Immune dysregulation, polyendocrinopathy, enteropathy, X-linked syndrome (IPEX) associated with pemphigoid nodularis: a case report and review of the literature

Understanding CD4+ T cells in autoimmune bullous diseases

Autoimmune bullous diseases (AIBDs) are a group of life-threatening blistering diseases caused by autoantibodies that target proteins in the skin and mucosa. Autoantibodies are the most important mediator in the pathogenesis of AIBDs, and various immune mechanisms contribute to the production of these pathogenic autoantibodies. Recently, significant progress has been made in understanding how CD4⁺ T cells drive autoantibody production in these diseases. Here, we review the critical role of CD4⁺ T cells in the production of pathogenic autoantibodies for the initiation and perpetuation of humoral response in AIBDs. To gain an in-depth understanding of CD4⁺ T-cell pathogenicity, antigen specificity, and mechanisms of immune tolerance, this review covers comprehensive mouse and human studies of pemphigus and bullous pemphigoid. Further exploration of pathogenic CD4⁺ T cells will potentially provide immune targets for improved treatment of AIBDs.

Novel PGM3 mutation in two siblings with combined immunodeficiency and childhood bullous pemphigoid: a case report and review of the literature

BACKGROUND

Bullous pemphigoid is the most common autoimmune subepidermal blistering disorder with a low incidence in childhood. Combined immunodeficiencies (CIDs) are a group of monogenic inborn errors of immunity (IEIs) characterized by T- and B-cell dysfunction leading to recurrent infections, lymphoproliferation, predisposition to malignancy, and autoimmunity. Here, we report two Afghan siblings with a diagnosis of CID and extremely rare manifestation of diffuse bullous pemphigoid skin lesions.

CASE PRESENTATION

The older sibling (patient 1) was a 32-month-old male with facial dysmorphism, protracted diarrhea, failure to thrive, recurrent oral candidiasis, recurrent otitis media with tympanic membrane perforation, who had been previously diagnosed with CID. While he was under treatment with intravenous immunoglobulin (IVIg), he developed extensive blistering lesions, which were diagnosed as childhood bullous pemphigoid. Methylprednisolone and azathioprine were added to the regimen, which resulted in a remarkable improvement of the skin lesions and also the feeding condition. However,2 weeks later, he was re-admitted to the intensive care unit (ICU) and eventually died due to fulminant sepsis. Later, his 12-month-old sister (patient 2) with similar facial dysmorphism and a history of developmental delay, food allergy, recurrent oral candidiasis, and respiratory tract infections also developed blistering skin lesions. She was under treatment for occasional eczematous lesions, and had been receiving IVIg for 3 months due to low levels of immunoglobulins. Further immunologic workup showed an underlying CID and thus treatment with IVIg continued, gradually improving her clinical condition. The genetic study of both siblings revealed a novel homozygous mutation in exon 7 of the PGM3 gene, c.845 T > C (p.Val282Ala).

CONCLUSIONS

Dermatologic disorders may be the presenting sign in patients with CID and mutated PGM3. This case report further extends the spectrum of skin manifestations that could be observed in PGM3 deficiency and emphasizes the importance of considering CIDs during the assessment of skin disorders, particularly if they are extensive, recurrent, refractory to treatment, and/or associated with other signs of IEIs.

Case Report: Pemphigoid Nodularis-Five Patients With Many Years of Follow-Up and Review of the Literature

Pemphigoid nodularis is a rare form of pemphigoid that joins the clinical picture of prurigo nodularis and the immunological features of bullous pemphigoid, which is therapeutically challenging. Here, we analyze five female patients with a long-lasting course of nodular pemphigoid in terms of clinical and immunological characteristics and therapy. All the patients fulfilled clinical and immunological criteria of nodular pemphigoid. We applied numerous techniques allowing the proper diagnosis: direct and indirect immunofluorescence, salt split skin, ELISA, BIOCHIP, and fluorescence overlay antigen mapping using laser scanning confocal microscopy. Our study showed that 4 of 5 patients fulfilled the clinical and immunological criteria of nodular bullous pemphigoid. Two out of 4 patients presented exclusively nodular lesions; in the other two patients, blisters and erythematous lesions preceded prurigo-like lesions by a few years. The remaining patient had clinical and immunological criteria of nodular mucous membrane pemphigoid, presenting oral erosions, scarring conjunctivitis, and numerous disseminated nodules on the skin. All the patients were treated with multiple medicines; however, it was observed that the use of clobetasol propionate on the entire body plus antidepressants best controlled the disease. Pemphigoid nodularis mainly occurs in elderly women. In cases with coexisting psychological problems, antidepressants should be considered as an important complementary therapy to the basic one with clobetasol propionate.

Immunopathology and Immunotherapy of Inflammatory Skin Diseases

Recently, there have been impressive advancements in understanding of the immune mechanisms underlying cutaneous inflammatory diseases. To understand these diseases on a deeper level and clarify the therapeutic targets more precisely, numerous studies including in vitro experiments, animal models, and clinical trials have been conducted. This has resulted in a paradigm shift from non-specific suppression of the immune system to selective, targeted immunotherapies. These approaches target the molecular pathways and cytokines responsible for generating inflammatory conditions and reinforcing feedback mechanisms to aggravate inflammation. Among the numerous types of skin inflammation, psoriasis and atopic dermatitis (AD) are common chronic cutaneous inflammatory diseases. Psoriasis is a IL-17–mediated disease driven by IL-23, while AD is predominantly mediated by Th2 immunity. Autoimmune bullous diseases are autoantibody-mediated blistering disorders, including pemphigus and bullous pemphigoid. Alopecia areata is an organ-specific autoimmune disease mediated by CD8⁺ T-cells that targets hair follicles. This review will give an updated, comprehensive summary of the pathophysiology and immune mechanisms of inflammatory skin diseases. Moreover, the therapeutic potential of current and upcoming immunotherapies will be discussed.

Calculation of Similarity Between 26 Autoimmune Diseases Based on Three Measurements Including Network, Function, and Semantics

Autoimmune diseases (ADs) are a broad range of diseases in which the immune response to self-antigens causes damage or disorder of tissues, and the genetic susceptibility is regarded as the key etiology of ADs. Accumulating evidence has suggested that there are certain commonalities among different ADs. However, the theoretical research about similarity between ADs is still limited. In this work, we first computed the genetic similarity between 26 ADs based on three measurements: network similarity (NetSim), functional similarity (FunSim), and semantic similarity (SemSim), and systematically identified three significant pairs of similar ADs: rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE), myasthenia gravis (MG) and autoimmune thyroiditis (AIT), and autoimmune polyendocrinopathies (AP) and uveomeningoencephalitic syndrome (Vogt-Koyanagi-Harada syndrome, VKH). Then we investigated the gene ontology terms and pathways enriched by the three significant AD pairs through functional analysis. By the cluster analysis on the similarity matrix of 26 ADs, we embedded the three significant AD pairs in three different disease clusters respectively, and the ADs of each disease cluster might have high genetic similarity. We also detected the risk genes in common among the ADs which belonged to the same disease cluster. Overall, our findings will provide significant insight in the commonalities of different ADs in genetics, and contribute to the discovery of novel biomarkers and the development of new therapeutic methods for ADs.

Generalized eczematous dermatitis and pruritus responsive to dupilumab in a patient with immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome

This case describes a patient with immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome with diffuse eczematous dermatitis and severe, intractable pruritus. Despite a bone marrow transplant and immunosuppressive therapy, his skin findings and pruritus persisted. Off-label dupilumab provided significant improvement and almost complete clearance of the dermatitis and pruritus. This is the first known report of dupilumab being used in a patient with IPEX syndrome.

Immune Dysregulation, Polyendocrinopathy, Enteropathy, X-Linked Syndrome Manifesting as Lymphocytic Interstitial Pneumonia and Treatment-Resistant Bullous Pemphigoid

Immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome is a rare immune deficiency with a broad clinical presentation. IPEX syndrome causes dysfunctional regulatory T cells, increasing the risk of autoimmune diseases. In this case report, we describe a 7-year-old boy with lymphocytic interstitial pneumonia and bullous pemphigoid who was recently diagnosed with IPEX syndrome.

Inborn errors of immunity with atopic phenotypes: A practical guide for allergists

Inborn errors of immunity (IEI) are a heterogeneous group of disorders, mainly resulting from mutations in genes associated with immunoregulation and immune host defense. These disorders are characterized by different combinations of recurrent infections, autoimmunity, inflammatory manifestations, lymphoproliferation, and malignancy. Interestingly, it has been increasingly observed that common allergic symptoms also can represent the expression of an underlying immunodeficiency and/or immune dysregulation.

Very high IgE levels, peripheral or organ-specific hypereosinophilia, usually combined with a variety of atopic symptoms, may sometimes be the epiphenomenon of a monogenic disease. Therefore, allergists should be aware that severe and/or therapy-resistant atopic disorders might be the main clinical phenotype of some IEI. This could pave the way to target therapies, leading to better quality of life and improved survival in affected patients.

IPEX Syndrome: Improved Knowledge of Immune Pathogenesis Empowers Diagnosis

Immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome is a rare monogenic autoimmune disease with variable clinical manifestations, ranging from early-onset severe autoimmunity, including enteropathy, eczema, and type 1 diabetes, to late-onset or atypical symptoms. Despite the clinical heterogeneity, the unifying feature of IPEX is mutation of the FOXP3 gene, which encodes a transcription factor essential for maintenance of thymus-derived regulatory T cells (Tregs). In IPEX patients, Tregs can be present, although unstable and impaired in function, unable to inhibit proliferation and cytokine production of effector T (Teff) cells. Mutated FOXP3 can also disrupt other compartments: FOXP3-deficient Teff cells proliferate more than the wild-type counterpart, display altered T-cell-receptor signaling response, a reduced T-naïve compartment and a skew toward a Th2 profile. Due to FOXP3 mutations, the frequency of autoreactive B cells is increased and the IgA and IgE production is altered, together with early emergence of tissue-specific autoantibodies. Recently, the awareness of the wide clinical spectrum of IPEX improved the diagnostic tools. In cases presenting with enteropathy, histological evaluation is helpful, although there are no pathognomonic signs of disease. On the other hand, the study of FOXP3 expression and in vitro Treg function, as well as the detection of specific circulating autoantibodies, is recommended to narrow the differential diagnosis. Nowadays, Sanger sequencing should be limited to cases presenting with the classical triad of symptoms; otherwise, next-generation sequencing is recommended, given the cost-effectiveness and the advantage of excluding IPEX-like syndromes. The latter approach could be time spearing in children with severe phenotypes and candidate to advanced therapies.

The Skin as a Window into Primary Immune Deficiency Diseases: Atopic Dermatitis and Chronic Mucocutaneous Candidiasis

Primary immune deficiency diseases characteristically present with recurrent, severe, or unusual infections. These infections may often involve the skin, with mucocutaneous candidal infections seen in a variety of different primary immune deficiencies. Primary immune deficiencies may also present with noninfectious cutaneous complications, of which eczema is the most common. In a patient with suspected primary immune deficiency, the presence of eczema or candidal skin infections offers critical information about the underlying immune defect, either the presence of atopy or defect in the T_H17 pathway, respectively. These skin manifestations also are often early or heralding findings of the underlying immunologic disease. Therefore, awareness of associations between these skin findings and specific immune deficiencies may aide in the early detection and treatment of serious or life-threatening immunologic defects. This review specifically will focus on the primary immune deficiencies commonly associated with eczema or mucocutaneous candidiasis.

Role of BP230 autoantibodies in bullous pemphigoid

Bullous pemphigoid (BP) is an autoimmune disease associated with subepidermal blistering due to autoantibodies directed against BP180 and BP230. BP180 is currently considered as the major pathogenic autoantigen. However, previous clinical findings suggested that anti-BP230 autoantibodies alone can cause skin lesions in animal models and many BP patients. The characteristics of BP230 and the pathogenic roles of anti-BP230 antibodies have been proposed. First, at the molecular level, BP230 mediates the attachment of keratin intermediate filaments to the hemidesmosomal plaque and interacts with other constituents of hemidesmosomes. Second, the presence of BP230 autoantibodies may correlate with specific clinical features of BP. The immunoglobulin (Ig)G autoantibodies from BP patients react mainly against the C-terminus of BP230, while the IgE autoantibodies are still inconclusive. Third, in vivo, autoantibodies against BP230 involved in the disease may not only induce the inflammatory response but also impair the structural stability of hemidesmosomes. This article reviews recently published work about the role of BP230 and its antibodies, including IgG and IgE, aiming to find clues of its clinical association and lay the foundation for the research on the pathogenicity of antibodies against BP230.

Autoimmunity and immunological tolerance in autoimmune bullous diseases

Autoimmune diseases are devastating conditions in which the immune system is directed against the host, leading to life-threatening destruction of organs. Although autoantigens are ill-defined in most autoimmune diseases, this is not the case in the skin. Autoimmune bullous diseases have been extensively studied with detailed characterization of autoantigens, the epitopes that are targeted, and the mechanisms of action that mediate autoimmune tissue destruction. Pemphigus is an autoimmune bullous disease caused by circulating IgG that targets two desmosomal proteins, desmoglein 1 and 3, which are crucial for cell-cell adhesion of keratinocytes. Binding of auto-antibodies to desmogleins impairs keratinocyte adhesion, leading to severe blistering disease. Mouse models that recapitulate the human disease have been instrumental in elucidating the detailed pathophysiology. Taking advantage of the fact that desmogleins are specifically targeted in pemphigus, studying humoral and cellular autoimmunity against these autoantigens provides us with an opportunity to understand not only the effector mechanisms of B and T cells in mediating pathology but also how autoreactive lymphocytes are regulated during development in the thymus and post-development in the periphery. This review introduces pemphigus and its subtypes as prototypic autoimmune diseases from which recent basic and translational developments should provide insight into how autoimmunity develops.

Malt1 Protease Deficiency in Mice Disrupts Immune Homeostasis at Environmental Barriers and Drives Systemic T Cell-Mediated Autoimmunity

The paracaspase Malt1 is a key regulator of canonical NF-κB activation downstream of multiple receptors in both immune and nonimmune cells. Genetic disruption of Malt1 protease function in mice and MALT1 mutations in humans results in reduced regulatory T cells and a progressive multiorgan inflammatory pathology. In this study, we evaluated the altered immune homeostasis and autoimmune disease in Malt1 protease-deficient (Malt1PD) mice and the Ags driving disease manifestations. Our data indicate that B cell activation and IgG1/IgE production is triggered by microbial and dietary Ags preferentially in lymphoid organs draining mucosal barriers, likely as a result of dysregulated mucosal immune homeostasis. Conversely, the disease was driven by a polyclonal T cell population directed against self-antigens. Characterization of the Malt1PD T cell compartment revealed expansion of T effector memory cells and concomitant loss of a CD4⁺ T cell population that phenotypically resembles anergic T cells. Therefore, we propose that the compromised regulatory T cell compartment in Malt1PD animals prevents the efficient maintenance of anergy and supports the progressive expansion of pathogenic, IFN-γ-producing T cells. Overall, our data revealed a crucial role of the Malt1 protease for the maintenance of intestinal and systemic immune homeostasis, which might provide insights into the mechanisms underlying IPEX-related diseases associated with mutations in MALT1.

Bullous Diseases in Children: A Review of Clinical Features and Treatment Options

Bullous diseases are uncommon in children; however, as they have the potential to affect quality of life, occasionally have long-term side effects in the setting of scarring processes, and carry a rare risk of underlying malignancy [e.g., with paraneoplastic pemphigus (PNP)], knowledge of their clinical presentation and treatment options is essential. Given the rarity of these conditions, our current state of knowledge is largely derived from case reports and case series, with a paucity of evidence-based recommendations. In this review, we discuss the clinical presentation of and treatment options for linear immunoglobulin A disease, dermatitis herpetiformis, pemphigus vulgaris, pemphigus foliaceus, PNP, bullous pemphigoid, mucus membrane pemphigoid, epidermolysis bullosa acquisita, and inherited epidermolysis bullosa. In general, when these conditions, except for PNP, occur in childhood, they have a better prognosis than when they occur in adults. Clinical, histopathological, and immunologic features frequently overlap, but distinct differences have also been reported, most commonly in clinical presentation. Treatment is often similar to that in adults, although specific considerations are necessary for a pediatric population.

Paraneoplastic Pemphigus: Paraneoplastic Autoimmune Disease of the Skin and Mucosa

Paraneoplastic pemphigus (PNP) is a rare but life-threatening mucocutaneous disease mediated by paraneoplastic autoimmunity. Various neoplasms are associated with PNP. Intractable stomatitis and polymorphous cutaneous eruptions, including blisters and lichenoid dermatitis, are characteristic clinical features caused by humoral and cell-mediated autoimmune reactions. Autoreactive T cells and IgG autoantibodies against heterogeneous antigens, including plakin family proteins and desmosomal cadherins, contribute to the pathogenesis of PNP. Several mechanisms of autoimmunity may be at play in this disease on the type of neoplasm present. Diagnosis can be made based on clinical and histopathological features, the presence of anti-plakin autoantibodies, and underlying neoplasms. Immunosuppressive agents and biologics including rituximab have been used for the treatment of PNP; however, the prognosis is poor due to underlying malignancies, severe infections during immunosuppressive treatment, and bronchiolitis obliterans mediated by autoimmunity. In this review, we overview the characteristics of PNP and focus on the immunopathology and the potential pathomechanisms of this disease.

Mogamulizumab Treatment Elicits Autoantibodies Attacking the Skin in Patients with Adult T-Cell Leukemia-Lymphoma

PURPOSE

The anti-CCR4 mAb, mogamulizumab, offers therapeutic benefit to patients with adult T-cell leukemia-lymphoma (ATL), but skin-related adverse events (AE) such as erythema multiforme occur frequently. The purpose of this study was to determine the mechanisms by which mogamulizumab causes skin-related AEs in patients with ATL.

EXPERIMENTAL DESIGN

We investigated whether autoantibodies were present in patients' sera using flow cytometry to determine binding to keratinocytes and melanocytes (n = 17), and immunofluorescence analysis of tissue sections. We analyzed the IgM heavy chain repertoire in peripheral blood mononuclear cells before and after mogamulizumab or other chemotherapy by next-generation sequencing (NGS; n = 16).

RESULTS

Autoantibodies recognizing human keratinocytes or melanocytes were found in the sera of 6 of 8 patients suffering from mogamulizumab-induced erythema multiforme. In one patient, complement-dependent cytotoxicity (CDC) mediated by autoantibodies against keratinocytes or melanocytes was proportionally related to the severity of the erythema multiforme. The presence of autoantibodies in the epidermis was confirmed in all biopsy specimens of mogamulizumab-induced erythema multiforme (n = 12). Furthermore, colocalization of autoantibodies and C1q, suggesting the activation of CDC, was observed in 67% (8/12). In contrast, no autoantibody or C1q was found in ATL tumor skin lesions (n = 13). Consistent with these findings, NGS demonstrated that IgM germline genes had newly emerged and expanded, resulting in IgM repertoire skewing at the time of erythema multiforme.

CONCLUSIONS

Mogamulizumab elicits autoantibodies playing an important role in skin-related AEs, possibly associated with regulatory T-cell depletion. This is the first report demonstrating the presence of skin-directed autoantibodies after mogamulizumab treatment.

Rituximab and Omalizumab for the Treatment of Bullous Pemphigoid: A Systematic Review of the Literature

BACKGROUND

Bullous pemphigoid (BP) is the most common autoimmune blistering skin disease worldwide. Systemic corticosteroids are considered the mainstay of therapy; however, they may cause significant adverse effects and treatment failures, so additional therapeutic modalities with better safety profiles are required. Rituximab and omalizumab are novel biologic agents administered in recent years for the treatment of BP, yet data regarding their use in the disease are limited.

OBJECTIVE

Our objective was to systematically review the current literature regarding the use of rituximab and omalizumab for the treatment of BP to evaluate their safety and efficacy.

METHODS

A systematic review of all publications evaluating patients with BP treated with rituximab or omalizumab was performed. The primary outcome was clinical response; secondary outcomes were adverse events and recurrence rate.

RESULTS

The systematic review included 35 publications (84 patients: 62 receiving rituximab and 22 receiving omalizumab). In total, 61 of 63 patients had not experienced disease control with systemic corticosteroids before receiving the biologic treatment. Complete response rates were 85% and 84% for rituximab and omalizumab, respectively. The recurrence rate was considerably lower with rituximab (29%) than with omalizumab (80%). Mean time to recurrence was 10.2 and 3.4 months, and adverse effects occurred in 24% and 20% of the patients, respectively.

CONCLUSIONS

Available data, although potentially limited because of publication bias, suggest that rituximab and omalizumab have similar safety profiles and provide clinical benefit for patients with BP. The reviewed data indicated that rituximab resulted in lower recurrence rates and a longer time until recurrence than omalizumab.

Pemphigoid nodularis - rare presentation of bullous pemphigoid: A case report and literature review

Pemphigoid nodularis (PN) is a rare clinical variant of bullous pemphigoid characterized by the presence of nodular prurigo-like lesions and pemphigoid blisters. The diagnosis is confirmed by direct immunofluorescence (DIF)/ indirect immunofluorescence (IIF) and immunoserology tests. For some patients, with long mean duration of symptoms, the correct diagnosis of PN is delayed because the disease is not recognized. We present a case and summarize the reported characteristics of PN. The search in MEDLINE database, after selection, resulted in 36 articles presenting 47 cases of PN. Between published cases a female predominance was noted (female to male ratio of 1.8:1), almost half of the reported patients were non-Caucasian, and the mean age at presentation was 66.2 years. The mean duration until the diagnosis was almost 2 years. Sixteen patients also had other autoimmune diseases. Twenty-two patients developed vesicles/bullae/urticarial plaques before or after the diagnosis. Peripheral eosinophilia and high levels of serum total IgE were reported in 10.6 and 27.2% of patients, respectively. ELISA for either BP180, BP230 or both were positive in all tested cases. DIF and IIF microscopy were positive overall in 100 and 92.3% of cases, respectively. Corticosteroids, either topical or systemic, were the most efficient therapeutic option, although many others were used. PN remains a diagnostic and therapeutic challenge in elderly patients with unexplained refractory chronic pruritus associated with papulo-nodular lesions.

Regulatory T-cell dysfunction induces autoantibodies to bullous pemphigoid antigens in mice and human subjects

BACKGROUND

Regulatory T (Treg) cells play a crucial role in peripheral immune tolerance in multiple organs, including the skin. Thus far, the effect of peripheral immune tolerance failure on autoantibody-related autoimmune reactions to the skin is unclear.

OBJECTIVE

We sought to elucidate the target autoantigens in the skin under the condition of Treg cell dysfunction caused by forkhead box P3 (Foxp3) gene mutations in scurfy mice and patients with immunodysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome.

METHODS

Sera and skin from scurfy mice and sera from patients with IPEX syndrome were analyzed to detect target autoantigens by using immunofluorescence studies, ELISAs, and immunoblotting. The pathogenicity of scurfy IgG was examined by using a passive transfer experiment. CD4⁺ T cells from scurfy mice were transferred to immunodeficient mice to examine their pathogenicity. Signal transducer and activator of transcription 6 (Stat6)^-/- scurfy mice were analyzed to further clarify the molecular pathway of autoantibody production. Follicular helper T-cell counts are measured in Stat6^-/- scurfy mice and scurfy mice.

RESULTS

Scurfy mice spontaneously generated IgG autoantibodies to the dermal-epidermal junction, which had been class-switched from IgM within 12 days after birth. The target autoantigens were murine BP230 and type XVII collagen (COL17). The scurfy polyclonal autoantibodies did not induce skin fragility in neonatal mice. Autoantibody production was induced by CD4⁺ T cells from scurfy mice and was ameliorated by Stat6 gene knockout in association with a decrease of follicular helper T cells. We also identified autoantibodies to COL17 and BP230 in patients with IPEX syndrome and found an association between production of autoantibodies to COL17 and an eczematous skin phenotype.

CONCLUSIONS

Dysregulation of Treg cells generates autoantibodies to COL17 and BP230 in vivo.

Regulatory T-cell deficiency leads to pathogenic bullous pemphigoid antigen 230 autoantibody and autoimmune bullous disease

BACKGROUND

Autoimmune bullous diseases/dermatoses (AIBDs) are severe autoantibody-mediated skin diseases. The pathogenic relevance of autoreactive CD4⁺ T cells for the induction of autoantibody production remains to be fully evaluated. Scurfy mice lack functional regulatory T (Treg) cells, experience spontaneous activation of autoreactive CD4⁺ T cells, and display severe erosive skin lesions suggestive of AIBDs.

OBJECTIVE

We sought to determine whether AIBDs develop in Treg cell-deficient scurfy mice.

METHODS

Histology, indirect immunofluorescence (IF) microscopy, direct IF, and ELISA were used to prove the presence of AIBDs in scurfy mice. Monoclonal autoantibodies from sera of scurfy mice were screened by using indirect IF on murine skin, and immunoprecipitation and mass spectrometry were used for target antigen identification, followed by confirmation in modified human embryonic kidney cells and murine keratinocytes. Pathogenicity was determined by injecting the autoantibody into neonatal mice and transferring scurfy CD4⁺ T cells into nu/nu mice.

RESULTS

Autoantibodies against different known autoantigens of AIBDs spontaneously develop in scurfy mice. Histology reveals subepidermal blisters, and direct IF of skin of scurfy mice shows a predominant linear staining pattern. The mAb 20B12 shows a linear staining pattern in indirect IF, recognizes the murine hemidesmosomal protein bullous pemphigoid antigen 230 (BP230) as the target antigen, and cross-reacts with human BP230. Purified mAb 20B12 induces subepidermal blisters in neonatal mice. Transfer of scurfy CD4⁺ T cells is sufficient to induce antibodies with reactivity to AIBD autoantigens and subepidermal blisters in the skin of recipient T cell-deficient nu/nu mice.

CONCLUSION

We show that the absence of Treg cells leads to AIBDs by pathogenic autoantibodies targeting BP230.

Regulatory T cells in autoimmune skin diseases

CD4⁺ Foxp3⁺ regulatory T cells (Tregs) are suppressors of immune activation and play a crucial role in the maintenance of peripheral tolerance. Mutations of Foxp3 result in fatal autoimmunity in multiple organs, including the skin, in both humans and mice. Many studies have demonstrated the altered frequency and functions of Tregs, changes in cytokine and chemokine levels related to Tregs and the differences in genetic background regarding Tregs in autoimmune skin disorders. Recent studies have extended our knowledge of certain properties of Tregs, especially skin-resident Tregs. In addition, some novel therapies have been performed by modulating the number and the function of Tregs. This review focuses on the role of Tregs in some autoimmune skin disorders, including alopecia areata, vitiligo, pemphigoid and pemphigus, and systemic sclerosis, and discusses questions that remain to be addressed.

Regulatory T Cell and Forkhead Box Protein 3 as Modulators of Immune Homeostasis

The transcription factor forkhead box protein 3 (FOXP3) is an essential molecular marker of regulatory T cell (Treg) development in different microenvironments. Tregs are cells specialized in the suppression of inadequate immune responses and the maintenance of homeostatic tolerance. Studies have addressed and elucidated the role played by FOXP3 and Treg in countless autoimmune and infectious diseases as well as in more specific cases, such as cancer. Within this context, the present article reviews aspects of the immunoregulatory profile of FOXP3 and Treg in the management of immune homeostasis, including issues relating to pathology as well as immune tolerance.

Primary immunodeficiency update: Part I. Syndromes associated with eczematous dermatitis

In the past decade, the availability of powerful molecular techniques has accelerated the pace of discovery of several new primary immunodeficiencies (PIDs) and revealed the biologic basis of other established PIDs. These genetic advances, in turn, have facilitated more precise phenotyping of associated skin and systemic manifestations and provide a unique opportunity to better understand the complex human immunologic response. These continuing medical education articles will provide an update of recent advances in PIDs that may be encountered by dermatologists through their association with eczematous dermatitis, infectious, and non-infectious cutaneous manifestations. Part I will discuss new primary immunodeficiencies that have an eczematous dermatitis. Part II will focus on primary immunodeficiencies that greatly increase susceptibility to fungal infection and the noninfectious presentations of PIDs.

The emerging role of rituximab in autoimmune blistering diseases

Rituximab is a chimeric monoclonal antibody that selectively binds to the CD20 molecule on B cells, resulting in their lysis. In autoimmune blistering diseases, the auto-antibody-producing B cells are destroyed and auto-antibody levels are reduced or eliminated. In the majority of patients, rituximab produces rapid clinical response and early resolution. In part, this accounts for the increased use of rituximab. Rituximab does not distinguish normal from pathologic B cells. Hence, shortly after its use, B-cell levels are zero and remain so for several months. In most patients, the use of systemic corticosteroids and immunosuppressive agents are continued after rituximab therapy, while their dosages are significantly decreased. In the majority of patients rituximab is used according to the protocol used in treating lymphoma patients or patients with rheumatoid arthritis. Approximately 50% of patients experience a relapse, requiring additional therapy. Serious adverse events and fatal outcomes have been reported, although their incidence is less than that observed with conventional therapy. Nonetheless, the causes, i.e. infections and septicemia, are similar. Several gaps exist in our understanding of how to optimally benefit from the use of this valuable biological agent. Future studies need to be targeted in designing and implanting protocols that maximize the benefit of rituximab and result in producing sustained prolonged remissions with minimal adverse events and a high quality of life.

Immune dysregulation, polyendocrinopathy, enteropathy, X-linked syndrome associated with neonatal epidermolysis bullosa acquisita

We report the case of a 2-week-old boy who presented with a vesiculopustular, bullous eruption in the setting of autoimmune enteropathy, hypothyroidism, membranous nephropathy, Coombs-positive hemolytic anemia, and persistent eosinophilia. Immunologic testing revealed a deficiency of FOXP3-expressing regulatory T cells, and a diagnosis of immune dysregulation, polyendocrinopathy, enteropathy, X-linked syndrome was made. Histologic analysis, immunofluorescence, and enzyme-linked immunosorbent assay confirmed the bullous eruption as epidermolysis bullosa acquisita with associated collagen VII autoantibody production. The skin lesions responded to systemic immunosuppressant therapy and have regressed after allogeneic bone marrow transplantation.

IPEX syndrome caused by a novel mutation in FOXP3 gene can be cured by bone marrow transplantation from an unrelated donor after myeloablative conditioning

Immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome is a rare primary immunodeficiency caused by inherited defects in the FOXP3 gene that impair regulatory T cells. IPEX syndrome can be cured by hematopoietic stem cell transplantation (HSCT) from HLA-matched unrelated donors (MUD); however, the best conditioning prior to HSCT for IPEX syndrome is not known.

Here we report on a patient suffering from IPEX syndrome, including immune-mediated colitis and membranous nephropathy, without polyendocrinopathy, caused by a novel mutation in the Forkhead domain of the FOXP3 gene. The patient's symptoms resolved following MUD HSCT after myeloablative conditioning performed at 16 months of age. The patient is clinically well, 3 years after HSCT, with robust immune reconstitution and fully engrafted. The lack of extensive autoimmune damage might have contributed to the patient's favourable outcome following MUD HSCT with myeloablative conditioning.

Statement of novelty: We describe a novel mutation in the FOXP3 gene causing IPEX syndrome and the correction of IPEX syndrome with bone marrow transplant from a HLA-matched unrelated donor following myeloablative conditioning.

B cells are critical for autoimmune pathology in Scurfy mice

Impaired regulatory T-cell function results in a severe chronic autoimmune disease affecting multiple organs in Scurfy mice and humans with the immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome. Previous studies have shown that T helper cells but not cytotoxic T cells are critical for the disease pathology. Whether this T-cell subset is responsible directly for tissue inflammation or rather indirectly via the interaction with B cells or myeloid cells is largely unknown. To study this and to identify potential therapeutic targets for this lethal disease we investigated the contribution of B cells to this complex autoimmune phenotype. We show that B cells and the production of autoantibodies plays a major role for skin, liver, lung, and kidney inflammation and therapeutic depletion of B cells resulted in reduced tissue pathology and in prolonged survival. In contrast, the absence of B cells did not impact systemic T-cell activation and hyperreactivity, indicating that autoantibody production by B cells may be a major factor for the autoimmune pathology in mice deficient for regulatory T cells.

Diagnostic value of the skin lesions in immune dysregulation, polyendocrinopathy, enteropathy, X-linked syndrome

We report a child with immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome due to a de novo c.1190G>A (p.R397Q) mutation in exon 11 of the forkhead domain of the FOXP3 gene. He had chronic dermatitis with an eczematous and ichthyosiform appearance and had an allogeneic bone marrow transplantation. IPEX syndrome is a rare, often fatal recessive disease caused by mutations in the FOXP3 gene on the X chromosome (Xp11.23-q13.3).

FOXP3: genetic and epigenetic implications for autoimmunity

FOXP3 plays an essential role in the maintenance of self-tolerance and, thus, in preventing autoimmune diseases. Inactivating mutations of FOXP3 cause immunodysregulation, polyendocrinopathy, and enteropathy, X-linked syndrome. FOXP3-expressing regulatory T cells attenuate autoimmunity as well as immunity against cancer and infection. More recent studies demonstrated that FOXP3 is an epithelial cell-intrinsic tumor suppressor for breast, prostate, ovary and other cancers. Corresponding to its broad function, FOXP3 regulates a broad spectrum of target genes. While it is now well established that FOXP3 binds to and regulates thousands of target genes in mouse and human genomes, the fundamental mechanisms of its broad impact on gene expression remain to be established. FOXP3 is known to both activate and repress target genes by epigenetically regulating histone modifications of target promoters. In this review, we first focus on germline mutations found in the FOXP3 gene among IPEX patients, then outline possible molecular mechanisms by which FOXP3 epigenetically regulates its targets. Finally, we discuss clinical implications of the function of FOXP3 as an epigenetic modifier. Accumulating results reveal an intriguing functional convergence between FOXP3 and inhibitors of histone deacetylases. The essential epigenetic function of FOXP3 provides a foundation for experimental therapies against autoimmune diseases.

The role of regulatory T cells in neurodegenerative diseases

A sustained neuroinflammatory response is the hallmark of many neurodegenerative diseases, including Parkinson's disease, Alzheimer's disease, amyotrophic lateral sclerosis, multiple sclerosis, and HIV-associated neurodegeneration. A specific subset of T cells, currently recognized as FOXP3(+) CD25(+) CD4(+) regulatory T cells (Tregs), are pivotal in suppressing autoimmunity and maintaining immune homeostasis by mediating self-tolerance at the periphery as shown in autoimmune diseases and cancers. A growing body of evidence shows that Tregs are not only important for maintaining immune balance at the periphery but also contribute to self-tolerance and immune privilege in the central nervous system. In this article, we first review the current status of knowledge concerning the development and the suppressive function of Tregs. We then discuss the evidence supporting a dysfunction of Tregs in several neurodegenerative diseases. Interestingly, a dysfunction of Tregs is mainly observed in the early stages of several neurodegenerative diseases, but not in their chronic stages, pointing to a causative role of inflammation in the pathogenesis of neurodegenerative diseases. Furthermore, we provide an overview of a number of molecules, such as hormones, neuropeptides, neurotransmitters, or ion channels, that affect the dysfunction of Tregs in neurodegenerative diseases. We also emphasize the effects of the intestinal microbiome on the induction and function of Tregs and the need to study the crosstalk between the enteric nervous system and Tregs in neurodegenerative diseases. Finally, we point out the need for a systems biology approach in the analysis of the enormous complexity regulating the function of Tregs and their potential role in neurodegenerative diseases.

Immune dysregulation, polyendocrinopathy, enteropathy, x-linked syndrome: a paradigm of immunodeficiency with autoimmunity

Immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome is a rare monogenic primary immunodeficiency (PID) due to mutations of FOXP3, a key transcription factor for naturally occurring (n) regulatory T (Treg) cells. The dysfunction of Treg cells is the main pathogenic event leading to the multi-organ autoimmunity that characterizes IPEX syndrome, a paradigm of genetically determined PID with autoimmunity. IPEX has a severe early onset and can become rapidly fatal within the first year of life regardless of the type and site of the mutation. The initial presenting symptoms are severe enteritis and/or type-1 diabetes mellitus, alone or in combination with eczema and elevated serum IgE. Other autoimmune symptoms, such as hypothyroidism, cytopenia, hepatitis, nephropathy, arthritis, and alopecia can develop in patients who survive the initial acute phase. The current therapeutic options for IPEX patients are limited. Supportive and replacement therapies combined with pharmacological immunosuppression are required to control symptoms at onset. However, these procedures can allow only a reduction of the clinical manifestations without a permanent control of the disease. The only known effective cure for IPEX syndrome is hematopoietic stem cell transplantation, but it is always limited by the availability of a suitable donor and the lack of specific guidelines for bone marrow transplant in the context of this disease. This review aims to summarize the clinical histories and genomic mutations of the IPEX patients described in the literature to date. We will focus on the clinical and immunological features that allow differential diagnosis of IPEX syndrome and distinguish it from other PID with autoimmunity. The efficacy of the current therapies will be reviewed, and possible innovative approaches, based on the latest highlights of the pathogenesis to treat this severe primary autoimmune disease of childhood, will be discussed.

Genetic disorders with immune dysregulation

We summarize the clinical presentation and molecular basis of a unique group of congenital immunodeficiency disorders in which defects in immune tolerance mechanisms result in severe autoimmunity. Patients with severe, familial forms of multi-organ autoimmunity have been recognized and clinically described for more than 40 years (Clin Exp Immunol 1: 119-128, 1966; Clin Exp Immunol 2: 19-30, 1967). Some are characterized primarily by autoimmunity and others by autoimmunity combined with susceptibility to specific infectious organisms. The first mechanistic understanding of these disorders began to emerge approximately 10 years ago with the initial identification of causative genes. As a result, our understanding of how immune tolerance is established and maintained in humans has expanded dramatically. Data generated over the last 3-4 years including identification of additional gene defects and functional characterization of each identified gene product in human and animal models have added clarity. This, in turn, has improved our ability to diagnose and effectively treat these severe, life-threatening disorders. Inherited disorders characterized by immune dysregulation have dramatically expanded our understanding of immune tolerance mechanisms in humans. Recognition and diagnosis of these disorders in the clinic allows timely initiation of life-saving therapies that may prevent death or irreversible damage to vital organs.

Recognizing gastrointestinal and hepatic manifestations of primary immunodeficiency diseases

Given the complex immune function of the gastrointestinal (GI) tract, it is not surprising that many children with primary immunodeficiencies present with GI tract manifestations. Although many immunodeficiency disorders present with overt evidence of immune dysregulation, a few can present in older children with more subtle signs and symptoms. Such children may present first to a gastroenterologist with common symptoms, including malabsorption, diarrhea, hepatomegaly, or inflammatory bowel disease, which may actually be a manifestation of their underlying immune disorder. A thorough clinical history in combination with a careful review of histology from biopsies may reveal clues that one is dealing with a disease entity outside the norm and may prompt additional laboratory studies beyond the usual set of screening laboratory tests. Once the true underlying diagnosis is revealed, more appropriate therapy can be initiated. Additionally, more appropriate anticipatory guidance regarding the expected disease course, response to medications, and any additional risks that therapy may entail can be provided to the family.

The spectrum of autoantibodies in IPEX syndrome is broad and includes anti-mitochondrial autoantibodies

IPEX syndrome is a congenital disorder of immune regulation caused by mutations in the FOXP3 gene, which is required for the suppressive function of naturally arising CD4 + CD25 + regulatory T cells. In this case series we evaluated serum samples from 12 patients with IPEX syndrome for the presence of common autoantibodies associated with a broad range of autoimmune disorders. We note that 75% of patients (9/12) had 1 or more autoantibodies, an incidence far above the cumulative rate observed in the general population. The range of autoantibodies differed between patients and there was no predominant autoantibody or pattern of autoantibodies present in this cohort. Surprisingly, one patient had high-titer anti-mitochondrial antibodies (AMA) typically associated with primary biliary cirrhosis (PBC) although the patient had no signs of cholestasis. PBC is a well-characterized autoimmune disease that occurs primarily in women and includes the serological hallmarks of serum AMA and elevated IgM which were both present in this patient. PBC is virtually absent in children with the exception of one reported child with interleukin 2 receptor α (CD25) deficiency which is associated with an IPEX-like regulatory T cell dysfunction. Based on the present data and the available literature we suggest a direct role for CD4 + CD25 + regulatory T cells in restraining B cell autoantibody production and that defects in regulatory T cells may be crucial to the development of PBC.

Immunopathogenesis of thyroid eye disease: emerging paradigms

Graves disease represents a systemic autoimmune process targeting the thyroid, orbit, and pretibial skin. The thyroid dysfunction is treatable, but no consistently effective medical therapy has yet been described for the orbital manifestations of Graves disease, also known as thyroid-associated ophthalmopathy or thyroid eye disease. Several autoantigens are potentially relevant to the pathogenesis of thyroid eye disease. Activating antibodies generated against the thyrotropin receptor can be detected in a majority of patients, and these drive hyperthyroidism. However, stimulating antibodies against the insulin-like growth factor-1 receptor (IGF-1R) may also play a role in the extra-thyroid manifestations of Graves disease. IGF-1R is overexpressed by orbital fibroblasts derived from patients with thyroid eye disease, whereas IGF-1R(+) T and IGF-1R(+) B cells are considerably more frequent in Graves disease. Actions of several cytokines and the molecular interplay peculiar to the orbit appear to provoke the inflammation, fat expansion, and deposition of excessive extracellular matrix molecules in thyroid eye disease. Based upon these new insights, several therapeutic strategies can now be proposed that, for the first time, might specifically interrupt its pathogenesis.

Current status on B-cell depletion therapy in autoimmune diseases other than rheumatoid arthritis

Since the approval of the chimeric anti-CD20 antibody rituximab for the treatment of adults with severe-to-moderate rheumatoid arthritis after an inadequate response to TNF blockade, B-cell depletion therapy has been used for the treatment of a broad range of refractory autoimmune disorders. Based on current experiences and a literature search, a systematic review and evaluation of the current status of B-cell depletion therapy in autoimmune diseases other than rheumatoid arthritis, including rheumatic, nephrologic, dermatologic and neurologic autoimmune entities, was performed by an international group of experts based at several academic centres. Although important questions remain about the value and place of B-cell depletion in autoimmune diseases other than RA, preliminary data indicate the value of this therapeutic approach in otherwise refractory patients. However, given the lack of robust data from large randomised controlled trials, anti-CD20 therapy should be considered on an individual basis in otherwise refractory patients and its use based on a risk/benefit net calculation.

Association of collagenous colitis with prurigo nodularis

The etiology and pathogenesis of collagenous colitis (CC) is poorly understood and probably multifactorial; many potential pathophysiological mechanisms have been described, although none have been conclusively proved. Circumstantial evidence suggests that CC appears as an autoimmune response to a luminal or epithelial antigen of unknown origin. Infections and certain drugs (e.g. NSAID, lansoprazole) may act as triggers for an immune-mediated process. CC is characterized clinically by chronic watery, nonbloody diarrhea with normal endoscopic appearance and without radiological abnormalities, but specific microscopic changes in the colon. Histopathology is featured by the presence of a thickened subepithelial collagen band adjacent to the basal membrane. Up to 40% of patients with CC have associated diseases of autoimmune or inflammatory origin, such as thyroid disease, coeliac disease, rheumatoid arthritis, diabetes mellitus, Sjögren's syndrome, CREST syndrome, scleroderma, pernicious anemia, and sarcoidosis. Prurigo nodularis is a chronic condition characterized by intensely pruritic, lichenified, or excoriated papules and nodules of unknown etiology. It is assumed to represent a cutaneous reaction pattern to repeated scrubbing or scratching caused by pruritus. We report a case of CC and prurigo nodularis. To our knowledge, this association has not been reported earlier.

From autoimmune enteropathy to the IPEX (immune dysfunction, polyendocrinopathy, enteropathy, X-linked) syndrome

The term autoimmune enteropathy (AIE) was applied to a form of "intractable diarrhoea" with serum gut autoantibodies, characterized by male predominance, early onset, poor response to parenteral nutrition and several autoimmune diseases, mainly type 1 diabetes. In recent years the vague concept of AIE has became more precise thanks to the discovery of its genetic and molecular basis. The FOXP3 molecule is crucial for the generation and maturation of regulatory T cells (Treg) expressing CD4+ and CD25+ molecules. Mutations of the FOXP3 gene, located in X chromosome, produce a syndrome with Immune dysfunction, Polyendocrinopathy, Enteropathy and X-linked inheritance (IPEX). The majority of the ancient so-called AIE cases probably correspond to the new IPEX syndrome, even in female patients who may have some autosomal genetic variants. Besides FOXP3, other molecules are likely to be involved in the generation and function of Treg and its deficiency may also enhance autoimmune disease and IPEX-like syndromes. Meanwhile, the important pathogenic role previously ascribed to gut autoantibodies has vanished, with it remaining as having only certain screening usefulness.

An integrated classification of pediatric inflammatory diseases, based on the concepts of autoinflammation and the immunological disease continuum

Historically, pediatric inflammatory diseases were viewed as autoimmune but developments in genetics of monogenic disease have supported our proposal that "inflammation against self" be viewed as an immunologic disease continuum (IDC), with genetic disorders of adaptive and innate immunity at either end. Innate immune-mediated diseases may be associated with significant tissue destruction without evident adaptive immune responses and are designated as autoinflammatory due to distinct immunopathologic features. However, the majority of pediatric inflammatory disorders are situated along this IDC. Innate immunity has been demonstrated in polygenic disorders, particularly Crohn's disease (CD). A genetic overlap exists between CD and some major histocompatibility complex (MHC) class I-associated diseases, including psoriasis; these diseases seem to represent a true intermediate between autoinflammation and autoimmunity. Conversely, classical autoimmune diseases, with autoantibody and MHC class II associations, including celiac disease and rheumatoid arthritis (RA), have adaptive immune genetic associations, including Cytotoxic T-Lymphocyte Antigen-4 (CTLA4) and PTPN22. This proposed classification is clinically relevant, because innate immune-mediated disorders may respond to cytokine antagonism whereas autoimmune-mediated diseases respond better to anti-T and B cell therapies. Furthermore, the etiopathogenesis of poorly defined "autoimmune" diseases, such as juvenile idiopathic arthritis, may be inferred to have substantial innate immune involvement, based on response to IL-1 antagonism.

Cutaneous manifestations of immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome

BACKGROUND

Immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome is a rare disorder characterized by neonatal autoimmune enteropathy, diabetes and thyroiditis, food allergies and skin rash. IPEX syndrome is caused by mutations in FOXP3, a master control gene of regulatory T cells (Tregs), resulting in absent or dysfunctional Tregs. Data in the literature are scarce and the cutaneous manifestations are rarely depicted.

OBJECTIVES

To evaluate the frequency and characteristics of cutaneous manifestations found in IPEX.

METHODS

Retrospective single-centre study of a case series of IPEX. Patients' data were retrieved from medical files and numerous parameters concerning general and cutaneous characteristics of the disease were recorded.

RESULTS

Ten children with IPEX were studied. Cutaneous involvement was present in seven of 10 children; age at onset was 0-4 months, median 1.5. All patients presented with atopic dermatitis (AD). Three presented more psoriasiform lesions. Eczema was severe; most affected areas were lower limbs, trunk and face. Pruritus was present in four of seven, and painful fissurary cheilitis in four of seven. Hyper-IgE was found in seven of 10 and hypereosinophilia in five of 10. Skin biopsies showed eczematiform or psoriasiform features. Affected patients were improved by dermocorticoids; no clear improvement was obtained with immunosuppressive regimens. Other features were urticaria secondary to food allergies and staphylococcal sepsis, mostly Staphylococcus aureus and catheter related.

CONCLUSIONS

AD seems to be a frequent finding in IPEX syndrome, which is characterized by Treg anomalies. This hints to a possible role of Tregs in AD, which is then discussed in this study.