Reorganization of the actin cytoskeleton during the formation of neutrophil extracellular traps (NETs).

We analyzed actin cytoskeleton alterations during NET extrusion by neutrophil-like dHL-60 cells and human neutrophils in the absence of DNase1 containing serum to avoid chromatin degradation and microfilament disassembly. NET-formation by dHL-60 cells and neutrophils was induced by Ionomycin or phorbol-12-myristat-13-acetate (PMA). Subsequent staining with anti-actin and TRITC-phalloidin showed depolymerization of the cortical F-actin at spatially confined areas, the NET extrusion sites, effected by transient activation of the monooxygenase MICAL-1 supported by the G-actin binding proteins cofilin, profilin, thymosin ß4 and probably the F-actin fragmenting activity of gelsolin and/or its fragments, which also decorated the formed NETs. MICAL-1 itself appeared to be proteolyzed by neutrophil elastase possibly to confine its activity to the NET-extrusion area. The F-actin oxidization activity of MICAL-1 is inhibited by Levosimendan leading to reduced NET-formation. Anti-gasdermin-D immunohistochemistry showed a cytoplasmic distribution in non-stimulated cells. After stimulation the NET-extrusion pore displayed reduced anti-gasdermin-D staining but accumulated underneath the plasma membrane of the remaining cell body. A similar distribution was observed for myosin that concentrated together with cortical F-actin along the periphery of the remaining cell body suggesting force production by acto-myosin interactions supporting NET expulsion as indicated by the inhibitory action of the myosin ATPase inhibitor blebbistatin. Isolated human neutrophils displayed differences in their content of certain cytoskeletal proteins. After stimulation neutrophils with high gelsolin content preferentially formed "cloud"-like NETs, whereas those with low or no gelsolin formed long "filamentous" NETs.

Analysis of Free Circulating Messenger Ribonucleic Acids in Serum Samples from Late-Onset Spinal Muscular Atrophy Patients Using nCounter NanoString Technology.

5q-related Spinal muscular atrophy (SMA) is a hereditary multi-systemic disorder leading to progressive muscle atrophy and weakness caused by the degeneration of spinal motor neurons (MNs) in the ventral horn of the spinal cord. Three SMN-enhancing drugs for SMA treatment are available. However, even if these drugs are highly effective when administrated early, several patients do not benefit sufficiently or remain non-responders, e.g., adults suffering from late-onset SMA and starting their therapy at advanced disease stages characterized by long-standing irreversible loss of MNs. Therefore, it is important to identify additional molecular targets to expand therapeutic strategies for SMA treatment and establish prognostic biomarkers related to the treatment response. Using high-throughput nCounter NanoString technology, we analyzed serum samples of late-onset SMA type 2 and type 3 patients before and six months under nusinersen treatment. Four genes (AMIGO1, CA2, CCL5, TLR2) were significantly altered in their transcript counts in the serum of patients, where differential expression patterns were dependent on SMA subtype and treatment response, assessed with outcome scales. No changes in gene expression were observed six months after nusinersen treatment, compared to healthy controls. These alterations in the transcription of four genes in SMA patients qualified those genes as potential SMN-independent therapeutic targets to complement current SMN-enhancing therapies.

Immune Response to Seasonal Influenza Vaccination in Multiple Sclerosis Patients Receiving Cladribine.

Cladribine has been approved for the treatment of multiple sclerosis (MS) and its administration results in a long-lasting depletion of lymphocytes. As lymphopenia is known to hamper immune responses to vaccination, we evaluated the immunogenicity of the influenza vaccine in patients undergoing cladribine treatment at different stages vs. controls. The antibody response in 90 cladribine-treated MS patients was prospectively compared with 10 control subjects receiving platform immunotherapy (NCT05019248). Serum samples were collected before and six months after vaccination. Response to vaccination was determined by the hemagglutination-inhibition test. Postvaccination seroprotection rates against influenza A were comparable in cladribine-treated patients and controls (H1N1: 94.4% vs. 100%; H3N2: 92.2% vs. 90.0%). Influenza B response was lower in the cladribine cohort (61.1% vs. 80%). The increase in geometric mean titers was lower in the cladribine group vs. controls (H1N1: +98.5 vs. +188.1; H3N2: +225.3 vs. +300.0; influenza B: +40.0 vs. +78.4); however, titers increased in both groups for all strains. Seroprotection was achieved irrespective of vaccination timing and lymphocyte subset counts at the time of vaccination in the cladribine cohort. To conclude, cladribine-treated MS patients can mount an adequate immune response to influenza independently of treatment duration and time interval to the last cladribine administration.

Rat Ovarian Function Is Impaired during Experimental Autoimmune Encephalomyelitis.

Multiple sclerosis (MS) is an autoimmune disease affecting the CNS and occurring far more prevalently in women than in men. In both MS and its animal models, sex hormones play important immunomodulatory roles. We have previously shown that experimental autoimmune encephalomyelitis (EAE) affects the hypothalamic-pituitary-gonadal axis in rats of both sexes and induces an arrest in the estrous cycle in females. To investigate the gonadal status in female rats with EAE, we explored ovarian morphometric parameters, circulating and intraovarian sex steroid levels, and the expression of steroidogenic machinery components in the ovarian tissue. A prolonged state of diestrus was recorded during the peak of EAE, with maintenance of the corpora lutea, elevated intraovarian progesterone levels, and increased gene and protein expression of StAR, similar to the state of pseudopregnancy. The decrease in CYP17A1 protein expression was followed by a decrease in ovarian testosterone and estradiol levels. On the contrary, serum testosterone levels were slightly increased. With unchanged serum estradiol levels, these results point at extra-gonadal sites of sex steroid biosynthesis and catabolism as important regulators of their circulating levels. Our study suggests alterations in the function of the female reproductive system during central autoimmunity and highlights the bidirectional relationships between hormonal status and EAE.

Immunological consequences of cladribine treatment in multiple sclerosis: A real-world study.

BACKGROUND: Cladribine is a synthetic deoxyadenosine analogue approved for the treatment of highly active relapsing multiple sclerosis (RMS). Cladribine is considered to be a semi-selective immune-reconstitution therapy (IRT) that induces long-term remission following short course of treatment. Here, we evaluated the effect of cladribine on immune cell reduction and reconstitution during the first two years of treatment. METHODS: We analyzed our longitudinal, prospective, real-world cohort of 80 cladribine-treated RMS patients from two tertiary centers in Germany. Laboratory testing was conducted monthly and included evaluation of cellular as well as soluble parameters. Laboratory outcomes were correlated with infectious adverse events (AEs) and clinical or paraclinical disease activity. RESULTS: Selective alterations in immune cell populations occurred following cladribine treatment, with the most marked effects observed in year two of treatment. Specifically, a rapid reduction in CD56+ natural killer cells (nadir: month 1 (year 1) and 14 (year 2); -37 and -41% from baseline) was followed by a greater reduction in CD19+ B cells (nadir: month 2 and 14; -81 and -82%); a moderate effect on CD4+ (nadir: month 3 and 15; -48 and -61%) and CD8+ T cells (nadir: month 5 and 18; -40 and -48%). Despite the marked effect on B cells, immunoglobulin levels were unaffected. There was no or minimal effect on thrombocytes and innate immune cells. Clinical and paraclinical disease activity was unrelated to the observed immune alterations. Lymphopenia was the most commonly observed AE (86.3% of patients; grade III-IV lymphopenia: 38.8%). The cumulative incidence of infections was 55% with cladribine treatment, which were mostly mild or moderate. In total, 19 herpes infections developed in 8 (10%) cladribine-treated patients; all cases were dermatomal and 94.7% of the herpetic infections occurred during a period of lymphopenia. CONCLUSIONS: The immunophenotyping data obtained in our real-world setting are comparable to those demonstrated in pivotal clinical trials and provide further evidence that cladribine may represent a form of IRT. However, regarding the side-effect profile of cladribine, severe lymphopenia (exceeding grade II CTCAE) was more frequent, which may have prompted the development of herpes infections. Of note, lymphocyte dynamics did not correlate with clinical and paraclinical measures of disease activity in the two-year follow-up period.

Anti-EBNA1 IgG titre is not associated with fatigue in multiple sclerosis patients.

INTRODUCTION: Fatigue is the most frequent symptom in multiple sclerosis (MS), although it is still poorly understood due to its complexity and subjective nature. There is an urgent need to identify reliable biomarkers to improve disease prognosis and therapeutic strategies. Epstein-Barr virus (EBV) is the major environmental risk factor associated with MS aetiology, and trials with EBV-targeted T cell therapies have reduced fatigue severity in MS patients. AIM OF THE STUDY: We investigated whether the serum amount of immunoglobulin (Ig)G-specific for EBV antigens could be a suitable prognostic marker for the assessment of MS-related fatigue. MATERIAL AND METHODS: A total of 194 MS patients were enrolled. We quantified EBV nuclear antigen 1 (EBNA1) and EBV viral capsid antigen (VCA) immunoglobulin (Ig) G levels and B cell-activating factor of the tumour necrosis factor family (BAFF) concentration in the serum of patients with relapsing-remitting MS (RRMS) and chronic progressive MS (CPMS), and we analysed their correlation with aspects of fatigue and other clinical disease parameters. RESULTS: A complete EBV seropositivity could be detected in our cohort. After adjusting for confounding variables and covariates, neither EBNA1 nor VCA antibody titres were associated with levels of fatigue, sleepiness, depression, or with any of the clinical values such as expanded disability status scale, lesion count, annual relapse rate, or disease duration. However, patients with RRMS had significantly higher EBNA1 IgG titre than those with CPMS, whereas this was not the case under therapies targeting CD20+ cells. BAFF levels in serum were inversely proportional to anti-EBNA1 IgG. CONCLUSIONS AND CLINICAL IMPLICATIONS: Our results show that EBNA1 IgG titre is not associated with the presence or level of fatigue. Whether the increased EBNA1 titre in RRMS plays a direct role in disease progression, or is only a consequence of excessive B cell activation, remains to be answered in future studies.

Autoimmune glomerulonephritis in a multiple sclerosis patient after cladribine treatment.

BACKGROUND: Oral cladribine is an approved disease-modifying drug for the treatment of relapsing multiple sclerosis. In controlled clinical trials as well as in post marketing safety assessments, autoimmune conditions have not yet been reported as a specific side effect of cladribine. OBJECTIVE AND RESULTS: Here, we report a case of anti-glomerular basement membrane antibody-mediated glomerulonephritis that occurred shortly after the fourth cladribine treatment cycle. CONCLUSION: Neurologists should be attentive to the development of secondary autoimmunity in cladribine-treated patients.

Lipopolysaccharide-induced sepsis-like state compromises post-ischemic neurological recovery, brain tissue survival and remodeling via mechanisms involving microvascular thrombosis and brain T cell infiltration.

Sepsis predisposes for poor stroke outcome. This association suggests that sepsis disturbs post-ischemic tissue survival and brain remodeling. To elucidate this link, we herein exposed mice to 30 min intraluminal middle cerebral artery occlusion (MCAO) and induced a sepsis-like state at 72 h post-ischemia by intraperitoneal delivery of Escherichia coli lipopolysaccharide (LPS; three doses of 0.1 or 1 mg/kg, separated by 6 h), a major component of the bacterium's outer membrane. Neurological recovery, ischemic injury, brain remodeling and immune responses were evaluated over up to 56 days post-sepsis (dps) by behavioral tests, immunohistochemistry and flow cytometry. Delivery of 1 mg/kg but not 0.1 mg/kg LPS reduced rectal temperature over 48 h by up to 3.4 ± 3.1 °C, increased general and focal neurological deficits in the Clark score over 72 h and increased motor-coordination deficits in the tight rope test over up to 21 days. Notably, 1 mg/kg, but not 0.1 mg/kg LPS increased intercellular adhesion molecule-1 abundance on ischemic microvessels, increased microvascular thrombosis and increased patrolling monocyte and T cell infiltrates in ischemic brain tissue at 3 dps. Infarct volume was increased by 1 mg/kg, but not 0.1 mg/kg LPS at 3 dps (that is, 6 days post-MCAO), as was brain atrophy at 28 and 56 dps. Microglial activation in ischemic brain tissue, evaluated by morphology analysis of Iba-1 immunostainings, was transiently increased by 0.1 and 1 mg/kg LPS at 3 dps. Our data provide evidence that neurological recovery and brain remodeling are profoundly compromised in the ischemic brain post-sepsis as a consequence of cerebral thromboinflammation.

Regulatory B cells control airway hyperreactivity and lung remodeling in a murine asthma model.

BACKGROUND: Asthma is a widespread, multifactorial chronic airway disease. The influence of regulatory B cells on airway hyperreactivity (AHR) and remodeling in asthma is poorly understood. OBJECTIVE: Our aim was to analyze the role of B cells in a house dust mite (HDM)-based murine asthma model. METHODS: The influence of B cells on lung function, tissue remodeling, and the immune response were analyzed by using wild-type and B-cell-deficient (µMT) mice and transfer of IL-10-proficient and IL-10-deficient B cells to µMT mice. RESULTS: After HDM-sensitization, both wild-type and µMT mice developed AHR, but the AHR was significantly stronger in µMT mice, as confirmed by 2 independent techniques: invasive lung function measurement in vivo and examination of precision-cut lung slices ex vivo. Moreover, airway remodeling was significantly increased in allergic µMT mice, as shown by enhanced collagen deposition in the airways, whereas the numbers of FoxP3+ and FoxP3- IL-10-secreting regulatory T cells were reduced. Adoptive transfer of IL-10-proficient but not IL-10-deficient B cells into µMT mice before HDM-sensitization attenuated AHR and lung remodeling. In contrast, FoxP3+ regulatory T cells were equally upregulated by transfer of IL-10-proficient and IL-10-deficient B cells. CONCLUSION: Our data in a murine asthma model illustrate a central role of regulatory B cells in the control of lung function and airway remodeling and may support future concepts for B-cell-targeted prevention and treatment strategies for allergic asthma.

Mesenchymal Stromal Cell-Derived Small Extracellular Vesicles Induce Ischemic Neuroprotection by Modulating Leukocytes and Specifically Neutrophils.

Background and Purpose- Small extracellular vesicles (sEVs) obtained from mesenchymal stromal cells (MSCs) were shown to induce neurological recovery after focal cerebral ischemia in rodents and to reverse postischemic lymphopenia in peripheral blood. Since peripheral blood cells, especially polymorphonuclear neutrophils (PMNs), contribute to ischemic brain injury, we analyzed brain leukocyte responses to sEVs and investigated the role of PMNs in sEV-induced neuroprotection. Methods- Male C57Bl6/j mice were exposed to transient intraluminal middle cerebral artery occlusion. After reperfusion, vehicle or sEVs prepared from conditioned media of MSCs raised from bone marrow samples of 3 randomly selected healthy human donors were intravenously administered. sEVs obtained from normoxic and hypoxic MSCs were applied. PMNs were depleted in vehicle and MSC-sEV-treated mice. Neurological deficits, ischemic injury, blood-brain barrier integrity, peripheral blood leukocyte responses, and brain leukocyte infiltration were evaluated over 72 hours. Results- sEV preparations of all 3 donors collected from normoxic MSCs significantly reduced neurological deficits. Preparations of 2 of these donors significantly decreased infarct volume and neuronal injury. sEV-induced neuroprotection was consistently associated with a decreased brain infiltration of leukocytes, namely of PMNs, monocytes/macrophages, and lymphocytes. sEVs obtained from hypoxic MSCs (1% O2) had similar effects on neurological deficits and ischemic injury as MSC-sEVs obtained under regular conditions (21% O2) but also reduced serum IgG extravasation-a marker of blood-brain barrier permeability. PMN depletion mimicked the effects of MSC-sEVs on neurological recovery, ischemic injury, and brain PMN, monocyte, and lymphocyte counts. Combined MSC-sEV administration and PMN depletion did not have any effects superior to PMN depletion in any of the readouts examined. Conclusions- Leukocytes and specifically PMNs contribute to MSC-sEV-induced ischemic neuroprotection. Individual MSC-sEV preparations may differ in their neuroprotective activities. Potency assays are urgently needed to identify their therapeutic efficacy before clinical application. Visual Overview- An online visual overview is available for this article.

FoxP3 deficiency causes no inflammation or neurodegeneration in the murine brain.

Regulatory T cells (Treg) maintain immunological self-tolerance and their functional or numerical deficits are associated with progression of several neurological diseases. We examined the effects of Treg absence on the structure and integrity of the unchallenged murine brain. When compared to control, Treg-deficient FoxP3sf mutant mice showed no differences in brain size, myelin amount and oligodendrocyte numbers. FoxP3sf strain displayed no variations in quantity of neurons and astrocytes, whereas microglia numbers were slightly reduced. We demonstrate lack of neuroinflammation and parenchymal responses in the brains of Treg-deficient mice, suggesting a minor Treg role in absence of blood-brain barrier breakdown.

IL-17 regulates DC migration to the peribronchial LNs and allergen presentation in experimental allergic asthma.

IL-17 is associated with different phenotypes of asthma, however, it is not fully elucidated how it influences induction and maintenance of asthma and allergy. In order to determine the role of IL-17 in development of allergic asthma, we used IL-17A/F double KO (IL-17A/F KO) and WT mice with or without neutralization of IL-17 in an experimental allergic asthma model and analyzed airway hyperresponsiveness, lung inflammation, T helper cell polarization, and DCs influx and activation. We report that the absence of IL-17 reduced influx of DCs into lungs and lung draining LNs. Compared to WT mice, IL-17A/F KO mice or WT mice after neutralization of IL-17A showed reduced airway hyperresponsiveness, eosinophilia, mucus hypersecretion, and IgE levels. DCs from draining LNs of allergen-challenged IL-17A/F KO mice showed a reduction in expression of migratory and costimulatory molecules CCR7, CCR2, MHC-II, and CD40 compared to WT DCs. Moreover, in vivo stimulation of adoptively transferred antigen-specific cells was attenuated in lung-draining LNs in the absence of IL-17. Thus, we report that IL-17 enhances airway DC activation, migration, and function. Consequently, lack of IL-17 leads to reduced antigen-specific T cell priming and impaired development of experimental allergic asthma.

Absence of Regulatory T Cells Causes Phenotypic and Functional Switch in Murine Peritoneal Macrophages.

Tissue macrophages are important components of tissue homeostasis and inflammatory pathologies. In the peritoneal cavity, resident macrophages interact with a variety of immune cells and can exhibit broad range of phenotypes and functions. Forkhead-box-P3 (FOXP3)+ regulatory T cells (Tregs) play an indispensable role in maintaining immunological tolerance, yet whether, and how the pathological condition that results from the lack of functional Tregs affects peritoneal macrophages (PM) is largely unknown. We used FOXP3-deficient scurfy (Sf) mice to investigate PM behavior in terms of the missing crosstalk with Tregs. Here, we report that Treg deficiency induced a marked increase in PM numbers, which was reversed after adoptive transfer of CD4+ T cells or neutralization of macrophage colony-stimulating factor. Ex vivo assays demonstrated a pro-inflammatory state of PM from Sf mice and signs of excessive activation and exhaustion. In-depth immunophenotyping of Sf PM using single-cell chipcytometry and transcriptome analysis revealed upregulation of molecules involved in the initiation of innate and adaptive immune responses. Moreover, upon transfer to non-inflammatory environment or after injection of CD4+ T cells, PM from Sf mice reprogramed their functional phenotype, indicating remarkable plasticity. Interestingly, frequencies, and immune polarization of large and small PM subsets were dramatically changed in the FOXP3-deficient mice, suggesting distinct origin and specialized function of these subsets in inflammatory conditions. Our findings demonstrate the significant impact of Tregs in shaping PM identity and dynamics. A better understanding of PM function in the Sf mouse model may have clinical implication for the treatment of immunodysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome, and other forms of immune-mediated enteropathies.

Improved protocol for simultaneous analysis of leukocyte subsets and epithelial cells from murine and human lung.

PURPOSE: To study and isolate lung cells by flow cytometry, enzymatic digestion and generation of single cell suspensions is required. This significantly influences expression of cellular epitopes and protocols need to be adapted for the best isolation and subsequent analysis of specific cellular subsets. MATERIALS AND METHODS: We optimized protocols for the simultaneous isolation and characterization of specific human and murine lung cell types. For alveolar epithelial cells (AEC), a primarily dispase based digestion method and for leukocytes, a primarily collagenase based technique was adapted. Protocols were applied in parallel in either single experimental mice or human lung specimens. RESULTS: Optimized dispase/DNase digestion yielded a high percentage of Epcam+CD45-CD31- AEC as assessed by flow cytometry. Epcam+CD45-CD3-CD11b-CD11c-CD16/32-CD19-CD31-F4/80- AEC were readily sortable with high purity and typical morphology and function upon in vitro stimulation with lipopolysaccharide or respiratory-syncytial-virus (RSV) infection. To analyze lung leukocytes, specimens were digested with an adapted collagenase/DNase protocol yielding high percentages of viable leukocytes with typical morphology, function, and preserved subset specific leukocyte markers. Both protocols could be applied simultaneously in a single experimental mouse post mortem. Application of both digestion methods in primary human lung specimens yielded similar results with high proportions of Epcam+CD45- human AEC after dispase/DNase digestion and preservation of human T cell epitopes after collagenase/DNase digestion. CONCLUSION: The here described protocols were optimized for the simple and efficient isolation of murine and human lung cells. In contrast to previously described techniques, they permit simultaneous in-depth characterization of pulmonary epithelial cells and leukocyte subsets such as T helper, cytotoxic T, and B cells from one sample. As such, they may help to comprehensively and sustainably characterize murine and human lung specimens and facilitate studies on the role of lung immune cells in different respiratory pathologies.

B cells control maternofetal priming of allergy and tolerance in a murine model of allergic airway inflammation.

BACKGROUND: Allergic asthma is a chronic lung disease resulting from inappropriate immune responses to environmental antigens. Early tolerance induction is an attractive approach for primary prevention of asthma. OBJECTIVE: We analyzed the mechanisms of perinatal tolerance induction to allergens, with particular focus on the role of B cells in preconception and early intrauterine immune priming. METHODS: Wild-type (WT) and B cell-deficient mice received ovalbumin (OVA) intranasally before mating. Their offspring were analyzed in a murine model of allergic airway inflammation. RESULTS: Although antigen application before conception protected WT progeny from allergy, it aggravated allergic airway inflammation in B cell-deficient offspring. B-cell transfer restored protection, demonstrating the crucial role of B cells in perinatal tolerance induction. Effective diaplacentar allergen transfer was detectable in pregnant WT mice but not in pregnant B-cell knockout dams, and antigen concentrations in WT amniotic fluid (AF) were higher than in IgG-free AF of B cell-deficient dams. Application of OVA/IgG immune complexes during pregnancy boosted OVA uptake by fetal dendritic cells (DCs). Fetal DCs in human subjects and mice expressed strikingly higher levels of Fcγ receptors compared with DCs from adults and were highly efficient in taking up OVA/IgG immune complexes. Moreover, murine fetal DCs effectively primed antigen-specific forkhead box P3+ regulatory T cells after in vitro coincubation with OVA/IgG-containing AF. CONCLUSION: Our data support a decisive role for B cells and immunoglobulins during in utero tolerance priming. These findings improve the understanding of perinatal immunity and might support the development of effective primary prevention strategies for allergy and asthma in the future.

Chimeric Antigen Receptor-Redirected Regulatory T Cells Suppress Experimental Allergic Airway Inflammation, a Model of Asthma.

Cellular therapy with chimeric antigen receptor (CAR)-redirected cytotoxic T cells has shown impressive efficacy in the treatment of hematologic malignancies. We explored a regulatory T cell (Treg)-based therapy in the treatment of allergic airway inflammation, a model for asthma, which is characterized by an airway hyper-reactivity (AHR) and a chronic, T helper-2 (Th2) cell-dominated immune response to allergen. To restore the immune balance in the lung, we redirected Tregs by a CAR toward lung epithelia in mice upon experimentally induced allergic asthma, closely mimicking the clinical situation. Adoptively transferred CAR Tregs accumulated in the lung and in tracheobronchial lymph nodes, reduced AHR and diminished eosinophilic airway inflammation, indicated by lower cell numbers in the bronchoalveolar lavage fluid and decreased cell infiltrates in the lung. CAR Treg cells furthermore prevented excessive pulmonary mucus production as well as increase in allergen-specific IgE and Th2 cytokine levels in exposed animals. CAR Tregs were more efficient in controlling asthma than non-modified Tregs, indicating the pivotal role of specific Treg cell activation in the affected organ. Data demonstrate that lung targeting CAR Treg cells ameliorate key features of experimental airway inflammation, paving the way for cell therapy of severe allergic asthma.

Gain-of-function STAT1 mutations are associated with intracranial aneurysms.

Chronic mucocutaneous candidiasis, characterized by persistent or recurrent fungal infections, represents the clinical hallmark in gain-of-function (GOF) signal transducer and activator of transcription 1 (STAT1) mutation carriers. Several cases of intracranial aneurysms have been reported in patients with GOF STAT1 mutation but the paucity of reported cases likely suggested this association still as serendipity. In order to endorse this association, we link the development of intracranial aneurysms with STAT1 GOF mutation by presenting the two different cases of a patient and her mother, and demonstrate upregulated phosphorylated STAT4 and IL-12 receptor ß1 upon stimulation in patient's blood cells. We also detected increased transforming growth factor (TGF)-ß type 2 receptor expression, particularly in CD14+ cells, and a slightly higher phosphorylation rate of SMAD3. In addition, the mother of the patient developed disseminated bacille Calmette-Guérin disease after vaccination, speculating that GOF STAT1 mutations may confer a predisposition to weakly virulent mycobacteria.

B cell subsets are modulated during allergic airway inflammation but are not required for the development of respiratory tolerance in a murine model.

Allergic asthma is a widespread chronic inflammatory disease of the airways. The role of different B cell subsets in developing asthma and respiratory tolerance is not well known. Especially regulatory B (Breg) cells are proposed to be important in asthma regulation. Using wild-type (WT) and B cell-deficient (µMT) mice we investigated how B cells are affected by induction of allergic airway inflammation and respiratory tolerance and whether they are necessary to develop these conditions. WT mice with an asthma-like phenotype, characterized by increased airway hyper reactivity, eosinophilic airway inflammation, mucus hypersecretion and elevated Th2 cytokines, exhibited increased MHCII and CD23 expression on follicular mature B cells in lung, bronchial lymph nodes (bLN) and spleen, which contributed to allergen-specific T cell proliferation in vitro. Germinal center B cell numbers were elevated and associated with increased production of allergen-specific immunoglobulins especially in bLN. In contrast, respiratory tolerance clearly attenuated these B cell alterations and directly enhanced marginal zone precursor B cells, which induced regulatory T cells in vitro. However, µMT mice developed asthma-like and tolerized phenotypes like WT mice. Our data indicate that although B cell subsets are affected by asthma-like and respiratory tolerant phenotypes, B cells are not required for tolerance induction.

IL-27 Is Essential for Suppression of Experimental Allergic Asthma by the TLR7/8 Agonist R848 (Resiquimod).

Different models of experimental allergic asthma have shown that the TLR7/8 agonist resiquimod (R848) is a potential inhibitor of type 2 helper cell-driven inflammatory responses. However, the mechanisms mediating its therapeutic effects are not fully understood. Using a model of experimental allergic asthma, we show that induction of IL-27 by R848 is critical for the observed ameliorative effects. R848 significantly inhibited all hallmarks of experimental allergic asthma, including airway hyperreactivity, eosinophilic airway inflammation, mucus hypersecretion, and Ag-specific Ig production. Whereas R848 significantly reduced IL-5, IL-13, and IL-17, it induced IFN-γ and IL-27. Neutralization of IL-27 completely reversed the therapeutic effect of R848 in the experimental asthma model, demonstrating dependence of R848-mediated suppression on IL-27. In vitro, R848 induced production of IL-27 by murine alveolar macrophages and dendritic cells and enhanced expression of programmed death-ligand 1, whose expression on monocytes and dendritic cells has been shown to regulate peripheral tolerance in both murine and human studies. Moreover, in vitro IL-27 enhanced secretion of IFN-γ whereas it inhibited IL-5 and IL-13, demonstrating its direct effect on attenuating Th2 responses. Taken together, our study proves that R848-mediated suppression of experimental asthma is dependent on IL-27. These data provide evidence of a central role of IL-27 for the control of Th2-mediated allergic diseases.

Monocyte/macrophage lineage commitment and distribution are affected by the lack of regulatory T cells in scurfy mice.

Foxp3(+) regulatory T (Treg) cells play a pivotal role in maintaining immunological tolerance. Loss-of-function mutations in the Foxp3 gene result in multiorgan inflammation known as immunodysregulation, polyendocrinopathy, enteropathy, X-linked syndrome in humans and scurfy (Sf) disease in mice. While the impact of missing Treg cells on adaptive immune cells is well documented, their role in regulation of myeloid cells remains unclear. Here we report that Sf mice exhibit an altered composition of stem and progenitor cells, characterized by increased numbers of myeloid precursors and higher efficiency of macrophage generation ex vivo. The proportion of monocytes/macrophages in the bone marrow, blood, and spleen was significantly elevated in Sf mice, which was accompanied with tissue-specific monocyte expression of homing receptor and phagocytic activity. Sf mice displayed high levels of M-CSF and other inflammatory cytokines, including monocyte-recruiting chemokines. Adoptive transfer of WT CD4(+) cells and in vivo neutralization of M-CSF normalized frequencies of monocyte subsets and their progenitors and reduced high levels of monocyte-related cytokines in Sf mice, while Treg cell transfer to RAG2(-/-) mice had no effect on myelopoiesis and monocyte/macrophage counts. Our findings illustrate that deregulated myelopoiesis in Sf mice is mainly caused by the inflammatory reaction resulting from the lack of Treg cells.