Follicular bronchiolitis as phenotype associated with CD25 deficiency

Single cell characterization of blood and expanded regulatory T cells in autoimmune polyendocrine syndrome type 1

Immune tolerance fails in autoimmune polyendocrine syndrome type 1 (APS-1) because of AIRE mutations. We have used single cell transcriptomics to characterize regulatory T cells (Tregs) sorted directly from blood and from in vitro expanded Tregs in APS-1 patients compared to healthy controls. We revealed only CD52 and LTB (down) and TXNIP (up) as consistently differentially expressed genes in the datasets. There were furthermore no large differences of the TCR-repertoire of expanded Tregs between the cohorts, but unique patients showed a more restricted use of specific clonotypes. We also found that in vitro expanded Tregs from APS-1 patients had similar suppressive capacity as controls in co-culture assays, despite expanding faster and having more exhausted cells. Our results suggest that APS-1 patients do not have intrinsic defects in their Treg functionality, and that their Tregs can be expanded ex vivo for potential therapeutic applications.

Tipping the balance in autoimmunity: are regulatory t cells the cause, the cure, or both?

Regulatory T cells (Tregs) are a specialized subgroup of T-cell lymphocytes that is crucial for maintaining immune homeostasis and preventing excessive immune responses. Depending on their differentiation route, Tregs can be subdivided into thymically derived Tregs (tTregs) and peripherally induced Tregs (pTregs), which originate from conventional T cells after extrathymic differentiation at peripheral sites. Although the regulatory attributes of tTregs and pTregs partially overlap, their modes of action, protein expression profiles, and functional stability exhibit specific characteristics unique to each subset. Over the last few years, our knowledge of Treg differentiation, maturation, plasticity, and correlations between their phenotypes and functions has increased. Genetic and functional studies in patients with numeric and functional Treg deficiencies have contributed to our mechanistic understanding of immune dysregulation and autoimmune pathologies. This review provides an overview of our current knowledge of Treg biology, discusses monogenetic Treg pathologies and explores the role of Tregs in various other autoimmune disorders. Additionally, we discuss novel approaches that explore Tregs as targets or agents of innovative treatment options.

Expanding IPEX: Inborn Errors of Regulatory T Cells

Regulatory T cells (Tregs) are critical for enforcing peripheral tolerance. Monogenic "Tregopathies" affecting Treg development, stability, and/or function commonly present with polyautoimmunity, atopic disease, and infection. While autoimmune manifestations may present in early childhood, as more disorders are characterized, conditions with later onset have been identified. Treg numbers in the blood may be decreased in Tregopathies, but this is not always the case, and genetic testing should be pursued when there is high clinical suspicion. Currently, hematopoietic cell transplantation is the only curative treatment, but gene therapies are in development, and small molecule inhibitors/biologics may also be used.

Too much of a good thing: a review of primary immune regulatory disorders

Primary immune regulatory disorders (PIRDs) are inborn errors of immunity caused by a loss in the regulatory mechanism of the inflammatory or immune response, leading to impaired immunological tolerance or an exuberant inflammatory response to various stimuli due to loss or gain of function mutations. Whilst PIRDs may feature susceptibility to recurrent, severe, or opportunistic infection in their phenotype, this group of syndromes has broadened the spectrum of disease caused by defects in immunity-related genes to include autoimmunity, autoinflammation, lymphoproliferation, malignancy, and allergy; increasing focus on PIRDs has thus redefined the classical 'primary immunodeficiency' as one aspect of an overarching group of inborn errors of immunity. The growing number of genetic defects associated with PIRDs has expanded our understanding of immune tolerance mechanisms and prompted identification of molecular targets for therapy. However, PIRDs remain difficult to recognize due to incomplete penetrance of their diverse phenotype, which may cross organ systems and present to multiple clinical specialists prior to review by an immunologist. Control of immune dysregulation with immunosuppressive therapies must be balanced against the enhanced infective risk posed by the underlying defect and accumulated end-organ damage, posing a challenge to clinicians. Whilst allogeneic hematopoietic stem cell transplantation may correct the underlying immune defect, identification of appropriate patients and timing of transplant is difficult. The relatively recent description of many PIRDs and rarity of individual genetic entities that comprise this group means data on natural history, clinical progression, and treatment are limited, and so international collaboration will be needed to better delineate phenotypes and the impact of existing and potential therapies. This review explores pathophysiology, clinical features, current therapeutic strategies for PIRDs including cellular platforms, and future directions for research.

Effect of Boswellic acids on T cell proliferation and activation

Boswellic acids have been recognized as anti-inflammatory and immunomodulatory agents with potentials to control autoimmune and inflammatory diseases. However, their effects on T cell proliferation and activation are not fully elucidated. In this study, we investigated effects of individual compounds including β-Boswellic acids (β-BA), 11-keto-β-Boswellic acid (β-KBA), 3-O-acetyl β-Boswellic acids (β-ABA), and 3-O-acetyl-11-keto-β-Boswellic acid (β-AKBA) on human peripheral blood mononuclear cells (PBMCs) and their potential role in modulating immune responses. We showed that β-BA, KBA, and AKBA at a 0.025 µM concentration significantly reduced T cell proliferation without inducing cytotoxicity, however, ABA showed cytotoxic effects at this concentration. β-BA and KBA showed significantly reduced T cell proliferation at 0.05 µM concentration without cytotoxic effects. Interestingly, we found that AKBA at 0.025 µM concentration significantly reduced CD25 expression on both CD4+ and CD8+ T cells without cytotoxic effects. Additionally, β-BA reduced CD25 expression on both CD4+ and CD8+ T cells at 0.05 µM concentration with no cytotoxicity. In this study, we determined the optimum concentration of each of these compounds that have the potential to reduce T cell activation without cytotoxic effects. Our findings show that both β-BA and AKBA have the ability to inhibit T cell proliferation and activation without inducing cytotoxicity. Further investigations are required to fully understand the mechanisms underlying these effects and the potential therapeutic benefits of these compounds in different autoimmune and inflammatory settings.

Whole exome sequencing identified a novel splice donor site variant in interleukin 2 receptor alpha chain

Interleukin 2 receptor alpha chain (IL-2Rα or CD25) deficiency (OMIM #606367) is an immune dysregulation disorder segregating in autosomal recessive form. The disease is caused by biallelic variants in the IL-2Rα gene encoding IL-2Rα also known as CD25 protein. IL-2Rα combines with γ and β chains of interleukin 2 receptor to form a functional interleukin 2 receptor (IL-2R). In the present study, we identified a Pakistani family presenting a unique presentation of IL-2Rα deficiency. Clinical whole exome sequencing revealed a novel splice donor site variant (NM_001378789.1 (NP_001365718); c.64 + 1G > A) in the IL-2Rα gene. American College of Medical Genetics (ACMG) guidelines interpreted the identified variant as likely pathogenic. The IL-2Rα gene mutation usually presents with autoimmunity and immunodeficiency but in our patient, it presents with congenital diarrhea, metabolic crisis, and strong family history of death in infancy due to the similar complications. Her congenital diarrhea is attributed to autoimmunity in the form of autoimmune enteropathy and eczema. The laboratory findings revealed severe metabolic acidosis hypokalemia and elevated lactate and ammonia levels. This is a new presentation of IL-2Rα gene mutation. The present study highlights the importance of clinical whole exome sequencing in the correct diagnosis of congenital disorders. The study will also help clinical geneticists for genetic counseling and prevention of the disease in the affected family.

High-yield genome engineering in primary cells using a hybrid ssDNA repair template and small-molecule cocktails

Enhancing CRISPR-mediated site-specific transgene insertion efficiency by homology-directed repair (HDR) using high concentrations of double-stranded DNA (dsDNA) with Cas9 target sequences (CTSs) can be toxic to primary cells. Here, we develop single-stranded DNA (ssDNA) HDR templates (HDRTs) incorporating CTSs with reduced toxicity that boost knock-in efficiency and yield by an average of around two- to threefold relative to dsDNA CTSs. Using small-molecule combinations that enhance HDR, we could further increase knock-in efficiencies by an additional roughly two- to threefold on average. Our method works across a variety of target loci, knock-in constructs and primary human cell types, reaching HDR efficiencies of >80-90%. We demonstrate application of this approach for both pathogenic gene variant modeling and gene-replacement strategies for IL2RA and CTLA4 mutations associated with Mendelian disorders. Finally, we develop a good manufacturing practice (GMP)-compatible process for nonviral chimeric antigen receptor-T cell manufacturing, with knock-in efficiencies (46-62%) and yields (>1.5 × 109 modified cells) exceeding those of conventional approaches.

A great disturbance in the force: IL-2 receptor defects disrupt immune homeostasis

PURPOSE OF REVIEW

The current review highlights how inborn errors of immunity (IEI) due to IL-2 receptor (IL-2R) subunit defects may result in children presenting with a wide variety of infectious and inflammatory presentations beyond typical X-linked severe combined immune deficiency (X-SCID) associated with IL-2Rγ.

RECENT FINDINGS

Newborn screening has made diagnosis of typical SCID presenting with severe infections less common. Instead, infants are typically diagnosed in the first days of life when they appear healthy. Although earlier diagnosis has improved clinical outcomes for X-SCID, atypical SCID or other IEI not detected on newborn screening may present with more limited infectious presentations and/or profound immune dysregulation. Early management to prevent/control infections and reduce inflammatory complications is important for optimal outcomes of definitive therapies. Hematopoietic stem cell transplant (HSCT) is curative for IL-2Rα, IL-2Rβ, and IL-2Rγ defects, but gene therapy may yield comparable results for X-SCID.

SUMMARY

Defects in IL-2R subunits present with infectious and inflammatory phenotypes that should raise clinician's concern for IEI. Immunophenotyping may support the suspicion for diagnosis, but ultimately genetic studies will confirm the diagnosis and enable family counseling. Management of infectious and inflammatory complications will determine the success of gene therapy or HSCT.

Granulomatous hepatitis in a Saudi child with IL2RA defect: a case report and literature review

Interleukin-2 receptor alpha (IL2RA) defect (OMIM- # 606367) is an immune disease where affected patients are vulnerable to developing recurrent microbial infections in addition to lymphadenopathy and dermatological manifestations. This condition is known to be caused by pathogenic variants in the IL2RA gene, which are inherited in an autosomal recessive fashion. In this case report, we present a patient with IL2RA defect from Saudi Arabia who presented with chronic diarrhea, poor weight gain, mild villous atrophy, malnutrition, hepatomegaly, nonspecific inflammation, and an eczematous skin rash. His genetic analysis revealed a novel, homozygous, and likely pathogenic variant, that is, c.504 C>A (Cys168Ter), located in the exon 4of the IL2RA gene, which was inherited from his parents in an autosomal recessive mode of inheritance. This variant produces a 272-amino-acid shorter IL2RA protein chain, which most likely becomes degraded in the cytosol. Thus, we assume that the c.504 C>A is a null allele that abolishes the synthesis of IL2RA, malforms the IL-2 receptor complex, and eventually causes immunodeficiency manifestations. To our knowledge, this is the first time a person with IL2RA defect has shown signs of granulomatous hepatitis on a liver biopsy.

Systematic discovery and perturbation of regulatory genes in human T cells reveals the architecture of immune networks

Gene regulatory networks ensure that important genes are expressed at precise levels. When gene expression is sufficiently perturbed, it can lead to disease. To understand how gene expression disruptions percolate through a network, we must first map connections between regulatory genes and their downstream targets. However, we lack comprehensive knowledge of the upstream regulators of most genes. Here, we developed an approach for systematic discovery of upstream regulators of critical immune factors-IL2RA, IL-2 and CTLA4-in primary human T cells. Then, we mapped the network of the target genes of these regulators and putative cis-regulatory elements using CRISPR perturbations, RNA-seq and ATAC-seq. These regulators form densely interconnected networks with extensive feedback loops. Furthermore, this network is enriched for immune-associated disease variants and genes. These results provide insight into how immune-associated disease genes are regulated in T cells and broader principles about the structure of human gene regulatory networks.

CRISPR-Cas9-mediated nuclear transport and genomic integration of nanostructured genes in human primary cells

DNA nanostructures are a promising tool to deliver molecular payloads to cells. DNA origami structures, where long single-stranded DNA is folded into a compact nanostructure, present an attractive approach to package genes; however, effective delivery of genetic material into cell nuclei has remained a critical challenge. Here, we describe the use of DNA nanostructures encoding an intact human gene and a fluorescent protein encoding gene as compact templates for gene integration by CRISPR-mediated homology-directed repair (HDR). Our design includes CRISPR–Cas9 ribonucleoprotein binding sites on DNA nanostructures to increase shuttling into the nucleus. We demonstrate efficient shuttling and genomic integration of DNA nanostructures using transfection and electroporation. These nanostructured templates display lower toxicity and higher insertion efficiency compared to unstructured double-stranded DNA templates in human primary cells. Furthermore, our study validates virus-like particles as an efficient method of DNA nanostructure delivery, opening the possibility of delivering nanostructures in vivo to specific cell types. Together, these results provide new approaches to gene delivery with DNA nanostructures and establish their use as HDR templates, exploiting both their design features and their ability to encode genetic information. This work also opens a door to translate other DNA nanodevice functions, such as biosensing, into cell nuclei.

Inborn Errors of Immunity With Fetal or Perinatal Clinical Manifestations

In this article we revised the literature on Inborn Errors of Immunity (IEI) keeping our focus on those diseases presenting with intrauterine or perinatal clinical manifestations. We opted to describe our findings according to the IEI categories established by the International Union of Immunological Societies, predominantly addressing the immunological features of each condition or group of diseases. The main finding is that such precocious manifestations are largely concentrated in the group of primary immune regulatory disorders (PIRDs) and not in the group of classical immunodeficiencies. The IEI categories with higher number of immunological manifestations in utero or in perinatal period are: (i) diseases of immune dysregulation (HLH, IPEX and other Tregopathies, autosomal recessive ALPS with complete lack of FAS protein expression) and (ii) autoinflammatory diseases (NOMID/CINCA, DIRA and some interferonopathies, such as Aicardi-Goutières syndrome, AGS, and USP18 deficiency). Regarding the other IEI categories, some patients with Omenn syndrome (an atypical form of SCID), and a few X-linked CGD patients present with clinical manifestations at birth associated to immune dysregulation. The most frequent clinical features were hydrops fetalis, intrauterine growth retardation leading to fetal loss, stillbirths, and prematurity, as in HLH and IPEX. Additionally, pseudo-TORCH syndrome was observed in AGS and in USP18 deficiency. The main goal of our review was to contribute to increasing the medical awareness of IEI with intrauterine and perinatal onset, which has obvious implications for diagnosis, treatment, and genetic counseling.

Early-onset, fatal interstitial lung disease in STAT3 gain-of-function patients

Gain-of-function variants in STAT3 are known to cause severe, multifaceted autoimmunity. Here we report three individuals with de-novo STAT3 GOF alleles and early-onset, severe interstitial lung disease manifesting during the first 3 years of life. Imaging and histology revealed different forms of interstitial pneumonia alongside fibrotic and cystic tissue destruction. Definitive diagnosis was established by postmortem whole exome sequencing and functional validation of two new STAT3 variants. Such lung-predominant forms of STAT3 GOF disease expand the phenotypic spectrum of diseases associated with activating STAT3 variants and add to our understanding of this life-threatening inborn error of immunity.

Clean up by aisle 2: roles for IL-2 receptors in host defense and tolerance

Although IL-2 was first recognized as growth factor for T cells, it is now also appreciated to be a key regulator of T cells through its effects on regulatory T cells (Treg). The IL-2 receptor (IL-2R) subunits' different (i) ligand affinities, (ii) dimerization or trimerization relationships with other cytokine subunits, (iii) expression across multiple cell types, and (iv) downstream signaling effects, largely dictate cellular tolerance and antimicrobial processes. Defects in IL-2Rγ result in profound and almost universally fatal immune deficiency, unless treated with hematopoietic stem cell transplantation (HSCT). Defects in IL-2Rα and IL-2Rβ result in more limited infection susceptibility, particularly to herpesviruses. However, the most prominent clinical symptomatology for IL-2Rα and IL-2Rβ defects include multi-organ autoimmunity and inflammation, consistent with the critical role of IL-2 in establishing and maintaining immune tolerance. Here, we review how we have arrived at our current understanding of the complex roles of IL-2/2R in host defense and tolerance focusing on the insights gained from human clinical immunology.

Cellular and molecular mechanisms breaking immune tolerance in inborn errors of immunity

In addition to susceptibility to infections, conventional primary immunodeficiency disorders (PIDs) and inborn errors of immunity (IEI) can cause immune dysregulation, manifesting as lymphoproliferative and/or autoimmune disease. Autoimmunity can be the prominent phenotype of PIDs and commonly includes cytopenias and rheumatological diseases, such as arthritis, systemic lupus erythematosus (SLE), and Sjogren's syndrome (SjS). Recent advances in understanding the genetic basis of systemic autoimmune diseases and PIDs suggest an at least partially shared genetic background and therefore common pathogenic mechanisms. Here, we explore the interconnected pathogenic pathways of autoimmunity and primary immunodeficiency, highlighting the mechanisms breaking the different layers of immune tolerance to self-antigens in selected IEI.

IL-2 Signaling Axis Defects: How Many Faces?

CD25, Signal transducer and activator of transcription 5B (STAT5B) and Forkhead box P3 (FOXP3) are critical mediators of Interleukin-2 (IL-2) signaling pathway in regulatory T cells (Tregs). CD25 (i.e., IL-2 Receptor α) binds with high affinity to IL-2, activating STAT5B-mediated signaling that eventually results in transcription of FOXP3, a master regulator of Treg function. Consequently, loss-of-function mutations in these proteins give rise to Treg disorders (i.e., Tregopathies) that clinically result in multiorgan autoimmunity. Immunodysregulation, Polyendocrinopathy Enteropathy X-linked (IPEX), due to mutations in FOXP3, has historically been the prototype of Tregopathies. This review describes current knowledge about defects in CD25, STAT5B, and FOXP3, highlighting that these disorders both share a common biological background and display comparable clinical features. However, specific phenotypes are associated with each of these syndromes, while certain laboratory findings could be helpful tools for clinicians, in order to achieve a prompt genetic diagnosis. Current treatment strategies will be outlined, keeping an eye on gene editing, an interesting therapeutic perspective that could definitely change the natural history of these disorders.

Immune Monitoring of Patients With Primary Immune Regulation Disorders Unravels Higher Frequencies of Follicular T Cells With Different Profiles That Associate With Alterations in B Cell Subsets

Primary immune regulation disorders lead to autoimmunity, allergy and inflammatory conditions due to defects in the immune homeostasis affecting different T, B and NK cell subsets. To improve our understanding of these conditions, in this work we analyzed the T and B cell compartments of 15 PID patients with dysregulation, including 3 patients with STAT1 GOF mutation, 7 patients with CVID with dysregulation, 3 patients with mutations in CTLA4, 1 patient with CD25 mutation and 1 patient with STAT5b mutation and compared them with healthy donors and with CVID patients without dysregulation. CD4⁺ and CD8⁺ T cells from the patients exhibited a significant decreased frequency of naïve and regulatory T cells with increased frequencies of activated cells, central memory CD4⁺ T cells, effector memory CD8⁺ T cells and terminal effector CD8⁺ T cells. Patients also exhibited a significantly increased frequency of circulating CD4⁺ follicular helper T cells, with altered frequencies of cTfh cell subsets. Such cTfh cells were skewed toward cTfh1 cells in STAT1 GOF, CTLA4, and CVID patients, while the STAT5b deficient patient presented a skew toward cTfh17 cells. These alterations confirmed the existence of an imbalance in the cTfh1/cTfh17 ratio in these diseases. In addition, we unraveled a marked dysregulation in the B cell compartment, characterized by a prevalence of transitional and naïve B cells in STAT1 GOF and CVID patients, and of switched-memory B cells and plasmablast cells in the STAT5b deficient patient. Moreover, we observed a significant positive correlation between the frequencies cTfh17 cells and switched-memory B cells and between the frequency of switched-memory B cells and the serum IgG. Therefore, primary immunodeficiencies with dysregulation are characterized by a skew toward an activated/memory phenotype within the CD4⁺ and CD8⁺ T cell compartment, accompanied by abnormal frequencies of Tregs, cTfh, and their cTfh1 and cTfh17 subsets that likely impact on B cell help for antibody production, which likely contributes to their autoimmune and inflammatory conditions. Therefore, assessment of these alterations by flow cytometry constitutes a simple and straightforward manner to improve diagnosis of these complex clinical entities that may impact early diagnosis and patients' treatment. Also, our findings unravel phenotypic alterations that might be associated, at least in part, with some of the clinical manifestations observed in these patients.

CD4+CD25-FoxP3+ T cells: a distinct subset or a heterogeneous population?

In addition to generating effective immunity against infectious agents, the immune system helps to fight against different noninfectious human diseases while maintaining the balance between self and non-self discrimination. The breakdown of tolerance in autoimmune diseases or sustainable tolerance in an abnormal microenvironment such as chronic inflammation may initiate the process of malignancy. Immune system regulation is controlled by a complex, dynamic network of cells and mediators. Understanding the cellular and molecular basis of immune regulation provides better insight into the mechanisms governing the immune pathology of diseases. Among several cellular subsets and mediators with regulatory roles, a subpopulation of CD4⁺ T cells was recently reported to be positive for FoxP3 and negative for CD25, with a suggested range of functional activities in both cancer and autoimmune diseases. This CD4 subset was first reported in 2006 and thought to have a role in the pathogenesis of cancer. However, the spectrum of roles played by this T cell subset is broad, and no consensus has been reached regarding its immunological functions. In this review, we focused on the possible origin of CD4⁺CD25^‒FoxP3⁺ T cells and their function in cancer and autoimmune diseases.

Intrauterine IPEX

IPEX is one of the few Inborn Errors of Immunity that may manifest in the fetal period, and its intrauterine forms certainly represent the earliest human autoimmune diseases. Here, we review the clinical, histopathologic, and genetic findings from 21 individuals in 11 unrelated families, with nine different mutations, described as cases of intrauterine IPEX. Recurrent male fetal death (multigenerational in five families) due to hydrops in the midsemester of pregnancy was the commonest presentation (13/21). Noteworthy, in the affected families, there were only fetal- or perinatal-onset cases, with no affected individuals presenting milder forms with later-life manifestation. Most alive births were preterm (5/6). Skin desquamation and intrauterine growth restriction were observed in part of the cases. Fetal ultrasonography showed hyperechoic bowel or dilated bowel loops in the five cases with available imaging data. Histopathology showed multi-visceral infiltrates with T lymphocytes and other cells, including eosinophils, the pancreas being affected in most of the cases (11/21) and as early as at 18 weeks of gestational age. Regarding the nine FOXP3 mutations found in these cases, six determine protein truncation and three predictably impair protein function. Having found distinct presentations for the same FOXP3 mutation in different families, we resorted to the mouse system and showed that the scurfy mutation also shows divergent severity of phenotype and age of death in C57BL/6 and BALB/c backgrounds. We also reviewed age-of-onset data from other monogenic Tregopathies leading to IPEX-like phenotypes. In monogenic IPEX-like syndromes, the intrauterine onset was only observed in two kindreds with IL2RB mutations, with two stillbirths and two premature neonates who did not survive. In conclusion, intrauterine IPEX cases seem to constitute a particular IPEX subgroup, certainly with the most severe clinical presentation, although no strict mutation-phenotype correlations could be drawn for these cases.

Small Airway Disease: A Step Closer to Etiology-Based Classification of Bronchiolitis

Three major histologic patterns of bronchiolitis: obliterative bronchiolitis, follicular bronchiolitis, and diffuse panbronchiolitis, are reviewed in detail. These distinct patterns of primary bronchiolar injury provide a useful starting point for formulating a differential diagnosis and considering possible causes. In support of the aim toward a cause-based classification system of small airway disease, a simple diagnostic algorithm is provided for further subclassification of the above 3 bronchiolitis patterns according to the major associated etiologic subgroups.

Tregopathies: Monogenic diseases resulting in regulatory T-cell deficiency

Monogenic diseases of the immune system, also known as inborn errors of immunity, are caused by single-gene mutations resulting in immune deficiency and dysregulation. More than 350 diseases have been described to date, and the number is rapidly expanding, with increasing availability of next-generation sequencing facilitating the diagnosis. The spectrum of immune dysregulation is wide, encompassing deficiencies in humoral, cellular, innate, and adaptive immunity; phagocytosis; and the complement system, which lead to autoinflammation and autoimmunity. Multiorgan autoimmunity is a dominant symptom when genetic mutations lead to defects in molecules essential for the development, survival, and/or function of regulatory T (Treg) cells. Studies of "Tregopathies" are providing critical mechanistic information on Treg cell biology, the role of Treg cell-associated molecules, and regulation of peripheral tolerance in human subjects. The pathogenic immune networks underlying these diseases need to be dissected to apply and develop immunomodulatory treatments and design curative treatments using cell and gene therapy. Here we review the pathogenetic mechanisms, clinical presentation, diagnosis, and current and future treatments of major known Tregopathies caused by mutations in FOXP3, CD25, cytotoxic T lymphocyte-associated antigen 4 (CTLA4), LPS-responsive and beige-like anchor protein (LRBA), and BTB domain and CNC homolog 2 (BACH2) and gain-of-function mutations in signal transducer and activator of transcription 3 (STAT3). We also discuss deficiencies in genes encoding STAT5b and IL-10 or IL-10 receptor as potential Tregopathies.

Genetic Mechanisms Highlight Shared Pathways for the Pathogenesis of Polygenic Type 1 Diabetes and Monogenic Autoimmune Diabetes

PURPOSE OF REVIEW

To highlight pathways important for the development of autoimmune diabetes by investigating shared mechanisms of disease in polygenic and monogenic diabetes.

RECENT FINDINGS

Genome-wide association studies have identified 57 genetic risk loci for type 1 diabetes. Progress has been made in unravelling the mechanistic effects of some of these variants, providing key insights into the pathogenesis of type 1 diabetes. Seven monogenic disorders have also been described where diabetes features as part of an autoimmune syndrome. Studying these genes in relation to polygenic risk loci provides a unique opportunity to dissect pathways important for the development of immune-mediated diabetes. Monogenic autoimmune diabetes can result from the dysregulation of multiple pathways suggesting that small effects on many immune processes are required to drive the autoimmune attack on pancreatic beta cells in polygenic type 1 diabetes. A breakdown in central and peripheral immune tolerance is a common theme in the genetic mechanisms of both monogenic and polygenic disease which highlights the importance of these checkpoints in the development and treatment of islet autoimmunity.

Revisiting IL-2: Biology and therapeutic prospects

Interleukin-2 (IL-2), the first cytokine that was molecularly cloned, was shown to be a T cell growth factor essential for the proliferation of T cells and the generation of effector and memory cells. On the basis of this activity, the earliest therapeutic application of IL-2 was to boost immune responses in cancer patients. Therefore, it was a surprise that genetic deletion of the cytokine or its receptor led not only to the expected immune deficiency but also to systemic autoimmunity and lymphoproliferation. Subsequent studies established that IL-2 is essential for the maintenance of Foxp3⁺ regulatory T cells (T_reg cells), and in its absence, there is a profound deficiency of T_reg cells and resulting autoimmunity. We now know that IL-2 promotes the generation, survival, and functional activity of T_reg cells and thus has dual and opposing functions: maintaining T_reg cells to control immune responses and stimulating conventional T cells to promote immune responses. It is well documented that certain IL-2 conformations result in selective targeting of T_reg cells by increasing reliance on CD25 binding while compromising CD122 binding. Recent therapeutic strategies have emerged to use IL-2, monoclonal antibodies to IL-2, or IL-2 variants to boost T_reg cell numbers and function to treat autoimmune diseases while dealing with the continuing challenges to minimize the generation of effector and memory cells, natural killer cells, and other innate lymphoid populations.

CD25 deficiency: A new conformational mutation prevents the receptor expression on cell surface

CD25 deficiency is a very rare autosomal recessive disorder that shows a clinical phenotype highly overlapping IPEX syndrome with an increased susceptibility to viral, bacterial, and fungal infections. It is due to mutations in the IL2Rα gene that codes for the α subunit of the IL2 receptor complex. Here we report the characterization of a novel IL2Rα gene mutation leading to a severe protein conformational alteration that abrogates its cell surface expression in a child presenting with early-onset IPEX-like disorder. Cytofluorimetric analysis revealed the total absence of CD25 cell surface expression and addressed IL2Rα molecular investigation. The early clinical and molecular diagnosis of CD25 deficiency in this patient promptly led to hematopoietic stem cell transplantation (HSCT), allowing complete resolution of the symptoms and definitive cure of the disease.

Reduced Corneal Innervation in the CD25 Null Model of Sjögren Syndrome

Decreased corneal innervation is frequent in patients with Sjögren Syndrome (SS). To investigate the density and morphology of the intraepithelial corneal nerves (ICNs), corneal sensitivity, epithelial cell proliferation, and changes in mRNA expression of genes that are involved in autophagy and axon targeting and extension were assessed using the IL-2 receptor alpha chain (CD25 null) model of SS. ICN density and thickness in male and female wt and CD25 null corneas were assessed at 4, 6, 8, and 10/11 wk of age. Cell proliferation was assessed using ki67. Mechanical corneal sensitivity was measured. Quantitative PCR was performed to quantify expression of beclin 1, LC3, Lamp-1, Lamp-2, CXCL-1, BDNF, NTN1, DCC, Unc5b1, Efna4, Efna5, Rgma, and p21 in corneal epithelial mRNA. A significant reduction in corneal axon density and mechanical sensitivity were observed, which negatively correlate with epithelial cell proliferation. CD25 null mice have increased expression of genes regulating autophagy (beclin-1, LC3, LAMP-1, LAMP-2, CXCL1, and BDNF) and no change was observed in genes that were related to axonal targeting and extension. Decreased anatomic corneal innervation in the CD25 null SS model is accompanied by reduced corneal sensitivity, increased corneal epithelial cell proliferation, and increased expression of genes regulating phagocytosis and autophagy.

Primary Immunodeficiencies Unravel the Role of IL-2/CD25/STAT5b in Human Natural Killer Cell Maturation

Natural killer (NK) cells play a pivotal role during immunity against viruses and circumstantial evidence also indicates that they can protect the host against developing tumors. Peripheral blood NK cells comprise CD56^brightCD16^lo/− cells that constitutively express CD25 (IL-2Rα) and CD56^dimCD16^hi cells that express CD25 upon activation. Using NK cells from two patients, one with a primary immunodeficiency characterized by a homozygous mutation in CD25 (born in year 2007 and studied since she was 3 years old) and one with a homozygous mutation in STAT5b (born in year 1992 and studied since she was 10 years old), we observed that the absence of IL-2 signaling through CD25 promotes the accumulation of CD56^brightCD16^high NK cells, and that CD56^brightCD16^lo, CD56^brightCD16^high, and CD56^dimCD16^high NK cells of this patient exhibited higher content of perforin and granzyme B, and proliferation capacity, compared to healthy donors. Also, CD56^bright and CD56^dim NK cells of this patient exhibited a reduced IFN-γ production in response to cytokine stimulation and increased degranulation against K562 cells. Also, the CD25-deficient patient presented a lower frequency of terminally differentiated NK cells in the CD56^dimCD16^hi NK subpopulation compared to the HD (assessed by CD57 and CD94 expression). Remarkably, CD56^dimCD16^high NK cells from both patients exhibited notoriously higher expression of CD62L compared to HD, suggesting that in the absence of IL-2 signaling through CD25 and STAT5b, NK cells fail to properly downregulate CD62L during their transition from CD56^brightCD16^lo/− to CD56^dimCD16^hi cells. Thus, we provide the first demonstration about the in vivo requirement of the integrity of the IL-2/CD25/STAT5b axis for proper human NK cell maturation.

The Clinical Characteristics and Outcomes of Follicular Bronchiolitis in Chinese Adult Patients

Follicular bronchiolitis (FB) is a rare interstitial lung disease (ILD) and has been reported in diverse clinical contexts. Six FB patients demonstrated by surgical lung biopsy (SLB) were reviewed between 2009 and 2017 from Nanjing Drum Tower Hospital in China. The average age of subjects was 42 years old (range: 31-55 years). The clinical symptoms were very mild. The laboratory findings showed elevated Erythrocyte sedimentation rate (ESR) and serum globulin and anemia. Pulmonary function tests were normal in four cases. Five cases had underlying diseases, such as, Sjo¨gren's syndrome, multi-centric castlemans' disease, idiopathic pneumonia with autoimmune features and abscess. Five cases presented as interstitial lung disease (ILD) on chest imaging with centrilobular or peribronchiolar nodules, ground glass opacities, interlobular septal thickening, cysts and bronchiectasis. Isolated mass was in one patient. The histopathology suggested the changes of FB in all subjects. Prednisone and/or cyclophosphamide were used in four cases, one did the surgery and the other was clinically monitored. All cases were alive at the end of follow up. The adult patients of FB usually have mild symptoms, ILD and underlying diseases. The definite diagnosis needs SLB. The prognosis is depended on their underlying conditions.

Novel molecular defects associated with very early-onset inflammatory bowel

PURPOSE OF REVIEW

Immune dysregulation disorders present with common clinical features of multiorgan autoimmunity. Gastrointestinal involvement is the hallmark of an impaired immune homeostasis. This review will give an overview on the novel phenotypes, highlighting the major points that will help to enable early diagnosis and treatment.

RECENT FINDINGS

The rapid progress on DNA sequencing technologies have led to the identification of monogenic defects that adversely impact the control of immune homeostasis. Lymphocytes may be present but dysfunctional, allowing for the development of excessive autoreactivity and resultant autoimmune disease. Regulatory T cells (Tregs) play an essential role in enforcing immune tolerance. Here we illustrate disorders caused by impairment of mechanisms ensuring Tregs function (Tregs related) in which autoimmunity is a hallmark of the clinical disease presentation and other disorders, affecting molecules more broadly involved in immune responses and indirectly causing immune dysregulation (Tregs unrelated). Clinical presentation is sometime mischievous and often symptoms are analogous in different diseases and can mislead diagnosis.

SUMMARY

The increasing comprehension of immunological concepts behind immune dysregulation diseases will allow better and in some cases possibly even targeted treatment. A genetic diagnosis therefore becomes important information in this group of patients, especially as some patients might require hematopoietic stem cell transplantation.

Severe Dry Eye in CD25 Deficiency Syndrome

CD25 deficiency (Interleukin-2 receptor alpha deficiency) is a rare subtype of combined B- and T-cell immunodeficiency. Recurrent infections and lymphocyte infiltration of multiple tissues are the main clinical presentations. Only four patients have been reported in whom ophthalmological findings were not described. In this article, ocular findings of CD25 deficiency in a 12-year-old child are highlighted.

Monogenic autoimmune diseases of the endocrine system

The most common endocrine diseases, type 1 diabetes, hyperthyroidism, and hypothyroidism, are the result of autoimmunity. Clustering of autoimmune endocrinopathies can result from polygenic predisposition, or more rarely, may present as part of a wider syndrome due to a mutation within one of seven genes. These monogenic autoimmune diseases show highly variable phenotypes both within and between families with the same mutations. The average age of onset of the monogenic forms of autoimmune endocrine disease is younger than that of the common polygenic forms, and this feature combined with the manifestation of other autoimmune diseases, specific hallmark features, or both, can inform clinicians as to the relevance of genetic testing. A genetic diagnosis can guide medical management, give an insight into prognosis, inform families of recurrence risk, and facilitate prenatal diagnoses.

T Regulatory Cell Biology in Health and Disease

Regulatory T (Treg) cells that express the transcription factor forkhead box protein P3 (FOXP3) play an essential role in enforcing immune tolerance to self tissues, regulating host-commensal flora interaction, and facilitating tissue repair. Their deficiency and/or dysfunction trigger unbridled autoimmunity and inflammation. A growing number of monogenic defects have been recognized that adversely impact Treg cell development, differentiation, and/or function, leading to heritable diseases of immune dysregulation and autoimmunity. In this article, we review recent insights into Treg cell biology and function, with particular attention to lessons learned from newly recognized clinical disorders of Treg cell deficiency.

Autoimmunity in primary T-cell immunodeficiencies

Primary immunodeficiency diseases (PID) are a genetically heterogeneous group of more than 270 disorders that affect distinct components of both humoral and cellular arms of the immune system. Primary T cell immunodeficiencies affect subjects at the early age of life. In most cases, T-cell PIDs become apparent as combined T- and B-cell deficiencies. Patients with T-cell PID are prone to life-threatening infections. On the other hand, non-infectious complications such as lymphoproliferative diseases, cancers and autoimmunity seem to be associated with the primary T-cell immunodeficiencies. Autoimmune disorders of all kinds (organ specific or systemic ones) could be subjected to this class of PIDs; however, the most frequent autoimmune disorders are immune thrombocytopenic purpura (ITP) and autoimmune hemolytic anemia (AIHA). In this review, we discuss the proposed mechanisms of autoimmunity and review the literature reported on autoimmune disorder in each type of primary T-cell immunodeficiencies.

Long-term follow-up of STAT5B deficiency in three argentinian patients: clinical and immunological features

The signal transducer and activator of transcription (STAT) family of proteins regulate gene transcription in response to a variety of cytokines. STAT5B, in particular, plays an important role in T cells, where it is a key mediator of interleukin-2 (IL-2) induced responses. STAT5B deficiency causes a rare autosomal recessive disorder reported in only a handful of individuals. There are currently ten published cases of STAT5B deficiency, four of which are Argentinians.

AIM

This is a report of more than 10 years follow up of the clinical and immunological features of three Argentinian STAT5B deficient patients.

CONCLUSION

More than a decade of follow-up demonstrates that STAT5B deficiency is associated with various clinical pathologies that cause significant morbidity. Early diagnosis is critical for the prevention and improvement of clinical outcomes for STAT5B deficient patients.

The diagnostic approach to monogenic very early onset inflammatory bowel disease

Patients with a diverse spectrum of rare genetic disorders can present with inflammatory bowel disease (monogenic IBD). Patients with these disorders often develop symptoms during infancy or early childhood, along with endoscopic or histological features of Crohn's disease, ulcerative colitis, or IBD unclassified. Defects in interleukin-10 signaling have a Mendelian inheritance pattern with complete penetrance of intestinal inflammation. Several genetic defects that disturb intestinal epithelial barrier function or affect innate and adaptive immune function have incomplete penetrance of the IBD-like phenotype. Several of these monogenic conditions do not respond to conventional therapy and are associated with high morbidity and mortality. Due to the broad spectrum of these extremely rare diseases, a correct diagnosis is frequently a challenge and often delayed. In many cases, these diseases cannot be categorized based on standard histological and immunologic features of IBD. Genetic analysis is required to identify the cause of the disorder and offer the patient appropriate treatment options, which include medical therapy, surgery, or allogeneic hematopoietic stem cell transplantation. In addition, diagnosis based on genetic analysis can lead to genetic counseling for family members of patients. We describe key intestinal, extraintestinal, and laboratory features of 50 genetic variants associated with IBD-like intestinal inflammation. In addition, we provide approaches for identifying patients likely to have these disorders. We also discuss classic approaches to identify these variants in patients, starting with phenotypic and functional assessments that lead to analysis of candidate genes. As a complementary approach, we discuss parallel genetic screening using next-generation sequencing followed by functional confirmation of genetic defects.