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 5 100), (2) the incidence of parental gonosomal mosaicism in families with PIDs with de novo mutations (n 5 92), and (3) the incidence of mosaicism in families with PIDs with moderate-to-high suspicion of gene mosaicism (n 5 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 moderateto-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.

Background: The SARS-CoV-2 infection has widely spread to become the greatest public health challenge to date, the COVID-19 pandemic. Different fatality rates among countries are probably due to non-standardized records being carried out by local health authorities. The Spanish case-fatality rate is 11.22%, far higher than those reported in Asia or by other European countries. A multicentre retrospective study of demographic, clinical, laboratory and immunological features of 584 Spanish COVID-19 hospitalized patients and their outcomes was performed. The use of renin-angiotensin system blockers was also analysed as a risk factor. Results: In this study, 27.4% of cases presented a mild course, 42.1% a moderate one and for 30.5% of cases, the course was severe. Ages ranged from 18 to 98 (average 63). Almost 60 % (59.8%) of patients were male. Interleukin 6 was higher as severity increased. On the other hand, CD8 lymphocyte count was significantly lower as severity grew and subpopulations CD4, CD8, CD19, and NK showed concordant lowering trends. Severity-related natural killer percent descents were evidenced just within aged cases. A significant severity-related decrease of CD4 lymphocytes was found in males. The use of angiotensin-converting enzyme inhibitors was associated with a better prognosis. The angiotensin II receptor blocker use was associated with a more severe course.

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.

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.

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.

Autosomal recessive (AR) complete Interferon-γ Receptor1 (IFN-γR1) deficiency is a rare variant of Mendelian susceptibility to mycobacterial disease (MSMD). Whilst 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.

Common variable immunodeficiency (CVID), the most prevalent symptomatic primary immunodeficiency, displays impaired terminal B-cell differentiation and defective antibody responses. Incomplete genetic penetrance and ample phenotypic expressivity in CVID suggest the participation of additional pathogenic mechanisms. Monozygotic (MZ) twins discordant for CVID are uniquely valuable for studying the contribution of epigenetics to the disease. Here, we generate a single-cell epigenomics and transcriptomics census of naïve-to-memory B cell differentiation in a CVID-discordant MZ twin pair. Our analysis identifies DNA methylation, chromatin accessibility and transcriptional defects in memory B-cells mirroring defective cell-cell communication upon activation. These findings are validated in a cohort of CVID patients and healthy donors. Our findings provide a comprehensive multi-omics map of alterations in naïve-to-memory B-cell transition in CVID and indicate links between the epigenome and immune cell cross-talk. Our resource, publicly available at the Human Cell Atlas, gives insight into future diagnosis and treatments of CVID patients.

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