STAT5b deficiency: an unsuspected cause of growth failure, immunodeficiency, and severe pulmonary disease

Identifying new molecular signatures and potential therapeutics for idiopathic pulmonary fibrosis: a network medicine approach

Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal lung disease characterized by excessive collagen deposition and fibrosis of the lung parenchyma, leading to respiratory failure. The molecular mechanisms underlying IPF pathogenesis remain incompletely understood, hindering the development of effective therapeutic strategies. We have used a network medicine approach to comprehensively analyze molecular interactions and identify novel molecular signatures and potential therapeutics associated with IPF progression. Our integrative analysis revealed dysregulated molecular networks that are central to IPF pathophysiology. We have highlighted key molecular players and signaling pathways that are implicated in aberrant fibrotic processes. This systems-level understanding enables the identification of new biomarkers and therapeutic targets for IPF, providing potential avenues for precision medicine. Drug repurposing analysis revealed several drug candidates with anti-fibrotic, anti-inflammatory, and anti-cancer activities that could potentially slow fibrotic progression and improve patient outcomes. This study offers new insights into the molecular underpinnings of IPF and highlights network medicine approaches in uncovering complex disease mechanisms. The molecular signatures and therapeutic targets identified hold promise for developing precision therapies tailored to individual patients, ultimately advancing the management of this debilitating lung disease.

TH2-driven manifestations of inborn errors of immunity

Monogenic lesions in pathways critical for effector functions responsible for immune surveillance, protection against autoinflammation, and appropriate responses to allergens and microorganisms underlie the pathophysiology of inborn errors of immunity (IEI). Variants in cytokine production, cytokine signaling, epithelial barrier function, antigen presentation, receptor signaling, and cellular processes and metabolism can drive autoimmunity, immunodeficiency, and/or allergic inflammation. Identification of these variants has improved our understanding of the role that many of these proteins play in skewing toward TH2-related allergic inflammation. Early-onset or atypical atopic disease, often in conjunction with immunodeficiency and/or autoimmunity, should raise suspicion for an IEI. This becomes a diagnostic dilemma if the initial clinical presentation is solely allergic inflammation, especially when the prevalence of allergic diseases is becoming more common. Genetic sequencing is necessary for IEI diagnosis and is helpful for early recognition and implementation of targeted treatment, if available. Although genetic evaluation is not feasible for all patients with atopy, identifying atopic patients with molecular immune abnormalities may be helpful for diagnostic, therapeutic, and prognostic purposes. In this review, we focus on IEI associated with TH2-driven allergic manifestations and classify them on the basis of the affected molecular pathways and predominant clinical manifestations.

JAK/STAT defects and immune dysregulation, and guiding therapeutic choices

Inborn errors of immunity (IEIs) encompass a diverse spectrum of genetic disorders that disrupt the intricate mechanisms of the immune system, leading to a variety of clinical manifestations. Traditionally associated with an increased susceptibility to recurrent infections, IEIs have unveiled a broader clinical landscape, encompassing immune dysregulation disorders characterized by autoimmunity, severe allergy, lymphoproliferation, and even malignancy. This review delves into the intricate interplay between IEIs and the JAK-STAT signaling pathway, a critical regulator of immune homeostasis. Mutations within this pathway can lead to a wide array of clinical presentations, even within the same gene. This heterogeneity poses a significant challenge, necessitating individually tailored therapeutic approaches to effectively manage the diverse manifestations of these disorders. Additionally, JAK-STAT pathway defects can lead to simultaneous susceptibility to both infection and immune dysregulation. JAK inhibitors, with their ability to suppress JAK-STAT signaling, have emerged as powerful tools in controlling immune dysregulation. However, questions remain regarding the optimal selection and dosing regimens for each specific condition. Hematopoietic stem cell transplantation (HSCT) holds promise as a curative therapy for many JAK-STAT pathway disorders, but this procedure carries significant risks. The use of JAK inhibitors as a bridge to HSCT has been proposed as a potential strategy to mitigate these risks.

Treg in inborn errors of immunity: gaps, knowns and future perspectives

Regulatory T cells (Treg) are essential for immune balance, preventing overreactive responses and autoimmunity. Although traditionally characterized as CD4+CD25+CD127lowFoxP3hi, recent research has revealed diverse Treg subsets such as Tr1, Tr1-like, and CD8 Treg. Treg dysfunction leads to severe autoimmune diseases and immune-mediated inflammatory disorders. Inborn errors of immunity (IEI) are a group of disorders that affect correct functioning of the immune system. IEI include Tregopathies caused by genetic mutations affecting Treg development or function. In addition, Treg dysfunction is also observed in other IEIs, whose underlying mechanisms are largely unknown, thus requiring further research. This review provides a comprehensive overview and discussion of Treg in IEI focused on: A) advances and controversies in the evaluation of Treg extended subphenotypes and function; B) current knowledge and gaps in Treg disturbances in Tregopathies and other IEI including Treg subpopulation changes, genotype-phenotype correlation, Treg changes with disease activity, and available therapies, and C) the potential of Treg cell-based therapies for IEI with immune dysregulation. The aim is to improve both the diagnostic and the therapeutic approaches to IEI when there is involvement of Treg. We performed a non-systematic targeted literature review with a knowledgeable selection of current, high-quality original and review articles on Treg and IEI available since 2003 (with 58% of the articles within the last 6 years) in the PubMed database.

STAT5b gain-of-function disease in a child with mycobacterial osteomyelitis of the skull: rare presentation of an emerging disease entity

PURPOSE

STAT proteins play a key role in several cellular functions related to cell development, differentiation, proliferation, and survival. Persistent STAT activation due to somatic STAT5b^N642H gain-of-function mutation is a rare mechanism of STAT dysregulation that results in hypereosinophilia, frequent infections, leukemias, and pulmonary diseases. Herein, we describe a case of a child with a rare early onset STAT5b gain-of-function disease treated with targeted JAK inhibition who developed a cranial Mycobacterium avium osteomyelitis.

METHODS

A 3-year-old male with a known STAT5b gain-of-function mutation presented with a 10-day history of a firm, immobile, non-painful cranial mycobacterium mass with dural infiltration located anterior to the coronal suture. Stepwise management finalized with complete resection of the lesion with calvarial reconstruction. A case-based literature review was performed evaluating all patients with this mutation who developed cranial disease.

RESULTS

The patient was symptom and lesion-free at 1 year since surgical resection and initiation of triple mycobacterial pharmacotherapy. Our literature review demonstrated the rarity of this disease, as well as other presentations of this disease in other patients.

CONCLUSION

Patients with STAT5b gain-of-function mutations have attenuated Th1 responses and are treated with medications, such as JAK inhibitors, which further inhibit other STAT proteins that regulate immunity against rare infectious entities, such as mycobacterium. Our case highlights the importance of considering these rare infections in patients on JAK inhibitors and with STAT protein mutations. Possessing a clear mechanistic understanding of this genetic mutation, its downstream effect, and the consequences of treatment may enhance a physician's diagnostic and clinical management of similar patients in the future.

Comparative Serum Proteome Analysis Indicates a Negative Correlation between a Higher Immune Level and Feed Efficiency in Pigs

Identifying and verifying appropriate biomarkers is instrumental in improving the prediction of early-stage pig production performance while reducing the cost of breeding and production. The main factor that affects the production cost and environmental protection cost of the pig industry is the feed efficiency of pigs. This study aimed to detect the differentially expressed proteins in the early blood index determination serum between high-feed efficiency and low-feed efficiency pigs and to provide a basis for further identification of biomarkers using the isobaric tandem mass tag and parallel reaction monitoring approach. In total, 350 (age, 90 ± 2 d; body weight, 41.20 ± 4.60 kg) purebred Yorkshire pigs were included in the study, and their serum samples were obtained during the early blood index determination. The pigs were then arranged based on their feed efficiency; 24 pigs with extreme phenotypes were grouped as high-feed efficiency and low-feed efficiency, with 12 pigs in each group. A total of 1364 proteins were found in the serum, and 137 of them showed differential expression between the groups with high- and low-feed efficiency, with 44 of them being upregulated and 93 being downregulated. PRM (parallel reaction monitoring) was used to verify 10 randomly chosen differentially expressed proteins. The proteins that were differentially expressed were shown to be involved in nine pathways, including the immune system, digestive system, human diseases, metabolism, cellular processing, and genetic information processing, according to the KEGG and GO analyses. Moreover, all of the proteins enriched in the immune system were downregulated in the high-feed efficiency pigs, suggesting that a higher immune level may not be conducive to improving feed efficiency in pigs. This study provides insights into the important feed efficiency proteins and pathways in pigs, promoting the further development of protein biomarkers for predicting and improving porcine feed efficiency.

Type 1 diabetes and inborn errors of immunity: Complete strangers or 2 sides of the same coin?

Type 1 diabetes (T1D) is a polygenic disease and does not follow a mendelian pattern. Inborn errors of immunity (IEIs), on the other hand, are caused by damaging germline variants, suggesting that T1D and IEIs have nothing in common. Some IEIs, resulting from mutations in genes regulating regulatory T-cell homeostasis, are associated with elevated incidence of T1D. The genetic spectrum of IEIs is gradually being unraveled; consequently, molecular pathways underlying human monogenic autoimmunity are being identified. There is an appreciable overlap between some of these pathways and the genetic variants that determine T1D susceptibility, suggesting that after all, IEI and T1D are 2 sides of the same coin. The study of monogenic IEIs with a variable incidence of T1D has the potential to provide crucial insights into the mechanisms leading to T1D. These insights contribute to the definition of T1D endotypes and explain disease heterogeneity. In this review, we discuss the interconnected pathogenic pathways of autoimmunity, β-cell function, and primary immunodeficiency. We also examine the role of environmental factors in disease penetrance as well as the circumstantial evidence of IEI drugs in preventing and curing T1D in individuals with IEIs, suggesting the repositioning of these drugs also for T1D therapy.

T-helper-2 cells and atopic disease: lessons learnt from inborn errors of immunity

Inborn errors of immunity (IEI) are caused by monogenic variants that affect the host response to bacterial, viral, and fungal pathogens. As such, individuals with IEI often present with severe, recurrent, and life-threatening infections. However, the spectrum of disease due to IEI is very broad and extends to include autoimmunity, malignancy, and atopic diseases such as eczema, atopic dermatitis, and food and environmental allergies. Here, I review IEI that affect cytokine signaling pathways that dysregulate CD4⁺ T-cell differentiation, resulting in increased T-helper-2 (Th2) cell development, function, and pathogenicity. These are elegant examples of how rare IEI can provide unique insights into more common pathologies such as allergic disease that are impacting the general population at increased frequency.

Cytokine-mediated STAT-dependent pathways underpinning human B-cell differentiation and function

B cells are fundamental to host defence against infectious diseases; indeed, the ability of humans to elicit robust antibody responses following exposure to foreign antigens underpins long-lived humoral immunity and serological memory, as well as the success of most currently administered vaccines. However, B cells also have a dark side - they can cause myriad diseases, including autoimmunity, atopy, allergy and malignancy. Thus, it is critical to understand the molecular requirements for generating effective, high-affinity, specific immune responses following natural infection or vaccination, as well as for constraining B-cell function to mitigate B-cell-mediated immune dyscrasias. In this review, we discuss recent developments that have been derived from the identification and detailed analysis of individuals with inborn errors of immunity that disrupt cytokine signalling, resulting in immune dysregulatory conditions. These studies have defined fundamental cytokine/cytokine receptor/signal transducer and activator of transcription (STAT) signalling pathways that are critical for the generation and maintenance of human memory B-cell and plasma cell subsets during host defence, as well as revealed mechanisms of disease pathogenesis causing immune deficiency, autoimmunity and atopy. More importantly, these studies have identified molecules that could be targeted to either enhance humoral immunity in the settings of infection or vaccination, or attenuate humoral immunity that contributes to antibody-mediated autoimmunity or allergy.

A zebrafish model of growth hormone insensitivity syndrome with immune dysregulation 1 (GHISID1)

Signal transducer and activator of transcription (STAT) proteins act downstream of cytokine receptors to facilitate changes in gene expression that impact a range of developmental and homeostatic processes. Patients harbouring loss-of-function (LOF) STAT5B mutations exhibit postnatal growth failure due to lack of responsiveness to growth hormone as well as immune perturbation, a disorder called growth hormone insensitivity syndrome with immune dysregulation 1 (GHISID1). This study aimed to generate a zebrafish model of this disease by targeting the stat5.1 gene using CRISPR/Cas9 and characterising the effects on growth and immunity. The zebrafish Stat5.1 mutants were smaller, but exhibited increased adiposity, with concomitant dysregulation of growth and lipid metabolism genes. The mutants also displayed impaired lymphopoiesis with reduced T cells throughout the lifespan, along with broader disruption of the lymphoid compartment in adulthood, including evidence of T cell activation. Collectively, these findings confirm that zebrafish Stat5.1 mutants mimic the clinical impacts of human STAT5B LOF mutations, establishing them as a model of GHISID1.

STAT5b: A master regulator of key biological pathways

The Signal Transducer and Activator of Transcription (STAT)-5 proteins are required in immune regulation and homeostasis and play a crucial role in the development and function of several hematopoietic cells. STAT5b activation is involved in the expression of genes that participate in cell development, proliferation, and survival. STAT5a and STAT5b are paralogs and only human mutations in STAT5B have been identified leading to immune dysregulation and hematopoietic malignant transformation. The inactivating STAT5B mutations cause impaired post-natal growth, recurrent infections and immune dysregulation, whereas gain of function somatic mutations cause dysregulated allergic inflammation. These mutations are rare, and they are associated with a wide spectrum of clinical manifestations which provide a disease model elucidating the biological mechanism of STAT5 by studying the consequences of perturbations in STAT5 activity. Further, the use of Jak inhibitors as therapy for a variety of autoimmune and malignant disorders has increased substantially heading relevant lessons for the consequences of Jak/STAT immunomodulation from the human model. This review summarizes the biology of the STAT5 proteins, human disease associate with molecular defects in STAT5b, and the connection between aberrant activation of STAT5b and the development of certain cancers.

Stafiba: A STAT5-Selective Small-Molecule Inhibitor

The transcription factors STAT5a and STAT5b are constitutively active in many human tumors. Combined inhibition of both STAT5 proteins is a valuable approach with promising applications in tumor biology. We recently reported resorcinol bisphosphate as a moderately active inhibitor of the protein-protein interaction domains, the SH2 domains, of both STAT5a and STAT5b. Here, we describe the development of resorcinol bisphosphate to Stafiba, a phosphatase-stable inhibitor of STAT5a and STAT5b with activity in the low micromolar concentration range. Our data provide insights into the structure-activity relationships of resorcinol bisphosphates and the corresponding bisphosphonates for use as inhibitors of both STAT5a and STAT5b.

STAT5B restrains human B-cell differentiation to maintain humoral immune homeostasis

BACKGROUND

Lymphocyte differentiation is regulated by coordinated actions of cytokines and signaling pathways. IL-21 activates STAT1, STAT3, and STAT5 and is fundamental for the differentiation of human B cells into memory cells and antibody-secreting cells. While STAT1 is largely nonessential and STAT3 is critical for this process, the role of STAT5 is unknown.

OBJECTIVES

This study sought to delineate unique roles of STAT5 in activation and differentiation of human naive and memory B cells.

METHODS

STAT activation was assessed by phospho-flow cytometry cell sorting. Differential gene expression was determined by RNA-sequencing and quantitative PCR. The requirement for STAT5B in B-cell and CD4+ T-cell differentiation was assessed using CRISPR-mediated STAT5B deletion from B-cell lines and investigating primary lymphocytes from individuals with germline STAT5B mutations.

RESULTS

IL-21 activated STAT5 and strongly induced SOCS3 in human naive, but not memory, B cells. Deletion of STAT5B in B-cell lines diminished IL-21-mediated SOCS3 induction. PBMCs from STAT5B-null individuals contained expanded populations of immunoglobulin class-switched B cells, CD21loTbet+ B cells, and follicular T helper cells. IL-21 induced greater differentiation of STAT5B-deficient B cells into plasmablasts in vitro than B cells from healthy donors, correlating with higher expression levels of transcription factors promoting plasma cell formation.

CONCLUSIONS

These findings reveal novel roles for STAT5B in regulating IL-21-induced human B-cell differentiation. This is achieved by inducing SOCS3 to attenuate IL-21 signaling, and BCL6 to repress class switching and plasma cell generation. Thus, STAT5B is critical for restraining IL-21-mediated B-cell differentiation. These findings provide insights into mechanisms underpinning B-cell responses during primary and subsequent antigen encounter and explain autoimmunity and dysfunctional humoral immunity in STAT5B deficiency.

Atopy as Immune Dysregulation: Offender Genes and Targets

Allergic diseases are a heterogeneous group of disorders resulting from exaggerated type 2 inflammation. Although typically viewed as polygenic multifactorial disorders caused by the interaction of several genes with the environment, we have come to appreciate that allergic diseases can also be caused by monogenic variants affecting the immune system and the skin epithelial barrier. Through a myriad of genetic association studies and high-throughput sequencing tools, many monogenic and polygenic culprits of allergic diseases have been described. Identifying the genetic causes of atopy has shaped our understanding of how these conditions occur and how they may be treated and even prevented. Precision diagnostic tools and therapies that address the specific molecular pathways implicated in allergic inflammation provide exciting opportunities to improve our care for patients across the field of allergy and immunology. Here, we highlight offender genes implicated in polygenic and monogenic allergic diseases and list targeted therapeutic approaches that address these disrupted pathways.

Inborn Errors of the Immune System Associated With Atopy

Atopic disorders, including atopic dermatitis, food and environmental allergies, and asthma, are increasingly prevalent diseases. Atopic disorders are often associated with eosinophilia, driven by T helper type 2 (Th2) immune responses, and triggered by disrupted barrier function leading to abnormal immune priming in a susceptible host. Immune deficiencies, in contrast, occur with a significantly lower incidence, but are associated with greater morbidity and mortality. A subset of atopic disorders with eosinophilia and elevated IgE are associated with monogenic inborn errors of immunity (IEI). In this review, we discuss current knowledge of IEI that are associated with atopy and the lessons these immunologic disorders provide regarding the fundamental mechanisms that regulate type 2 immunity in humans. We also discuss further mechanistic insights provided by animal models.

Novel Insights Into the Genetic Causes of Short Stature in Children

Short stature is a common reason for consulting a growth specialist during childhood. Normal height is a polygenic trait involving a complex interaction between hormonal, nutritional and psychosocial components. Genetic factors are becoming very important in the understanding of short stature. After exclusion of the most frequent causes of growth failure, clinicians need to evaluate whether a genetic cause might be taken into consideration. In fact, genetic causes of short stature are probably misdiagnosed during clinical practice and the underlying cause of short stature frequently remains unknown, thus classifying children as having idiopathic short stature (ISS). However, over the past decade, novel genetic techniques have led to the discovery of novel genes associated with linear growth and thus to the ability to define new possible aetiologies of short stature. In fact, thanks to the newer genetic advances, it is possible to properly re-classify about 25–40% of children previously diagnosed with ISS. The purpose of this article is to describe the main monogenic causes of short stature, which, thanks to advances in molecular genetics, are assuming an increasingly important role in the clinical approach to short children.

Role of JAK/STAT in Interstitial Lung Diseases; Molecular and Cellular Mechanisms

Interstitial lung diseases (ILDs) comprise different fibrotic lung disorders characterized by cellular proliferation, interstitial inflammation, and fibrosis. The JAK/STAT molecular pathway is activated under the interaction of a broad number of profibrotic/pro-inflammatory cytokines, such as IL-6, IL-11, and IL-13, among others, which are increased in different ILDs. Similarly, several growth factors over-expressed in ILDs, such as platelet-derived growth factor (PDGF), transforming growth factor β1 (TGF-β1), and fibroblast growth factor (FGF) activate JAK/STAT by canonical or non-canonical pathways, which indicates a predominant role of JAK/STAT in ILDs. Between the different JAK/STAT isoforms, it appears that JAK2/STAT3 are predominant, initiating cellular changes observed in ILDs. This review analyzes the expression and distribution of different JAK/STAT isoforms in ILDs lung tissue and different cell types related to ILDs, such as lung fibroblasts and alveolar epithelial type II cells and analyzes JAK/STAT activation. The effect of JAK/STAT phosphorylation on cellular fibrotic processes, such as proliferation, senescence, autophagy, endoplasmic reticulum stress, or epithelial/fibroblast to mesenchymal transition will be described. The small molecules directed to inhibit JAK/STAT activation were assayed in vitro and in in vivo models of pulmonary fibrosis, and different JAK inhibitors are currently approved for myeloproliferative disorders. Recent evidence indicates that JAK inhibitors or monoclonal antibodies directed to block IL-6 are used as compassionate use to attenuate the excessive inflammation and lung fibrosis related to SARS-CoV-2 virus. These altogether indicate that JAK/STAT pathway is an attractive target to be proven in future clinical trials of lung fibrotic disorders.

Dynamic Roles for IL-2-STAT5 Signaling in Effector and Regulatory CD4+ T Cell Populations

CD4⁺ Th cells are responsible for orchestrating diverse, pathogen-specific immune responses through their differentiation into a number of subsets, including T_H1, T_H2, T_H9, T follicular helper, T follicular regulatory, and regulatory T cells. The differentiation of each subset is guided by distinct regulatory requirements, including those derived from extracellular cytokine signals. IL-2 has emerged as a critical immunomodulatory cytokine that both positively and negatively affects the differentiation of individual Th cell subsets. IL-2 signals are propagated, in part, via activation of STAT5, which functions as a key regulator of CD4⁺ T cell gene programs. In this review, we discuss current understanding of the mechanisms that allow IL-2-STAT5 signaling to exert divergent effects across CD4⁺ T cell subsets and highlight specific roles for this pathway in the regulation of individual Th cell differentiation programs.

Human growth disorders associated with impaired GH action: Defects in STAT5B and JAK2

Growth hormone (GH) promotes postnatal human growth primarily by regulating insulin-like growth factor (IGF)-I production through activation of the GH receptor (GHR)-JAK2-signal transducer and activator of transcription (STAT)-5B signaling pathway. Inactivating STAT5B mutations, both autosomal recessive (AR) and dominant-negative (DN), are causal of a spectrum of GH insensitivity (GHI) syndrome, IGF-I deficiency and postnatal growth failure. Only AR STAT5B defects, however, confer additional characteristics of immune dysfunction which can manifest as chronic, potentially fatal, pulmonary disease. Somatic activating STAT5B and JAK2 mutations are associated with a plethora of immune abnormalities but appear not to impact human linear growth. In this review, molecular defects associated with STAT5B deficiency is highlighted and insights towards understanding human growth and immunity is emphasized.

Developmental Adaptive Immune Defects Associated with STAT5B Deficiency in Three Young Siblings

Patients with rare homozygous mutations in signal transducer and activator of transcription 5B (STAT5B) develop immunodeficiency resulting in chronic eczema, chronic infections, autoimmunity, and chronic lung disease. STAT5B-deficient patients are typically diagnosed in the teenage years, limiting our understanding of the development of associated phenotypic immune abnormalities. We report the first detailed chronological account of post-natal immune dysfunction associated with STAT5B deficiency in humans. Annual immunophenotyping of three siblings carrying a novel homozygous nonsense mutation in STAT5B was carried out over 4 years between the ages of 7 months to 8 years. All three siblings demonstrated consistent B cell hyperactivity including elevated IgE levels and autoantibody production, associated with diagnoses of atopy and autoimmunity. Total T cell levels in each sibling remained normal, with regulatory T cells decreasing in the oldest sibling. Interestingly, a skewing toward memory T cells was identified, with the greatest changes in CD8+ effector memory T cells. These results suggest an importance of STAT5B in B cell function and naïve versus memory T cell survival. Progressive dysregulation of FOXP3+ regulatory T cells and CD8+ memory T cell subsets reveal a crucial role of STAT5B in T cell homeostasis. The early diagnosis and focused immune evaluations of these three young STAT5B-deficient siblings support an important role of STAT5B in adaptive immune development and function.

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.

Cyba-deficient mice display an increase in hematopoietic stem cells and an overproduction of immunoglobulins

The regulation of protein function by reversible oxidation is increasingly recognized as a key mechanism for the control of cellular signaling, modulating crucial biological processes such as cell differentiation. In this scenario, NADPH oxidases must occupy a prominent position. Our results show that hematopoietic stem and progenitor cells express three p22^phox -dependent NADPH oxidase members (NOX1, NOX2 and NOX4). By deleting the p22^phox coding gene (Cyba), here we have analyzed the importance of this family of enzymes during in vivo hematopoiesis. Cyba^-/- mice show a myeloid bias, and an enrichment of hematopoietic stem cell populations. By means of hematopoietic transplant experiments we have also tried to dissect the specific role of the NADPH oxidases. While the absence of NOX1 or NOX2 provides a higher level of reconstitution, a lack of NOX4 rendered the opposite result, suggesting a functional specificity among the different NADPH oxidases. Cyba^-/- cells showed a hampered activation of AKT1 and a sharp decrease in STAT5 protein. This is in line with the diminished response to IL-7 shown by our results, which could explain the overproduction of immunoglobulins observed in Cyba^-/- mice.

A Review of Autoimmune Enteropathy and Its Associated Syndromes

Autoimmune enteropathy is an extremely rare condition characterized by an abnormal intestinal immune response which typically manifests within the first 6 months of life as severe, intractable diarrhea that does not respond to dietary modification. Affected individuals frequently present with other signs of autoimmunity. The diagnosis is made based on a characteristic combination of clinical symptoms, laboratory studies, and histological features on small bowel biopsy. Autoimmune enteropathy is associated with a number of other conditions and syndromes, most notably immunodysregulation polyendocrinopathy enteropathy X-linked (IPEX) syndrome and autoimmune polyglandular syndrome type 1 (APS-1). Diagnosis and treatment is challenging, and further research is needed to better understand the pathogenesis, disease progression, and long-term outcomes of these conditions.

[Genetically modified regulatory T cells: therapeutic concepts and regulatory aspects]

Adoptive T‑Zelltherapien sind neuartige Konzepte zur Behandlung verschiedener Krankheiten. CAR-T-Zellen sind dabei als Letztlinientherapie für fortgeschrittene B‑Zelllymphome und die B‑Zellleukämie etabliert und zugelassen. TCR-basierte T‑Zellen als Behandlungsoption verschiedener hämatologischer und solider Tumoren befinden sich in der klinischen Entwicklung. Genetisch modifizierte regulatorische T‑Zellen stehen dagegen noch am Anfang ihrer klinischen Entwicklung zur Induktion von Immuntoleranz in einer Vielzahl von Anwendungsgebieten.

In diesem Artikel wird zunächst ein Überblick über die Funktion der regulatorischen T‑Zellen für die Induktion der Immuntoleranz sowie über ihre Rolle im Pathomechanismus bestimmter Immunerkrankungen gegeben und der aktuelle Stand der klinischen Entwicklungen von therapeutischen Ansätzen auf Basis genetisch modifizierter regulatorischer T‑Zellen zusammengefasst. Im Weiteren werden die regulatorisch-wissenschaftlichen Anforderungen und Herausforderungen hinsichtlich Herstellung und Qualitätskontrolle sowie nichtklinischer und klinischer Testung genetisch modifizierter regulatorischer T‑Zellen als Arzneimittel für neuartige Therapien diskutiert.

MKL-1 is a coactivator for STAT5b, the regulator of Treg cell development and function

Background

Foxp3⁺CD4⁺ regulatory T cells (Treg) constitutes a key event in autoimmune diseases. STAT5b is the critical link between the IL-2/15 and FOXP3, the master regulator of Treg cells.

Methods

The CD3⁺T cell and Foxp3⁺CD4⁺ regulatory T cells were overexpressioned or knockdown MKL-1 and STAT5a and tested for Treg cell development and function. Direct interaction of MKL-1 and STAT5a were analyzed by coimmunoprecipitation assays, Luciferase assay, Immunofluoresence Staining and Yeast two-hybrid screening. The effect of MKL-1 and STAT5a on the Treg genes expression was analyzed by qPCR and western blotting and Flow cytometry.

Results

However, the molecular mechanisms mediating STAT5b-dependent Treg genes expression and Treg cell phenotype and function in autoimmune diseases are not well defined. Here, we report that the MKL-1 is a coactivator for the major Treg genes transcription factor STAT5b, which is required for human Treg cell phenotype and function. The N terminus of STAT5b, which contains a basic coiled-coil protein–protein interaction domain, binds the C-terminal activation domain of MKL-1 and enhances MKL-1 mediated transcriptional activation of Treg-specific, CArG containing promoters, including the Treg-specific genes Foxp3. Suppression of endogenous STAT5b expression by specific small interfering RNA attenuates MKL-1 transcriptional activation in cultured human cells. The STAT5b–MKL-1 interaction identifies a role of Treg-specific gene regulation and regulated mouse Treg cell development and function and suggests a possible mechanism for the protective effects of autoimmune disease Idiopathic Thrombocytopenic Purpura (ITP).

Conclusions

Our studies demonstrate for the first time that MKL-1 is a coactivator for STAT5b, the regulator of Treg cell development and function.

Mapping signal transducer and activator of transcription (STAT) activity in different stages of mycosis fungoides and Sezary syndrome

BACKGROUND

Deregulation of signal transducer and activator of transcription (STAT) signaling is known to participate in the pathogenesis of cutaneous T-cell lymphomas (CTCLs). However, published results regarding STAT expression in different stages of CTCLs are conflicting. The aim of the study was to define the pattern of STAT expression in skin and detect any differences between pruritic and nonpruritic patients but also different stages of disease.

METHODS

Thirty-nine skin biopsies from CTCL patients and 24 biopsies from healthy volunteers were taken. Immunohistochemical staining for STAT 3, 5a, 5b, and 6 was performed in formalin-fixed paraffin-embedded sections of mycosis fungoides (MF) and Sezary syndrome (SS) specimens.

RESULTS

We found increased expression of STAT proteins in CTCL: MF and SS skin in comparison to the control group. STAT5 but also STAT6 and to a lesser extent STAT3 seems to be constitutively activated in MF and SS. Moreover, also downregulation of STAT5b protein in advanced-stage CTCL appears to contribute to its pathogenesis. There were no significant associations between expression of STATs and pruritus severity.

CONCLUSIONS

Our results confirm the possible pathogenetic role of STATs in CTCL. STATs seem to be a promising target for new effective therapeutic agents in CTCL.

Primary Atopic Disorders

Primary atopic disorders describes a series of monogenic diseases that have allergy- or atopic effector–related symptoms as a substantial feature. The underlying pathogenic genetic lesions help illustrate fundamental pathways in atopy, opening up diagnostic and therapeutic options for further study in those patients, but ultimately for common allergic diseases as well. Key pathways affected in these disorders include T cell receptor and B cell receptor signaling, cytokine signaling, skin barrier function, and mast cell function, as well as pathways that have not yet been elucidated. While comorbidities such as classically syndromic presentation or immune deficiency are often present, in some cases allergy alone is the presenting symptom, suggesting that commonly encountered allergic diseases exist on a spectrum of monogenic and complex genetic etiologies that are impacted by environmental risk factors.

The Role of MiR-5094 as a Proliferation Suppressor during Cellular Radiation Response via Downregulating STAT5b

MicroRNAs (miRNAs) play important roles in the regulation of cellular stress responses. We previously uncovered 10 novel human miRNAs which are induced by X-ray irradiation in HeLa cells using Solexa deep sequencing. The most highly expressed new miRNA, miR-5094, was predicted to target STAT5b. This study wonders whether miR-5094 participates in cellular radiation response via STAT5b. Firstly, direct interaction between miRNA-5094 and the STAT5b 3'-UTR was confirmed by luciferase reporter assay. Then, the radiation responsive expression of miR-5094 and STAT5b were measured in HeLa and Jurkat cells, and the expressions of down-stream genes of STAT5b after ionizing radiation (IR) were detected in HeLa cells. At last, the effects of miR-5094 on survival fraction, cell proliferation, cell cycle arrest and apoptosis induced by IR were investigated in HeLa cells, Jurkat cells and human peripheral blood T cells. It was found that up-regulation of miR-5094 by radiation induction or miRNA mimic transfection suppressed expression of STAT5b, and consequently decreased the transcription of down-stream Igf-1 and Bcl-2. Additionally, over expression of miR-5094 resulted in proliferation suppression and knockdown of miR-5094 by miRNA inhibitor after irradiation partially reversed the proliferation suppression induced by miR-5094 in HeLa cells, Jurkat cells and CD4⁺ T cells. Collectively, our findings demonstrate that up-regulation of miR-5094 down-regulated the expression of STAT5b, thereby suppressing cell proliferation after X-ray irradiation.

Human Inborn Errors of Immunity: 2019 Update on the Classification from the International Union of Immunological Societies Expert Committee

We report the updated classification of Inborn Errors of Immunity/Primary Immunodeficiencies, compiled by the International Union of Immunological Societies Expert Committee. This report documents the key clinical and laboratory features of 430 inborn errors of immunity, including 64 gene defects that have either been discovered in the past 2 years since the previous update (published January 2018) or were characterized earlier but have since been confirmed or expanded upon in subsequent studies. The application of next-generation sequencing continues to expedite the rapid identification of novel gene defects, rare or common; broaden the immunological and clinical phenotypes of conditions arising from known gene defects and even known variants; and implement gene-specific therapies. These advances are contributing to greater understanding of the molecular, cellular, and immunological mechanisms of disease, thereby enhancing immunological knowledge while improving the management of patients and their families. This report serves as a valuable resource for the molecular diagnosis of individuals with heritable immunological disorders and also for the scientific dissection of cellular and molecular mechanisms underlying inborn errors of immunity and related human diseases.

Treg cells in health and autoimmune diseases: New insights from single cell analysis

Autoimmune diseases, such as Systemic Lupus Erythematosus (SLE) or Rheumatoid Arthritis (RA) are characterized by the breakdown of immunological tolerance. Defects of regulatory T cells have been described among the various mechanisms, that are important for the development of autoimmune diseases, due to their critical role as regulators of peripheral immune tolerance and homeostasis. Initially T suppressor cells have been described as one population of peripheral T cells. Based on new technological advances a new understanding of the heterogeneity of different Treg cell populations in the lymphoid and non-lymphoid tissue has evolved over the last years. While initially Foxp3 has been defined as the main master regulator of Treg cells, we have learned that Treg cells from various tissue can be identified by a specific transcriptomic and epigenetic signature. Epigenetic mechanisms allow Treg cell stability, but we have also learned that certain Treg subsets are plastic and can under specific circumstances even enhance autoimmunity and inflammatory processes. Quantitative and functional defects of Treg cells have been observed in a variety of autoimmune diseases. Due to our understanding of the nature of this cell population, Treg cells have been a target of new Treg based therapies, such as low-dose IL-2. In addition, ongoing clinical trials aim to test safety and efficacy of transferred, in vitro expanded Treg cells in patients with autoimmune diseases and transplant patients.

The clinical and mechanistic intersection of primary atopic disorders and inborn errors of growth and metabolism

Dynamic changes in metabolism have long been understood as critical for both the initiation and maintenance of innate and adaptive immune responses. A number of recent advances have clarified details of how metabolic pathways can specifically affect cellular function in immune cells. Critical to this understanding is ongoing study of the congenital disorders of glycosylation and other genetic disorders of metabolism that lead to altered immune function in humans. While there are a number of immune phenotypes associated with metabolic derangements caused by single gene disorders, several genetic mutations have begun to link discrete alterations in metabolism and growth specifically with allergic disease. This subset of primary atopic disorders is of particular interest as they illuminate how hypomorphic mutations which allow for some residual function of mutated protein products permit the "abnormal" allergic response. This review will highlight how mutations altering sugar metabolism and mTOR activation place similar constraints on T lymphocyte metabolism to engender atopy, and how alterations in JAK/STAT signaling can impair growth and cellular metabolism while concomitantly promoting allergic diseases and reactions in humans.

Human diseases caused by impaired signal transducer and activator of transcription and Janus kinase signaling

PURPOSE OF REVIEW

The Janus kinase (JAK) and signal transducer of activation (STAT) pathway plays a key role in the immune system. It is employed by diverse cytokines, interferons, growth factors and related molecules. Mutations in JAK/STAT pathway have been implicated in human disease. Here we review JAK/STAT biology and diseases associated with mutations in this pathway.

RECENT FINDINGS

Over the past 10 years, many mutations in JAK/STAT pathway has been discovered. These disorders have provided insights to human immunology.

SUMMARY

In this review, we summarize the biology of each STAT and JAK as well as discuss the human disease that results from somatic or germline mutations to include typical presentation, immunological parameters and treatment.

Human signal transducer and activator of transcription 5b (STAT5b) mutation causes dysregulated human natural killer cell maturation and impaired lytic function

BACKGROUND

Patients with signal transducer and activator of transcription 5b (STAT5b) deficiency have impairment in T-cell homeostasis and natural killer (NK) cells which leads to autoimmunity, recurrent infections, and combined immune deficiency.

OBJECTIVE

In this study we characterized the NK cell defect in STAT5b-deficient human NK cells, as well as Stat5b^-/- mice.

METHODS

We used multiparametric flow cytometry, functional NK cell assays, microscopy, and a Stat5b^-/- mouse model to elucidate the effect of impaired and/or absent STAT5b on NK cell development and function.

RESULTS

This alteration generated a nonfunctional CD56^bright NK cell subset characterized by low cytokine production. The CD56^dim NK cell subset had decreased expression of perforin and CD16 and a greater frequency of cells expressing markers of immature NK cells. We observed low NK cell numbers and impaired NK cell maturation, suggesting that STAT5b is involved in terminal NK cell maturation in Stat5b^-/- mice. Furthermore, human STAT5b-deficient NK cells had low cytolytic capacity, and fixed-cell microscopy showed poor convergence of lytic granules. This was accompanied by decreased expression of costimulatory and activating receptors. Interestingly, granule convergence and cytolytic function were restored after IL-2 stimulation.

CONCLUSIONS

Our results show that in addition to the impaired terminal maturation of NK cells, human STAT5b mutation leads to impairments in early activation events in NK cell lytic synapse formation. Our data provide further insight into NK cell defects caused by STAT5b deficiency.

Expression profiling of genes in rheumatoid fibroblast-like synoviocytes regulated by tumor necrosis factor-like ligand 1A using cDNA microarray analysis

Rheumatoid arthritis (RA) is an autoimmune disease that causes chronic inflammation in synovial tissues. Hyperplasia of synovial tissue leads to the formation of pannus, which invades joint cartilage and bone resulting in joint destruction. Tumor necrosis factor-like ligand 1A (TL1A), a member of the tumor necrosis factor superfamily (TNFSF15), contributes to the pathogenesis of autoimmune diseases, including RA. In the present study, a cDNA microarray was used to search for genes whose expression in rheumatoid fibroblast-like synoviocytes (RA-FLS) were regulated by TL1A. Four individual lines of primary cultured RA-FLS were incubated either with recombinant human TL1A protein or phosphate-buffered saline, as an unstimulated control, for 12 h. Gene expression was then detected through the microarray assay. The results revealed the expression profiles of genes in RA-FLS regulated by TL1A. The present study also demonstrated the functions of those genes whose expression in RA-FLS was regulated by TL1A. Among the genes in this profile, the present study focused on the following genes: Spectrin repeat-containing nuclear envelope 1, Fc receptor-like 2, PYD (pyrin domain)-containing 1, cell division cycle 45 homolog, signal transducer and activator of transcription 5B, and interferon regulatory factor 4. These genes may affect the pathogenesis of RA, including proliferation, regulation of B cells and T cells, inflammation, and cytokine processing. The present study revealed for the first time, to the best of our knowledge, the expression profile of genes in RA-FLS regulated by TL1A. The data indicate that TL1A may regulate the gene expression of various key molecules in RA-FLS, thus affecting the pathogenesis of RA. Further investigations of the genes detected in the current profiles may provide a deeper understanding of the pathogenesis and a novel target for the treatment of RA.

Fine-Tuning Cytokine Signals

Cytokines are secreted or otherwise released polypeptide factors that exert autocrine and/or paracrine actions, with most cytokines acting in the immune and/or hematopoietic system. They are typically pleiotropic, controlling development, cell growth, survival, and/or differentiation. Correspondingly, cytokines are clinically important, and augmenting or attenuating cytokine signals can have deleterious or therapeutic effects. Besides physiological fine-tuning of cytokine signals, altering the nature or potency of the signal can be important in pathophysiological responses and can also provide novel therapeutic approaches. Here, we give an overview of cytokines, their signaling and actions, and the physiological mechanisms and pharmacologic strategies to fine-tune their actions. In particular, the differential utilization of STAT proteins by a single cytokine or by different cytokines and STAT dimerization versus tetramerization are physiological mechanisms of fine-tuning, whereas anticytokine and anticytokine receptor antibodies and cytokines with altered activities, including cytokine superagonists, partial agonists, and antagonists, represent new ways of fine-tuning cytokine signals.

The STAT5b Linker Domain Mediates the Selectivity of Catechol Bisphosphates for STAT5b over STAT5a

STAT family proteins are important mediators of cell signaling and represent therapeutic targets for the treatment of human diseases. Most STAT inhibitors target the protein-protein interaction domain, the SH2 domain, but specificity for a single STAT protein is often limited. Recently, we developed catechol bisphosphates as the first inhibitors of STAT5b demonstrated to exhibit a high degree of selectivity over the close homologue STAT5a. Here, we show that the amino acid in position 566 of the linker domain, not the SH2 domain, is the main determinant of specificity. Arg566 in wild-type STAT5b favors tight binding of catechol bisphosphates, while Trp566 in wild-type STAT5a does not. Amino acid 566 also determines the affinity for a tyrosine-phosphorylated peptide derived from the EPO receptor for STAT5a and STAT5b, demonstrating the functional relevance of the STAT5 linker domain for the adjacent SH2 domain. These results provide the first demonstration that a residue in the linker domain can determine the affinity of nonpeptidic small-molecule inhibitors for the SH2 domain of STAT proteins. We propose targeting the interface between the SH2 domain and linker domain as a novel design approach for the development of potent and selective STAT inhibitors. In addition, our data suggest that the linker domain could contribute to the enigmatically divergent biological functions of the two STAT5 proteins.

Treg cells in autoimmunity: from identification to Treg-based therapies

Regulatory (Treg) cells are key regulators of inflammation and important for immune tolerance and homeostasis. A major progress has been made in the identification and classification of Treg cells. Due to technological advances, we have gained deep insights in the epigenetic regulation of Treg cells. The use of fate reporter mice allowed addressing the functional consequences of loss of Foxp3 expression. Depending on the environment Treg cells gain effector functions upon loss of Foxp3 expression. However, the traditional view that Treg cells become necessarily pathogenic by gaining effector functions was challenged by recent findings and supports the notion of Treg cell lineage plasticity. Treg cell stability is also a major issue for Treg cell therapies. Clinical trials are designed to use polyclonal Treg cells as therapeutic tools. Here, we summarize the role of Treg cells in selected autoimmune diseases and recent advances in the field of Treg targeted therapies.

Nonclassical GH Insensitivity: Characterization of Mild Abnormalities of GH Action

GH insensitivity (GHI) presents in childhood with growth failure and in its severe form is associated with extreme short stature and dysmorphic and metabolic abnormalities. In recent years, the clinical, biochemical, and genetic characteristics of GHI and other overlapping short stature syndromes have rapidly expanded. This can be attributed to advancing genetic techniques and a greater awareness of this group of disorders. We review this important spectrum of defects, which present with phenotypes at the milder end of the GHI continuum. We discuss their clinical, biochemical, and genetic characteristics. The objective of this review is to clarify the definition, identification, and investigation of this clinically relevant group of growth defects. We also review the therapeutic challenges of mild GHI.

Repercussions of inborn errors of immunity on growth

OBJECTIVES

This study aimed to review the literature on the repercussions of the different inborn errors of immunity on growth, drawing attention to the diagnosis of this group of diseases in patients with growth disorders, as well as to enable the identification of the different causes of growth disorders in patients with inborn errors of immunity, which can help in their treatment.

DATA SOURCES

Non-systematic review of the literature, searching articles since 2000 in PubMed with the terms "growth", "growth disorders", "failure to thrive", or "short stature" AND "immunologic deficiency syndromes", "immune deficiency disease", or "immune deficiency" NOT HIV. The Online Mendelian Inheritance in Man (OMIN) database was searched for immunodeficiencies and short stature or failure to thrive.

DATA SUMMARY

Inborn errors of immunity can affect growth in different ways, and some of them can change growth through multiple simultaneous mechanisms: genetic syndromes; disorders of the osteoarticular system; disorders of the endocrine system; reduction in caloric intake; catabolic processes; loss of nutrients; and inflammatory and/or infectious conditions.

CONCLUSIONS

The type of inborn errors of immunity allows anticipating what type of growth disorder can be expected. The type of growth disorder can help in the diagnosis of clinical conditions related to inborn errors of immunity. In many inborn errors of immunity, the causes of poor growth are mixed, involving more than one factor. In many cases, impaired growth can be adjusted with proper inborn errors of immunity treatment or proper approach to the mechanism of growth impairment.

JAK/STAT proteins and their biological impact on NK cell development and function

NK cells are important early effectors in the innate immune response to a variety of viral infections and for elimination of tumor cells. The JAK/STAT signaling cascade is critical for NK cell development, maturation, survival, and proliferation, therefore, it is important to understand the role of this pathway in NK cell biology. Many cytokines can activate multiple JAK/STAT protein family members, creating a severe phenotype when mutations impair their function or expression. Here we discuss the impact of defective JAK/STAT signaling pathways on NK cell development, activation and cytotoxicity.

The Impact of Immunodeficiency on NK Cell Maturation and Function

PURPOSE OF REVIEW

Natural killer cells are innate lymphoid cells (ILCs) that play critical roles in human host defense and are especially useful in combating viral pathogens and malignancy.

RECENT FINDINGS

The NK cell deficiency (NKD) is particularly underscored in patients with a congenital immunodeficiency in which NK cell development or function is affected. The classical NK cell deficiency (cNKD) is a result of absent or a profound decrease in the number of circulating NK cells. In contrast, functional NKD (fNKD) is characterized by abnormal NK cell function but with normal number of NK cells. The combined immune deficiencies with significant impact on NK cells are not considered classical or functional NK cell deficiencies. In these disorders, the impairment of NK cells represents an important aspect of the overall immunodeficiency. In turn, this leads to improved insights on the NK cell development and function. Here, we detail the NK cell biology based upon recent natural killer cell defects described in combined immune deficiencies.

IRF and STAT Transcription Factors - From Basic Biology to Roles in Infection, Protective Immunity, and Primary Immunodeficiencies

The induction and action of type I interferon (IFN) is of fundamental importance in human immune defenses toward microbial pathogens, particularly viruses. Basic discoveries within the molecular and cellular signaling pathways regulating type I IFN induction and downstream actions have shown the essential role of the IFN regulatory factor (IRF) and the signal transducer and activator of transcription (STAT) families, respectively. However, the exact biological and immunological functions of these factors have been most clearly revealed through the study of inborn errors of immunity and the resultant infectious phenotypes in humans. The spectrum of human inborn errors of immunity caused by mutations in IRFs and STATs has proven very diverse. These diseases encompass herpes simplex encephalitis (HSE) and severe influenza in IRF3- and IRF7/IRF9 deficiency, respectively. They also include Mendelian susceptibility to mycobacterial infection (MSMD) in STAT1 deficiency, through disseminated measles infection associated with STAT2 deficiency, and finally staphylococcal abscesses and chronic mucocutaneous candidiasis (CMC) classically described with Hyper-IgE syndrome (HIES) in the case of STAT3 deficiency. More recently, increasing focus has been on aspects of autoimmunity and autoinflammation playing an important part in many primary immunodeficiency diseases (PID)s, as exemplified by STAT1 gain-of-function causing CMC and autoimmune thyroiditis, as well as a recently described autoinflammatory syndrome with hypogammaglobulinemia and lymphoproliferation as a result of STAT3 gain-of-function. Here I review the infectious, inflammatory, and autoimmune disorders arising from mutations in IRF and STAT transcription factors in humans, highlightning the underlying molecular mechanisms and immunopathogenesis as well as the clinical/therapeutic perspectives of these new insights.

Complete Resolution of Lymphoid Interstitial Pneumonia in a Patient With Juvenile Myelomonocytic Leukemia Treated With Allogeneic Bone Marrow Transplant: Killing 2 Birds With 1 Stone

Lymphoid interstitial pneumonia (LIP) is a rare disease characterized by benign reactive polyclonal proliferation of bronchus-associated lymphoid tissue after exposure to inhaled or circulating antigen(s), leading to a disease symptomatology similar to idiopathic interstitial pneumonia. Its association with diseases that are caused due to immune dysregulation (autoimmune diseases, congenital/acquired immunodeficiency, and allogeneic bone marrow transplant) and response to immunomodulatory/suppressive medications suggests an immunologic pathophysiology. Although LIP has been reported in association with lymphoproliferative diseases like Castleman disease, it has never been described in patients with leukemia. We report the first case of LIP in a patient with juvenile myelomonocytic leukemia (JMML) who was found to have a novel germline mutation of unknown significance in additional sex combs-like-1 (ASXL1) gene and a pathogenic somatic mutation of protein tyrosine phosphatase, nonreceptor type 11 (PTPN11) gene at diagnosis. The patient underwent a matched unrelated bone marrow transplant for JMML with complete resolution of JMML and LIP with no recurrence to date. We also emphasize the importance of considering LIP in differential diagnosis of pulmonary lesions seen in conjunction with hematologic malignancies and distinguishing it from malignant infiltration of the lung.

Dominant-negative STAT5B mutations cause growth hormone insensitivity with short stature and mild immune dysregulation

Growth hormone (GH) insensitivity syndrome (GHIS) is a rare clinical condition in which production of insulin-like growth factor 1 is blunted and, consequently, postnatal growth impaired. Autosomal-recessive mutations in signal transducer and activator of transcription (STAT5B), the key signal transducer for GH, cause severe GHIS with additional characteristics of immune and, often fatal, pulmonary complications. Here we report dominant-negative, inactivating STAT5B germline mutations in patients with growth failure, eczema, and elevated IgE but without severe immune and pulmonary problems. These STAT5B missense mutants are robustly tyrosine phosphorylated upon stimulation, but are unable to nuclear localize, or fail to bind canonical STAT5B DNA response elements. Importantly, each variant retains the ability to dimerize with wild-type STAT5B, disrupting the normal transcriptional functions of wild-type STAT5B. We conclude that these STAT5B variants exert dominant-negative effects through distinct pathomechanisms, manifesting in milder clinical GHIS with general sparing of the immune system.

Severe growth hormone insensitivity syndrome (GHIS) with immunodeficiency is caused by autosomal recessive mutations in STAT5B. Here the authors report heterozygous STAT5B mutations with dominant-negative effects, causing mild GHIS without immune defects.

Short Stature in a Boy with Multiple Early-Onset Autoimmune Conditions due to a STAT3 Activating Mutation: Could Intracellular Growth Hormone Signalling Be Compromised?

BACKGROUND

Germline STAT3 gain-of-function (GOF) mutations cause multiple endocrine and haematologic autoimmune disorders, lymphoproliferation, and growth impairment. As the JAK-STAT pathway is known to transduce the growth hormone (GH) signalling, and STAT3 interacts with STAT5 in growth regulation, we hypothesised that short stature in STAT3 GOF mutations results mostly from GH insensitivity via involving activation of STAT5.

CASE REPORT

A boy with a novel STAT3 c.2144C>T (p.Pro715Leu) mutation presented with short stature (-2.60 SD at 5.5 years). He developed diabetes mellitus at 11 months, generalised lympho-proliferation, autoimmune thyroid disease, and immune bicytopenia in the subsequent years. At 5.5 years, his insulin-like growth factor-1 (IGF-I) was 37 µg/L (-2.22 SD) but stimulated GH was 27.7 µg/L. Both a standard IGF-I generation test (GH 0.033 mg/kg/day sc; 4 days) and a high-dose prolonged IGF-I generation test (GH 0.067 mg/kg/day sc; 14 days) failed to significantly increase IGF-I levels (37-46 and 72-87 µg/L, respectively). The boy underwent haematopoietic stem cell transplantation at 6 years due to severe neutropenia and massive lymphoproliferation, but unfortunately deceased 42 days after transplantation from reactivated generalised adenoviral infection.

CONCLUSIONS

Our findings confirm the effect of STAT3 GOF mutation on the downstream activation of STAT5 resulting in partial GH insensitivity. 
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Primary atopic disorders

Important insights from monogenic disorders into the immunopathogenesis of allergic diseases and reactions are discussed.

Monogenic disorders have provided fundamental insights into human immunity and the pathogenesis of allergic diseases. The pathways identified as critical in the development of atopy range from focal defects in immune cells and epithelial barrier function to global changes in metabolism. A major goal of studying heritable single-gene disorders that lead to severe clinical allergic diseases is to identify fundamental pathways leading to hypersensitivity that can be targeted to provide novel therapeutic strategies for patients with allergic diseases, syndromic and nonsyndromic alike. Here, we review known single-gene disorders leading to severe allergic phenotypes in humans, discuss how the revealed pathways fit within our current understanding of the atopic diathesis, and propose how some pathways might be targeted for therapeutic benefit.