IgG4-related disease and B-cell malignancy due to an IKZF1 gain-of-function variant.

BACKGROUND: Monoallelic loss-of-function IKZF1 (IKAROS) variants cause B-cell deficiency or combined immunodeficiency, whereas monoallelic gain-of-function (GOF) IKZF1 variants have recently been reported to cause hypergammaglobulinemia, abnormal plasma cell differentiation, autoimmune and allergic manifestations, and infections. OBJECTIVE: We studied 7 relatives with autoimmune/inflammatory and lymphoproliferative manifestations to identify the immunologic disturbances and the genetic cause of their disease. METHODS: We analyzed biopsy results and performed whole-exome sequencing and immunologic studies. RESULTS: Disease onset occurred at a mean age of 25.2 years (range, 10-64, years). Six patients suffered from autoimmune/inflammatory diseases, 4 had confirmed IG4-related disease (IgG4-RD), and 5 developed B-cell malignancies: lymphoma in 4 and multiple myeloma in the remaining patient. Patients without immunosuppression were not particularly prone to infectious diseases. Three patients suffered from life-threatening coronavirus disease 2019 pneumonia, of whom 1 had autoantibodies neutralizing IFN-α. The recently described IKZF1 GOF p.R183H variant was found in the 5 affected relatives tested and in a 6-year-old asymptomatic girl. Immunologic analysis revealed hypergammaglobulinemia and high frequencies of certain lymphocyte subsets (exhausted B cells, effector memory CD4 T cells, effector memory CD4 T cells that have regained surface expression of CD45RA and CD28-CD57+ CD4+ and CD8+ T cells, TH2, and Tfh2 cells) attesting to immune dysregulation. Partial clinical responses to rituximab and corticosteroids were observed, and treatment with lenalidomide, which promotes IKAROS degradation, was initiated in 3 patients. CONCLUSIONS: Heterozygosity for GOF IKZF1 variants underlies autoimmunity/inflammatory diseases, IgG4-RD, and B-cell malignancies, the onset of which may occur in adulthood. Clinical and immunologic data are similar to those for patients with unexplained IgG4-RD. Patients may therefore benefit from treatments inhibiting pathways displaying IKAROS-mediated overactivity.

Unexpected relevant role of gene mosaicism in patients with primary immunodeficiency diseases.

BACKGROUND: Postzygotic de novo mutations lead to the phenomenon of gene mosaicism. The 3 main types are called somatic, gonadal, and gonosomal mosaicism, which differ in terms of the body distribution of postzygotic mutations. Mosaicism has been reported occasionally in patients with primary immunodeficiency diseases (PIDs) since the early 1990s, but its real involvement has not been systematically addressed. OBJECTIVE: We sought to investigate the incidence of gene mosaicism in patients with PIDs. METHODS: The amplicon-based deep sequencing method was used in the 3 parts of the study that establish (1) the allele frequency of germline variants (n = 100), (2) the incidence of parental gonosomal mosaicism in families with PIDs with de novo mutations (n = 92), and (3) the incidence of mosaicism in families with PIDs with moderate-to-high suspicion of gene mosaicism (n = 36). Additional investigations evaluated body distribution of postzygotic mutations, their stability over time, and their characteristics. RESULTS: The range of allele frequency (44.1% to 55.6%) was established for germline variants. Those with minor allele frequencies of less than 44.1% were assumed to be postzygotic. Mosaicism was detected in 30 (23.4%) of 128 families with PIDs, with a variable minor allele frequency (0.8% to 40.5%). Parental gonosomal mosaicism was detected in 6 (6.5%) of 92 families with de novo mutations, and a high incidence of mosaicism (63.9%) was detected among families with moderate-to-high suspicion of gene mosaicism. In most analyzed cases mosaicism was found to be both uniformly distributed and stable over time. CONCLUSION: This study represents the largest performed to date to investigate mosaicism in patients with PIDs, revealing that it affects approximately 25% of enrolled families. Our results might have serious consequences regarding treatment and genetic counseling and reinforce the use of next-generation sequencing-based methods in the routine analyses of PIDs.

Laboratory evaluation of the IFN-γ circuit for the molecular diagnosis of Mendelian susceptibility to mycobacterial disease.

The integrity of the interferon (IFN)-γ circuit is necessary to mount an effective immune response to intra-macrophagic pathogens, especially Mycobacteria. Inherited monogenic defects in this circuit that disrupt the production of, or response to, IFN-γ underlie a primary immunodeficiency known as Mendelian susceptibility to mycobacterial disease (MSMD). Otherwise healthy patients display a selective susceptibility to clinical disease caused by poorly virulent mycobacteria such as BCG (bacille Calmette-Guérin) vaccines and environmental mycobacteria, and more rarely by other intra-macrophagic pathogens, particularly Salmonella and M. tuberculosis. There is high genetic and allelic heterogeneity, with 19 genetic etiologies due to mutations in 10 genes that account for only about half of the patients reported. An efficient laboratory diagnostic approach to suspected MSMD patients is important, because it enables the establishment of specific therapeutic measures that will improve the patient's prognosis and quality of life. Moreover, it is essential to offer genetic counseling to affected families. Herein, we review the various genetic and immunological diagnostic approaches that can be used in concert to reach a molecular and cellular diagnosis in patients with MSMD.

Lethal Influenza in Two Related Adults with Inherited GATA2 Deficiency.

The pathogenesis of life-threatening influenza A virus (IAV) disease remains elusive, as infection is benign in most individuals. We studied two relatives who died from influenza. We Sanger sequenced GATA2 and evaluated the mutation by gene transfer, measured serum cytokine levels, and analyzed circulating T- and B-cells. Both patients (father and son, P1 and P2) died in 2011 of H1N1pdm IAV infection at the ages of 54 and 31 years, respectively. They had not suffered from severe or moderately severe infections in the last 17 (P1) and 15 years (P2). A daughter of P1 had died at 20 years from infectious complications. Low B-cell, NK- cell, and monocyte numbers and myelodysplastic syndrome led to sequence GATA2. Patients were heterozygous for a novel, hypomorphic, R396L mutation leading to haplo-insufficiency. B- and T-cell rearrangement in peripheral blood from P1 during the influenza episode showed expansion of one major clone. No T-cell receptor excision circles were detected in P1 and P3 since they were 35 and 18 years, respectively. Both patients presented an exuberant, interferon (IFN)-γ-mediated hypercytokinemia during H1N1pdm infection. No data about patients with viremia was available. Two previously reported adult GATA2-deficient patients died from severe H1N1 IAV infection; GATA2 deficiency may predispose to life-threatening influenza in adulthood. However, a role of other genetic variants involved in immune responses cannot be ruled out. Patients with GATA2 deficiency can reach young adulthood without severe infections, including influenza, despite long-lasting complete B-cell and natural killer (NK) cell deficiency, as well as profoundly diminished T-cell thymic output.

Gain-of-function mutation in PIK3R1 in a patient with a narrow clinical phenotype of respiratory infections.

Antibody deficiencies can be caused by a variety of defects that interfere with B-cell development, maturation, and/or function. Using whole-exome sequencing we found a PIK3R1 mutation in a patient with hypogammaglobulinemia and a narrow clinical phenotype of respiratory infections. Early diagnosis is crucial; careful analysis of B and T-cells followed by genetic analyses may help to distinguish activated PI3K-delta syndrome (APDS) from other, less severe, predominantly antibody deficiencies.

Altered Profile of Circulating Endothelial-Derived Microparticles in Ventilator-Induced Lung Injury.

OBJECTIVES: Pulmonary endothelial cell injury is central to the pathophysiology of acute lung injury. Mechanical ventilation can cause endothelial disruption and injury, even in the absence of preexisting inflammation. Platelet-endothelial cell adhesion molecule-1 is a transmembrane protein connecting adjacent endothelial cells. We hypothesized that injurious mechanical ventilation will increase circulating lung endothelial-derived microparticles, defined as microparticles positive for platelet-endothelial cell adhesion molecule-1, which could serve as potential biomarkers and mediators of ventilator-induced lung injury. DESIGN: Prospective randomized, controlled, animal investigation. SETTING: A hospital preclinical animal laboratory. SUBJECTS: Forty-eight Sprague-Dawley rats. INTERVENTIONS: Animals were randomly allocated to one of the three following ventilatory protocols for 4 hours: spontaneous breathing (control group), mechanical ventilation with low tidal volume (6 mL/kg), and mechanical ventilation with high tidal volume (20 mL/kg). In both mechanical ventilation groups, positive end-expiratory pressure of 2 cm H2O was applied. MEASUREMENTS AND MAIN RESULTS: We analyzed histologic lung damage, gas exchange, wet-to-dry lung weight ratio, serum cytokines levels, circulating endothelial-derived microparticles, platelet-endothelial cell adhesion molecule-1 lung protein content, and immunohistochemistry. When compared with low-tidal volume mechanical ventilation, high-tidal volume ventilation increased lung edema score and caused gas-exchange deterioration. These changes were associated with a marked increased of circulating endothelial-derived microparticles and a reduction of platelet-endothelial cell adhesion molecule-1 protein levels in the high-tidal volume lungs (p < 0.0001). CONCLUSIONS: There is an endothelial-derived microparticle profile associated with disease-specific features of ventilator-induced lung injury. This profile could serve both as a biomarker of acute lung injury and, potentially, as a mediator of systemic propagation of pulmonary inflammatory response.

Diagnostic and therapeutic challenges in a child with complete interferon-γ receptor 1 deficiency.

Autosomal recessive (AR) complete Interferon-γ Receptor1 (IFN-γR1) deficiency is a rare variant of Mendelian susceptibility to mycobacterial disease (MSMD). Although hematopoietic stem cell transplantation (HSCT) remains the only curative treatment, outcomes are heterogeneous; delayed engraftment and/or graft rejection being commonly observed. This case report and literature review expands the knowledge about this rare but potentially fatal pathology, providing details regarding diagnosis, antimicrobial treatment, transplant performance, and outcome that may help to guide physicians caring for patients with AR complete IFN-γR1 or IFN-γR2 deficiency.

A novel gain-of-function STAT1 mutation resulting in basal phosphorylation of STAT1 and increased distal IFN-γ-mediated responses in chronic mucocutaneous candidiasis.

Gain-of-function STAT1 mutations have recently been associated with autosomal dominant chronic mucocutaneous candidiasis (CMC). The purpose of this study was to characterize the three members of a non-consanguineous family, the father and his two sons, who presented with recurrent oral thrush and ocular candidiasis since early childhood. The three patients had reduced levels of IL-17-producing T cells. This reduction affected specifically IL-17(+)IFN-γ(-) T cells, because the levels of IL-17(+)IFN-γ(+) T cells were similar to controls. We found that PBMC (peripheral blood mononuclear cells) from the patients did not respond to Candida albicans ex vivo. Moreover, after polyclonal activation, patients' PBMC produced lower levels of IL-17 and IL-6 and higher levels of IL-4 than healthy controls. Genetic analyses showed that the three patients were heterozygous for a new mutation in STAT1 (c.894A>C, p.K298N) that affects a highly conserved residue of the coiled-coil domain of STAT1. STAT1 phosphorylation levels were significantly higher in patients' cells than in healthy controls, both in basal conditions and after IFN-γ stimulation, suggesting a permanent activation of STAT1. Cells from the patients also presented increased IFN-γ-mediated responses measured as MIG and IP-10 production. In conclusion, we report a novel gain-of-function mutation in the coiled-coil domain of STAT1, which increases STAT1 phosphorylation and impairs IL-17-mediated immunity. The mutation is responsible for CMC in this family with autosomal dominant inheritance of the disease.

Multiple system organ response induced by hyperoxia in a clinically relevant animal model of sepsis.

Oxygen therapy is currently used as a supportive treatment in septic patients to improve tissue oxygenation. However, oxygen can exert deleterious effects on the inflammatory response triggered by infection. We postulated that the use of high oxygen concentrations may be partially responsible for the worsening of sepsis-induced multiple system organ dysfunction in an experimental clinically relevant model of sepsis. We used Sprague-Dawley rats. Sepsis was induced by cecal ligation and puncture. Sham-septic controls (n = 16) and septic animals (n = 32) were randomly assigned to four groups and placed in a sealed Plexiglas cage continuously flushed for 24 h with medical air (group 1), 40% oxygen (group 2), 60% oxygen (group 3), or 100% oxygen (group 4). We examined the effects of these oxygen concentrations on the spread of infection in blood, urine, peritoneal fluid, bronchoalveolar lavage, and meninges; serum levels of inflammatory biomarkers and reactive oxygen species production; and hematological parameters in all experimental groups. In cecal ligation and puncture animals, the use of higher oxygen concentrations was associated with a greater number of infected biological samples (P < 0.0001), higher serum levels of interleukin-6 (P < 0.0001), interleukin-10 (P = 0.033), and tumor necrosis factor-α (P = 0.034), a marked decrease in platelet counts (P < 0.001), and a marked elevation of reactive oxygen species serum levels (P = 0.0006) after 24 h of oxygen exposure. Oxygen therapy greatly influences the progression and clinical manifestation of multiple system organ dysfunction in experimental sepsis. If these results are extrapolated to humans, they suggest that oxygen therapy should be carefully managed in septic patients to minimize its deleterious effects.