintain and restore natural tolerance against Dsg3. Dsg3-responsive IL-10-secreting Tr1 cells were isolated by MACS cytokine secretion assay from healthy carriers of the PV-associated HLA class II alleles, DRB1*0402 and DQB1*0503, but were only rarely detected in PV patients. The Dsg3-specific Tr1 cells secreted IL-10, TGF-β, and IL-5 upon Ag stimulation, proliferated in response to IL-2 but not to Dsg3 or mitogenic stimuli, and inhibited the proliferative response of Dsg3- and tetanus toxoid-responsive Th clones in an Ag-specific (Dsg3) and cell number-dependent manner. Moreover, their inhibitory effect was blocked by Ab against IL-10, TGF-β, and by paraformaldehyde fixation. These observations strongly suggest that 1) Dsg3-responsive Tr1 cells predominate in healthy individuals, 2) their growth requires the presence of IL-2, and 3) they exert their Dsg3-dependent inhibitory function by the secretion of IL-10 and TGF-β. Because autoaggressive T cells responsive to identical epitopes of Dsg3 were recently found both in PV patients and healthy individuals, the identified Tr1 cells may be critically involved in the maintenance and restoration of tolerance against Dsg3.

Definitions and outcome measures for bullous pemphigoid: recommendations by an international panel of experts

Our scientific knowledge of bullous pemphigoid (BP) has dramatically progressed in recent years. However, despite the availability of various therapeutic options for the treatment of inflammatory diseases, only a few multicenter controlled trials have helped to define effective therapies in BP. A major obstacle in sharing multicenter-based evidences for therapeutic efforts is the lack of generally accepted definitions for the clinical evaluation of patients with BP. Common terms and end points of BP are needed so that experts in the field can accurately measure and assess disease extent, activity, severity, and therapeutic response, and thus facilitate and advance clinical trials. These recommendations from the International Pemphigoid Committee represent 2 years of collaborative efforts to attain mutually acceptable common definitions for BP and proposes a disease extent score, the BP Disease Area Index. These items should assist in the development of consistent reporting of outcomes in future BP reports and studies.

Rituximab Exerts a Dual Effect in Pemphigus Vulgaris

Pemphigus vulgaris (PV) is a severe autoimmune blistering disease affecting the skin and mucous membranes. Autoreactive CD4(+) T helper (Th) lymphocytes are crucial for the autoantibody response against the desmosomal adhesion molecules, desmoglein (dsg)-3 and dsg1. Eleven patients with extensive PV were treated with the anti-CD20 antibody, rituximab (375 mg per m(2) body surface area once weekly for 4 weeks). Frequencies of autoreactive CD4(+) Th cells in the peripheral blood of the PV patients were determined 0, 1, 3, 6, and 12 months after rituximab treatment. Additionally, the clinical response was evaluated and serum autoantibody titers were quantified by ELISA. Rituximab induced peripheral B-cell depletion for 6-12 months, leading to a dramatic decline of serum autoantibodies and significant clinical improvement in all PV patients. The frequencies of dsg3-specific CD4(+) Th1 and Th2 cells decreased significantly for 6 and 12 months, respectively, while the overall count of CD3(+)CD4(+) T lymphocytes and the frequency of tetanus toxoid-reactive CD4(+) Th cells remained unaffected. Our findings indicate that the response to rituximab in PV involves two mechanisms: (1) the depletion of autoreactive B cells and (2) the herein demonstrated, presumably specific downregulation of dsg3-specific CD4(+) Th cells.

Safety and clinical outcomes of rituximab therapy in patients with different autoimmune diseases: experience from a national registry (GRAID)

IntroductionEvidence from a number of open-label, uncontrolled studies has suggested that rituximab may benefit patients with autoimmune diseases who are refractory to standard-of-care. The objective of this study was to evaluate the safety and clinical outcomes of rituximab in several standard-of-care-refractory autoimmune diseases (within rheumatology, nephrology, dermatology and neurology) other than rheumatoid arthritis or non-Hodgkins lymphoma in a real-life clinical setting.MethodsPatients who received rituximab having shown an inadequate response to standard-of-care had their safety and clinical outcomes data retrospectively analysed as part of the German Registry of Autoimmune Diseases. The main outcome measures were safety and clinical response, as judged at the discretion of the investigators.ResultsA total of 370 patients (299 patient-years) with various autoimmune diseases (23.0% with systemic lupus erythematosus, 15.7% antineutrophil cytoplasmic antibody-associated granulomatous vasculitides, 15.1% multiple sclerosis and 10.0% pemphigus) from 42 centres received a mean dose of 2,440 mg of rituximab over a median (range) of 194 (180 to 1,407) days. The overall rate of serious infections was 5.3 per 100 patient-years during rituximab therapy. Opportunistic infections were infrequent across the whole study population, and mostly occurred in patients with systemic lupus erythematosus. There were 11 deaths (3.0% of patients) after rituximab treatment (mean 11.6 months after first infusion, range 0.8 to 31.3 months), with most of the deaths caused by infections. Overall (n = 293), 13.3% of patients showed no response, 45.1% showed a partial response and 41.6% showed a complete response. Responses were also reflected by reduced use of glucocorticoids and various immunosuppressives during rituximab therapy and follow-up compared with before rituximab. Rituximab generally had a positive effect on patient well-being (physicians visual analogue scale; mean improvement from baseline of 12.1 mm).ConclusionsData from this registry indicate that rituximab is a commonly employed, well-tolerated therapy with potential beneficial effects in standard of care-refractory autoimmune diseases, and support the results from other open-label, uncontrolled studies.

Recommendations for the use of rituximab (anti-CD20 antibody) in the treatment of autoimmune bullous skin diseases.

Autoimmune bullous skin disorders are induced by autoantibodies against distinct adhesion complexes of the epidermal and dermal‐epidermal junction. Since most of these disorders are characterized by a severe, potentially lethal course,they require long‐term immunosuppressive treatment to reduce the de novo synthesis of pathogenic autoantibodies by B lymphocytes. Rituximab, a chimeric monoclonal antibody against CD20 on B lymphocytes, has shown promise in several case reports or cohort studies in the treatment of paraneo‐plastic pemphigus,refractory cases of pemphigus vulgaris and foliaceus and in other autoimmune bullous disorders.Treatment with rituximab leads to depletion of pathogenic B‐cells which may last up to 12 months resulting in a reduction of plasma cells secreting pathogenic autoantibodies.Rituximab is usually administered in an adjuvant setting at a dose of 375 mg/m2 i.v.in weekly intervals for four consecutive weeks in addition to the standard immunosuppressive treatment.The present consensus statement of German‐speaking derma‐tologists,rheumatologists and oncologists summarizes and evaluates the current evidence for the use and mode of application of rituximab in autoimmune bullous skin disorders.

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.