Central tolerance to self revealed by the autoimmune regulator

Comparison of Shared Class I HLA-Bound Noncanonical Neoepitopes between Normal and Neoplastic Tissues of Pancreatic Adenocarcinoma

PURPOSE

Developing T-cell or vaccine therapies for pancreatic ductal adenocarcinoma (PDAC) has been challenging because of a lack of knowledge regarding immunodominant, cancer-specific antigens as PDAC are characterized by a scarcity of genomic mutation-associated neoepitopes, and effective approaches to discover them are limited.

EXPERIMENTAL DESIGN

An advanced mass spectrometry approach was employed to compare the immunopeptidome of PDAC tissues and matched normal tissues from the same patients.

RESULTS

This study identified HLA class I-binding variant peptides derived from canonical proteins, which had single amino-acid substitutions not attributed to genetic mutations or RNA editing. These amino-acid substitutions appeared to result from translational errors. The variant peptides were predominantly found in tumor tissues, with certain peptides common among multiple patients. Importantly, several of these variant peptides were more immunogenic than their wild-type counterparts.

CONCLUSIONS

The shared noncanonical neoepitopes identified in this study offer promising candidates for vaccine and T-cell therapy development, potentially providing new avenues for immunotherapy in PDAC. See related commentary by Yuan et al., p. 1821.

Association Between AIRE Polymorphisms rs870881(C>T), rs1003854(T>C) and Rheumatoid Arthritis Risk: A Hungarian Case-control Study

BACKGROUND/AIM

Autoimmune regulator (AIRE) is a transcription factor that plays pivotal role in controlling autoimmunity. In the thymus, it supports the presentation of peripheral tissue antigens to developing T cells, where recognition of these self-antigens negatively selects the autoimmune naïve T-cells by central tolerance. Studies demonstrated that single-nucleotide polymorphisms (SNPs) in AIRE alter transcription and propagate clonal survival of autoimmune T cells, therefore increase susceptibility to autoimmune diseases. This study intended to identify SNPs in exon and intron sequences that determine AIRE transcription, where their genotypes are associated with rheumatoid arthritis (RA) risk and clinical parameters.

PATIENTS AND METHODS

After a thorough in silico research, we enrolled 100 patients with RA and 100 healthy controls to analyze the association of SNP rs870881(C>T) and rs1003854(T>C) in AIRE coding sequence with RA risk by using five different genetic models and selected clinical parameters. Multiplex quantitative polymerase chain reaction was used to determine allelic discrimination of SNPs. RA risk was assessed by odds ratios (ORs) and confidence intervals (CIs).

RESULTS

In a recessive model of rs878081, minor allele TT homozygotes were associated with RA (p=0.032, OR=5.44, 95%CI=1.16-25.52); in a recessive model of rs1003854, minor allele CC homozygotes were associated with RA (p=0.047, OR=4.84, 95%CI=1.02-23.02). Higher C-reactive protein (CRP) levels in patients with RA were significantly associated with minor allele homozygotes in recessive and codominant genetic models (p=0.029 and p=0.043, respectively) of rs1003854.

CONCLUSION

Genotypes for minor alleles of rs878081 and rs1003854 might be involved in RA pathogenesis and risk prediction.

Transmigration of macrophages through primary adult rat Sertoli cells

The blood testis barrier (BTB) is often studied with isolated immature Sertoli cells (SCs), transepithelial resistance (TER) measurements and FITC dextran diffusion assays. Recently, it was found that even in the absence of SCs, only few immune cells enter the seminiferous tubules. Thus, in this study, we evaluated the testicular immunological barrier (TIB) in vitro by transmigration of macrophages through SCs with and without peritubular cells (PCs) and with or without matrigel (MG). Primary PCs were isolated from adult rat testis and kept in mono- or co-cultures with the conditionally reprogrammed primary adult Sertoli cell line (PASC1) from rat that has been recently generated by our group. Rat monocytes isolated from fresh blood were differentiated into M0 macrophages, and after polarization to M1 or M2 macrophages characterized by gene expression of CXCL11 and TNF-α for M1, or CCL17 and CCL22 for M2. Transmigration of LeukoTracker-labeled M0, M1, and M2 macrophages through mono- and co-cultures of PCs/SCs with and without MG demonstrated that SCs are the main constituent of the TIB in vitro with only a negligible contribution of PCs or MG. Moreover, M2 macrophages showed less migration activity compared to M0 or M1. Treatment of SCs with testosterone (T) showed positive effects on the barrier in contrast to negative effects by interleukin-6 (IL-6) or tumor necrosis factor-α (TNF-α). The new transmigration model is suitable to evaluate transmigration of macrophages through a barrier consisting of testicular cells and can be applied to study the integrity of testicular barriers with respect to immunological aspects.

Histopathologic and transcriptomic phenotypes of a conditional RANKL transgenic mouse thymus

Although conventional knockout and transgenic mouse models have significantly advanced our understanding of Receptor Activator of NF-κB Ligand (RANKL) signaling in intra-thymic crosstalk that establishes self-tolerance and later stages of lymphopoiesis, the unique advantages of conditional mouse transgenesis have yet to be explored. A main advantage of conditional transgenesis is the ability to express a transgene in a spatiotemporal restricted manner, enabling the induction (or de-induction) of transgene expression during predetermined stages of embryogenesis or during defined postnatal developmental or physiological states, such as puberty, adulthood, and pregnancy. Here, we describe the K5: RANKL bigenic mouse, in which transgene derived RANKL expression is induced by doxycycline and targeted to cytokeratin 5 positive medullary thymic epithelial cells (mTECs). Short-term doxycycline induction reveals that RANKL transgene expression is significantly induced in the thymic medulla and only in response to doxycycline. Prolonged doxycycline induction in the K5: RANKL bigenic results in a significantly enlarged thymus in which mTECs are hyperproliferative. Flow cytometry showed that there is a marked enrichment of CD4+ and CD8+ single positive thymocytes with a concomitant depletion of CD4+ CD8+ double positives. Furthermore, there is an increase in the number of FOXP3+ T regulatory (Treg) cells and Ulex Europaeus Agglutinin 1+ (UEA1+) mTECs. Transcriptomics revealed that a remarkable array of signals-cytokines, chemokines, growth factors, transcription factors, and morphogens-are governed by RANKL and drive in part the K5: RANKL thymic phenotype. Extended doxycycline administration to 6-weeks results in a K5: RANKL thymus that begins to display distinct histopathological features, such as medullary epithelial hyperplasia, extensive immune cell infiltration, and central tissue necrosis. As there are intense efforts to develop clinical approaches to restore thymic medullary function in the adult to treat immunopathological conditions in which immune cell function is compromised following cancer therapy or toxin exposure, an improved molecular understanding of RANKL's involvement in thymic medulla enlargement will be required. We believe the versatility of the conditional K5: RANKL mouse represents a tractable model system to assist in addressing this requirement as well as many other questions related to RANKL's role in thymic normal physiology and disease processes.

Immunopeptidomic analyses of colorectal cancers with and without microsatellite instability

Colorectal cancer is the second leading cause of cancer death worldwide, and the incidence of this disease is expected to increase as global socioeconomic changes occur. Immune checkpoint inhibition therapy is effective in treating a minority of colorectal cancer tumors; however, microsatellite stable tumors do not respond well to this treatment. Emerging cancer immunotherapeutic strategies aim to activate a cytotoxic T cell response against tumor-specific antigens, presented exclusively at the cell surface of cancer cells. These antigens are rare and are most effectively identified with a mass spectrometry-based approach, which allows the direct sampling and sequencing of these peptides. Although the few tumor-specific antigens identified to date are derived from coding regions of the genome, recent findings indicate that a large proportion of tumor-specific antigens originate from allegedly noncoding regions. Here, we employed a novel proteogenomic approach to identify tumor antigens in a collection of colorectal cancer-derived cell lines and biopsy samples consisting of matched tumor and normal adjacent tissue. The generation of personalized cancer databases paired with mass spectrometry analyses permitted the identification of more than 30,000 unique MHC I-associated peptides. We identified 19 tumor-specific antigens in both microsatellite stable and unstable tumors, over two-thirds of which were derived from noncoding regions. Many of these peptides were derived from source genes known to be involved in colorectal cancer progression, suggesting that antigens from these genes could have therapeutic potential in a wide range of tumors. These findings could benefit the development of T cell-based vaccines, in which T cells are primed against these antigens to target and eradicate tumors. Such a vaccine could be used in tandem with existing immune checkpoint inhibition therapies, to bridge the gap in treatment efficacy across subtypes of colorectal cancer with varying prognoses. Data are available via ProteomeXchange with identifier PXD028309.

Preexisting autoantibodies to type I IFNs underlie critical COVID-19 pneumonia in patients with APS-1

Patients with biallelic loss-of-function variants of AIRE suffer from autoimmune polyendocrine syndrome type-1 (APS-1) and produce a broad range of autoantibodies (auto-Abs), including circulating auto-Abs neutralizing most type I interferons (IFNs). These auto-Abs were recently reported to account for at least 10% of cases of life-threatening COVID-19 pneumonia in the general population. We report 22 APS-1 patients from 21 kindreds in seven countries, aged between 8 and 48 yr and infected with SARS-CoV-2 since February 2020. The 21 patients tested had auto-Abs neutralizing IFN-α subtypes and/or IFN-ω; one had anti-IFN-β and another anti-IFN-ε, but none had anti-IFN-κ. Strikingly, 19 patients (86%) were hospitalized for COVID-19 pneumonia, including 15 (68%) admitted to an intensive care unit, 11 (50%) who required mechanical ventilation, and four (18%) who died. Ambulatory disease in three patients (14%) was possibly accounted for by prior or early specific interventions. Preexisting auto-Abs neutralizing type I IFNs in APS-1 patients confer a very high risk of life-threatening COVID-19 pneumonia at any age.

Alopecia areata: a review on diagnosis, immunological etiopathogenesis and treatment options

Patients suffering from alopecia areata (AA) can lose hair in focal regions, the complete scalp, including eyelashes and eyebrows, or even the entire body. The exact pathology is not yet known, but the most described theory is a collapse of the immune privilege system, which can be found in some specific regions of the body. Different treatment options, local and systemic, are available, but none of them have been proven to be effective in the long term as well for every treatment there should be considered for the possible side effects. In many cases, treated or non-treated, relapse often occurs. The prognosis is uncertain and is negatively influenced by the subtypes alopecia totalis and alopecia universalis and characteristics such as associated nail lesions, hair loss for more than 10 years and a positive familial history. The unpredictable course of the disease also makes it a mental struggle and AA patients are more often associated with depression and anxiety compared to the healthy population. Research into immunology and genetics, more particularly in the field of dendritic cells (DC), is recommended for AA as there is evidence of the possible role of DC in the treatment of other autoimmune diseases such as multiple Sclerosis and cancer. Promising therapies for the future treatment of AA are JAK-STAT inhibitors and PRP.

Novel Pathogenic Variants of the AIRE Gene in Two Autoimmune Polyendocrine Syndrome Type I Cases with Atypical Presentation: Role of the NGS in Diagnostic Pathway and Review of the Literature

Background. Autoimmune polyglandular syndrome type 1 (APS-1) with or without reversible metaphyseal dysplasia is a rare genetic disorder due to inactivating variants of the autoimmune regulator, AIRE, gene. Clinical variability of APS-1 relates to pleiotropy, and the general dysfunction of self-tolerance to organ-specific antigens and autoimmune reactions towards peripheral tissues caused by the underlying molecular defect. Thus, early recognition of the syndrome is often delayed, mostly in cases with atypical presentation, and the molecular confirm through the genetic analysis of the AIRE gene might be of great benefit. Methods. Our methods were to investigate, with a multigene panel next generation sequencing approach, two clinical cases, both presenting with idiopathic hypoparathyroidism, also comprising the AIRE gene; as well as to comment our findings as part of a more extensive review of literature data. Results. In the first clinical case, two compound heterozygote pathogenic variants of the AIRE gene were identified, thus indicating an autosomal recessive inheritance of the disease. In the second case, only one AIRE gene variant was found and an atypical dominant negative form of APS-1 suggested, later confirmed by further medical ascertainments. Conclusions. APS-1 might present with variable and sometimes monosymptomatic presentations and, if not recognized, might associate with severe complications. In this context, next generation diagnostics focused on a set of genes causative of partially overlapping disorders may allow early diagnosis.

A Roadmap Toward the Definition of Actionable Tumor-Specific Antigens

The search for tumor-specific antigens (TSAs) has considerably accelerated during the past decade due to the improvement of proteogenomic detection methods. This provides new opportunities for the development of novel antitumoral immunotherapies to mount an efficient T cell response against one or multiple types of tumors. While the identification of mutated antigens originating from coding exons has provided relatively few TSA candidates, the possibility of enlarging the repertoire of targetable TSAs by looking at antigens arising from non-canonical open reading frames opens up interesting avenues for cancer immunotherapy. In this review, we outline the potential sources of TSAs and the mechanisms responsible for their expression strictly in cancer cells. In line with the heterogeneity of cancer, we propose that discrete families of TSAs may be enriched in specific cancer types.

Germline PTEN mutations are associated with a skewed peripheral immune repertoire in humans and mice

Individuals with germline mutations in the gene encoding phosphatase and tensin homolog on chromosome ten (PTEN) are diagnosed with PTEN hamartoma tumor syndrome (PHTS) and are at high risk for developing breast, thyroid and other cancers and/or autoimmunity or neurodevelopmental issues including autism spectrum disorders. Although well recognized as a tumor suppressor, involvement of PTEN mutations in mediating such a diverse range of phenotypes indicates a more central involvement for PTEN in immunity than previously recognized. To address this, sequencing of the T-cell receptor variable-region β-chain was performed on peripheral blood from PHTS patients. Based on patient findings, we performed mechanistic studies in two Pten knock-in murine models, distinct from each other in cell compartment-specific predominance of Pten. We found that PTEN mutations in humans and mice are associated with a skewed T- and B-cell gene repertoire, characterized by increased prevalence of high-frequency clones. Immunological characterization showed that Pten mutants have increased B-cell proliferation and a proclivity towards increased T-cell reactivity upon Toll-like-receptor stimulation. Furthermore, decreases in nuclear but not cytoplasmic Pten levels associated with a reduction in expression of the autoimmune regulator (Aire), a critical mediator of central immune tolerance. Mechanistically, we show that nuclear PTEN most likely regulates Aire expression via its emerging role in splicing regulation. We conclude that germline disruption of PTEN, both in human and mouse, results in compromised central immune tolerance processes that may significantly impact individual stress responses and therefore predisposition to autoimmunity and cancer.

Differentiation of human pluripotent stem cells toward pharyngeal endoderm derivatives: Current status and potential

The pharyngeal apparatus, a transient embryological structure, includes diverse cells from all three germ layers that ultimately contribute to a variety of adult tissues. In particular, pharyngeal endoderm produces cells of the inner ear, palatine tonsils, the thymus, parathyroid and thyroid glands, and ultimobranchial bodies. Each of these structures and organs contribute to vital human physiological processes, including central immune tolerance (thymus) and metabolic homeostasis (parathyroid and thyroid glands, and ultimobranchial bodies). Thus, improper development or damage to pharyngeal endoderm derivatives leads to complicated and severe human maladies, such as autoimmunity, immunodeficiency, hypothyroidism, and/or hypoparathyroidism. To study and treat such diseases, we can utilize human pluripotent stem cells (hPSCs), which differentiate into functionally mature cells in vitro given the proper developmental signals. Here, we discuss current efforts regarding the directed differentiation of hPSCs toward pharyngeal endoderm derivatives. We further discuss model system and therapeutic applications of pharyngeal endoderm cell types produced from hPSCs. Finally, we provide suggestions for improving hPSC differentiation approaches to pharyngeal endoderm derivatives with emphasis on current single cell-omics and 3D culture system technologies.

Hassall’s corpuscles with cellular-senescence features maintain IFNα production through neutrophils and pDC activation in the thymus

Hassall’s corpuscles (HCs) are composed of cornifying, terminally differentiated medullary thymic epithelial cells (mTECs) that are developed under the control of Aire. Here, we demonstrated that HC-mTECs show features of cellular senescence and produce inflammatory cytokines and chemokines including CXCL5, thereby recruiting and activating neutrophils to produce IL-23 in the thymic medulla. We further indicated that thymic plasmacytoid dendritic cells (pDCs) expressing IL-23 receptors constitutively produced Ifna, which plays a role in single positive (SP) cell maturation, in an Il23a-dependent manner. Neutrophil depletion with anti-Ly6G antibody injection resulted in a significant decrease of Ifna expression in the thymic pDCs, suggesting that thymic neutrophil activation underlies the Ifna expression in thymic pDCs in steady state conditions. A New Zealand White mouse strain showing HC hyperplasia exhibited greater numbers and activation of thymic neutrophils and pDCs than B6 mice, whereas Aire-deficient B6 mice with defective HC development and SP thymocyte maturation showed significantly compromised numbers and activation of these cells. These results collectively suggested that HC-mTECs with cell-senescence features initiate a unique cell activation cascade including neutrophils and pDCs leading to the constitutive IFNα expression required for SP T-cell maturation in the thymic medulla.

Autologous Hematopoietic Stem Cell Transplantation for Autoimmune Diseases: From Mechanistic Insights to Biomarkers

Phase I/II clinical trials of autologous hematopoietic stem cell transplantation (AHSCT) have led to increased safety and efficacy of this therapy for severe and refractory autoimmune diseases (AD). Recent phase III randomized studies have demonstrated that AHSCT induces long-term disease remission in most patients without any further immunosuppression, with superior efficacy when compared to conventional treatments. Immune monitoring studies have revealed the regeneration of a self-tolerant T and B cell repertoire, enhancement of immune regulatory mechanisms, and changes toward an anti-inflammatory milieu in patients that are responsive to AHSCT. However, some patients reactivate the disease after transplantation due to reasons not yet completely understood. This scenario emphasizes that additional specific immunological interventions are still required to improve or sustain therapeutic efficacy of AHSCT in patients with AD. Here, we critically review the current knowledge about the operating immune mechanisms or established mechanistic biomarkers of AHSCT for AD. In addition, we suggest recommendations for future immune monitoring studies and biobanking to allow discovery and development of biomarkers. In our view, AHSCT for AD has entered a new era and researchers of this field should work to identify robust predictive, prognostic, treatment-response biomarkers and to establish new guidelines for immune monitoring studies and combined therapeutic interventions to further improve the AHSCT protocols and their therapeutic efficacy.

Transfer of Cell-Surface Antigens by Scavenger Receptor CD36 Promotes Thymic Regulatory T Cell Receptor Repertoire Development and Allo-tolerance

The development of T cell tolerance in the thymus requires the presentation of host proteins by multiple antigen-presenting cell (APC) types. However, the importance of transferring host antigens from transcription factor AIRE-dependent medullary thymic epithelial cells (mTECs) to bone marrow (BM) APCs is unknown. We report that antigen was primarily transferred from mTECs to CD8α⁺ dendritic cells (DCs) and showed that CD36, a scavenger receptor selectively expressed on CD8α⁺ DCs, mediated the transfer of cell-surface, but not cytoplasmic, antigens. The absence of CD8α⁺ DCs or CD36 altered thymic T cell selection, as evidenced by TCR repertoire analysis and the loss of allo-tolerance in murine allogeneic BM transplantation (allo-BMT) studies. Decreases in these DCs and CD36 expression in peripheral blood of human allo-BMT patients correlated with graft-versus-host disease. Our findings suggest that CD36 facilitates transfer of mTEC-derived cell-surface antigen on CD8α⁺ DCs to promote tolerance to host antigens during homeostasis and allo-BMT.

Twenty Years of AIRE

About two decades ago, cloning of the autoimmune regulator (AIRE) gene materialized one of the most important actors on the scene of self-tolerance. Thymic transcription of genes encoding tissue-specific antigens (ts-ags) is activated by AIRE protein and embodies the essence of thymic self-representation. Pathogenic AIRE variants cause the autoimmune polyglandular syndrome type 1, which is a rare and complex disease that is gaining attention in research on autoimmunity. The animal models of disease, although not identically reproducing the human picture, supply fundamental information on mechanisms and extent of AIRE action: thanks to its multidomain structure, AIRE localizes to chromatin enclosing the target genes, binds to histones, and offers an anchorage to multimolecular complexes involved in initiation and post-initiation events of gene transcription. In addition, AIRE enhances mRNA diversity by favoring alternative mRNA splicing. Once synthesized, ts-ags are presented to, and cause deletion of the self-reactive thymocyte clones. However, AIRE function is not restricted to the activation of gene transcription. AIRE would control presentation and transfer of self-antigens for thymic cellular interplay: such mechanism is aimed at increasing the likelihood of engagement of the thymocytes that carry the corresponding T-cell receptors. Another fundamental role of AIRE in promoting self-tolerance is related to the development of thymocyte anergy, as thymic self-representation shapes at the same time the repertoire of regulatory T cells. Finally, AIRE seems to replicate its action in the secondary lymphoid organs, albeit the cell lineage detaining such property has not been fully characterized. Delineation of AIRE functions adds interesting data to the knowledge of the mechanisms of self-tolerance and introduces exciting perspectives of therapeutic interventions against the related diseases.

What can we learn from Fli1-deficient mice, new animal models of systemic sclerosis?

Systemic sclerosis is a complex multifactorial disease characterized by autoimmunity, vasculopathy, and selective organ fibrosis. A series of genetic and epidemiological studies have demonstrated that environmental influences play a central role in the onset of systemic sclerosis, while genetic factors determine the susceptibility to and the severity of this disease. Therefore, the identification of predisposing factors related to environmental influences would provide us with an informative clue to better understand the pathological process of this disease. Based on this concept, the deficiency of transcription factor Friend leukemia virus integration 1, which is epigenetically suppressed in systemic sclerosis, seems to be a potential candidate acting as the predisposing factor of this disease. Indeed, Fli1-mutated mice serve as a set of useful disease models to disclose the complex pathology of systemic sclerosis. This article overviews the recent advancement in systemic sclerosis animal models associated with Friend leukemia virus integration 1 deficiency.

Polyglandular autoimmune syndromes

BACKGROUND

In recent years, scientific knowledge pertaining to the rare ORPHAN polyglandular autoimmune syndrome (registered code ORPHA 282196) has accumulated.

OBJECTIVE

To offer current demographic, clinical, serological and immunogenic data on PAS.

METHODS

Review of the pertinent and current literature.

RESULTS

Polyglandular autoimmune syndromes (PAS) are multifactorial diseases with at least two coexisting autoimmune-mediated endocrinopathies. PAS show a great heterogeneity of syndromes and manifest sequentially with a large time interval between the occurrence of the first and second glandular autoimmune disease. PAS cluster with several non-endocrine autoimmune diseases. In most endocrinopathies of PAS, the autoimmune process causes an irreversible loss of function, while chronic autoimmune aggressions can simultaneously modify physiological processes in the affected tissue and lead to altered organ function. The rare juvenile PAS type I is inherited in a monogenetic manner, whereas several susceptibility gene polymorphisms have been reported for the more prevalent adult types. Relevant for a timely diagnosis at an early stage is the screening for polyglandular autoimmunity in patients with monoglandular autoimmune disease and/or first degree relatives of patients with PAS. The most prevalent adult PAS type is the combination of type 1 diabetes with autoimmune thyroid disease.

CONCLUSIONS

Early detection of specific autoantibodies and latent organ-specific dysfunction is advocated to alert physicians to take appropriate action in order to prevent full-blown PAS disease.

Case of thymoma-associated cutaneous graft-versus-host disease-like disease successfully improved by narrowband ultraviolet B phototherapy

Thymoma-associated graft-versus-host disease (GVHD)-like disease is a rare paraneoplastic disease seen in patients with thymoma. Here, we describe the first case of thymoma-associated GVHD-like disease localized to the skin that was successfully improved by a combination of systemic corticosteroids and whole-body narrowband ultraviolet (UV)-B phototherapy. The patient had developed toxic epidermal necrolysis-like erosive skin lesions over the whole body. Although systemic corticosteroids were effective up to a point, we were unable to begin the steroid taper. The addition of systemic narrowband UV-B phototherapy improved the skin manifestation of this disease, allowing corticosteroids to be reduced to a third of the original dose. Histopathologically, it was confirmed that the proportion of Foxp3-positive lymphocytes in the skin increased after narrowband UV-B irradiation. We propose that whole-body narrowband UV-B phototherapy is a good therapeutic option for the skin manifestation of thymoma-associated GVHD-like disease.

Jmjd6, a JmjC Dioxygenase with Many Interaction Partners and Pleiotropic Functions

Lysyl hydroxylation and arginyl demethylation are post-translational events that are important for many cellular processes. The jumonji domain containing protein 6 (JMJD6) has been reported to catalyze both lysyl hydroxylation and arginyl demethylation on diverse protein substrates. It also interacts directly with RNA. This review summarizes knowledge of JMJD6 functions that have emerged in the last 15 years and considers how a single Jumonji C (JmjC) domain-containing enzyme can target so many different substrates. New links and synergies between the three main proposed functions of Jmjd6 in histone demethylation, promoter proximal pause release of polymerase II and RNA splicing are discussed. The physiological context of the described molecular functions is considered and recently described novel roles for JMJD6 in cancer and immune biology are reviewed. The increased knowledge of JMJD6 functions has wider implications for our general understanding of the JmjC protein family of which JMJD6 is a member.

[Autoimmune disease predisposition: Aire « protects » men]

Autoimmune diseases are a group of about 80 different diseases affecting 5-8% of the population. They are due to a deregulation of the immune system that attacks specific molecules and/or cells in the body. The thymus is the school of T cells that must be able to react to foreign molecules penetrating into the body. This education process is mediated by interactions between T cells and thymic epithelial cells (TEC) that express specific proteins of the peripheral tissues (TSA, "tissue-specific antigen"). This complex mechanism is called central tolerance. Most of the autoimmune diseases display a common feature : women are more susceptible to these diseases than men. Since the thymus is the main organ of central tolerance, we conducted a comparative study of thymic transcriptome of women and men. Our data revealed sex-associated differences in the expression of TSAs that are controlled by the autoimmune regulator (AIRE), a key factor in central tolerance. By studying human and murine cell models, we analyzed the relationship between gender, hormones and AIRE. Our work shows that AIRE is less expressed in women than in men after puberty. Furthermore, we show that estrogen induces decreased thymic AIRE expression by epigenetic modifications through increased number of methylation sites within the AIRE promoter. Consequently, these data suggest that from puberty, women have a reduced effectiveness of central tolerance process, leading to increased number of autoreactive lymphocytes, and as a result, increased susceptibility to autoimmune diseases. Together, these data may question the impact of exposure to "estrogen-like" molecules on the growing incidence of autoimmune diseases.

Environmental Factors Contribute to β Cell Endoplasmic Reticulum Stress and Neo-Antigen Formation in Type 1 Diabetes

Type 1 diabetes (T1D) is an autoimmune disease in which immune-mediated targeting and destruction of insulin-producing pancreatic islet β cells leads to chronic hyperglycemia. There are many β cell proteins that are targeted by autoreactive T cells in their native state. However, recent studies have demonstrated that many β cell proteins are recognized as neo-antigens following posttranslational modification (PTM). Although modified neo-antigens are well-established targets of pathology in other autoimmune diseases, the effects of neo-antigens in T1D progression and the mechanisms by which they are generated are not well understood. We have demonstrated that PTM occurs during endoplasmic reticulum (ER) stress, a process to which β cells are uniquely susceptible due to the high rate of insulin production in response to dynamic glucose sensing. In the context of genetic susceptibility to autoimmunity, presentation of these modified neo-antigens may activate autoreactive T cells and cause pathology. However, inherent β cell ER stress and protein PTM do not cause T1D in every genetically susceptible individual, suggesting the contribution of additional factors. Indeed, many environmental factors, such as viral infection, chemicals, or inflammatory cytokines, are associated with T1D onset, but the mechanisms by which these factors lead to disease onset remain unknown. Since these environmental factors also cause ER stress, exposure to these factors may enhance production of neo-antigens, therefore boosting β cell recognition by autoreactive T cells and exacerbating T1D pathogenesis. Therefore, the combined effects of physiological ER stress and the stress that is induced by environmental factors may lead to breaks in peripheral tolerance, contribute to antigen spread, and hasten disease onset. This Hypothesis and Theory article summarizes what is currently known about ER stress and protein PTM in autoimmune diseases including T1D and proposes a role for environmental factors in breaking immune tolerance to β cell antigens through neo-antigen formation.

Ocular manifestations of autoimmune polyendocrinopathy syndrome type 1

PURPOSE OF REVIEW

The ocular manifestations in autoimmune polyendocrinopathy syndrome type 1 (APS1) are frequent and have a poor prognosis. The phenotype of these APS1-associated ocular features have been recently characterized in molecularly confirmed patients with APS1.

RECENT FINDINGS

Keratopathy and retinopathy can be severe manifestations of APS1. Heterogeneous corneal involvement can be observed, ranging from minimal superficial punctate staining to severe stromal scarring with deep corneal neovascularization. This phenotypic heterogeneity, observed even in patients with identical AIRE mutations, is suggestive of a poor genotype-phenotype correlation. Similarly, in patients with retinopathy, peripheral pigmentary changes are noted in all cases, yet with heterogeneous severity, ranging from isolated patchy atrophy of the retinal pigment epithelium to a retinitis pigmentosa-like fundus. Macular atrophy with vision loss is found in most cases. The severity of ophthalmic findings is uncorrelated to that of systemic manifestations. An autoimmune origin with specific autoantibodies directed against corneal and/or retinal autoantigens is the main mechanism believed to be responsible for the ocular manifestations of APS1.

SUMMARY

Progressive keratopathy and/or retinopathy can lead to severe visual loss and pain in patients with APS1. Although no treatment has shown efficacy regarding the APS1-associated ocular manifestations, ophthalmologic examinations are recommended in these patients.

Identification of autoimmune polyendocrine syndrome type 1 in patients with isolated hypoparathyroidism

OBJECTIVE

The prevalence of autoimmune polyendocrine syndrome type 1 (APS1) among isolated hypoparathyroidism (HP) or primary adrenal insufficiency (PAI) is not well established. We studied the frequency of APS1 in patients with HP or PAI by measuring interferon-α (IFN-α) antibody levels, a highly sensitive and specific marker for APS1.

DESIGN, PATIENTS AND MEASUREMENTS

In a single-centre cross-sectional study, 37 Indian patients with isolated HP and 40 patients with PAI were tested for IFN-α antibody using an indirect ELISA. In patients with elevated IFN-α antibody, the autoimmune regulator (AIRE) gene was bidirectionally sequenced.

RESULTS

Three (8·1%) patients with isolated HP had elevated IFN-α antibody levels (range: 367-17382 units; positive titre >56 units). Homozygous or compound heterozygous AIRE mutations were detected in all three patients, including a novel mutation (p.T68P). All three APS1 patients had atypical features. The first patient, diagnosed at 7 years of age, died suddenly 5 months later. The second patient had late-onset HP (at the age of 34 years) and a solitary episode of transient mucocutaneous candidiasis 5 years later. The final patient developed HP at the age of 14 years and premature ovarian insufficiency 14 years later. Interleukin-22 antibodies, as well as most other organ-specific antibodies, were absent in the 3 APS1 patients. All patients with PAI were negative for IFN-α antibody.

CONCLUSION

Eight percentage of patients with isolated HP had elevated IFN-α antibody levels and AIRE mutation-positive APS1. All APS1 patients had atypical clinical features. Testing for IFN-α antibody should be considered in patients with idiopathic HP.