JAKing up immunity.

Janus kinase (JAK) inhibitors improve antitumor responses.

Microbial ligand-independent regulation of lymphopoiesis by NOD1.

Aberrant differentiation of progenitor cells in the hematopoietic system is known to severely impact host immune responsiveness. Here we demonstrate that NOD1, a cytosolic innate sensor of bacterial peptidoglycan, also functions in murine hematopoietic cells as a major regulator of both the generation and differentiation of lymphoid progenitors as well as peripheral T lymphocyte homeostasis. We further show that NOD1 mediates these functions by facilitating STAT5 signaling downstream of hematopoietic cytokines. In steady-state, loss of NOD1 resulted in a modest but significant decrease in numbers of mature T, B and natural killer cells. During systemic protozoan infection this defect was markedly enhanced, leading to host mortality. Lack of functional NOD1 also impaired T cell-dependent anti-tumor immunity while preventing colitis. These findings reveal that, in addition to its classical role as a bacterial ligand receptor, NOD1 plays an important function in regulating adaptive immunity through interaction with a major host cytokine signaling pathway.

Complete heart block is a significant predictor of mortality in immune checkpoint inhibitor myocarditis.

BACKGROUND: Immune checkpoint inhibitor (ICI) myocarditis is associated with significant mortality risk. Electrocardiogram (ECG) changes in ICI myocarditis have strong prognostic value. However the impact of complete heart block (CHB) is not well defined. This study sought to evaluate the impact of CHB on mortality in ICI myocarditis, and to identify clinical predictors of mortality and CHB incidence. METHODS: We conducted a retrospective cohort study of patients with ICI myocarditis at three Mayo Clinic sites from 1st January 2010 to 31st September 2022 to evaluate mortality rates at 180 days. Clinical, laboratory, ECG, echocardiographic, and cardiac magnetic resonance imaging (CMR) characteristics were assessed. Cox and logistic regression were performed for associations with mortality and CHB respectively. RESULTS: Of 34 identified cases of ICI myocarditis, 7 (20.6%) had CHB. CHB was associated with higher mortality (HR 7.41, p = 0.03, attributable fraction 86.5%). Among those with CHB, troponin T (TnT) < 1000 ng/dL, low white blood cell count and high ventricular rate at admission were protective. There was trend towards increased survival among patients who underwent permanent pacemaker insertion (p = 0.051), although most experienced device lead complications. Factors associated with development of CHB included prolonged PR and QRS intervals and low Sokolow Lyon Index. Where these were normal and TnT was < 1000 ng/dL, no deaths occurred. Impaired myocardial longitudinal strain was sensitive for ICI myocarditis but was not prognostically significant. CONCLUSION: There is a strong temporal association between CHB and early mortality in people with ICI myocarditis. Focusing on arrhythmogenic complications can be helpful in predicting outcomes for this group of critically ill individuals.

Infectious Aortitis Due to Salmonella Species Masquerading as Lung Malignancy.

Infectious aortitis is a rare but devastating vascular infection with mortality exceeding 40%. Early diagnosis is crucial but often hampered by radiographic mimickers. We report a patient who was thought to have lung cancer but ultimately found to have an infected aortic aneurysm and bacteremia owing to Salmonella species. Owing to surgical contraindications, he was treated palliatively with an initial regimen of intravenous ampicillin/sulbactam followed by lifelong oral antibiotic suppression. He ultimately rejected his diagnosis, discontinued medications, and was lost to follow-up. (Level of Difficulty: Intermediate.).

TGF-ß uncouples glycolysis and inflammation in macrophages and controls survival during sepsis.

Changes in metabolism of macrophages are required to sustain macrophage activation in response to different stimuli. We showed that the cytokine TGF-ß (transforming growth factor-ß) regulates glycolysis in macrophages independently of inflammatory cytokine production and affects survival in mouse models of sepsis. During macrophage activation, TGF-ß increased the expression and activity of the glycolytic enzyme PFKL (phosphofructokinase-1 liver type) and promoted glycolysis but suppressed the production of proinflammatory cytokines. The increase in glycolysis was mediated by an mTOR-c-MYC-dependent pathway, whereas the inhibition of cytokine production was due to activation of the transcriptional coactivator SMAD3 and suppression of the activity of the proinflammatory transcription factors AP-1, NF-κB, and STAT1. In mice with LPS-induced endotoxemia and experimentally induced sepsis, the TGF-ß-induced enhancement in macrophage glycolysis led to decreased survival, which was associated with increased blood coagulation. Analysis of septic patient cohorts revealed that the expression of PFKL, TGFBRI (which encodes a TGF-ß receptor), and F13A1 (which encodes a coagulation factor) in myeloid cells positively correlated with COVID-19 disease. Thus, these results suggest that TGF-ß is a critical regulator of macrophage metabolism and could be a therapeutic target in patients with sepsis.

Protein kinases: drug targets for immunological disorders.

Protein kinases play a major role in cellular activation processes, including signal transduction by diverse immunoreceptors. Given their roles in cell growth and death and in the production of inflammatory mediators, targeting kinases has proven to be an effective treatment strategy, initially as anticancer therapies, but shortly thereafter in immune-mediated diseases. Herein, we provide an overview of the status of small molecule inhibitors specifically generated to target protein kinases relevant to immune cell function, with an emphasis on those approved for the treatment of immune-mediated diseases. The development of inhibitors of Janus kinases that target cytokine receptor signalling has been a particularly active area, with Janus kinase inhibitors being approved for the treatment of multiple autoimmune and allergic diseases as well as COVID-19. In addition, TEC family kinase inhibitors (including Bruton's tyrosine kinase inhibitors) targeting antigen receptor signalling have been approved for haematological malignancies and graft versus host disease. This experience provides multiple important lessons regarding the importance (or not) of selectivity and the limits to which genetic information informs efficacy and safety. Many new agents are being generated, along with new approaches for targeting kinases.

Variant STAT4 and Response to Ruxolitinib in an Autoinflammatory Syndrome.

BACKGROUND: Disabling pansclerotic morphea (DPM) is a rare systemic inflammatory disorder, characterized by poor wound healing, fibrosis, cytopenias, hypogammaglobulinemia, and squamous-cell carcinoma. The cause is unknown, and mortality is high. METHODS: We evaluated four patients from three unrelated families with an autosomal dominant pattern of inheritance of DPM. Genomic sequencing independently identified three heterozygous variants in a specific region of the gene that encodes signal transducer and activator of transcription 4 (STAT4). Primary skin fibroblast and cell-line assays were used to define the functional nature of the genetic defect. We also assayed gene expression using single-cell RNA sequencing of peripheral-blood mononuclear cells to identify inflammatory pathways that may be affected in DPM and that may respond to therapy. RESULTS: Genome sequencing revealed three novel heterozygous missense gain-of-function variants in STAT4. In vitro, primary skin fibroblasts showed enhanced interleukin-6 secretion, with impaired wound healing, contraction of the collagen matrix, and matrix secretion. Inhibition of Janus kinase (JAK)-STAT signaling with ruxolitinib led to improvement in the hyperinflammatory fibroblast phenotype in vitro and resolution of inflammatory markers and clinical symptoms in treated patients, without adverse effects. Single-cell RNA sequencing revealed expression patterns consistent with an immunodysregulatory phenotype that were appropriately modified through JAK inhibition. CONCLUSIONS: Gain-of-function variants in STAT4 caused DPM in the families that we studied. The JAK inhibitor ruxolitinib attenuated the dermatologic and inflammatory phenotype in vitro and in the affected family members. (Funded by the American Academy of Allergy, Asthma, and Immunology Foundation and others.).

From thymus to tissues and tumors: A review of T-cell biology.

T cells are critical orchestrators of the adaptive immune response that optimally eliminate a specific pathogen. Aberrant T-cell development and function are implicated in a broad range of human disease including immunodeficiencies, autoimmune diseases, and allergic diseases. Accordingly, therapies targeting T cells and their effector cytokines have markedly improved the care of patients with immune dysregulatory diseases. Newer discoveries concerning T-cell-mediated antitumor immunity and T-cell exhaustion have further prompted development of highly effective and novel treatment modalities for malignancies, including checkpoint inhibitors and antigen-reactive T cells. Recent discoveries are also uncovering the depth and variability of T-cell phenotypes: while T cells have long been described using a subset-based classification system, next-generation sequencing technologies suggest an astounding degree of complexity and heterogeneity at the single-cell level.

The JAK-STAT pathway at 30: Much learned, much more to do.

The discovery of the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway arose from investigations of how cells respond to interferons (IFNs), revealing a paradigm in cell signaling conserved from slime molds to mammals. These discoveries revealed mechanisms underlying rapid gene expression mediated by a wide variety of extracellular polypeptides including cytokines, interleukins, and related factors. This knowledge has provided numerous insights into human disease, from immune deficiencies to cancer, and was rapidly translated to new drugs for autoimmune, allergic, and infectious diseases, including COVID-19. Despite these advances, major challenges and opportunities remain.

Foreign accent syndrome post tonsillectomy: A case report.

Foreign Accent Syndrome (FAS) is a rare clinical entity in which affected patients experience a new pattern of speech resembling an unusual accent. Reported cases are scarce in published literature and are usually the result of a neurological insult. FAS as a complication from a general anesthetic or surgery has not been reported to date. We present the case of a healthy 27-year-old Australian woman who developed FAS following a tonsillectomy. Post operatively, speech patterns resembled an Irish accent. We discuss the potential mechanisms of the unusual complication as well as review the available literature surrounding FAS.

Cashew-Induced Oxalate Nephropathy: A Rare Cause of Acute Renal Failure.

We present a rare case of cashew-induced oxalate nephropathy in a 69 year old veteran male with history of type 2 diabetes mellitus, nephrolithiasis, and undiagnosed chronic kidney disease (CKD). Oxalate nephropathy is a rare cause of acute renal failure with poor prognosis. The various causes of oxalate nephropathy are categorized as primary or secondary hyperoxaluria. Primary hyperoxaluria is caused by genetic mutation in genes involved in the metabolism of glyoxylate. Secondary hyperoxaluria is caused by mal-absorptive state, excessive intake of oxalate-rich diet, inflammatory diseases, and medications such as orlistat and antibiotics. Diet-induced oxalate nephropathy is often identified after unexplained acute kidney injury in patients with underlying CKD. Definitive diagnosis requires renal biopsy as laboratory tests are non-specific. A simple dietary history in CKD patients during routine primary care visit may lead to early diagnosis and lead to prevention of acute renal failure and progression of renal disease.

PI3Kδ coordinates transcriptional, chromatin, and metabolic changes to promote effector CD8+ T cells at the expense of central memory.

Patients with activated phosphatidylinositol 3-kinase delta (PI3Kδ) syndrome (APDS) present with sinopulmonary infections, lymphadenopathy, and cytomegalvirus (CMV) and/or Epstein-Barr virus (EBV) viremia, yet why patients fail to clear certain chronic viral infections remains incompletely understood. Using patient samples and a mouse model (Pik3cdE1020K/+ mice), we demonstrate that, upon activation, Pik3cdE1020K/+ CD8+ T cells exhibit exaggerated features of effector populations both in vitro and after viral infection that are associated with increased Fas-mediated apoptosis due to sustained FoxO1 phosphorylation and Fasl derepression, enhanced mTORC1 and c-Myc signatures, metabolic perturbations, and an altered chromatin landscape. Conversely, Pik3cdE1020K/+ CD8+ cells fail to sustain expression of proteins critical for central memory, including TCF1. Strikingly, activated Pik3cdE1020K/+ CD8+ cells exhibit altered transcriptional and epigenetic circuits characterized by pronounced interleukin-2 (IL-2)/STAT5 signatures and heightened IL-2 responses that prevent differentiation to memory-like cells in IL-15. Our data position PI3Kδ as integrating multiple signaling nodes that promote CD8+ T cell effector differentiation, providing insight into phenotypes of patients with APDS.

JAK-STAT signaling in human disease: From genetic syndromes to clinical inhibition.

Since its discovery, the Janus kinase-signal transduction and activation of transcription (JAK-STAT) pathway has become recognized as a central mediator of widespread and varied human physiological processes. The field of JAK-STAT biology, particularly its clinical relevance, continues to be shaped by 2 important advances. First, the increased use of genomic sequencing has led to the discovery of novel clinical syndromes caused by mutations in JAK and STAT genes. This has provided insights regarding the consequences of aberrant JAK-STAT signaling for immunity, lymphoproliferation, and malignancy. In addition, since the approval of ruxolitinib and tofacitinib, the therapeutic use of JAK inhibitors (jakinibs) has expanded to include a large spectrum of diseases. Efficacy and safety data from over a decade of clinical studies have provided additional mechanistic insights while improving the care of patients with inflammatory and neoplastic conditions. This review discusses major advances in the field, focusing on updates in genetic diseases and in studies of clinical jakinibs in human disease.

A Case of Cardiac Papillary Fibroelastoma - An Increasingly Described Cardiac Tumor with Fatal Consequences.

Papillary fibroelastomas (PFE) are rare primary cardiac tumors characterized by non-malignant, pedunculated, endocardial lesions with a significant risk of embolic potential and death. With improvements in the imaging quality and availability of transthoracic echocardiograms (TTE), the diagnosis of PFE has become more common in the last 2 decades. PFE is changing from a rare "zebra" diagnosis to one that community providers will encounter in their practice and must appropriately treat to prevent morbidity and mortality. Data shows that there are significant survival and morbidity benefit associated with surgical excision over non-operative management, with the benefit of anticoagulation remaining unclear at this time. We report a case describing the diagnostic workup and management of a 58-year-old woman who presented with an unidentified endocardial mass determined to be a PFE. Based on current literature, we favor a strategy of early surgical excision of PFE for an optimal reduction in mortality and thromboembolic sequelae associated with this pathology.

JAK inhibitors: Ten years after.

The European Journal of Immunology was launched 50 years ago, coinciding with the discovery of many cytokines and growth factors and the emergence of an entirely new field of research. Ultimately, our knowledge about the biological activity of these factors allowed us to better understand how the immune system functions in the context of inflammatory and autoimmune diseases leading to the development of targeted biologic therapies. The study of cytokine signal transduction led to the discovery of Janus kinases (JAK), and the consideration of therapeutically targeting JAKs to treat immune and inflammatory diseases. This year also marks the tenth anniversary of the approval of the first JAK inhibitor (jakinib) and now there are a total of nine approved jakinibs for treatment of rheumatologic, dermatologic, gastrointestinal, and neoplastic indications and most recently COVID-19. Here, we summarized the discoveries that led to development of first-generation jakinibs, discussed some of the newer, possibly more selective jakinibs, as well as jakinibs that also target other kinases. We also illustrated the rationale behind the application of these drugs in the treatment of COVID-19 cytokine storm. In this review, we will discuss the clinical success of jakinibs, the gaps in our understanding of their biological activities as well as challenges in regard to their clinical application.

MicroRNA-221 and -222 modulate intestinal inflammatory Th17 cell response as negative feedback regulators downstream of interleukin-23.

MicroRNAs are important regulators of immune responses. Here, we show miR-221 and miR-222 modulate the intestinal Th17 cell response. Expression of miR-221 and miR-222 was induced by proinflammatory cytokines and repressed by the cytokine TGF-ß. Molecular targets of miR-221 and miR-222 included Maf and Il23r, and loss of miR-221 and miR-222 expression shifted the transcriptomic spectrum of intestinal Th17 cells to a proinflammatory signature. Although the loss of miR-221 and miR-222 was tolerated for maintaining intestinal Th17 cell homeostasis in healthy mice, Th17 cells lacking miR-221 and miR-222 expanded more efficiently in response to IL-23. Both global and T cell-specific deletion of miR-221 and miR-222 rendered mice prone to mucosal barrier damage. Collectively, these findings demonstrate that miR-221 and miR-222 are an integral part of intestinal Th17 cell response that are induced after IL-23 stimulation to constrain the magnitude of proinflammatory response.

BACH2 enforces the transcriptional and epigenetic programs of stem-like CD8+ T cells.

During chronic infection and cancer, a self-renewing CD8+ T cell subset maintains long-term immunity and is critical to the effectiveness of immunotherapy. These stem-like CD8+ T cells diverge from other CD8+ subsets early after chronic viral infection. However, pathways guarding stem-like CD8+ T cells against terminal exhaustion remain unclear. Here, we show that the gene encoding transcriptional repressor BACH2 is transcriptionally and epigenetically active in stem-like CD8+ T cells but not terminally exhausted cells early after infection. BACH2 overexpression enforced stem-like cell fate, whereas BACH2 deficiency impaired stem-like CD8+ T cell differentiation. Single-cell transcriptomic and epigenomic approaches revealed that BACH2 established the transcriptional and epigenetic programs of stem-like CD8+ T cells. In addition, BACH2 suppressed the molecular program driving terminal exhaustion through transcriptional repression and epigenetic silencing. Thus, our study reveals a new pathway that enforces commitment to stem-like CD8+ lineage and prevents an alternative terminally exhausted cell fate.

Compromised counterselection by FAS creates an aggressive subtype of germinal center lymphoma.

Fas is highly expressed on germinal center (GC) B cells, and mutations of FAS have been reported in diffuse large B cell lymphoma (DLBCL). Although GC-derived DLBCL has better overall outcomes than other DLBCL types, some cases are refractory, and the molecular basis for this is often unknown. We show that Fas is a strong cell-intrinsic regulator of GC B cells that promotes cell death in the light zone, likely via T follicular helper (Tfh) cell-derived Fas ligand. In the absence of Fas, GCs were more clonally diverse due to an accumulation of cells that did not demonstrably bind antigen. FAS alterations occurred most commonly in GC-derived DLBCL, were associated with inferior outcomes and an enrichment of Tfh cells, and co-occurred with deficiency in HVEM and PD-L1 that regulate the Tfh-B cell interaction. This work shows that Fas is critically required for GC homeostasis and suggests that loss of Tfh-mediated counterselection in the GC contributes to lethality in GC-derived lymphoma.

Rapid Enhancer Remodeling and Transcription Factor Repurposing Enable High Magnitude Gene Induction upon Acute Activation of NK Cells.

Innate immune responses rely on rapid and precise gene regulation mediated by accessibility of regulatory regions to transcription factors (TFs). In natural killer (NK) cells and other innate lymphoid cells, competent enhancers are primed during lineage acquisition, and formation of de novo enhancers characterizes the acquisition of innate memory in activated NK cells and macrophages. Here, we investigated how primed and de novo enhancers coordinate to facilitate high-magnitude gene induction during acute activation. Epigenomic and transcriptomic analyses of regions near highly induced genes (HIGs) in NK cells both in vitro and in a model of Toxoplasma gondii infection revealed de novo chromatin accessibility and enhancer remodeling controlled by signal-regulated TFs STATs. Acute NK cell activation redeployed the lineage-determining TF T-bet to de novo enhancers, independent of DNA-sequence-specific motif recognition. Thus, acute stimulation reshapes enhancer function through the combinatorial usage and repurposing of both lineage-determining and signal-regulated TFs to ensure an effective response.