Patients and mice with deficiency in the SNARE protein SYNTAXIN-11 have a secondary B cell defect.

SYNTAXIN-11 (STX11) is a SNARE protein that mediates the fusion of cytotoxic granules with the plasma membrane at the immunological synapses of CD8 T or NK cells. Autosomal recessive inheritance of deleterious STX11 variants impairs cytotoxic granule exocytosis, causing familial hemophagocytic lymphohistiocytosis type 4 (FHL-4). In several FHL-4 patients, we also observed hypogammaglobulinemia, elevated frequencies of naive B cells, and increased double-negative DN2:DN1 B cell ratios, indicating a hitherto unrecognized role of STX11 in humoral immunity. Detailed analysis of Stx11-deficient mice revealed impaired CD4 T cell help for B cells, associated with disrupted germinal center formation, reduced isotype class switching, and low antibody avidity. Mechanistically, Stx11-/- CD4 T cells exhibit impaired membrane fusion leading to reduced CD107a and CD40L surface mobilization and diminished IL-2 and IL-10 secretion. Our findings highlight a critical role of STX11 in SNARE-mediated membrane trafficking and vesicle exocytosis in CD4 T cells, important for successful CD4 T cell-B cell interactions. Deficiency in STX11 impairs CD4 T cell-dependent B cell differentiation and humoral responses.

Ruxolitinib Pharmacokinetics and Pharmacodynamics in Children with Acute and Chronic Graft-versus-Host Disease.

We evaluated the pharmacokinetics (PK) of oral ruxolitinib in children with steroid-refractory acute graft-versus-host disease (aGVHD) (age <12 years) and chronic GVHD (cGVHD) (age ≤18 years) using our published pediatric dosing. PK sampling was performed before and 2 hours after ruxolitinib administration in patients with established cGVHD. More extensive PK analyses were performed in patients with newly diagnosed aGVHD or cGVHD before and .5, 1, 2, 4, and 6 hours after ruxolitinib administration in patients weighing >10 kg and before, 3+, and 6+ hours in children weighing <10 kg. pSTAT1, pSTAT3, and pSTAT5 expression levels were measured on CD4+ and CD8+ T cells before and 2 hours after ruxolitinib administration as a pharmacodynamic marker of JAK/STAT inhibition. Thirteen patients were prospectively enrolled, including 8 with existing cGVHD (age 0 to ≤18 years), 4 with new-onset steroid-refractory aGVHD (age 0 to <12 years) and 1 with newly diagnosed steroid-refractory cGVHD. Great variability in PK was seen. Mean oral clearance (CL/F) was 7.76 ± 4.09 L/h (range, 3.1 to 15.3 L/h). The average elimination half-life was 2.32 ± 1.0 hours. Mean ruxolitinib clearance was higher in children age <2 years versus those age >2 years (12.1 ± 3.0 L/h versus 5.7 ± 2.8 L/h; P = .005) and was reduced with concurrent treatment with azoles and azithromycin. We saw a variable reduction in pSTAT1/3/5 expression on T cells at time of peak ruxolitinib absorption (2 hours after dosing). Children <10 kg had lower ruxolitinib exposure, possibly due to inherent increased drug clearance or variability in dosing methods, leading to decreased drug absorption.

Quercetin ameliorates XIAP deficiency-associated hyperinflammation.

XIAP (X-linked inhibitor of apoptosis) deficiency is a rare inborn error of immunity. XIAP deficiency causes hyperinflammatory disease manifestations due to dysregulated TNF (tumor necrosis factor)-receptor signaling and NLRP3 (NOD- [nucleotide-binding oligomerization domain], LRR- [leucine-rich repeat] and pyrin domain-containing protein 3) inflammasome function. Safe and effective long-term treatments are needed and are especially important to help prevent the need for high-risk allogeneic hematopoietic cell transplantation. Here we evaluated inflammasome inhibitors as potential therapeutics with a focus on the natural flavonoid antioxidant quercetin. Bone marrow (BM)-derived macrophages were derived from XIAP-deficient or wild-type (WT) mice. Human monocytes were obtained from control or XIAP-deficient patients. Cells were stimulated with TLR (Toll-like receptor) agonists or TNF-α ± inhibitors or quercetin. For in vivo lipopolysaccharide (LPS) challenge experiments, XIAP-deficient or WT mice were fed mouse chow ± supplemental quercetin (50 mg/kg per day exposure) for 7 days followed by a challenge with 10 ng/kg LPS. IL-1ß (interleukin-1ß) and IL-18 were measured by ELISA (enzyme-linked immunosorbent assay). In murine studies, quercetin prevented IL-1ß secretion from XIAP knockout cells following TLR agonists or TNF-α stimulation (P < .05) and strongly reduced constitutive production of IL-18 by both WT and XIAP-deficient cells (P < .05). At 4 hours after in vivo LPS challenge, blood levels of IL-1ß and IL-18 were significantly decreased in mice that had received quercetin-supplemented chow (P < .05). In experiments using human cells, quercetin greatly reduced IL-1ß secretion by monocytes following TNF-α stimulation (P < .05). Our data suggest that quercetin may be an effective natural therapeutic for the prevention of XIAP deficiency-associated hyperinflammation. Clinical trials, including careful pharmacokinetic and pharmacodynamic studies to ensure that effective levels of quercetin can be obtained, are warranted.

Intestinal-derived FGF15 protects against deleterious effects of vertical sleeve gastrectomy in mice.

Bariatric surgeries such as the Vertical Sleeve Gastrectomy (VSG) are invasive but provide the most effective improvements in obesity and Type 2 diabetes. We hypothesized a potential role for the gut hormone Fibroblast-Growth Factor 15/19 which is increased after VSG and pharmacologically can improve energy homeostasis and glucose handling. We generated intestinal-specific FGF15 knockout (FGF15INT-KO) mice which were maintained on high-fat diet. FGF15INT-KO mice lost more weight after VSG as a result of increased lean tissue loss. FGF15INT-KO mice also lost more bone density and bone marrow adipose tissue after VSG. The effect of VSG to improve glucose tolerance was also absent in FGF15INT-KO. VSG resulted in increased plasma bile acid levels but were considerably higher in VSG-FGF15INT-KO mice. These data point to an important role after VSG for intestinal FGF15 to protect the organism from deleterious effects of VSG potentially by limiting the increase in circulating bile acids.

A Toolkit and Framework for Optimal Laboratory Evaluation of Individuals with Suspected Primary Immunodeficiency.

Knowledge related to the biology of inborn errors of immunity and associated laboratory testing methods continues to expand at a tremendous rate. Despite this, many patients with inborn errors of immunity suffer for prolonged periods of time before identification of their underlying condition, thereby delaying appropriate care. Understanding that test selection and optimal evaluation for patients with recurrent infections or unusual patterns of inflammation can be unclear, we present a document that distills relevant clinical features of immunologic disease due to inborn errors of immunity and related appropriate and available test options. This document is intended to serve the practicing clinical immunologist and, in turn, patients by describing best available test options for initial and expanded immunologic evaluations across the disease spectrum. Our goal is to demystify the process of evaluating patients with suspected immune dysfunction and to enable more rapid and accurate diagnosis of such individuals.

The transcription factor Bcl11b promotes both canonical and adaptive NK cell differentiation.

Epigenetic landscapes can provide insight into regulation of gene expression and cellular diversity. Here, we examined the transcriptional and epigenetic profiles of seven human blood natural killer (NK) cell populations, including adaptive NK cells. The BCL11B gene, encoding a transcription factor (TF) essential for T cell development and function, was the most extensively regulated, with expression increasing throughout NK cell differentiation. Several Bcl11b-regulated genes associated with T cell signaling were specifically expressed in adaptive NK cell subsets. Regulatory networks revealed reciprocal regulation at distinct stages of NK cell differentiation, with Bcl11b repressing RUNX2 and ZBTB16 in canonical and adaptive NK cells, respectively. A critical role for Bcl11b in driving NK cell differentiation was corroborated in BCL11B-mutated patients and by ectopic Bcl11b expression. Moreover, Bcl11b was required for adaptive NK cell responses in a murine cytomegalovirus model, supporting expansion of these cells. Together, we define the TF regulatory circuitry of human NK cells and uncover a critical role for Bcl11b in promoting NK cell differentiation and function.

Efficacy of Moderately Dosed Etoposide in Macrophage Activation Syndrome-Hemophagocytic Lymphohistiocytosis.

OBJECTIVE: Macrophage activation syndrome (MAS) constitutes 1 subtype of the hyperinflammatory syndrome hemophagocytic lymphohistiocytosis (HLH), and the term MAS-HLH was recently proposed for HLH with underlying autoimmune/autoinflammatory conditions. The mortality of MAS-HLH has been estimated at 5-10%. Here we report our experiences with moderately dosed etoposide in severe MAS-HLH; the objective was to effectively reduce severe hyperinflammatory activity with limited side effects. METHODS: In addition to conventional antiinflammatory treatment, moderately dosed etoposide was administered to 7 children affected by rapidly progressing MAS-HLH with central nervous system (n = 5) and/or pulmonary (n = 5) involvement. Three had underlying systemic juvenile idiopathic arthritis (sJIA), 2 had atypical sJIA (no arthritis at diagnosis), and 2 had systemic lupus erythematosus. We performed lymphocyte cytotoxicity analyses in all 7 and genetic analyses in 6. RESULTS: All children promptly responded to moderately dosed etoposide (50-100 mg/m2 once weekly), added to conventional MAS-HLH treatment that was considered insufficient. The mean accumulated etoposide dose was 671 mg/m2 (range 300-1050 mg/m2) as compared to 1500 mg/m2 recommended in the first 8 weeks of the HLH-94/HLH-2004 protocols. One child developed neutropenic fever and another neutropenic sepsis (neutrophils 0.3 × 109/L at therapy onset). Five of 7 children had low percentages (< 5%) of circulating natural killer (NK) cells prior to or in association with diagnosis; NK cell activity was pathologically low in 2 of 5 children studied. Disease-causing variants in HLH-associated genes were not found. All children were alive at latest follow-up (2-9 yrs after onset); neurological symptoms had normalized in 4 of 5 affected children. CONCLUSION: Moderately dosed etoposide may be beneficial in severe and/or refractory MAS-HLH.

RhoG deficiency abrogates cytotoxicity of human lymphocytes and causes hemophagocytic lymphohistiocytosis.

Exocytosis of cytotoxic granules (CG) by lymphocytes is required for the elimination of infected and malignant cells. Impairments in this process underly a group of diseases with dramatic hyperferritinemic inflammation termed hemophagocytic lymphohistiocytosis (HLH). Although genetic and functional studies of HLH have identified proteins controlling distinct steps of CG exocytosis, the molecular mechanisms that spatiotemporally coordinate CG release remain partially elusive. We studied a patient exhibiting characteristic clinical features of HLH associated with markedly impaired cytotoxic T lymphocyte (CTL) and natural killer (NK) cell exocytosis functions, who beared biallelic deleterious mutations in the gene encoding the small GTPase RhoG. Experimental ablation of RHOG in a model cell line and primary CTLs from healthy individuals uncovered a hitherto unappreciated role of RhoG in retaining CGs in the vicinity of the plasma membrane (PM), a fundamental prerequisite for CG exocytotic release. We discovered that RhoG engages in a protein-protein interaction with Munc13-4, an exocytosis protein essential for CG fusion with the PM. We show that this interaction is critical for docking of Munc13-4+ CGs to the PM and subsequent membrane fusion and release of CG content. Thus, our study illuminates RhoG as a novel essential regulator of human lymphocyte cytotoxicity and provides the molecular pathomechanism behind the identified here and previously unreported genetically determined form of HLH.

Clinical and laboratory signs of haemophagocytic lymphohistiocytosis associated with pandemic influenza A (H1N1) infection in patients needing extracorporeal membrane oxygenation: A retrospective observational study.

BACKGROUND: Severe pandemic influenza has been associated with the hyperinflammatory condition secondary haemophagocytic lymphohistiocytosis (HLH). OBJECTIVES: To determine the frequency, degree, character and possible cause of influenza-associated HLH in critically ill patients with severe acute respiratory distress syndrome due to influenza A (H1N1) infection requiring extracorporeal membrane oxygenation (ECMO) support at our hospital. DESIGN: A retrospective observational study. PATIENTS AND SETTING: Medical data were retrieved retrospectively from 11 consenting patients of thirteen adults infected with pandemic influenza A (H1N1) 2009 requiring ECMO between July 2009 and January 2010 at the ECMO Centre of Karolinska University Hospital, Stockholm, Sweden. All patients were evaluated for HLH using HLH-2004 criteria and HScore. RESULTS: Eleven patients (median age 31 years) were included in the study and all survived. All patients showed signs of multiple organ dysfunction and pronounced inflammation, more severe in the four patients with HLH who had significantly higher peak serum concentrations of ferritin (P = 0.024), alkaline phosphatase (P = 0.012) and gamma-glutamyl transferase (P = 0.024), lower concentration of albumin (P = 0.0086) and more frequently hepatomegaly (P = 0.048). Abnormal lymphocyte cytotoxicity (lytic units <10) and a low proportion of natural killer (NK) cells were observed in three of four patients with HLH. Notably, we found a significant inverse correlation between serum ferritin concentration and NK cell and cytotoxic T lymphocyte percentages (rs = -0.74, P = 0.0013 and rs = -0.79, P = 0.0025, respectively). One HLH patient received HLH-directed cytotoxic therapy, another intravenous immunoglobulin and the other two no specific HLH-directed therapy. CONCLUSION: Critically ill patients, including healthy young adults, with pandemic influenza may develop HLH and should be monitored for signs of hyperinflammation and increasing organ dysfunction, and evaluated promptly for HLH because HLH-directed therapy may then be beneficial. The association of low NK percentages with hyperferritinaemia may suggest a role for reduced NK cell numbers, possibly also cytotoxic T lymphocytes, and subsequently reduced lymphocyte cytotoxicity, in the pathogenesis of hyperinflammation and secondary HLH.

Additive effect of atropine eye drops and short-term retinal defocus on choroidal thickness in children with myopia.

Atropine eye drops and myopic retinal defocus each slow progression of myopia (short-sight). They also cause thickening of the choroid, and it has been suggested that the thickening is a precursor for reduced eye growth and slowed myopia progression. We investigated whether choroidal thickening due to optical defocus would add to thickening due to atropine when both were applied simultaneously. Addition would suggest that combining the two clinical treatments may improve efficacy of myopia control. We studied 20 children receiving 0.3% atropine daily for myopia control, over a period of 6 months. We imposed short periods of retinal defocus (1 h of myopic or hyperopic defocus (± 2.00D)) both before, and after 1 week and 3 and 6 months of atropine treatment. Prior to atropine, myopic or hyperopic defocus caused significantly thicker or thinner choroids respectively (± 12 µm, p < 0.001). After one week of atropine alone, thickness had increased (+ 21 µm; SD 17 µm; p < 0.001), and it increased further (by + 13 µm; SD 6 µm; p < 0.001) when exposed to myopic defocus. Atropine abolished choroidal thinning in response to hyperopic defocus. These effects remained the same after 3 and 6 months of atropine treatment. Our results show that additive effects of atropine and optical defocus are present at the level of the choroid, and suggest that combining optical and pharmaceutical treatments is likely to enhance efficacy of clinical myopia control.

Diagnostic challenges for a novel SH2D1A mutation associated with X-linked lymphoproliferative disease.

Mutations in SH2D1A, encoding the intracellular adaptor signaling lymphocyte activation molecule associated protein (SAP), are associated with X-linked lymphoproliferative disease type 1 (XLP1). We identified a novel hemizygous SH2D1A c.49G > A (p.E17K) variant in a 21-year-old patient with fatal Epstein-Barr virus infection-associated hemophagocytic lymphohistiocytosis. Cellular and biochemical assays revealed normal expression of the SAP variant protein, yet binding to phosphorylated CD244 receptor was reduced by >95%. Three healthy brothers carried the SH2D1A c.49G > A variant. Thus, data suggest that this variant represents a pathogenic mutation, but with variable expressivity. Importantly, our results highlight challenges in the clinical interpretation of SH2D1A variants and caution in using functional flow cytometry assays for the diagnosis of XLP1.

A Rare Case of Activated Phosphoinositide 3-Kinase Delta Syndrome (APDS) Presenting With Hemophagocytosis Complicated With Hodgkin Lymphoma.

Gain of function mutations in the p110δ catalytic subunit of the phosphatidylinositol-3-OH kinase (PIK3CD) classified as activated phosphoinositide 3-kinase delta syndrome (APDS) are the cause of a primary immunodeficiency characterized by recurrent sinopulmonary infections, and lymphoproliferation. Previously, autoimmunity and Epstein-Barr virus-related B-cell lymphoma have been documented for patients with APDS; here, we present a case that extends the picture, as the patient shows the full diagnostic criteria of hemophagocytic lymphohistiocytosis at 6 months of age. He experienced Hodgkin lymphoma as a 2.5-year-old baby. Next-generation sequencing returned a de novo heterozygous missense variant in PIK3CD (LRG_191t1: c.3061G>A; p.Glu1021Lys), confirming the primary immunodeficiency. After 2 courses of ifosfamide, cisplatin, and etoposide combined with brentuximab, the patient successfully underwent allogeneic hematopoietic stem cell transplantation from his HLA full matched sister, and he has been well for 18 months after that. The hematologist treating Hodgkin lymphoma and/or hemophagocytic lymphohistiocytosis should be vigilant about the possible underlying immune deficiency, and they should consider APDS in their differential diagnosis.

Different Clinical Presentation of 3 Children With Familial Hemophagocytic Lymphohistiocytosis With 2 Novel Mutations.

Although familial hemophagocytic lymphohistiocytosis (FHL) generally manifest with a combination of unremitting fever, hepatosplenomegaly, and pancytopenia; unusual presentations should also be taken into account. Herein, we present 3 FHL cases with 2 novel mutations with different initial presentations. The first patient bearing a homozygous truncation mutation in UNC13D (c.2650C>T.p.Gln884Ter) presented with central nervous system involvement and skin rash. The patient responded to the HLH-2004 protocol, and allogenic hematopoietic stem cell transplantation was performed from her healthy sister. The second and third patients with homozygous splice site mutation (c.430-1G>A) in STXBP2 were siblings who presented at birth with fevers, elevated aspartate aminotransferase, alanine aminotransferase, and hyperferritinemia but did not fulfill FHL criteria. The last 2 infants died despite intervention. Hematologists should be vigilant about the different presentation of FHL in children.

Elevated ferritin and soluble CD25 in critically ill patients are associated with parameters of (hyper) inflammation and lymphocyte cytotoxicity.

BACKGROUND: Critically ill patients may develop a potentially fatal hyperinflammatory condition known as secondary (acquired) hemophagocytic lymphohistiocytosis (sHLH), the cause of which is unclear. We evaluated serum ferritin and soluble CD25 (sCD25) in critically ill patients, and their association with other parameters of inflammation and critical illness. Moreover, aiming to better understand the pathogenesis of sHLH, we also evaluated lymphocyte cytotoxicity parameters and correlations with the inflammatory markers ferritin and sCD25. METHODS: In a prospective observational study, 32 patients with ferritin ≥500 µg/L (24 with sepsis) were studied on admission to an intensive care unit (ICU) with regard to ferritin and corresponding clinical and laboratory features including sCD25, and detailed lymphocyte cytotoxicity and genetic analyses whenever possible. RESULTS: Critically ill patients had elevated, positively correlated levels of serum ferritin and sCD25 (rs=0.465, P=0.008); both associated with other risk factors of poor outcome in critically ill, such as thrombocytopenia (rs=-0.534, P=0.002 and rs=-0.421, P=0.018, respectively), and sCD25 with hypoalbuminemia (rs=-0.678, P<0.001) and life support treatments (rs=0.479, P=0.006). Interestingly, ferritin levels were inversely associated with natural killer (NK)-cell cytotoxicity (rs=-0.462, P=0.047) and degranulation (rs=-0.504, P=0.030). Moreover, of four patients with abnormally low cytotoxicity, three (75%) had <5% circulating NK-cells. CONCLUSIONS: Our study suggests that hyperferritinemia and sCD25 correlate with other laboratory parameters indicative of severe hyperinflammation and organ dysfunction in critically ill ICU-patients, indicating their value in identifying hyperinflammatory critically ill patients for early intervention. Furthermore, it suggests that hyperferritinemia and hyperinflammation may partly be associated with a low percentage circulating NK-cells, and hence, the associated low lymphocyte cytotoxicity.

Current Flow Cytometric Assays for the Screening and Diagnosis of Primary HLH.

Advances in flow cytometry have led to greatly improved primary immunodeficiency (PID) diagnostics. This is due to the fact that patient blood cells in suspension do not require further processing for analysis by flow cytometry, and many PIDs lead to alterations in leukocyte numbers, phenotype, and function. A large portion of current PID assays can be classified as "phenotyping" assays, where absolute numbers, frequencies, and markers are investigated using specific antibodies. Inherent drawbacks of antibody technology are the main limitation to this type of testing. On the other hand, "functional" assays measure cellular responses to certain stimuli. While these latter assays are powerful tools that can be used to detect defects in entire pathways and distinguish variants of significance, it requires samples with robust viability and also skilled processing. In this review, we concentrate on hemophagocytic lymphohistiocytosis (HLH), describing the principles and accuracies of flow cytometric assays that have been proven to assist in the screening diagnosis of primary HLH.

Dominant TOM1 mutation associated with combined immunodeficiency and autoimmune disease.

Mutations in several proteins functioning as endolysosomal components cause monogenic autoimmune diseases, of which pathogenesis is linked to increased endoplasmic reticulum stress, inefficient autophagy, and defective recycling of immune receptors. We report here a heterozygous TOM1 p.G307D missense mutation, detected by whole-exome sequencing, in two related patients presenting with early-onset autoimmunity, antibody deficiency, and features of combined immunodeficiency. The index patient suffered from recurrent respiratory tract infections and oligoarthritis since early teens, and later developed persistent low-copy EBV-viremia, as well as an antibody deficiency. Her infant son developed hypogammaglobulinemia, autoimmune enteropathy, interstitial lung disease, profound growth failure, and treatment-resistant psoriasis vulgaris. Consistent with previous knowledge on TOM1 protein function, we detected impaired autophagy and enhanced susceptibility to apoptosis in patient-derived cells. In addition, we noted diminished STAT and ERK1/2 signaling in patient fibroblasts, as well as poor IFN-γ and IL-17 secretion in T cells. The mutant TOM1 failed to interact with TOLLIP, a protein required for IL-1 recycling, PAMP signaling and autophagosome maturation, further strengthening the link between the candidate mutation and patient pathophysiology. In sum, we report here an identification of a novel gene, TOM1, associating with early-onset autoimmunity, antibody deficiency, and features of combined immunodeficiency. Other patient cases from unrelated families are needed to firmly establish a causal relationship between the genotype and the phenotype.