Loss of enteroendocrine cells in autoimmune-polyendocrine-candidiasis-ectodermal-dystrophy (APECED) syndrome with gastrointestinal dysfunction

The Role of Interferon-γ in Autoimmune Polyendocrine Syndrome Type 1

BACKGROUND

Autoimmune polyendocrine syndrome type 1 (APS-1) is a life-threatening, autosomal recessive syndrome caused by autoimmune regulator (AIRE) deficiency. In APS-1, self-reactive T cells escape thymic negative selection, infiltrate organs, and drive autoimmune injury. The effector mechanisms governing T-cell-mediated damage in APS-1 remain poorly understood.

METHODS

We examined whether APS-1 could be classified as a disease mediated by interferon-γ. We first assessed patients with APS-1 who were participating in a prospective natural history study and evaluated mRNA and protein expression in blood and tissues. We then examined the pathogenic role of interferon-γ using Aire-/-Ifng-/- mice and Aire-/- mice treated with the Janus kinase (JAK) inhibitor ruxolitinib. On the basis of our findings, we used ruxolitinib to treat five patients with APS-1 and assessed clinical, immunologic, histologic, transcriptional, and autoantibody responses.

RESULTS

Patients with APS-1 had enhanced interferon-γ responses in blood and in all examined autoimmunity-affected tissues. Aire-/- mice had selectively increased interferon-γ production by T cells and enhanced interferon-γ, phosphorylated signal transducer and activator of transcription 1 (pSTAT1), and CXCL9 signals in multiple organs. Ifng ablation or ruxolitinib-induced JAK-STAT blockade in Aire-/- mice normalized interferon-γ responses and averted T-cell infiltration and damage in organs. Ruxolitinib treatment of five patients with APS-1 led to decreased levels of T-cell-derived interferon-γ, normalized interferon-γ and CXCL9 levels, and remission of alopecia, oral candidiasis, nail dystrophy, gastritis, enteritis, arthritis, Sjögren's-like syndrome, urticaria, and thyroiditis. No serious adverse effects from ruxolitinib were identified in these patients.

CONCLUSIONS

Our findings indicate that APS-1, which is caused by AIRE deficiency, is characterized by excessive, multiorgan interferon-γ-mediated responses. JAK inhibition with ruxolitinib in five patients showed promising results. (Funded by the National Institute of Allergy and Infectious Diseases and others.).

APECED and the place of AIRE in the puzzle of the immune network associated with autoimmunity

In the last 20 years, discoveries about the autoimmune regulator (AIRE) protein and its critical role in immune tolerance have provided fundamental insights into understanding the molecular basis of autoimmunity. This review provides a comprehensive overview of the effect of AIRE on immunological tolerance and the characteristics of autoimmune diseases in Autoimmune Polyendocrinopathy-Candidiasis-Ectodermal Dystrophy (APECED), which is caused by biallelic AIRE mutations. A better understanding of the immunological mechanisms of AIRE deficiency may enlighten immune tolerance mechanisms and new diagnostic and treatment strategies for autoimmune diseases. Considering that not all clinical features of APECED are present in a given follow-up period, the diagnosis is not easy in a patient at the first visit. Longer follow-up and a multidisciplinary approach are essential for diagnosis. It is challenging to prevent endocrine and other organ damage compared with other diseases associated with multiple autoimmunities, such as FOXP3, LRBA, and CTLA4 deficiencies. Unfortunately, no curative therapy like haematopoietic stem cell transplantation or specific immunomodulation is present that is successful in the treatment.

Analysis of a series of Italian APECED patients with autoimmune hepatitis and gastro-enteropathies

Introduction

Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) syndrome is a rare monogenic disease determined by biallelic mutations in AIRE gene, which encodes a transcription factor essential for central immune tolerance. Classic diagnosis is determined by the presence of two of the main APECED clinical diseases: chronic mucocutaneous candidiasis, chronic hypoparathyroidism, and Addison's disease. Non-endocrine autoimmunity, involving the liver, intestine, eyes, and kidneys, is generally reported in a minority of European patients, while American APECED patients have a higher tendency of developing organ-specific non-endocrine manifestations early in life. This observation led to the revision of the diagnostic criteria to permit earlier diagnosis based on the appearance of one classic triad symptom or one non-classical manifestation at a young age in the presence of IFNωAbs or AIRE mutations (Ferre-Lionakis criteria).

Patients and methods

We analyzed the clinical, genetic, and autoantibody (Ab) profiles in a series of 14 pediatric Italian APECED patients with gastrointestinal manifestations (seven male and seven female patients). Ten patients presented hepatitis (APECED-associated hepatitis (APAH)), while seven were affected by constipation, diarrhea, and malabsorption. Four patients had developed APAH before classic triad symptoms.

Results

Based on the age of appearance of non-endocrine manifestations including APAH and gastro-enteropathy, the Ferre-Lionakis criteria would have allowed an expedited diagnosis in 11/14 patients. Abs to tryptophan hydroxylase (TPHAb) and hepatic aromatic l-amino acid decarboxylase (AADC) were significantly associated with APECED patients of the present series. Abs to cP4501A2 were detectable in the serum of 4/8 patients with APAH, and Abs to cP4502A6 were detectable in 3/8 patients. AADC Abs tested positive in 5/7 patients, which is indicative of gastrointestinal dysfunction in APECED and TPHAb in 5/7 patients with gastrointestinal dysfunction. IFNAb was significantly associated with the syndrome.

Conclusion

Although Ferre-Lionakis expanded criteria applied to the American cohorts of APECED patients would require validation in independent large cohorts of European patients, the results of this study emphasize the importance to evaluate the presence and the age of appearance of APAH and autoimmune enteropathy even in European cohorts for an earlier APECED diagnosis. An earlier APECED diagnosis would also allow the prevention of episodes of life-threatening hypocalcemic seizures and adrenal crisis, which are the main manifestations of undiagnosed APECED.

Potential determinants of low circulating glucagon-like peptide 2 concentrations in Zambian children with non-responsive stunting

NEW FINDINGS

What is the central question of this study? Non-responsive stunting is characterised by a progressive decline of circulating glucagon-like peptide 2: what are the possible causes of this decline? What is the main finding and its importance? In contrast with the established loss of Paneth and goblet cells in environmental enteropathy, there was no evidence of a parallel loss of enteroendocrine cells as seen by positive tissue staining for chromogranin A. Transcriptomic and genomic analyses showed evidence of genetic transcripts that could account for some of the variability seen in circulating glucagon-like peptide 2 values.

ABSTRACT

Nutrient sensing determines digestive and hormonal responses following nutrient ingestion. We have previously reported decreased levels of glucagon-like peptide 2 (GLP-2) in children with stunting. Here we demonstrate the presence of enteroendocrine cells in stunted children and explore potential pathways that may be involved in reduced circulating levels of GLP-2. At the time of performing diagnostic endoscopies for non-responsive stunted children, intestinal biopsies were collected for immunofluorescence staining of enteroendocrine cells and transcriptomic analysis. Circulating levels of GLP-2 were also measured and correlated with transcriptomic data. An exploratory genome-wide association study (GWAS) was conducted on DNA samples (n = 158) to assess genetic contribution to GLP-2 variability. Intestinal tissue sections collected from non-responsive stunted children stained positive for chromogranin A (88/89), alongside G-protein-coupled receptors G-protein receptor 119 (75/87), free fatty acid receptor 3 (76/89) and taste 1 receptor 1 (39/45). Transcriptomic analysis found three pathways correlated with circulating GLP-2: sugar metabolism, epithelial transport, and barrier function, which likely reflect downstream events following receptor-ligand interaction. GWAS analysis revealed potential genetic contributions to GLP-2 half-life and receptor binding. Enteroendocrine cell loss was not identified in stunted Zambian children as has been observed for goblet and Paneth cells. Transcriptomic analysis suggests that GLP-2 has pleiotrophic actions on the intestinal mucosa in malnutrition, but further work is needed to dissect pathways leading to perturbations in nutrient sensing.

Understanding inborn errors of immunity: A lens into the pathophysiology of monogenic inflammatory bowel disease

Inflammatory bowel diseases (IBD) are chronic inflammatory conditions of the gastrointestinal tract, including Crohn’s disease, ulcerative colitis and inflammatory bowel disease-undefined (IBD-U). IBD are understood to be multifactorial, involving genetic, immune, microbial and environmental factors. Advances in next generation sequencing facilitated the growing identification of over 80 monogenic causes of IBD, many of which overlap with Inborn errors of immunity (IEI); Approximately a third of currently identified IEI result in gastrointestinal manifestations, many of which are inflammatory in nature, such as IBD. Indeed, the gastrointestinal tract represents an opportune system to study IEI as it consists of the largest mass of lymphoid tissue in the body and employs a thin layer of intestinal epithelial cells as the critical barrier between the intestinal lumen and the host. In this mini-review, a selection of pertinent IEI resulting in monogenic IBD is described involving disorders in the intestinal epithelial barrier, phagocytosis, T and B cell defects, as well as those impairing central and peripheral tolerance. The contribution of disrupted gut-microbiota-host interactions in disturbing intestinal homeostasis among patients with intestinal disease is also discussed. The molecular mechanisms driving pathogenesis are reviewed along with the personalized therapeutic interventions and investigational avenues this growing knowledge has enabled.

Mechanistic dissection of dominant AIRE mutations in mouse models reveals AIRE autoregulation

The autoimmune regulator (AIRE) is essential for the establishment of central tolerance and prevention of autoimmunity. Interestingly, different AIRE mutations cause autoimmunity in either recessive or dominant-negative manners. Using engineered mouse models, we establish that some monoallelic mutants, including C311Y and C446G, cause breakdown of central tolerance. By using RNAseq, ATACseq, ChIPseq, and protein analyses, we dissect the underlying mechanisms for their dominancy. Specifically, we show that recessive mutations result in a lack of AIRE protein expression, while the dominant mutations in both PHD domains augment the expression of dysfunctional AIRE with altered capacity to bind chromatin and induce gene expression. Finally, we demonstrate that enhanced AIRE expression is partially due to increased chromatin accessibility of the AIRE proximal enhancer, which serves as a docking site for AIRE binding. Therefore, our data not only elucidate why some AIRE mutations are recessive while others dominant, but also identify an autoregulatory mechanism by which AIRE negatively modulates its own expression.

Case Report: Severe Hypocalcemic Episodes Due to Autoimmune Enteropathy

Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) is a rare monogenic disorder, associated with endocrine deficiencies and non-endocrine involvement. Gastrointestinal (GI) manifestations appear in approximately 25% of patients and are the presenting symptom in about 10% of them. Limited awareness among pediatricians of autoimmune enteropathy (AIE) caused by destruction of the gut endocrine cells in APECED patients delays diagnosis and appropriate therapy. We describe an 18-year-old female presenting at the age of 6.10 years with hypoparathyroidism, oral candidiasis and vitiligo. The clinical diagnosis of APECED was confirmed by sequencing the autoimmune regulator-encoding (AIRE) gene. Several characteristics of the disease-Hashimoto's thyroiditis, Addison's disease, diabetes mellitus type 1 and primary ovarian insufficiency-developed over the years. She had recurrent episodes of severe intractable hypocalcemia. Extensive GI investigations for possible malabsorption, including laboratory analyses, imaging and endoscopy with biopsies were unremarkable. Revision of the biopsies and chromogranin A (CgA) immunostaining demonstrated complete loss of enteroendocrine cells in the duodenum and small intestine, confirming the diagnosis of AIE. Management of hypocalcemia was challenging. Only intravenous calcitriol maintained calcium in the normal range. Between hypocalcemic episodes, the proband maintained normal calcium levels, suggesting a fluctuating disease course. Repeated intestinal biopsy revealed positive intestinal CgA immunostaining. The attribution of severe hypocalcemic episodes to AIE emphasizes the need for increased awareness of this unique presentation of APECED. The fluctuating disease course and repeated intestinal biopsy showing positive CgA immunostaining support a reversible effect of GI involvement. CgA immunostaining is indicated in patients with APECED for whom all other investigations have failed to reveal an explanation for the malabsorption.

Autoimmune Polyendocrinopathy-Candidiasis-Ectodermal Dystrophy in Two Siblings: Same Mutations but Very Different Phenotypes

Autoimmune polyendocrinopathy–candidiasis–ectodermal dystrophy (APECED), caused by mutations in the AIRE gene, is mainly characterized by the triad of hypoparathyroidism, primary adrenocortical insufficiency and chronic mucocutaneous candidiasis, but can include many other manifestations, with no currently clear genotype–phenotype correlation. We present the clinical features of two siblings, a male and a female, with the same mutations in the AIRE gene associated with two very different phenotypes. Interestingly, the brother recently experienced COVID-19 infection with pneumonia, complicated by hypertension, hypokalemia and hypercalcemia. Although APECED is a monogenic disease, its expressiveness can be extremely different. In addition to the genetic basis, epigenetic and environmental factors might influence the phenotypic expression, although their exact role remains to be elucidated.

A Patient With AIRE Mutation Who Presented With Severe Diarrhea and Lung Abscess

Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) (polyglandular endocrinopathy type 1) is a rare autosomal recessive disorder caused by mutations in the autoimmune regulator gene (AIRE). The major clinical features of APECED are hypoparathyroidism, adrenal insufficiency (Addison disease), and chronic mucocutaneous candidiasis. This disease is also associated with multiple other and uncommon autoimmune (autoimmune hepatitis, autoimmune enteropathy, atrophic gastritis with or without pernicious anemia, gonadal failure, diabetes mellitus, hypothyroidism, functional hyposplenism), ectodermal (alopecia and vitiligo), and inflammatory (intestinal lung disease, nephritis) features. Here, we report a case of a 13-year-old Turkish boy who presented wih enteropathy and lung abscess. Molecular genetic analysis demonstrated a homozygous frameshift mutation (p.Asp70fs, c.208_209insCAGG) in exon 2, in AIRE gene. APECED may present with severe, life-threatening infections due to functional hyposplenism. Multidisciplinary approach, careful follow-up, and molecular genetic studies are needed.

Updates in Pediatric Congenital Enteropathies: Differential Diagnosis, Testing, and Genetics

Congenital enteropathies comprise a heterogeneous group of disorders typically resulting in severe diarrhea and intestinal failure. Recent advances in and more widespread application of genetic testing have allowed more accurate diagnosis of these entities as well as identification of new disorders, provided a deeper understanding of intestinal pathophysiology through genotype-phenotype correlations, and permitted the exploration of more specific therapies to diseases that have heretofore been resistant to conventional treatments. The therapeutic armamentarium for these disorders now includes intestinal and hematopoietic stem cell transplantation, specific targeted therapy, such as the use of interleukin-1 receptor antagonists and, in some cases, gene therapy. These considerations are particularly applicable to the group of disorders identified as "very-early onset inflammatory bowel disease" (VEO-IBD), for which a veritable explosion of knowledge has occurred in the last decade. The pathologist plays a crucial role in assisting in the diagnosis of these entities and in ruling out other disorders that enter into the differential diagnosis.

[The gut: center of immunity : Rare inflammatory bowel diseases caused by immunodeficiencies]

The gut is the largest immune organ of the human body with an enormous mucosal interface. By acting as a physical barrier and by hosting many of the body's immune cells and tissues, the gut is the first line of defense against potentially harmful substances. Therefore, diseases leading to impaired immune response or disruption of the epithelial barrier result in autoimmune, infectious, or inflammatory bowel disease, frequently associated with diarrhea, malabsorption, melena, and growth failure. The differential diagnosis represents an interdisciplinary challenge in this group of rare diseases. The diseases are characterized by clinical, immunological, and histopathological features caused by mutations in single genes. In the following, we will focus on histological findings within the various entities of immunodeficiencies.

Identification of novel, clinically correlated autoantigens in the monogenic autoimmune syndrome APS1 by proteome-wide PhIP-Seq

The identification of autoantigens remains a critical challenge for understanding and treating autoimmune diseases. Autoimmune polyendocrine syndrome type 1 (APS1), a rare monogenic form of autoimmunity, presents as widespread autoimmunity with T and B cell responses to multiple organs. Importantly, autoantibody discovery in APS1 can illuminate fundamental disease pathogenesis, and many of the antigens found in APS1 extend to more common autoimmune diseases. Here, we performed proteome-wide programmable phage-display (PhIP-Seq) on sera from a cohort of people with APS1 and discovered multiple common antibody targets. These novel APS1 autoantigens exhibit tissue-restricted expression, including expression in enteroendocrine cells, pineal gland, and dental enamel. Using detailed clinical phenotyping, we find novel associations between autoantibodies and organ-restricted autoimmunity, including a link between anti-KHDC3L autoantibodies and premature ovarian insufficiency, and between anti-RFX6 autoantibodies and diarrheal-type intestinal dysfunction. Our study highlights the utility of PhIP-Seq for extensively interrogating antigenic repertoires in human autoimmunity and the importance of antigen discovery for improved understanding of disease mechanisms.

Serotonin and tryptophan metabolites, autoantibodies and gut microbiome in APECED

Objective Intestinal autoimmunity with gastrointestinal (GI) dysfunction has been shown in patients with autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED). Patients lack entero-endocrine (EE) cells and have circulating autoantibodies (Aabs) against critical enzymes in serotonin (5-HT) biosynthesis. Design We sought to determine the serum levels of 5-HT, tryptophan (Trp) metabolites and L-DOPA in 37 Finnish APECED patients and to correlate their abundance with the presence of TPH and AADC Aabs, GI dysfunction and depressive symptoms. We also performed an exploratory analysis of the gut microbiome. Methods Serum 5-HT, L-DOPA and Trp metabolite levels were determined by liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS). TPH and AADC Aabs were measured by ELISA. Depression was assessed with a structured RBDI questionnaire. The V3-V4 regions of the bacterial 16S rRNA gene were sequenced for gut microbiome exploration. Results Serum 5-HT levels were significantly decreased (130 ± 131 nmol/L vs 686 ± 233 nmol/L, P < 0.0001) in APECED patients with TPH-1 (±AADC) Aabs compared to controls and patients with only AADC Aabs. Reduced 5-HT levels correlated with constipation. The genus Escherichia/Shigella was overrepresented in the intestinal microbiome. No correlation between serum Trp, 5-HT or l-DOPA levels and the RBDI total score, fatigue or sleep disorders was found. Conclusions This exploratory study found low serum levels of 5-HT to be associated with constipation and the presence of TPH-1 and AADC Aabs, but not with symptoms of depression. Hence, serum 5-HT, TPH1 and AADC Aabs should be determined in APECED patients presenting with GI symptoms.

Lipid malabsorption from altered hormonal signaling changes early gut microbial responses

Infants with congenital diarrheal disorders caused by enteroendocrine cell dysgenesis, or the loss of intestinal endocrine cells, causes severe malabsorptive diarrhea, though the mechanism is not fully understood. The transcription factor "aristaless-related homeobox" (Arx) is specifically expressed in intestinal endocrine cells. This study seeks to characterize the early malabsorptive phenotype of mice deficient for Arx using cell-type specific gene ablation in Villin-Cre; ArxloxP/Y ( Arxint) mice. In neonatal mice, the loss of intestinal Arx caused the loss of intestinal hormones, such as cholecystokinin, secretin, neurotensin, glucose-dependent insulinotropic peptide, glucagon-like peptide (GLP)-1 and GLP-2 but also upregulation of somatostatin. Arxint mice exhibited steatorrhea with the loss of lipid transport in duodenal enterocytes, upregulation of lysozyme-positive Paneth cells, and a secondary increase in antimicrobial peptides, specifically Reg3β. When the epithelium from Arxint mice was cultured ex vivo into enteroids, however, the Reg3β upregulation was lost under the sterile conditions. Thus, Arx is required for the appropriate lineage allocation of multiple enteroendocrine subtypes. We concluded that altered hormonal signaling caused by Arx deficiency results in lipid malabsorption, premature Paneth cell differentiation, and an inflammatory response, including neutrophilic infiltrates and a microbiota-triggered upregulation of Reg3β. NEW & NOTEWORTHY The enteroendocrine transcription factor aristaless-related homeobox (Arx) plays a key role in lineage specification. Changes in hormonal expression mediated by Arx lead to lipid malabsorption and premature Paneth cell development. Furthermore, global profiling of whole intestine from Arx-deficient mice revealed significant upregulation of antimicrobial peptides. This antimicrobial response in Arx-deficient animals is lost under sterile culture conditions of enteroids.

Newcomers in paediatric GI pathology: childhood enteropathies including very early onset monogenic IBD

Childhood enteropathies are a group of diseases causing severe chronic (>2-3 weeks) diarrhoea often starting in the first week of life with the potential for fatal complications for the affected infant. Early identification and accurate classification of childhood enteropathies are, therefore, crucial for making treatment decisions to prevent life-threatening complications. Childhood enteropathies are classified into four groups based on the underlying pathology: (i) conditions related to defective digestion, absorption and transport of nutrients and electrolytes; (ii) disorders related to enterocyte differentiation and polarization; (iii) defects of enteroendocrine cell differentiation; and (iv) disorders associated with defective modulation of intestinal immune response. While the intestinal mucosa is usually normal in enteropathies related to congenital transport or enzyme deficiencies, the intestinal biopsy in other disorders may reveal a wide range of abnormalities varying from normal villous architecture to villous atrophy and/or inflammation, or features specific to the underlying disorder including epithelial abnormalities, lipid vacuolization in the enterocytes, absence of plasma cells, lymphangiectasia, microorganisms, and mucosal eosinophilic or histiocytic infiltration. This review intends to provide an update on small intestinal biopsy findings in childhood enteropathies, the "newcomers", including very early onset monogenic inflammatory bowel disease (IBD), in particular, for the practicing pathologist.

α-Synuclein in gut endocrine cells and its implications for Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative disease with devastating clinical manifestations. In PD, neuronal death is associated with intracellular aggregates of the neuronal protein α-synuclein known as Lewy bodies. Although the cause of sporadic PD is not well understood, abundant clinical and pathological evidence show that misfolded α-synuclein is found in enteric nerves before it appears in the brain. This suggests a model in which PD pathology originates in the gut and spreads to the central nervous system via cell-to-cell prion-like propagation, such that transfer of misfolded α-synuclein initiates misfolding of native α-synuclein in recipient cells. We recently discovered that enteroendocrine cells (EECs), which are part of the gut epithelium and directly face the gut lumen, also possess many neuron-like properties and connect to enteric nerves. In this report, we demonstrate that α-synuclein is expressed in the EEC line, STC-1, and native EECs of mouse and human intestine. Furthermore, α-synuclein-containing EECs directly connect to α-synuclein-containing nerves, forming a neural circuit between the gut and the nervous system in which toxins or other environmental influences in the gut lumen could affect α-synuclein folding in the EECs, thereby beginning a process by which misfolded α-synuclein could propagate from the gut epithelium to the brain.

Childhood Polyarthritis As Early Manifestation of Autoimmune Polyendocrinopathy with Candidiasis and Ectodermal Dystrophy Syndrome

Autoimmune polyendocrinopathy with candidiasis and ectodermal dystrophy (APECED) is a rare disorder of immune dysregulation caused by mutations in the autoimmune regulator (AIRE) gene. Individuals affected with APECED develop a clinical syndrome characterized by ectodermal abnormalities, autoantibody production, and organ-specific autoimmune manifestations. Inflammatory arthritis is usually not described as a part of the syndrome, and only sporadic cases are reported. We describe the case of a preschool-age girl who presented with hypoparathyroidism, hepatitis, interstitial pneumonitis, and chronic polyarthritis at 4 years of age and was found to have two compound heterozygous disease-associated mutations in the AIRE gene. We also conducted a literature review of the main characteristics of inflammatory arthritis in APECED patients. Our case and review demonstrate that (1) inflammatory arthritis, although rare, can be an early manifestation of APECED; (2) the diagnosis of APECED should be considered if mucocutaneous candidiasis, multiple organ-specific autoimmune manifestations, polyendocrinopathy, especially hypoparathyroidism or adrenal failure, or ectodermal dystrophy accompany joint symptoms; and (3) genotyping interpretation should take into account that mutations are found in the 14 exons of the gene, compound heterozygosity is common, and in some cases, only one or no mutated alleles are found.

Pathogenic and Protective Autoantibodies in Autoimmune Polyendocrinopathy-Candidiasis-Ectodermal Dystrophy (APECED)

Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) is a rare disorder caused by mutations in the autoimmune regulator (AIRE) gene, leading to defects in T cell selection. The disease manifestations include both autoimmune tissue destruction and immunodeficiency, with specific susceptibility to chronic mucocutaneous candidiasis. Studies have demonstrated a wide repertoire of high affinity tissue- and cytokine-specific antibodies in patients with APECED. Here, we review the antigenic targets and function of these disease-causing and disease-ameliorating antibodies.

[Polyglandular autoimmune syndromes : An overview]

Polyglandular autoimmune syndromes (PGAS), also known as autoimmune polyendocrinopathy syndromes (APS), are a heterogeneous group of rare, genetically caused diseases of the immune system which lead to inflammatory damage of various endocrine glands resulting in malfunctions. In addition, autoimmune diseases of non-endocrine organs may also be found. Early diagnosis of PGAS is often overlooked because of heterogeneous symptoms and the progressive occurrence of the individual diseases. The two most important forms of PGAS are the juvenile and adult types. The juvenile type (PGAS type 1) is caused by mutations in the autoimmune regulator (AIRE) gene on chromosome 21, exhibits geographic variations in incidence and is defined by the combination of mucocutaneous candidiasis, Addison's disease and hypoparathyroidism. In addition, autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) syndrome and other autoimmune diseases can also occur. The adult form of PGAS (PGAS type 2) is a multigenetic disorder associated with some HLA haplotypes, is more common than the juvenile type, shows female predominance and exhibits the combination of type 1 diabetes, autoimmune thyroid disease, Addison's disease and other autoimmune disorders. The histological alterations in affected organs of PGAS patients are similar to findings in sporadically occurring autoimmune diseases of these organs but there are no pathognomic fine tissue findings. If patients exhibit autoimmune changes in two different endocrine glands or if there are indications of several autoimmune disorders from the patient history, it is important to consider PGAS and inform the clinicians of this suspicion.

Congenital intestinal diarrhoeal diseases: A diagnostic and therapeutic challenge

Congenital diarrhoeal disorders are a heterogeneous group of inherited malabsorptive or secretory diseases typically appearing in the first weeks of life, which may be triggered by the introduction of distinct nutrients. However, they may also be unrecognised for a while and triggered by exogenous factors later on. In principle, they can be clinically classified as osmotic, secretory or inflammatory diarrhoea. In recent years the disease-causing molecular defects of these congenital disorders have been identified. According to the underlying pathophysiology they can be classified into four main groups: 1) Defects of digestion, absorption and transport of nutrients or electrolytes 2) Defects of absorptive enterocyte differentiation or polarisation 3) Defects of the enteroendocrine cells 4) Defects of the immune system affecting the intestine. Here, we describe the clinical presentation of congenital intestinal diarrhoeal diseases, the diagnostic work-up and specific treatment aspects.

Anticommensal Responses Are Associated with Regulatory T Cell Defect in Autoimmune Polyendocrinopathy-Candidiasis-Ectodermal Dystrophy Patients

Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) is a monogenic autoimmune disease caused by mutations in the AIRE gene. Although mainly an endocrine disease, a substantial fraction of patients have gastrointestinal manifestations. In this study, we have examined the role of anticommensal responses and their regulation. APECED patients had increased levels of Abs against Saccharomyces cerevisiae (p < 0.0001) and against several species of commensal gut bacteria, but not against species predominantly associated with other locations. The anticommensal Ab levels did not correlate with gastrointestinal autoantibodies, neutralizing anti-IL-17 or -IL-22 Abs, or gastrointestinal symptoms, although scarcity of the available clinical data suggests that further study is required. However, the anti-S. cerevisiae Ab levels showed a significant inverse correlation with FOXP3 expression levels in regulatory T cells (Treg), previously shown to be dysfunctional in APECED. The correlation was strongest in the activated CD45RO(+) population (ρ = -0.706; p < 0.01). APECED patients also had decreased numbers of FOXP3(+) cells in gut biopsies. These results show that APECED patients develop early and sustained responses to gut microbial Ags in a pattern reminiscent of Crohn's disease. This abnormal immune recognition of gut commensals is linked to a systemic Treg defect, which is also reflected as a local decrease of gut-associated Treg. To our knowledge, these data are the first to show dysregulated responses to non-self commensal Ags in APECED and indicate that AIRE contributes to the regulation of gut homeostasis, at least indirectly. The data also raise the possibility of persistent microbial stimulation as a contributing factor in the pathogenesis of APECED.

Lymphopenia-induced proliferation in the absence of functional Autoimmune regulator (Aire) induces colitis in mice

Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) is caused by mutations in Autoimmune regulator (Aire), a transcriptional regulator of negative selection in thymus. However, Aire is also expressed in periphery, but the full range of Aire's peripheral function is unknown. Here, we transferred lymphocytes from wildtype donors into lymphopenic recipients with or without functional Aire. Following cell proliferation thus took place in Aire-sufficient or deficient environment. The wildtype lymphocytes hyperproliferated and induced disease in lymphopenic Aire(-/-) but not in Aire(+/+) recipients. The disease was characterized by diarrhea, inflammation, and colitis, and in some recipients pancreatitis, gastritis, and hepatitis was also found. Our results identify Aire as an important regulator of peripheral T cell homeostasis in gastrointestinal tissues. Given a suitable trigger the absence of peripheral Aire leads to dysregulated T cell proliferation and disease.

Gastrointestinal Autoimmunity Associated With Loss of Central Tolerance to Enteric α-Defensins

BACKGROUND & AIMS

Autoimmune polyendocrinopathy candidiasis ectodermal dystrophy (APECED) is an autoimmune disorder characterized by chronic mucocutaneous candidiasis, hypoparathyroidism, and adrenal insufficiency, but patients also develop intestinal disorders. APECED is an autosomal recessive disorder caused by mutations in the autoimmune regulator (AIRE, which regulates immune tolerance) that allow self-reactive T cells to enter the periphery. Enteric α-defensins are antimicrobial peptides secreted by Paneth cells. Patients with APECED frequently have gastrointestinal symptoms and seroreactivity against secretory granules of Paneth cells. We investigated whether enteric α-defensins are autoantigens in humans and mice with AIRE deficiency.

METHODS

We analyzed clinical data, along with serum and stool samples and available duodenal biopsies from 50 patients with APECED collected from multiple centers in Europe. Samples were assessed for expression of defensins and other molecules by quantitative reverse transcription polymerase chain reaction and flow cytometry; levels of antibodies and other proteins were measured by immunohistochemical and immunoblot analyses. Histologic analyses were performed on biopsy samples. We used Aire(-/-) mice as a model of APECED, and studied the effects of transferring immune cells from these mice to athymic mice.

RESULTS

Enteric defensins were detected in extraintestinal tissues of patients with APECED, especially in medullary thymic epithelial cells. Some patients with APECED lacked Paneth cells and were seropositive for defensin-specific autoantibodies; the presence of autoantibodies correlated with frequent diarrhea. Aire(-/-) mice developed defensin-specific T cells. Adoptive transfer of these T cells to athymic mice resulted in T-cell infiltration of the gut, loss of Paneth cells, microbial dysbiosis, and the induction of T-helper 17 cell-mediated autoimmune responses resembling those observed in patients with APECED.

CONCLUSIONS

In patients with APECED, loss of AIRE appears to cause an autoimmune response against enteric defensins and loss of Paneth cells. Aire(-/-) mice developed defensin-specific T cells that cause intestinal defects similar to those observed in patients with APECED. These findings provide a mechanism by which loss of AIRE-mediated immune tolerance leads to intestinal disorders in patients with APECED.

Autoimmune polyendocrinopathy candidiasis ectodermal dystrophy

Autoimmune polyendocrinopathy candidiasis ectodermal dystrophy (APECED) is an autosomal recessive disease caused by mutations in the autoimmune regulator (AIRE) gene. This review focuses on the clinical and immunological features of APECED, summarizes the current knowledge on the function of AIRE and discusses the importance of autoantibodies in disease diagnosis and prognosis. Additionally, we review the outcome of recent immunomodulatory treatments in APECED patients.

Gastrointestinal immunity against tryptophan hydroxylase-1, aromatic L-amino-acid decarboxylase, AIE-75, villin and Paneth cells in APECED

Gastrointestinal dysfunction is a disabling manifestation of APECED possibly related to an autoimmune intestinal aggression. We evaluated its features in a cohort of 31 Finnish patients. The most frequent manifestations were constipation (48%), diarrhea, dysphagia and retrosternal pain (45%). AADC and TPH-1 autoantibodies were detected in 51% and 45% of the patients, respectively. Forty-three percent displayed a T-cell response to AADC. One third of the patients also had AIE-75 (33%) and villin (29%)-specific autoantibodies while antibodies against brush borders and Paneth cells were detected in 29% and 20%, respectively. Intestinal IL-17 expression was absent/decreased in 77% of the cases. Duodenal CgA and serotonin expression was absent/decreased in 50% and 66% of the patients, respectively. Constipation correlated with lacking serotonin expression and AADC antibodies (p < 0.05).

Clinical, Genetic and Immunological Characteristics of Paediatric Autoimmune Polyglandular Syndrome Type 1 Patients in Slovenia

Introduction

Autoimmune polyglandular syndrome type 1 (APS-1) is an autosomal recessive disorder, caused by mutations in the AIRE gene. The major components of APS-1 are chronic mucocutaneous candidiasis (CMC), hypoparathyroidism (HP) and Addison’s disease (AD). Clinical, genetic and immunological characteristics of Slovenian paediatric APS-1 patients were investigated.

Methods

Existing medical records of 15 APS-1 patients were rewieved, when necessary, additional clinical and laboratory investigations were issued. AIRE gene analysis was performed to identify causative mutations, and autoantibodies against type I interferons were measured by luminescence immunoprecipitation system.

Results

Patients had one to eight different manifestations of the disease. CMC was present in all, HP in 12/15 (80 %) and AD in 8/15 (53 %) patients. Growth retardation, due to hyposomatotropism, growth hormone resistance, autoimmune thyroiditis, corticosteroid treatment, malabsorption or secretory failure of exocrine pancreas, was observed in altogether 7 (46 %) patients. Six different AIRE gene mutations were detected and p.R257X mutation was present in 63.3 % of pathological alleles. Antibodies against type I interferons were detected in all patients.

Conclusion

APS-1 is a rare disorder with a broad spectrum of clinical manifestations, which, if unrecognized or inadequately treated may be fatal. AIRE gene mutational analysis and autoantibodies against type I interferons are important in early identification of the disease. The aetiology of growth retardation was shown to be extremely diverse, frequently caused by less characteristic manifestations. APS-1 may affect patients’ quality of life in numerous ways, and may cause great psychosocial burden leading to depression and suicidal thoughts even in paediatric patients.

Dysgenesis of enteroendocrine cells in Aristaless-Related Homeobox polyalanine expansion mutations

OBJECTIVES

Severe congenital diarrhea occurs in approximately half of patients with Aristaless-Related Homeobox (ARX) null mutations. The cause of this diarrhea is unknown. In a mouse model of intestinal Arx deficiency, the prevalence of a subset of enteroendocrine cells is altered, leading to diarrhea. Because polyalanine expansions within the ARX protein are the most common mutations found in ARX-related disorders, we sought to characterize the enteroendocrine population in human tissue of an ARX mutation and in a mouse model of the corresponding polyalanine expansion (Arx).

METHODS

Immunohistochemistry and quantitative real-time polymerase chain reaction were the primary modalities used to characterize the enteroendocrine populations. Daily weights were determined for the growth curves, and Oil-Red-O staining on stool and tissue identified neutral fats.

RESULTS

An expansion of 7 alanines in the first polyalanine tract of both human ARX and mouse Arx altered enteroendocrine differentiation. In human tissue, cholecystokinin, glucagon-like peptide 1, and somatostatin populations were reduced, whereas the chromogranin A population was unchanged. In the mouse model, cholecystokinin and glucagon-like peptide 1 populations were also lost, although the somatostatin-expressing population was increased. The ARX protein was present in human tissue, whereas the Arx protein was degraded in the mouse intestine.

CONCLUSIONS

ARX/Arx is required for the specification of a subset of enteroendocrine cells in both humans and mice. Owing to protein degradation, the Arx mouse recapitulates findings of the intestinal Arx null model, but is not able to further the study of the differential effects of the ARX protein on its transcriptional targets in the intestine.

Features of gastric and colonic mucosa in congenital enteropathies: a study in histology and immunohistochemistry

Congenital enteropathies comprise a constellation of rare clinicopathologic diagnoses characterized by intractable watery diarrhea and failure to thrive in infants. These diagnoses include, but are not limited to, tufting enteropathy (TE), microvillous inclusion disease (MID), and enteroendocrine cell dysgenesis (EED). Commonly, the diagnosis is based on identification of their characteristic histologic and/or ultrastructural features in small intestinal mucosa. In cases in which the changes in the small intestine are inconclusive or a small intestine biopsy is not performed, the diagnosis can be hampered or significantly delayed. We describe the histologic features and immunohistochemical staining patterns of gastric and colonic mucosa in patients with confirmed TE (3), MID (2), and EED (1). Specifically, focal epithelial tufts were found in the gastric mucosa of one TE patient and multifocally in the colonic mucosa of another. All TE patients showed complete loss of membranous epithelial EpCAM expression in gastric and colonic mucosa, characteristic of the diagnosis. Gastric biopsies were available in 1 patient with MID; this showed focal disruption of the gastric glandular architecture. Three colon biopsies and 1 resection from 2 patients with MID showed characteristic cytoplasmic vacuoles and periodic acid-Schiff/villin-positive cytoplasmic inclusions. Chromogranin stains showed complete absence of enteroendocrine cells within the colon and a normal distribution in the gastric mucosa of the EED patient. On the basis of our findings, we conclude that the characteristic histologic and immunohistochemical features associated with the small intestine can be confirmed within the gastric and/or colonic mucosa by careful histologic examination and immunohistochemistry.

Recalcitrant hypocalcaemia in autoimmune enteropathy

Autoimmune polyendocrinopathy candidiasis ectodermal dystrophy syndrome is a monogenic disorder associated with autoimmune destruction of both endocrine and nonendocrine tissues. The classic triad includes candidiasis, hypoparathyroidism, and Addison disease. Up to 25% of patients with autoimmune polyendocrinopathy candidiasis ectodermal dystrophy syndrome also have gastrointestinal manifestations, which can have an impact on the management of other aspects of the disease. The management of the case discussed was challenging because of the complex interplay between the manifestations and treatment of his hypoparathyroidism, Addison disease, and autoimmune enteropathy. Attempts at management of hypocalcemia were largely unsuccessful until the introduction of immunosuppressive therapy for autoimmune enteropathy. This case supports early consideration of immunosuppression in this condition.

Cutaneous vasculitis in patients with autoimmune polyendocrine syndrome type 1: report of a case and brief review of the literature

Background

Autoimmune polyendocrine syndrome type 1, also known as autoimmune polyendocrinopathy-candidiasis-ectodermal-dystrophy, is a rare autosomal recessive disease due to pathogenic variants in the AIRE gene. Classic features of the syndrome are mucocutaneous candidiasis, chronic idiopathic hypoparathyroidism and Addison disease. However, other endocrine and non-endocrine components, may occur with a different prevalence. In addition to ectodermal features, which are quite common features of the disease, APS 1 patients may experience other types of skin alterations, such as vasculitic skin rash. An early diagnosis of APS 1 can be very challenging, due to the high clinical heterogeneity, and a considerable delay may occur between the appearance of symptoms and the diagnosis.

Case presentation

We report on a girl affected by APS 1 who presented with cutaneous vasculitis when she was seven-months old, some years before the onset of the common components of the disease.

Conclusion

Clinical picture of APS 1 may be characterized by isolated rare or atypical autoimmune or immune-mediated manifestations, even years before the onset of the classic components of the disease. Among these uncommon features, skin rashes of variable form and duration may occur, most of them being associated with histopathological features of vasculitis. Our case suggests that cutaneous vasculitis may represent a first sign of APS 1. The clinical significance of cutaneous vasculitis in the context of APS 1 is still debated. It may represent a rare, unusual, early component of the disease or a clinical manifestation secondarily related to the typical APS 1 components (i.e. autoimmune thyroid disease), which are frequently associated with rheumatologic-like signs and symptoms. Alternatively, it may be the expression of an independent disease co-occuring with APS 1. In conclusion, our case suggests that children presenting with unexplained vasculitic skin rash should be followed-up in order to early identify APS 1.

Enteroendocrine cells in gastrointestinal pathophysiology

Enteroendocrine cells in the gastrointestinal tract play an important role in the regulation of appetite and digestive responses through the secretion of peptides. Their involvement in gastrointestinal diseases has been acknowledged, but relatively few studies have sought to clearly define their role in the pathogenesis or as therapeutic targets. Recent, but still limited, work has identified new roles for EEC in GI diseases.

Absence of some common organ-specific and non-organ-specific autoimmunity in autoimmune polyendocrinopathy candidiasis ectodermal dystrophy

BACKGROUND

Autoimmune polyendocrinopathy candidiasis ectodermal dystrophy (APECED) is a rare autosomal recessive disorder caused by mutations of the autoimmune regulator (AIRE) gene, whose loss of function leads to the escape of self-reactive T cells from the thymus and autoimmunity. APECED patients typically develop tissue-specific autoantibodies and anti-cytokine antibodies. Consequently, various endocrine and non-endocrine autoimmune disorders appear. However, only a certain number of autoimmune diseases develop, while some common autoimmune conditions have not been reported or are seen only anecdotally.

OBJECTIVE

We investigated the clinical manifestations and occurrence of antinuclear antibodies (AN-Abs) and antibodies against extractable nuclear antigens, citrullinated peptide, and transglutaminase in 24 patients and against bullous pemphigoid antigen 180 and desmogleins 1 (Dsg1) and Dsg3 in 30 patients of a Finnish cohort of APECED patients.

RESULTS

Despite the loss of central tolerance, the autoantibodies investigated were not overrepresented among the APECED patients. None of the patients had a history of autoimmune connective tissue disease, rheumatoid arthritis, celiac disease, or autoimmune cutaneous bullous disorders. Altogether, 25% (6/24) had low-titer (1:80) AN-Abs. Two patients had anti-BP180 antibodies and two others had anti-Dsg3 antibodies without any cutaneous or mucosal symptoms. No anti-citrullinated peptide and anti-transglutaminase reactivity was found.

CONCLUSIONS

The mechanisms that drives tolerance to tissue autoantigens is not fully understood as even APECED patients, who are genetically prone to develop autoantibodies, are tolerant against some common autoantigens. The hypothesis that some of the anti-cytokine antibodies commonly found in APECED patients may be protective should be investigated in larger series.

Gastrointestinal manifestations in APECED syndrome

Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) (or autoimmune polyendocrine syndrome type 1) is a rare autosomal recessive disorder caused by mutations in the autoimmune regulator gene. It causes a loss in central immune tolerance, failure to eliminate autoreactive T cells in the thymus, and their escape to the periphery. APECED patients are susceptible to mucocutaneous candidiasis and multiple endocrine and nonendocrine autoimmune diseases. Although it depends on the series, approximately 25% of APECED patients are affected by gastrointestinal (GI) manifestations, mainly autoimmune-related disorders like autoimmune hepatitis, atrophic gastritis with or without pernicious anemia (Biermer disease), intestinal infections, and malabsorption. In contrast to the major organ-specific autoimmune symptoms of APECED, the GI symptoms and their underlying pathogenesis are poorly understood. Yet isolated case reports and small series depict severe intestinal involvement in children, leading to malabsorption, multiple deficiencies, growth impairment, and possible death. Moreover, very few systematic studies of GI function with intestinal biopsies have been performed. GI symptoms may be the first manifestation of APECED, yet they may have various causes; effective treatment will therefore vary. We provide here an updated review of GI manifestations in APECED, including principles of diagnosis and therapy.

Erkrankungen und Therapieformen des unteren Gastrointestinaltrakts

Duodenalatresien sind Hemmungsfehlbildungen und können proximal oder distal der Papilla Vateri entstehen, wobei die präpapillären Obstruktionen selten sind. Grundsätzlich kann zwischen einer Membranatresie und einer Defektatresie unterschieden werden. Die Unterscheidung beruht nicht nur auf embryologischen Gesichtspunkten, sondern hat auch eine klinische Bedeutung: Bei der Membranatresie kann die quergestellte, partiell offene oder geschlossene Membran weit in den distalen Duodenalanteil reichen („Windsackphänomen“), was zu diagnostischen und auch intraoperativen Problemen führen kann. Ein Pancreas anulare findet sich bei etwa 20 % aller Patienten mit Duodenalatresie.

APECED: is this a model for failure of T cell and B cell tolerance?

In APECED, the key abnormality is in the T cell defect that may lead to tissue destruction chiefly in endocrine organs. Besides, APECED is characterized by high-titer antibodies against a wide variety of cytokines that could partly be responsible for the clinical symptoms during APECED, mainly chronic mucocutaneous candidiasis, and linked to antibodies against Th17 cells effector molecules, IL-17 and IL-22. On the other hand, the same antibodies, together with antibodies against type I interferons may prevent the patients from other immunological diseases, such as psoriasis and systemic lupus erythematous. The same effector Th17 cells, present in the lymphocytic infiltrate of target organs of APECED, could be responsible for the tissue destruction. Here again, the antibodies against the corresponding effector molecules, anti-IL-17 and anti-IL-22 could be protective. The occurrence of several effector mechanisms (CD4(+) Th17 cell and CD8(+) CTL and the effector cytokines IL-17 and IL-22), and simultaneous existence of regulatory mechanisms (CD4(+) Treg and antibodies neutralizing the effect of the effector cytokines) may explain the polymorphism of APECED. Almost all the patients develop the characteristic manifestations of the complex, but temporal course and severity of the symptoms vary considerably, even among siblings. The autoantibody profile does not correlate with the clinical picture. One could speculate that a secondary homeostatic balance between the harmful effector mechanisms, and the favorable regulatory mechanisms, finally define both the extent and severity of the clinical condition in the AIRE defective individuals. The proposed hypothesis that in APECED, in addition to strong tissue destructive mechanisms, a controlling regulatory mechanism does exist, allow us to conclude that APECED could be treated, and even cured, with immunological manipulation.