[Spontaneous remission of urticaria: does it exist and if so, when?]

BACKGROUND

Urticaria mostly occurs acutely with a very high probability of spontaneous remission. When it persists for more than 6 weeks a chronic urticaria is manifest, which occurs either spontaneously or inducible by specific triggers. The underlying mechanisms are not fully understood but recent research points to defined pathogenetic factors.

QUESTION AND AIM

Whether spontaneous remission is possible in urticaria is summarized descriptively in this review, and suggestions are given for the "step down" of urticaria treatment after remission. The mechanisms including autoallergic, immunoglobulin E (IgE)-dependent type I reactions and autoimmune, activating IgG-dependent type IIb reactions are presented. These are discussed in the context of spontaneous remission and the possibilities of induced remission.

Laminin β4 is a constituent of the cutaneous basement membrane zone and additional autoantigen of anti-p200 pemphigoid

BACKGROUND

Anti-p200 pemphigoid is a subepidermal autoimmune blistering disease (AIBD) characterized by autoantibodies against a 200 kDa protein. Laminin γ1 has been described as target antigen in 70% to 90% of patients. No diagnostic assay is widely available for anti-p200 pemphigoid, which might be due to the unclear pathogenic relevance of anti-laminin γ1 autoantibodies.

OBJECTIVE

To identify a target antigen with higher clinical and diagnostic relevance.

METHODS

Immunoprecipitation, mass spectrometry, and immunoblotting were employed for analysis of skin extracts and sera of patients with anti-p200 pemphigoid (n = 60), other AIBD (n = 33), and healthy blood donors (n = 29). To localize the new antigen in skin, cultured keratinocytes and fibroblasts, quantitative real-time polymerase chain reaction and immunofluorescence microscopy were performed.

RESULTS

Laminin β4 was identified as target antigen of anti-p200 pemphigoid in all analyzed patients. It was located at the level of the basement membrane zone of the skin with predominant expression in keratinocytes.

LIMITATIONS

A higher number of sera needs to be tested to verify that laminin β4 is the diagnostically relevant antigen of anti-p200 pemphigoid.

CONCLUSION

The identification of laminin β4 as an additional target antigen in anti-p200 pemphigoid will allow its differentiation from other AIBD and as such, improve the management of these rare disorders.

Corrigendum: Blocking soluble Fas Ligand ameliorates pemphigus: PC111 efficacy in ex-vivo human pemphigus models

[This corrects the article DOI: 10.3389/fimmu.2023.1193032.].

Serum reactivity in dermatitis herpetiformis: an international multicentre study

BACKGROUND

Dermatitis herpetiformis (DH) is a rare gluten-induced skin disorder characterized predominantly by IgA autoantibodies against endomysium, tissue transglutaminase (TG2/tTG), epidermal transglutaminase (TG3/eTG) and deamidated gliadin. To date, circulating autoantibody reactivity has not been systematically described.

OBJECTIVES

Characterization of serum reactivities in DH.

METHODS

This multicentre international study analysed sera from 242 patients with DH taken at the time of initial diagnosis. DH-specific IgA and IgG serum autoantibodies were analysed by indirect immunofluorescence (IF) on monkey oesophagus, and by enzyme-linked immunosorbent assay (ELISA) based on recombinant TG2/tTG, TG3/eTG and deamidated gliadin (GAF3X).

RESULTS

IgA indirect IF microscopy on monkey oesophagus revealed the highest reactivity (84.3%; specificity 100%) followed by IgA TG2/tTG ELISA (78.5%, specificity 99.0%), IgA TG3/eTG ELISA (72.7%, specificity 95.0%) and IgA GAF3X ELISA (69.0%, specificity 98.5%).

CONCLUSIONS

Serum IgA and IgG autoantibodies against endomysium, TG2/tTG, TG3/eTG and deamidated gliadin are highly prevalent in DH. Indirect IF microscopy on monkey oesophagus (IgA) provides the highest diagnostic accuracy that can be further enhanced by 4.5% when combined with IgA TG2/tTG ELISA.

The gut microbiome in bullous pemphigoid: implications of the gut-skin axis for disease susceptibility

Bullous pemphigoid (BP) is an autoimmune blistering disease that primarily affects the elderly. An altered skin microbiota in BP was recently revealed. Accumulating evidence points toward a link between the gut microbiota and skin diseases; however, the gut microbiota composition of BP patients remains largely underexplored, with only one pilot study to date, with a very limited sample size and no functional profiling of gut microbiota. To thoroughly investigate the composition and function of the gut microbiota in BP patients, and explore possible links between skin conditions and gut microbiota, we here investigated the gut microbiota of 66 patients (81.8% firstly diagnosed) suffering from BP and 66 age-, sex-, and study center-matched controls (CL) with non-inflammatory skin diseases (132 total participants), using 16S rRNA gene and shotgun sequencing data. Decreased alpha-diversity and an overall altered gut microbial community is observed in BP patients. Similar trends are observed in subclassifications of BP patients, including first diagnoses and relapsed cases. Furthermore, we observe a set of BP disease-associated gut microbial features, including reduced Faecalibacterium prausnitzii and greater abundance of pathways related to gamma-aminobutyric acid (GABA) metabolism in BP patients. Interestingly, F. prausnitzii is a well-known microbiomarker of inflammatory diseases, which has been reported to be reduced in the gut microbiome of atopic dermatitis and psoriasis patients. Moreover, GABA plays multiple roles in maintaining skin health, including the inhibition of itching by acting as a neurotransmitter, attenuating skin lesions by balancing Th1 and Th2 levels, and maintaining skin elasticity by increasing the expression of type I collagen. These findings thus suggest that gut microbiota alterations present in BP may play a role in the disease, and certain key microbes and functions may contribute to the link between gut dysbiosis and BP disease activity. Further studies to investigate the underlying mechanisms of the gut-skin interaction are thus clearly warranted, which could aid in the development of potential therapeutic interventions.

A life for autoimmune blistering diseases: in memoriam Detlef Zillikens

Detlef Zillikens, MD, director and chair of the Department of Dermatology at the University of Lübeck, Lübeck, Germany, died in September 2022, aged only 64. He dedicated his professional life to autoimmune blistering diseases (AIBDs) and built his department into one of the world's leading centers for these diseases. Herein, his professional life and the impact on the field of AIBDs and the research landscape at the University of Lübeck are addressed. With his warm, integrative, open-minded, ever-optimistic attitude, he was a highly reliable colleague, mentor, and friend to many in the field including each of the authors. Combined with his in-depth knowledge of dermatology, interest in many fields of life science, and hard work, Detlef Zillikens initiated the founding of two independent research institutes, the Lübeck Institute of Experimental Dermatology and the Institute and Comprehensive Center for Inflammation Medicine. He was also instrumental in establishing the Center for Research on Inflammation of the Skin, where in a new research building, over 140 scientists pursue research questions related to skin inflammation. By inviting numerous researchers and clinicians to his department and hosting two large international meetings, he brought the field of AIBDs much closer together and inspired multiple national and international research initiatives. His ideas will live on and grow in many of his colleagues and mentees.

The human skin organ culture model as an optimal complementary tool for murine pemphigus models

Pemphigus is a severe autoimmune bullous disease of the skin and/or mucous membranes caused by autoantibodies that mainly target the adhesion proteins desmoglein (Dsg) 3 and/or Dsg1. Clinically, pemphigus is characterized by flaccid blistering, leading to severe water and electrolyte loss. Before the introduction of corticosteroid treatment, the disease turned out to be fatal in many cases. Despite recent therapeutic improvements, treatment of pemphigus patients is centred on prolonged systemic immunosuppression and remains challenging. Current drug development for pemphigus has a strong focus on disease-causing B cells and autoantibodies and, more recently, also on modulating autoantibody-induced tissue pathology and keratinocyte signalling. This drug development requires reliable pre-clinical model systems replicating the pathogenesis of the human disease. Among those are neonatal and adult mouse models based on the transfer of Dsg3, Dsg1/3 or Dsg1-specific autoantibodies. To reduce the number of animal experiments, we recently established a standardized human skin organ culture (HSOC) model for pemphigus. This model reproduces the clinical phenotype of autoantibody-induced tissue pathology in pemphigus vulgaris. For induction of blistering, a recombinant single-chain variable fragment (scFv) targeting both Dsg1 and 3 is injected into pieces of human skin (obtained from plastic surgeries). Further characterization of the HSOC model demonstrated that key morphologic, molecular and immunologic features of pemphigus are being replicated. Thus, the pemphigus HSOC model is an excellent alternative to pemphigus animal model systems that are based on the transfer of (auto)antibodies.

Blocking soluble Fas Ligand ameliorates pemphigus: PC111 efficacy in ex-vivo human pemphigus models

Pemphigus is a life-threatening, chronic, autoimmune bullous disease affecting both the skin and the mucous membranes. Based on the mainstream concept that blister formation occurs upon binding of autoantibodies to their antigen proteins (desmoglein1, DSG1 and desmoglein3, DSG3), current therapies mostly aim to suppress the immune system. To avoid the severe side effects associated with the chronic use of immunosuppressive treatments, we have developed PC111, a fully human monoclonal antibody targeting human Fas ligand (FasL). We have provided a number of in vitro and in vivo evidences showing that soluble FasL induces keratinocyte apoptosis followed by acantholysis. An anti-murine FasL prevents blister formation in the pemphigus neonatal mouse model. To confirm the mechanism of action (MoA) and the efficacy of PC111 in a human pemphigus context, we used the keratinocyte dissociation assay and two independent Human Skin Organ Cultures (HSOC) pemphigus models. PC111 reduced acantholysis in vitro, as shown by the dose-dependent reduction of fragments in the monolayer cultures. In the first HSOC model, normal human skin was subcutaneously injected with a scFv antibody fragment directed against DSG1 and DSG3, resulting in a severe acantholysis (70-100%) after 24 hours. PC111 inhibited blister formation to around 50% of control. In the second model, normal human skin was injected with a mixture of pemphigus patients' autoantibodies resulting in a less severe acantholysis (20-30%). PC111 significantly suppressed blister formation to more than 75% up to 72 hours. These results confirm PC111 MoA and demonstrates the efficacy of the anti-FasL antibody also in a pemphigus setting.

Autoimmune pre-disease

Approximately 5% of the world-wide population is affected by autoimmune diseases. Overall, autoimmune diseases are still difficult to treat, impose a high burden on patients, and have a significant economic impact. Like other complex diseases, e.g., cancer, autoimmune diseases develop over several years. Decisive steps in the development of autoimmune diseases are (i) the development of autoantigen-specific lymphocytes and (often) autoantibodies and (ii) potentially clinical disease manifestation at a later stage. However, not all healthy individuals with autoantibodies develop disease manifestations. Identifying autoantibody-positive healthy individuals and monitoring and inhibiting their switch to inflammatory autoimmune disease conditions are currently in their infancy. The switch from harmless to inflammatory autoantigen-specific T and B-cell and autoantibody responses seems to be the hallmark for the decisive factor in inflammatory autoimmune disease conditions. Accordingly, biomarkers allowing us to predict this progression would have a significant impact. Several factors, such as genetics and the environment, especially diet, smoking, exposure to pollutants, infections, stress, and shift work, might influence the progression from harmless to inflammatory autoimmune conditions. To inspire research directed at defining and ultimately targeting autoimmune predisease, here, we review published evidence underlying the progression from health to autoimmune predisease and ultimately to clinically manifest inflammatory autoimmune disease, addressing the following 3 questions: (i) what is the current status, (ii) what is missing, (iii) and what are the future perspectives for defining and modulating autoimmune predisease.

Analysis of T cell repertoires of CD45RO CD4 T cells in cohorts of patients with bullous pemphigoid: A pilot study

Autoimmune diseases develop over years - starting from a subclinical phenotype to clinically manifest autoimmune disease. The factors that drive this transition are ill-defined. To predict the turning point towards clinical disease and to intervene in the progress of autoimmune-mediated dysfunction, the establishment of new biomarkers is needed. Especially CD4 T cells are crucially involved in autoimmunity: first, during the initiation phase, because they lose their tolerance towards self-peptides, and second, by the subsequent ongoing presentation of self-peptides during the active autoimmune disease. Accordingly, changes in the degree of diversity of T cell receptor (TCR) repertoires in autoimmunity have been reported. These findings led to the hypothesis that transition from pre-disease to autoimmune disease is associated with an increase of abnormally expanded T cell clones that occupy large portions of the TCR repertoire. In this pilot study, we asked whether the ratio and the diversity of the TCR repertoires of circulating memory (CD45RO) and naïve (CD45RA) CD4 T cells could serve as a predictive factor for the development of autoimmunity. To find out, we analyzed the TCRβ repertoires of memory and naïve CD4 T cells in a small cohort of four gender- and age-matched elderly patients having the autoimmune blistering disease bullous pemphigoid or non-melanoma skin cancers. We found that the extent of clonal expansions in the TCRβ repertoires from the circulating memory and naïve CD4 populations did not differ between the patient groups. This result shows that the diversity of TCR repertoires from peripheral CD4 T cells does not reflect the manifestation of the skin-associated autoimmune disease BP and does not qualify as a prognostic factor. We propose that longitudinal TCR repertoire analysis of younger patients might be more informative.

Electron microscopy of desmosomal structures in the pemphigus human skin organ culture model

Pemphigus is a chronic autoimmune skin blistering disease, characterized by acantholysis and by the production of autoantibodies directed against the structural desmosomal proteins desmoglein 1 (DSG1) and/or DSG3. Model systems allow the identification and testing of new therapeutic targets. Here, we evaluated ultrastructural desmosomal morphology in the human skin organ culture (HSOC) model injected with either anti-desmoglein (DSG) 1/3 single-chain variable fragment (scFv, termed Px4-3), Staphylococcus aureus exfoliative toxin (ETA) as a reference and positive control, and normal human IgG as a negative control. Each experimental condition was evaluated in abdominal skin biopsies from five different donors. After 24 h of incubation, we processed the samples for histological and ultrastructural electron microscopy analyses. We found that Px4-3 or ETA induced a loss of desmosomes and increased interdesmosomal widening, similar to patient skin biopsies and other pemphigus models. Thus, we propose the HSOC pemphigus model as an attractive tool to unravel novel therapeutic targets.

The relevance of complement in pemphigoid diseases: A critical appraisal

Pemphigoid diseases are autoimmune chronic inflammatory skin diseases, which are characterized by blistering of the skin and/or mucous membranes, and circulating and tissue-bound autoantibodies. The well-established pathomechanisms comprise autoantibodies targeting various structural proteins located at the dermal-epidermal junction, leading to complement factor binding and activation. Several effector cells are thus attracted and activated, which in turn inflict characteristic tissue damage and subepidermal blistering. Moreover, the detection of linear complement deposits in the skin is a diagnostic hallmark of all pemphigoid diseases. However, recent studies showed that blistering might also occur independently of complement. This review reassesses the importance of complement in pemphigoid diseases based on current research by contrasting and contextualizing data from in vitro, murine and human studies.

Evaluation of Nomacopan for Treatment of Bullous Pemphigoid: A Phase 2a Nonrandomized Controlled Trial

Importance

Bullous pemphigoid is a difficult-to-treat autoimmune blistering skin disease that predominantly affects older adults and is associated with an increased mortality rate.

Objective

To examine the safety and therapeutic potential of nomacopan, an inhibitor of leukotriene B4 and complement C5, in patients with bullous pemphigoid.

Design, Setting, and Participants

This multicenter, single-group, phase 2a nonrandomized controlled trial was conducted in the dermatology departments of universities in the Netherlands and Germany. Participants were enrolled between September 2018 and April 2020. Older adult patients (aged ≥55 years) with mild to moderate, new-onset or relapsing bullous pemphigoid were recruited into the study.

Interventions

Patients received nomacopan, 90 mg, subcutaneously on day 1 and 30 mg subcutaneously daily until day 42.

Main Outcomes and Measures

The primary end point was the proportion of patients with grade 3 to 5 (severe) adverse events associated or possibly associated with nomacopan. Secondary end points included mean absolute and percentage changes in the Bullous Pemphigoid Disease Area Index (BPDAI) activity score, the BPDAI pruritus score, and the patient-reported outcome measures Dermatology Life Quality Index (DLQI) and Treatment of Autoimmune Bullous Disease Quality of Life (TABQOL).

Results

A total of 9 patients (median [range] age, 75 [55-85] years) with bullous pemphigoid were included in the trial, of whom 5 were women (55.6%). No serious adverse events associated with nomacopan were found. The mean (90% CI) BPDAI activity score decreased from 32.0 (8.7) points on day 1 to 19.6 (9.0) points on day 42. Seven of 9 patients (77.8%) responded to nomacopan with a reduction in the BPDAI activity score of at least 8 points between days 1 and 42; in 3 responders, the reduction was 80% or greater. On day 42, the mean (90% CI) BPDAI pruritus score had decreased by 6.8 (4.6) points from 17.6 (4.0) points on day 1. The mean (90% CI) DLQI score decreased from 11.3 (4.2) points at baseline to 6.4 (3.8) points by day 42, and the mean (90% CI) TABQOL score decreased from 14.6 (5.4) points at baseline to 10.3 (5.0) points on day 42.

Conclusions and Relevance

Results of this nonrandomized controlled trial suggest that nomacopan can be well tolerated in older patients with bullous pemphigoid and may have therapeutic benefits for suppressing acute flares of this disease. A larger, placebo-controlled randomized clinical trial is warranted to confirm this safety profile and to establish nomacopan as a new therapeutic option for bullous pemphigoid.

Trial Registration

ClinicalTrials.gov Identifier: NCT04035733.

Sustained CD19+CD27+ Memory B Cell Depletion after Rituximab Treatment in Patients with Pemphigus Vulgaris

Abstract is missing (Short communication)

Immunization with desmoglein 3 induces non-pathogenic autoantibodies in mice

Background

Pemphigus vulgaris (PV) is a rare autoimmune blistering disease characterized by the development of autoantibodies targeting desmoglein (Dsg) 3, but also against Dsg1 in mucocutaneous disease. Given that existing PV animal models only recapitulate aspects of the disease, we aimed to establish a more comprehensive disease model based on the immunization of mice with PV autoantigen(s).

Methods

The following immunization strategies were tested: (i) C57Bl/6J, B6.SJL-H2s C3c/1CyJ, DBA2/J, or SJL/J mice were immunized with recombinant murine Dsg3 (mDsg3), (ii) DBA2/J and SJL/J mice were immunized with mDsg3 and additionally injected a single non-blister inducing dose of exfoliative toxin A (ETA), and (iii) DBA2/J and SJL/J mice were immunized with human Dsg (hDsg) 1 and 3.

Results

Despite the induction of autoantibodies in each immunization protocol, the mice did not develop a clinical phenotype. Tissue-bound autoantibodies were not detected in the skin or mucosa. Circulating autoantibodies did not bind to the native antigen in indirect immunofluorescence microscopy using monkey esophagus as a substrate.

Conclusion

Immunization with PV autoantigens induced non-pathogenic Dsg1/3 antibodies, but did not cause skin/mucous membrane disease in mice. These findings, confirmed by failure of binding of the induced autoantibodies to their target in the skin, suggest that the autoantibodies which were formed were unable to bind to the conformational epitope present in vivo.

Survival of Adjuvant Drugs for Treatment of Pemphigus: A Population-based Cohort Study

Drug survival reflects the real-life efficacy and safety of therapeutic agents. Evidence regarding the durability of adjuvant agents in the treatment of pemphigus is sparse. The aims of this study were to investigate the survival of adjuvant agents used to manage patients with pemphigus, and to identify predictors of treatment dropout. A retrospective population-based cohort study was designed to follow patients with pemphigus managed by adjuvant agents. The study population included 436 patients with pemphigus managed by 608 adjuvant agent courses. The highest median drug survival time was observed for rituximab (43.6 months, 95% confidence interval (95% CI) 5.3-81.9), followed by cyclophosphamide (30.5 months; 95% CI 10.5-50.5), azathioprine (22.9 months; 95% CI 15.6-30.2), and mycophenolate mofetil (20.2 months; 95% CI 10.0-30.4). Compared with azathioprine, cyclosporine (adjusted hazard ratio 2.98; 95% CI 1.57-5.62; p = 0.005) and dapsone (adjusted hazard ratio 1.83; 95% CI 1.07-3.15; p = 0.027) were associated with a significantly increased risk of drug discontinuation. To conclude, rituximab, azathioprine, and mycophenolate mofetil demonstrated better durability, whilst dapsone and cyclosporine were associated with low drug survival and high dropout.

Receptor repertoires of murine follicular T helper cells reveal a high clonal overlap in separate lymph nodes in autoimmunity

Follicular T helper cells (Tfh) are a specialized subset of CD4 effector T cells that are crucial for germinal center (GC) reactions and for selecting B cells to undergo affinity maturation. Despite this central role for humoral immunity, only few data exist about their clonal distribution when multiple lymphoid organs are exposed to the same antigen (Ag) as it is the case in autoimmunity. Here, we used an autoantibody-mediated disease model of the skin and injected one auto-Ag into the two footpads of the same mouse and analyzed the T cell receptor (TCR)β sequences of Tfh located in GCs of both contralateral draining lymph nodes. We found that over 90% of the dominant GC-Tfh clonotypes were shared in both lymph nodes but only transiently. The initially dominant Tfh clonotypes especially declined after establishment of chronic disease while GC reaction and autoimmune disease continued. Our data demonstrates a dynamic behavior of Tfh clonotypes under autoimmune conditions and emphasizes the importance of the time point for distinguishing auto-Ag-specific Tfh clonotypes from potential bystander activated ones.

Pathogenic Activation and Therapeutic Blockage of FcαR-Expressing Polymorphonuclear Leukocytes in IgA Pemphigus

Pathomechanisms in IgA pemphigus are assumed to rely on Fc-dependent cellular activation by antigen-specific IgA autoantibodies; however, models for the disease and more detailed pathophysiologic data are lacking. In this study, we aimed to establish in vitro models of disease for IgA pemphigus, allowing us to study the effects of the interaction of anti-keratinocyte IgA with cell surface FcαRs. Employing multiple in vitro assays, such as a skin cryosection assay and a human skin organ culture model, in this study, we present mechanistic data for the pathogenesis of IgA pemphigus, mediated by anti-desmoglein 3 IgA autoantibodies. Our results reveal that this disease is dependent on FcαR-mediated activation of leukocytes in the epidermis. Importantly, this cell-dependent pathology can be dose-dependently abrogated by peptide-mediated inhibition of FcαR:IgA-Fc interaction, as confirmed in an additional model for IgA-dependent disease, that is, IgA vasculitis. These data suggest that IgA pemphigus can be modeled in vitro and that IgA pemphigus and IgA vasculitis are FcαR-dependent disease entities that can be specifically targeted in these experimental systems.

The impact of lesional inflammatory cellular infiltrate on the phenotype of bullous pemphigoid

BACKGROUND

The influence of cutaneous cellular infiltration on the phenotype of bullous pemphigoid (BP) remains to be established.

OBJECTIVES

To evaluate the main histopathological characteristics of patients with BP and to assess the association between the composition of lesional inflammatory infiltrate and the various clinical, immunological and immunopathological aspects of the disease.

METHODS

Retrospective study encompassing patients diagnosed with BP throughout the years 2009-2020 in a specialized tertiary referral centre.

RESULTS

The study encompassed 136 patients with BP, of whom 27 (19.9%) demonstrated a cell-poor inflammatory infiltrate in lesional skin specimens. Overall, 78 (57.4%), 71 (52.2%) and 5 (3.7%) specimens were found to include eosinophil-predominant, lymphocyte-predominant and neutrophil-predominant inflammatory infiltrates, respectively. Relative to the remaining patients with BP, those with an eosinophil-predominant inflammatory infiltrate had higher (90.8% vs. 77.2%; P = 0.030) whilst those with a cell-poor inflammatory infiltrate lower (70.3% vs. 88.7%; P = 0.017) seropositivity of anti-BP180 NC16A IgG. The latter subgroup presented with higher prevalence of mucosal involvement (25.9% vs. 8.3%; P = 0.011) and a non-inflammatory clinical phenotype (50.0% vs. 17.1%; P = 0.041). Patients with lymphocyte-predominant inflammatory infiltrate manifested with higher severity BPDAI scores and a lower frequency of the non-inflammatory subtype (11.1% vs. 36.4%; P = 0.035), whilst those with a neutrophilic infiltrate presented with lower mean (SD) levels of anti-BP180 NC16A IgG [269.3 (227.6) vs. 722.7 (1499.6) U/mL; P = 0.003].

CONCLUSIONS

Eosinophil-predominance and high cellularity in the lesional inflammatory infiltrate of BP skin are associated with increased seropositivity of anti-BP180 NC16A IgG. Lymphocyte-predominant infiltrates predict a more severe phenotype, pointing towards a pathogenic role of autoreactive lymphocytes.

Metabolic Interdependency of Th2 Cell-Mediated Type 2 Immunity and the Tumor Microenvironment

The function of T cells is critically dependent on their ability to generate metabolic building blocks to fulfil energy demands for proliferation and consecutive differentiation into various T helper (Th) cells. Th cells then have to adapt their metabolism to specific microenvironments within different organs during physiological and pathological immune responses. In this context, Th2 cells mediate immunity to parasites and are involved in the pathogenesis of allergic diseases including asthma, while CD8+ T cells and Th1 cells mediate immunity to viruses and tumors. Importantly, recent studies have investigated the metabolism of Th2 cells in more detail, while others have studied the influence of Th2 cell-mediated type 2 immunity on the tumor microenvironment (TME) and on tumor progression. We here review recent findings on the metabolism of Th2 cells and discuss how Th2 cells contribute to antitumor immunity. Combining the evidence from both types of studies, we provide here for the first time a perspective on how the energy metabolism of Th2 cells and the TME interact. Finally, we elaborate how a more detailed understanding of the unique metabolic interdependency between Th2 cells and the TME could reveal novel avenues for the development of immunotherapies in treating cancer.

Coexistence of bullous pemphigoid with neuropsychiatric comorbidities is associated with anti-BP230 seropositivity

BACKGROUND

While clustering of bullous pemphigoid (BP) with neuropsychiatric diseases is well-established, the clinical and immunological profile of BP patients with this comorbidity remains to be decisively determined.

OBJECTIVES

To evaluate the burden of neurological and psychiatric comorbidities among patients with BP and to elucidate the clinical, immunological and immunopathological features of patients with BP and comorbid neuropsychiatric conditions.

METHODS

We performed a retrospective study encompassing patients diagnosed with BP throughout the years 2009-2020 in a specialized tertiary referral centre. Multivariate logistic regression model was used to identify predictors of neuropsychiatric conditions among patients with BP.

RESULTS

The study included 273 patients with BP, of whom 123 (45.1%) presented with comorbid neuropsychiatric disease. Compared to the remaining patients with BP (n = 150), those with pre-existing neuropsychiatric diseases demonstrated older mean [standard deviation (SD)] age [81.7 (9.1) vs. 76.9 (10.1); P < 0.001], female preponderance (65.0% vs. 49.3%; P = 0.009), higher seropositivity rate of anti-BP230 (67.7% vs. 36.5%; P = 0.006) and higher levels of anti-BP180 NC16A IgG [651.3 (1279.6) vs. 370.4 (818.6) U/mL; P = 0.039]. In multivariate analysis, anti-BP230 seropositivity was independently associated with coexistence of BP with neuropsychiatric conditions [adjusted odds ratio (OR), 3.43; 95% CI, 1.24-9.52; P = 0.018]. In a sensitivity analysis confined to patients with neurological diseases (n = 103), older age [82.1 (8.4) vs. 77.2 (10.3); P < 0.001] and increased anti-BP230 seropositivity (68.0% vs. 39.7%; P = 0.018) were identified.

CONCLUSIONS

The coexistence of BP with neuropsychiatric diseases is independently associated with the generation of anti-BP230 antibodies.

Immunomodulator Galectin-9 is Increased in Blood and Skin of Patients with Bullous Pemphigoid

Massive recruitment of eosinophils into the dermis is a hallmark of bullous pemphigoid pathogenesis. Identifying the chemoattractant(s) guiding eosinophils into the skin in bullous pemphigoid is a prerequisite to thera-peutic targeting of eosinophil recruitment. Galectin -9 is a potent chemoattractant for eosinophils, but its potential role in bullous pemphigoid is unknown. The aim of this study was to determine the expression levels of galectin-9 in serum and skin of patients with bullous pemphigoid. Galectin-9 levels were significantly elevated in serum of patients with bullous pemphigoid compared with age- and sex-matched controls, but did not correlate with disease activity assessed with the Bullous Pemphigoid Disease Area Index. Galectin-9 expression was also increased in lesional skin of patients with bullous pemphigoid, and was expressed predominantly in eosinophils, neutrophils and keratinocytes. In conclusion, these results support the notion that galectin-9 may play a role in the patho-genesis of bullous pemphigoid.

Incidence of pemphigoid diseases in Northern Germany in 2016 - first data from the Schleswig-Holstein Registry of Autoimmune Bullous Diseases

BACKGROUND

Autoimmune bullous diseases (AIBD) are rare disorders characterized by autoantibody formation against components of adhesion molecules; in pemphigoid diseases (PD), these are proteins of hemidesmosomes and basement membrane, important for cell-matrix adhesion in skin and/or mucous membranes. Incidences of these diseases vary considerably between different populations.

OBJECTIVES

To establish a registry prospectively recruiting all AIBD patients in a geographically well-defined region in Northern Germany (Schleswig-Holstein).

METHODS

Only patients with verified disease (by clinical presentation, histology, direct and/or indirect immunofluorescence and /or ELISA) living in Schleswig-Holstein were included. Incidences of PD were estimated based on the total number of inhabitants in Schleswig-Holstein, stratified by birth year and sex.

RESULTS

Of 67 patients with PD [35 male, 32 female, mean age 75 (standard deviation 14.3 years)], 83% were patients with bullous pemphigoid [n = 56, 28 male, 28 female, mean age 78 (SD 9.9)]. The resulting crude incidences were 23.4 patients/million/year for all pemphigoid patients, 19.6 patients/million/year for bullous pemphigoid (age-standardized 16.9 patients/million/year) with a strong increase in bullous pemphigoid patients in the age group of 85-90 years with 262 patients/million/year. Incidences for bullous pemphigoid were higher in urban compared to rural areas. Other PD (mucous membrane pemphigoid, linear IgA disease, anti-p200 pemphigoid) were less frequent with crude incidences of 2.1, 1.0 and 0.7 patients/million/year, respectively.

CONCLUSIONS

This study prospectively analyses the incidence of PD in a carefully defined geographical area. The highest incidence among PD patients was found for bullous pemphigoid. The incidence of bullous pemphigoid is considerably increased compared to previous reports and reveals regional differences. Further studies are needed in order to clarify these findings.

Immunoglobulin M pemphigoid

BACKGROUND

Pemphigoid diseases are a heterogeneous group of autoimmune blistering disorders characterized by predominant deposition of immunoglobulin G or immunoglobulin A autoantibodies against structural proteins of the dermoepidermal junction (DEJ). Sole linear immunoglobulin M (IgM) deposits at the DEJ in pemphigoid diseases have been observed; however, IgM-specific target antigens have not been identified.

OBJECTIVE

Characterization of patients with IgM pemphigoid.

METHODS

Skin biopsy specimens and sera from IgM-positive patients were assessed using histopathology, direct and indirect immunofluorescence microscopy, enzyme-linked immunosorbent assays, immunoblotting, cryosection assay, complement fixation test, and internalization assays.

RESULTS

Tissue-bound linear IgM deposits along the DEJ and circulating IgM autoantibodies against type XVII collagen (Col17) were detected. These circulating IgM autoantibodies showed no complement activating or blister inducing capacity, but the ability of Col17 internalization ex vivo.

LIMITATIONS

Limited number of patients.

CONCLUSION

This study provides further evidence for the role of IgM autoantibodies in pemphigoid disease and highlights Col17 as a target antigen in IgM pemphigoid.

Analysis of the autoimmune response against BP180 in patients with Alzheimer's disease

Background

Current epidemiological studies suggest a significant correlation between Alzheimer's disease (AD) and bullous pemphigoid (BP). However, the autoimmune response against BP180 in patients with AD has not been fully understood. investigated.

Methods

We randomly enrolled 48 patients with AD and 50 sex- and age-matched healthy controls. We detected the presence/absence and the level of anti-BP180/BP230 immunoglobulin G (IgG) autoantibodies in the patients' serum to determine whether said antibodies possess reactivity against the BP180 protein in the human brain and skin.

Results

The enzyme-linked immunosorbent assay (ELISA) results revealed that the positive rate of anti-BP180 autoantibodies in patients with AD (23/48, 47.9%) was significantly higher than that in controls (4/50, 8.0%; P<0.0001). These ELISA-positive patients were further examined through immunoblotting. Sera from nine patients with AD (9/23, 39.1%) and one control (1/4, 25.0%) reacted with human cutaneous recombinant full-length BP180 and BP180-noncollagenous 16A (NC16A). Sera from 11 (11/23, 47.8%) patients with AD reacted with a 180-kDa protein from the human brain extract, but none of the controls' sera recognized the corresponding protein band. The majority of the patients in the anti-BP180-positive AD group were men (14/23, 60.9%) who were older (74.0 years) compared with those in the control group (6/25, 24.0%; P<0.05) (72.2 years; P<0.01).

Conclusions

Anti-BP180 autoantibodies are present in AD and recognize human recombinant full-length BP180 and a 180-kDa protein from the human brain extract, suggesting that BP180 is a shared autoantigen in AD and BP and may help clarify the mechanism to explain why a high risk of BP exists in AD. Elderly male patients with AD are significantly more likely to develop BP180 serum autoreactivity compared with other patients with AD.

Risk of solid malignancies in bullous pemphigoid: A large-scale population-based cohort study

The association of bullous pemphigoid (BP) with solid malignancies (SM) is a matter of controversy, as previous studies produced inconclusive findings. The aim of this study was to assess the risk of SM among patients with BP and to evaluate whether a history of SM predisposes individuals to develop subsequent BP. A population-based cohort study was performed comparing BP patients (n = 3924) with age-, sex- and race-matched control subjects (n = 19 280) with regard to incident cases of SM. Adjusted hazard ratios (HR) and adjusted odds ratios (OR) were estimated by Cox regression and logistic regression, respectively. The incidence of SM was 13.4 (95% confidence interval [CI], 11.6-15.3) and 14.3 (95% CI, 13.5-15.1) per 1000 person-years among patients with BP and controls, respectively. BP was not associated with an increased risk of SM (adjusted HR, 0.90; 95% CI, 0.77-1.05). Additionally, a history of SM was not related to the risk of subsequent BP (adjusted OR, 1.00; 95% CI, 0.90-1.10). In a stratified analysis, patients with BP had an increased risk of uterine cancer (adjusted HR, 2.56; 95% CI, 1.39-4.72) unlike the 18 remaining analyzed types of SM. Relative to BP patients without SM, those with BP and SM were older, had a male predominance, a higher prevalence of smoking, a higher burden of comorbidities and comparable survival rates. Although patients with BP do not experience an overall increased risk of developing SM, they are more likely to have uterine cancer. Our findings argue against routine extended cancer screening for patients with incident BP, but raise the awareness of uterine cancer among females with BP.

Patients with pemphigus are at an increased risk of developing rheumatoid arthritis: a large-scale cohort study

Data regarding the association between pemphigus and rheumatoid arthritis (RA) is inconclusive and yet to be firmly established. In the current study, we aimed to evaluate the risk of developing RA during the course of pemphigus. A large-scale population-based longitudinal cohort study was conducted to evaluate the hazard ratio (HR) of RA among 1985 patients with pemphigus relative to 9874 age-, sex-, and ethnicity-matched control subjects. A multivariate Cox regression model was utilized. The incidence of RA was 1.07 (95% CI, 0.62-1.72) and 0.36 (95% CI, 0.24-0.52) per 1000 person-years among patients with pemphigus and controls, respectively. The lifetime prevalence of RA was 2.3% (95% CI, 1.7-3.1%) among cases and 1.8% (95% CI, 1.5-2.0%) among controls. Patients with pemphigus were more than twice as likely to develop RA as compared to control subjects (adjusted HR, 2.54; 95% confidence interval [CI], 1.31-4.92). The increased risk was robust to a sensitivity analysis that included only cases managed by pemphigus-related systemic medications (adjusted HR, 2.56; 95% CI, 1.30-5.05). In conclusion, pemphigus is associated with an increased risk of RA. Physicians treating patients with pemphigus should be aware of this possible association. Further research is required to better understand the mechanism underlying this association.

Identification of novel therapeutic targets for blocking acantholysis in pemphigus

Background and Purpose

Pemphigus is caused by autoantibodies against desmoglein (Dsg) 1, Dsg3, and/or non‐Dsg antigens. Pemphigus vulgaris (PV) is the most common manifestation of pemphigus, with painful erosions on mucous membranes. In most cases, blistering also occurs on the skin, leading to areas of extensive denudation. Despite improvements in pemphigus treatment, time to achieve remission is long, severe adverse events are frequent and 20% of patients do not respond adequately. Current clinical developments focus exclusively on modulating B cell function or autoantibody half‐life. However, topical modulation of PV autoantibody‐induced blistering is an attractive target because it could promptly relieve symptoms.

Experimental Approach

To address this issue, we performed an unbiased screening in a complex biological system using 141 low MW inhibitors from a chemical library. Specifically, we evaluated PV IgG‐induced Dsg3 internalization in HaCaT keratinocytes. Validation of the 20 identified compounds was performed using keratinocyte fragmentation assays, as well as a human skin organ culture (HSOC) model.

key Results

Overall, this approach led to the identification of four molecules involved in PV IgG‐induced skin pathology: MEK1, TrkA, PI3Kα, and VEGFR2.

Conclusion and Implications

This unbiased screening revealed novel mechanisms by which PV autoantibodies induce blistering in keratinocytes and identified new treatment targets for this severe and potentially life‐threatening skin disease.

Long-term outcomes of rituximab therapy in pemphigus

BACKGROUND

Rituximab induces a rapid remission in most patients with pemphigus.

OBJECTIVE

Our aim was to assess the long-term efficacy of rituximab in this disease.

METHOD

We conducted a retrospective study of 59 patients with pemphigus treated with rituximab and observed over a median period of 104 months.

RESULTS

The rate of complete remission off therapy (CRoff) after the first rituximab cycle was 39%, increasing to 61% with additional rituximab courses. Long-term CRoff was achieved in 27% of patients. The recurrence rate after the first rituximab cycle was 63%, decreasing to approximately 40% with subsequent rituximab cycles. Median time to relapse after the first and subsequent rituximab cycles was 25 months. Renewed rituximab therapy reinduced complete remission in 94% of cases. Baseline anti-desmoglein antibody levels of ≤250 U/mL were significantly associated with the outcome of CRoff. In paired serum samples obtained before the first and six months after the last rituximab therapy, significant reductions of desmoglein-specific autoantibodies were observed. Patients relapsing after a complete remission induced by the first rituximab cycle were more likely to achieve CRoff than patients relapsing after a less favourable outcome and non-responders. There was no significant difference in age, sex, pemphigus subtype, rituximab dosing and disease duration between patients achieving CRoff and those not meeting this end point.

CONCLUSIONS

Lower desmoglein-specific antibody levels at baseline were predictive of CRoff. In patients receiving multiple rituximab cycles, complete remission after the first cycle was associated with a favourable long-term outcome. Repeated rituximab courses were highly effective for relapsed disease and improved the overall outcome.

Dual inhibition of complement factor 5 and leukotriene B4 synergistically suppresses murine pemphigoid disease

The treatment of most autoimmune diseases still relies on systemic immunosuppression and is associated with severe side effects. The development of drugs that more specifically abrogate pathogenic pathways is therefore most desirable. In nature, such specificity is exemplified, e.g., by the soft tick-derived biotherapeutic Coversin, which locally suppresses immune responses by inhibiting complement factor 5 (C5) and leukotriene B4 (LTB4). C5a, a proteolytic fragment of C5, and LTB4 are critical drivers of skin inflammation in pemphigoid diseases (PDs), a group of autoimmune blistering skin diseases. Here, we demonstrate that both Coversin and its mutated form L-Coversin, which inhibits LTB4 only, dose dependently attenuate disease in a model of bullous pemphigoid-like epidermolysis bullosa acquisita (BP-like EBA). Coversin, however, reduces disease more effectively than L-Coversin, indicating that inhibition of C5 and LTB4 synergize in their suppressing effects in this model. Further supporting the therapeutic potential of Coversin in humans, we found that C5a and LTB4 are both present in the blister fluid of patients with BP in quantities inducing the recruitment of granulocytes and that the number of cells expressing their receptors, C5aR1 and BLT1, respectively, is increased in perilesional skin. Collectively, our results highlight Coversin and possibly L-Coversin as potential therapeutics for PDs.

Anti-BP180 Autoantibodies Are Present in Stroke and Recognize Human Cutaneous BP180 and BP180-NC16A

Objective: Current evidence has revealed a significant association between bullous pemphigoid (BP) and neurological diseases (ND), including stroke, but the incidence of BP autoantibodies in patients with stroke has not previously been investigated. Our study aimed to assess BP antigen-specific antibodies in stroke patients. Design: One hundred patients with stroke and 100 matched healthy controls were randomly selected for measurement of anti-BP180/BP230 IgG autoantibodies by enzyme-linked immunosorbent assay (ELISA), salt-split indirect immunofluorescence (IIF), and immunoblotting against human cutaneous BP180 and BP180-NC16A. Results: Anti-BP180 autoantibodies were found in 14 (14.0%) patients with stroke and 5 (5.0%) of controls by ELISA (p < 0.05). Sera from 13 (13.0%) patients with stroke and 3 (3.0%) controls reacted with 180-kDa proteins from human epidermal extract (p < 0.05). 11 (11.0%) of stroke and 2 (2.0%) of control sera recognized the human recombinant full length BP180 and NC16A (p < 0.05). The anti-BP180-positive patients were significantly younger than the negative patients at the time of stroke (p < 0.001). Conclusion: Development of anti-BP180 autoantibodies occurs at a higher frequency after stroke, suggesting BP180 as a relatively common autoantigen after stroke and providing novel insights into BP pathogenesis in aging.

In situ detection of PR3-ANCA+ B cells and alterations in the variable region of immunoglobulin genes support a role of inflamed tissue in the emergence of auto-reactivity in granulomatosis with polyangiitis

Circulating anti-neutrophilic cytoplasmic autoantibodies targeting proteinase 3 (PR3-ANCA) are a diagnostic and pathogenic hallmark of granulomatosis with polyangiitis (GPA). It is, however, incompletely understood if inflamed tissue supports presence or emergence of PR3-ANCA⁺ B cells. In search of such cells in inflamed tissue of GPA, immunofluorescence staining for IgG and a common PR3-ANCA idiotype (5/7 Id) was undertaken. Few 5/7 Id⁺/IgG⁺ B cells were detected in respiratory and kidney tissue of GPA. To gain more insight into surrogate markers possibly indicative of an anti-PR3-response, a meta-analysis comprising IGVH and IGVL genes derived from respiratory tract tissue of GPA (231 clones) was performed. Next generation sequencing-based IGHV genes derived from peripheral blood of healthy donors (244.353 clones) and previously published IGLV genes (148 clones) served as controls. Additionally, Ig genes of three murine and five known human monoclonal anti-PR3 antibodies were analyzed. Primary and probably secondary rearrangements led to altered VDJ usage and an extended complementarity determining region 3 (CDR3) of IGHV clones from GPA tissue. Selection against amino acid exchanges was prominent in the framework region of IGHV clones from GPA tissue. The comparison of V(D)J rearrangements and deduced amino acid sequences of the CDR3 yielded no identities and few similarities between clones derived from respiratory tissue of GPA and anti-PR3 antibodies, arguing against a presence of B cells that carry PR3-ANCA-prone Ig genes among the clones. In line with the scarcity of 5/7 Id⁺ B lymphocytes in GPA tissue, the results suggest that with respect to a local anti-PR3 response, methods detecting rare clones are required.

Autoantibodies in Serum of Systemic Scleroderma Patients: Peptide-Based Epitope Mapping Indicates Increased Binding to Cytoplasmic Domains of CXCR3

Systemic sclerosis (SSc) is a severe chronic autoimmune disease with high morbidity and mortality. Sera of patients with SSc contain a large variety of autoantibody (aab) reactivities. Among these are functionally active aab that bind to G protein-coupled receptors (GPCR) such as C-X-C motif chemokine receptor 3 (CXCR3) and 4 (CXCR4). Aab binding to the N-terminal portion of these two GPCRs have been shown to be associated with slower disease progression in SSc, especially deterioration of lung function. Aabs binding to GPCRs exhibit functional activities by stimulating or inhibiting GPCR signaling. The specific functional activity of aabs crucially depends on the epitopes they bind to. To identify the location of important epitopes on CXCR3 recognized by aabs from SSc patients, we applied an array of 36 overlapping 18-20mer peptides covering the entire CXCR3 sequence, comparing epitope specificity of SSc patient sera (N = 32, with positive reactivity with CXCR3) to healthy controls (N = 30). Binding of SSc patient and control sera to these peptides was determined by ELISA. Using a Bayesian model approach, we found increased binding of SSc patient sera to peptides corresponding to intracellular epitopes within CXCR3, while the binding signal to extracellular portions of CXCR3 was found to be reduced. Experimentally determined epitopes showed a good correspondence to those predicted by the ABCpred tool. To verify these results and to translate them into a novel diagnostic ELISA, we combined the peptides that represent SSc-associated epitopes into a single ELISA and evaluated its potential to discriminate SSc patients (N = 31) from normal healthy controls (N = 47). This ELISA had a sensitivity of 0.61 and a specificity of 0.85. Our data reveals that SSc sera preferentially bind intracellular epitopes of CXCR3, while an extracellular epitope in the N-terminal domain that appears to be target of aabs in healthy individuals is not bound by SSc sera. Based upon our results, we could devise a novel ELISA concept that may be helpful for monitoring of SSc patients.

Proteomic Analysis of Pemphigus Autoantibodies Indicates a Larger, More Diverse, and More Dynamic Repertoire than Determined by B Cell Genetics

In autoantibody-mediated diseases such as pemphigus, serum antibodies lead to disease. Genetic analysis of B cells has allowed characterization of antibody repertoires in such diseases but would be complemented by proteomic analysis of serum autoantibodies. Here, we show using proteomic analysis that the serum autoantibody repertoire in pemphigus is much more polyclonal than that found by genetic studies of B cells. In addition, many B cells encode pemphigus autoantibodies that are not secreted into the serum. Heavy chain variable gene usage of serum autoantibodies is not shared among patients, implying targeting of the coded proteins will not be a useful therapeutic strategy. Analysis of autoantibodies in individual patients over several years indicates that many antibody clones persist but the proportion of each changes. These studies indicate a dynamic and diverse autoantibody response not revealed by genetic studies and explain why similar overall autoantibody titers may give variable disease activity.

Mechanisms of Autoantibody-Induced Pathology

Autoantibodies are frequently observed in healthy individuals. In a minority of these individuals, they lead to manifestation of autoimmune diseases, such as rheumatoid arthritis or Graves' disease. Overall, more than 2.5% of the population is affected by autoantibody-driven autoimmune disease. Pathways leading to autoantibody-induced pathology greatly differ among different diseases, and autoantibodies directed against the same antigen, depending on the targeted epitope, can have diverse effects. To foster knowledge in autoantibody-induced pathology and to encourage development of urgently needed novel therapeutic strategies, we here categorized autoantibodies according to their effects. According to our algorithm, autoantibodies can be classified into the following categories: (1) mimic receptor stimulation, (2) blocking of neural transmission, (3) induction of altered signaling, triggering uncontrolled (4) microthrombosis, (5) cell lysis, (6) neutrophil activation, and (7) induction of inflammation. These mechanisms in relation to disease, as well as principles of autoantibody generation and detection, are reviewed herein.

Determinants of VH1-46 Cross-Reactivity to Pemphigus Vulgaris Autoantigen Desmoglein 3 and Rotavirus Antigen VP6

Shared VH1-46 gene usage has been described in B cells reacting to desmoglein 3 (Dsg3) in the autoimmune disease pemphigus vulgaris (PV), as well as B cells responding to rotavirus capsid protein VP6. In both diseases, VH1-46 B cells bearing few to no somatic mutations can recognize the disease Ag. This intriguing connection between an autoimmune response to self-antigen and an immune response to foreign Ag prompted us to investigate whether VH1-46 B cells may be predisposed to Dsg3-VP6 cross-reactivity. Focused testing of VH1-46 mAbs previously isolated from PV and rotavirus-exposed individuals indicates that cross-reactivity is rare, found in only one of seven VH1-46 IgG clonotypes. High-throughput screening of IgG B cell repertoires from two PV patients identified no additional cross-reactive clonotypes. Screening of IgM B cell repertoires from one non-PV and three PV patients identified specific cross-reactive Abs in one PV patient, but notably all six cross-reactive clonotypes used VH1-46. Site-directed mutagenesis studies indicate that amino acid residues predisposing VH1-46 Abs to Dsg3 reactivity reside in CDR2. However, somatic mutations only rarely promote Dsg3-VP6 cross-reactivity; most mutations abolish VP6 and/or Dsg3 reactivity. Nevertheless, functional testing identified two cross-reactive VH1-46 Abs that both disrupt keratinocyte adhesion and inhibit rotavirus replication, indicating the potential for VH1-46 Abs to have both pathologic autoimmune and protective immune functions. Taken together, these studies suggest that certain VH1-46 B cell populations may be predisposed to Dsg3-VP6 cross-reactivity, but multiple mechanisms prevent the onset of autoimmunity after rotavirus exposure.