Respiratory virome profiles reflect antiviral immune responses.

BACKGROUND: From early life, respiratory viruses are implicated in the development, exacerbation and persistence of respiratory conditions such as asthma. Complex dynamics between microbial communities and host immune responses shape immune maturation and homeostasis, influencing health outcomes. We evaluated the hypothesis that the respiratory virome is linked to systemic immune responses, using peripheral blood and nasopharyngeal swab samples from preschool-age children in the PreDicta cohort. METHODS: Peripheral blood mononuclear cells from 51 children (32 asthmatics and 19 healthy controls) participating in the 2-year multinational PreDicta cohort were cultured with bacterial (Bacterial-DNA, LPS) or viral (R848, Poly:IC, RV) stimuli. Supernatants were analysed by Luminex for the presence of 22 relevant cytokines. Virome composition was obtained using untargeted high throughput sequencing of nasopharyngeal samples. The metagenomic data were used for the characterization of virome profiles and the presence of key viral families (Picornaviridae, Anelloviridae, Siphoviridae). These were correlated to cytokine secretion patterns, identified through hierarchical clustering and principal component analysis. RESULTS: High spontaneous cytokine release was associated with increased presence of Prokaryotic virome profiles and reduced presence of Eukaryotic and Anellovirus profiles. Antibacterial responses did not correlate with specific viral families or virome profile; however, low antiviral responders had more Prokaryotic and less Eukaryotic virome profiles. Anelloviruses and Anellovirus-dominated profiles were equally distributed among immune response clusters. The presence of Picornaviridae and Siphoviridae was associated with low interferon-λ responses. Asthma or allergy did not modify these correlations. CONCLUSION: Antiviral cytokine responses at a systemic level reflect the upper airway virome composition. Individuals with low innate interferon responses have higher abundance of Picornaviruses (mostly Rhinoviruses) and bacteriophages. Bacteriophages, particularly Siphoviridae, appear to be sensitive sensors of host antimicrobial capacity, while Anelloviruses are not correlated with TLR-induced immune responses.

Effect of Haemophilus influenzae, Streptococcus pneumoniae and influenza vaccinations on infections, immune response and asthma control in preschool children with asthma.

BACKGROUND: Haemophilus influenzae (H. influenzae), Streptococcus pneumoniae (pneumococcus) and influenza vaccines are administered in children to prevent infections caused by these pathogens. The benefits of vaccination for asthma control in children and the elicited immune response are not fully understood. This study aimed to investigate the impact of these vaccinations on respiratory infections, asthma symptoms, asthma severity and control status, pathogen colonization and in vitro immune responses to different stimulants mimicking infections in asthmatic children. METHODS: Children aged 4-6 years were recruited into the multicentre prospective PreDicta study conducted across five European countries. Information about vaccination history, infections, antibiotic use, inhaled corticosteroid (ICS) use and asthma symptoms in the last 12 months were obtained from questionnaires of the study. Nasopharyngeal samples were collected at the first visit to assess bacterial and viral colonization, and venous blood for isolation of peripheral blood mononuclear cells (PBMCs). The PBMCs were stimulated with phytohemagglutinin, R848, Poly I:C and zymosan. The levels of 22 cytokines and chemokines were measured in cell culture supernatants using a luminometric multiplex assay. RESULTS: One-hundred and forty asthmatic preschool children (5.3 ± 0.7 years) and 53 healthy children (5.0 ± 0.8 years) from the PreDicta cohort were included in the current study. Asthmatic children were associated with more frequent upper and lower respiratory infections, and more frequent and longer duration of antibiotic use compared with healthy children. In asthmatic children, sufficient H. influenzae vaccination was associated with a shorter duration of upper respiratory infection (URI) and overall use and average dose of ICS. The airway colonization was characterized by less pneumococcus and more rhinovirus. Pneumococcal vaccination was associated with a reduction in the use rate and average dose of ICS, improved asthma control, and less human enterovirus and more H. influenzae and rhinovirus (RV) airway colonization. Influenza vaccination in the last 12 months was associated with a longer duration of URI, but with a decrease in the occurrence of lower respiratory infection (LRI) and the duration of gastrointestinal (GI) infection and antibiotic use. Asthmatic preschoolers vaccinated with H. influenzae, pneumococcus or influenza presented higher levels of Th1-, Th2-, Th17- and regulatory T cells (Treg)-related cytokines in unstimulated PBMCs. Under stimulation, PBMCs from asthmatic preschoolers with pneumococcal vaccination displayed a predominant anti-inflammatory immune response, whereas PBMCs from asthmatic children with sufficient H. influenzae or influenza vaccination were associated with both pro- and anti-inflammatory immune responses. CONCLUSION: In asthmatic preschoolers, the standard childhood vaccinations to common respiratory pathogens have beneficial effects on asthma control and may modulate immune responses relevant to asthma pathogenesis.

Experimental rhinovirus infection induces an antiviral response in circulating B cells which is dysregulated in patients with asthma.

BACKGROUND: Rhinoviruses are the predominant cause of respiratory viral infections and are strongly associated with asthma exacerbations. While humoral immunity plays an important role during virus infections, cellular aspects of this response are less well understood. Here, we investigated the antiviral response of circulating B cells upon experimental rhinovirus infection in healthy individuals and asthma patients. METHODS: We purified B cells from experimentally infected healthy individuals and patients with asthma and subjected them to total RNA-sequencing. Rhinovirus-derived RNA was measured in isolated B cells using a highly sensitive PCR. B cells were stimulated with rhinovirus in vitro to further study gene expression, expression of antiviral proteins and B-cell differentiation in response rhinovirus stimulation. Protein expression of pro-inflammatory cytokines in response to rhinovirus was assessed using a proximity extension assay. RESULTS: B cells isolated from experimentally infected subjects exhibited an antiviral gene profile linked to IFN-alpha, carried viral RNA in vivo and were transiently infected by rhinovirus in vitro. B cells rapidly differentiated into plasmablasts upon rhinovirus stimulation. While B cells lacked expression of interferons in response to rhinovirus exposure, co-stimulation with rhinovirus and IFN-alpha upregulated pro-inflammatory cytokine expression suggesting a potential new function of B cells during virus infections. Asthma patients showed extensive upregulation and dysregulation of antiviral gene expression. CONCLUSION: These findings add to the understanding of systemic effects of rhinovirus infections on B-cell responses in the periphery, show potential dysregulation in patients with asthma and might also have implications during infection with other respiratory viruses.

Physical activity in asthma control and its immune modulatory effect in asthmatic preschoolers.

BACKGROUND: The impact of physical activity on immune response is a hot topic in exercise immunology, but studies involving asthmatic children are scarce. Our aims were to examine whether there were any differences in the level of physical activity and daily TV attendance, to assess its role on asthma control and immune responses to various immune stimulants. METHODS: Weekly physical activity and daily television attendance were obtained from questionnaires at inclusion of the PreDicta study. PBMC cultures were stimulated with phytohemagglutinin (PHA), R848, poly I:C, and zymosan. A panel of cytokines was measured and quantified in cell culture supernatants using luminometric multiplex immunofluorescence beads-based assay. RESULTS: Asthmatic preschoolers showed significantly more TV attendance than their healthy peers (58.6% vs. 41.5% 1-3 h daily and only 25.7% vs. 47.2% ≤1 h daily) and poor asthma control was associated with less frequent physical activity (PA) (75% no or occasional activity in uncontrolled vs. 20% in controlled asthma; 25% ≥3 times weekly vs. 62%). Asthmatics with increased PA exhibited elevated cytokine levels in response to polyclonal stimulants, suggesting a readiness of circulating immune cells for type 1, 2, and 17 cytokine release compared to subjects with low PA and high TV attendance. This may also represent a proinflammatory state in high PA asthmatic children. Low physical activity and high TV attendance were associated with a decrease in proinflammatory cytokines. Proinflammatory cytokines were correlating with each other in in vitro immune responses of asthmatic children, but not healthy controls, this correlation was more pronounced in children with sedentary behavior. CONCLUSION: Asthmatic children show more sedentary behavior than healthy subjects, while poor asthma control is associated with a substantial decrease in physical activity. Our results suggest that asthmatic children may profit from regular exercise, as elevated cytokine levels in stimulated conditions indicate an immune system prepared for responding strongly in case of different types of infections. However, it has to be considered that a hyperinflammatory state in high PA may not be beneficial in asthmatic children.

TLR7/8 regulates type I and type III interferon signalling in rhinovirus 1b-induced allergic asthma.

INTRODUCTION: Interferon (IFN) responses have been reported to be defective in rhinovirus (RV)-induced asthma. The heterodimeric receptor of type I IFN (IFN-α/ß) is composed of IFN-αR1 and IFN-αR2. Ligand binding to the IFN-α/ß receptor complex activates signal transducer and activator of transcription (STAT) proteins STAT1 and STAT2 intracellularly. Although type III IFN (IFN-λ) binds to a different receptor containing IFN-λR1 and interleukin-10R2, its triggering leads to activation of the same downstream transcription factors. Here, we analysed the effects of RV on IFN type I and III receptors, and asked about possible Toll-like receptor 7/8 (TLR7/8) agonist R848-mediated IFN-αR1 and IFN-λR1 regulation. METHODS: We measured IFN-α, IFN-ß and IFN-λ and their receptor levels in peripheral blood mononuclear cell (PBMC) supernatants and cell pellets stimulated with RV1b and R848 in two cohorts of children with and without asthma recruited at pre-school age (PreDicta) and at primary school age (AGENDAS) as well as in cell supernatants from total lung cells isolated from mice. RESULTS: We observed that R848 induced IFN-λR mRNA expression in PBMCs of healthy and asthmatic children, but suppressed IFN-αR mRNA levels. In murine lung cells, RV1b alone and together with R848 suppressed IFN-αR protein in T-cells compared with controls and in total lung IFN-λR mRNA compared with RV1b infection alone. CONCLUSIONS: In PBMCs from pre-school age children, IFN-αR mRNA was reduced and IFN-λR1 mRNA was induced upon treatment with the TLR7/8 agonist R848, thus suggesting new avenues for induction of antiviral immune responses in paediatric asthma.

An Exopolysaccharide Produced by Bifidobacterium longum 35624® Inhibits Osteoclast Formation via a TLR2-Dependent Mechanism.

The probiotic Bifidobacterium longum subsp. longum 35624® (B. longum 35624®), with its surface exopolysaccharide (EPS624), has previously been demonstrated to induce immunoregulatory responses in the host and may, therefore, be a novel approach to prevent bone loss in inflammatory conditions such as post-menopausal osteoporosis (PMO). The aim of this study was to investigate the effect of EPS624 on osteoclast and osteoblast differentiation and to assess the potential of B. longum 35624® to prevent bone loss in vivo. In vitro cell assays were used to assess the impact of EPS624 on osteoclast and osteoblast differentiation. The potential of two probiotic B. longum 35624® strains, including an EPS-deficient strain, for preventing ovariectomy (Ovx)-induced bone loss was assessed in a murine model. EPS624 prevented osteoclast formation from murine bone marrow precursors under both normal and TNFα-induced inflammatory conditions and modestly increased mineralized matrix deposition in osteogenic cell cultures. However, in the presence of an anti-TLR2 blocking antibody, or in MyD88-/- osteoclast precursors, the inhibitory effect of EPS624 on osteoclast formation was diminished or completely prevented, respectively. Moreover, EPS624 induced IL-10 production in osteoclast precursors in a TLR2-dependent manner, although IL-10 was dispensable in the EPS624-mediated inhibition of osteoclast formation. In addition, EPS624-producing B. longum 35624® partially prevented bone loss in Ovx mice when administered by oral gavage. This study introduced EPS624 as a potential anti-resorptive therapy, although optimal in vivo delivery of the probiotic strain for treating low-grade inflammatory diseases such as PMO remains to be determined.

Human CD40 ligand-expressing type 3 innate lymphoid cells induce IL-10-producing immature transitional regulatory B cells.

BACKGROUND: Type 3 innate lymphoid cells (ILC3s) are involved in maintenance of mucosal homeostasis; however, their role in immunoregulation has been unknown. Immature transitional regulatory B (itBreg) cells are innate-like B cells with immunosuppressive properties, and the in vivo mechanisms by which they are induced have not been fully clarified. OBJECTIVE: We aimed to investigate the ILC3-B-cell interaction that probably takes place in human tonsils. METHODS: ILC3s were isolated from peripheral blood and palatine tonsils, expanded, and cocultured with naive B cells. Tonsillar ILC3s and regulatory B cells were visualized with immunofluorescence histology. ILC3 frequencies were measured in tonsil tissue of allergic and nonallergic patients and in peripheral blood of allergic asthmatic patients and healthy control subjects. RESULTS: A mutually beneficial relationship was revealed between ILC3s and B cells: ILC3s induced IL-15 production in B cells through B cell-activating factor receptor, whereas IL-15, a potent growth factor for ILC3s, induced CD40 ligand (CD40L) expression on circulating and tonsillar ILC3s. IL-15-activated CD40L+ ILC3s helped B-cell survival, proliferation, and differentiation of IL-10-secreting, PD-L1-expressing functional itBreg cells in a CD40L- and B cell-activating factor receptor-dependent manner. ILC3s and regulatory B cells were in close connection with each other in palatine tonsils. ILC3 frequency was reduced in tonsil tissue of allergic patients and in peripheral blood of allergic asthmatic patients. CONCLUSION: Human CD40L+ ILC3s provide innate B-cell help and are involved in an innate immunoregulatory mechanism through induction of itBreg cell differentiation, which takes place in palatine tonsils in vivo. This mechanism, which can contribute to maintenance of immune tolerance, becomes insufficient in allergic diseases.

Role of regulatory B cells in immune tolerance to allergens and beyond.

Immune tolerance to both self-antigens and innocuous non-self-antigens is essential to protect the host against chronic inflammatory diseases and tissue damage. A wide range of cell types and suppressive molecules are involved in induction and maintenance of tolerance. In addition to their key function in the production of immunoglobulins, B cells can regulate immune responses through their surface molecules and secretion of cytokines. Regulatory B (Breg) cells are characterized by their immunosuppressive capacity, which is often mediated through IL-10 secretion. However, IL-35 and TGF-ß have also been associated with B cell-mediated immunosuppression. Several types of murine and human Breg cells have been described, such as mouse CD5(+)CD1d(hi) B10 cells, CD21(hi)CD23(hi)CD24(hi) transitional stage 2-like B cells, and CD138(+) plasma cells and plasmablasts. Human Breg cell types include CD27(+)CD24(high) B10 cells, CD24(hi)CD38(hi) immature transitional B cells, and CD73(-)CD25(+)CD71(+) BR1 cells and a subset of plasma cells. Support for the in vivo existence of allergen-specific human Breg cells comes from direct detection of their increase during the course of allergen-specific immunotherapy, as well as their increased expression in nonallergic but high-dose allergen-exposed beekeepers. Human BR1 cells selectively upregulate IgG4 antibodies on differentiation to plasma cells. This suggests an additional immune regulatory role because of the noninflammatory and blocking antibody function of IgG4. Taken together, Breg cells appear to be involved in mediating allergen tolerance, but many open questions remain to be answered.

Interleukins (from IL-1 to IL-38), interferons, transforming growth factor ß, and TNF-α: Receptors, functions, and roles in diseases.

There have been extensive developments on cellular and molecular mechanisms of immune regulation in allergy, asthma, autoimmune diseases, tumor development, organ transplantation, and chronic infections during the last few years. Better understanding the functions, reciprocal regulation, and counterbalance of subsets of immune and inflammatory cells that interact through interleukins, interferons, TNF-α, and TGF-ß offer opportunities for immune interventions and novel treatment modalities in the era of development of biological immune response modifiers particularly targeting these molecules or their receptors. More than 60 cytokines have been designated as interleukins since the initial discoveries of monocyte and lymphocyte interleukins (called IL-1 and IL-2, respectively). Studies of transgenic or gene-deficient mice with altered expression of these cytokines or their receptors and analyses of mutations and polymorphisms in human genes that encode these products have provided essential information about their functions. Here we review recent developments on IL-1 to IL-38, TNF-α, TGF-ß, and interferons. We highlight recent advances during the last few years in this area and extensively discuss their cellular sources, targets, receptors, signaling pathways, and roles in immune regulation in patients with allergy and asthma and other inflammatory diseases.

IL-10-overexpressing B cells regulate innate and adaptive immune responses.

BACKGROUND: Distinct human IL-10-producing B-cell subsets with immunoregulatory properties have been described. However, the broader spectrum of their direct cellular targets and suppressive mechanisms has not been extensively studied, particularly in relation to direct and indirect IL-10-mediated functions. OBJECTIVE: The aim of the study was to investigate the effects of IL-10 overexpression on the phenotype and immunoregulatory capacity of B cells. METHODS: Primary human B cells were transfected with hIL-10, and IL-10-overexpressing B cells were characterized for cytokine and immunoglobulin production by means of specific ELISA and bead-based assays. Antigen presentation, costimulation capacity, and transcription factor signatures were analyzed by means of flow cytometry and quantitative RT-PCR. Effects of IL-10-overexpresing B cells on Toll-like receptor-triggered cytokine release from PBMCs, LPS-triggered maturation of monocyte-derived dendritic cells, and tetanus toxoid-induced PBMC proliferation were assessed in autologous cocultures. RESULTS: IL-10-overexpressing B cells acquired a prominent immunoregulatory profile comprising upregulation of suppressor of cytokine signaling 3 (SOCS3), glycoprotein A repetitions predominant (GARP), the IL-2 receptor α chain (CD25), and programmed cell death 1 ligand 1 (PD-L1). Concurrently, their secretion profile was characterized by a significant reduction in levels of proinflammatory cytokines (TNF-α, IL-8, and macrophage inflammatory protein 1α) and augmented production of anti-inflammatory IL-1 receptor antagonist and vascular endothelial growth factor. Furthermore, IL-10 overexpression was associated with a decrease in costimulatory potential. IL-10-overexpressing B cells secreted less IgE and potently suppressed proinflammatory cytokines in PBMCs, maturation of monocyte-derived dendritic cells (rendering their profile to regulatory phenotype), and antigen-specific proliferation in vitro. CONCLUSION: Our data demonstrate an essential role for IL-10 in inducing an immunoregulatory phenotype in B cells that exerts substantial anti-inflammatory and immunosuppressive functions.

IgG4 production is confined to human IL-10-producing regulatory B cells that suppress antigen-specific immune responses.

BACKGROUND: IL-10-producing regulatory B cells suppress immune responses, and lack of these cells leads to exacerbated symptoms in mouse models of chronic inflammation, transplantation, and chronic infection. IgG4 is a blocking antibody isotype with anti-inflammatory potential that is induced in human high-dose antigen tolerance models. OBJECTIVE: We sought to characterize human inducible IL-10-secreting B regulatory 1 (BR1) cells and to investigate their immunoregulatory capacity through suppression of cellular immune responses and production of anti-inflammatory immunoglobulins. METHODS: Highly purified IL-10-secreting B cells were phenotypically and functionally characterized by means of whole-genome expression analysis, flow cytometry, suppression assay, and antibody production. B cells specific for the major bee venom allergen phospholipase A2 (PLA) were isolated from beekeepers who displayed tolerance to bee venom antigens and allergic patients before and after specific immunotherapy. RESULTS: Human IL-10+ BR1 cells expressed high surface CD25 and CD71 and low CD73 levels. Sorting of CD73-CD25+CD71+ B cells allowed enrichment of human BR1 cells, which produced high levels of IL-10 and potently suppressed antigen-specific CD4+ T-cell proliferation. IgG4 was selectively confined to human BR1 cells. B cells specific for the major bee venom allergen PLA isolated from nonallergic beekeepers show increased expression of IL-10 and IgG4. Furthermore, the frequency of IL-10+ PLA-specific B cells increased in allergic patients receiving allergen-specific immunotherapy. CONCLUSION: Our data show the characterization of IL-10+ BR1 cells and in vivo evidence for 2 essential features of allergen tolerance: the suppressive B cells and IgG4-expressing B cells that are confined to IL-10+ BR1 cells in human subjects.

Macrolactonolides: a novel class of anti-inflammatory compounds.

A new concept in design of safe glucocorticoid therapy was introduced by conjugating potent glucocorticoid steroids with macrolides (macrolactonolides). These compounds were synthesized from various steroid 17ß-carboxylic acids and 9a-N-(3-aminoalkyl) derivatives of 9-deokso-9a-aza-9a-homoeritromicin A and 3-descladinosyl-9-deokso-9a-aza-9a-homoeritromicin A using stable alkyl chain. Combining property of macrolides to preferentially accumulate in immune cells, especially in phagocyte cells, with anti-inflammatory activity of classic steroids, we designed molecules which showed good anti-inflammatory activity in ovalbumin (OVA) induced asthma in rats. The synthesis, in vitro and in vivo anti-inflammatory activity of this novel class of compounds are described.

Fracture biomechanics influence local and systemic immune responses in a murine fracture-related infection model.

Biomechanical stability plays an important role in fracture healing, with unstable fixation being associated with healing disturbances. A lack of stability is also considered a risk factor for fracture-related infection (FRI), although confirmatory studies and an understanding of the underlying mechanisms are lacking. In the present study, we investigate whether biomechanical (in)stability can lead to altered immune responses in mice under sterile or experimentally inoculated conditions. In non-inoculated C57BL/6 mice, instability resulted in an early increase of inflammatory markers such as granulocyte-colony stimulating factor (G-CSF), keratinocyte chemoattractant (KC) and interleukin (IL)-6 within the bone. When inoculated with Staphylococcus epidermidis, instability resulted in a further significant increase in G-CSF, IL-6 and KC in bone tissue. Staphylococcus aureus infection led to rapid osteolysis and instability in all animals and was not further studied. Gene expression measurements also showed significant upregulation in CCL2 and G-CSF in these mice. IL-17A was found to be upregulated in all S. epidermidis infected mice, with higher systemic IL-17A cell responses in mice that cleared the infection, which was found to be produced by CD4+ and γδ+ T cells in the bone marrow. IL-17A knock-out (KO) mice displayed a trend of delayed clearance of infection (P=0.22, Fisher's exact test) and an increase in interferon (IFN)-γ production. Biomechanical instability leads to a more pronounced local inflammatory response, which is exaggerated by bacterial infection. This study provides insights into long-held beliefs that biomechanics are crucial not only for fracture healing, but also for control of infection.

Regulated on Activation, Normal T cell Expressed and Secreted (RANTES) drives the resolution of allergic asthma.

RANTES is implicated in allergic asthma and in T cell-dependent clearance of infection. RANTES receptor family comprises CCR1, CCR3, and CCR5, which are G-protein-coupled receptors consisting of seven transmembrane helices. Infections with respiratory viruses like Rhinovirus cause induction of RANTES production by epithelial cells. Here, we studied the role of RANTES in the peripheral blood mononuclear cells in cohorts of children with and without asthma and validated and extended this study to the airways of adults with and without asthma. We further translated these studies to a murine model of asthma induced by house dust mite allergen in wild-type RANTES and CCR5-deficient mice. Here we show an unpredicted therapeutic role of RANTES in the resolution of allergen-induced asthma by orchestrating the transition of effector GATA-3+CD4+ T cells into immune-regulatory-type T cells and inflammatory eosinophils into resident eosinophils as well as increased IL-10 production in the lung.

Role of nuclear factor of activated T cells 2 (NFATc2) in allergic asthma.

BACKGROUND: We recently described increased NFATc1, IRF4, and NIP45 messenger RNA (mRNA) expression in peripheral blood mononuclear cells (PBMCs) of asthmatic children and adults with multiple allergies. OBJECTIVE: NFATc2 has been described to associate with IRF4 to induce interleukin-4, and to be inhibited by T-bet. Here, we analyzed the role of NFATc2 in asthmatic children and adults. METHODS: PBMCs were isolated from the blood of control of asthmatics subjects. Some PBMCs were analyzed untreated and some cultured with and without phytohemagglutinin. Then, RNA was extracted from the cells and cytokines were measured in the supernatants via enzyme-linked immunosorbent assay or multiplex analysis. RNA was then reverse-transcribed and NFATc1, NFATC2, IRF4, and T-bet mRNA were analyzed by real-time polymerase chain reaction. In addition, in peripheral blood cells, NFATc2 expression was analyzed, in a population of asthmatic children and adults from the Asthma BRIDGE study. RESULTS: In addition to NFATc1 and NIP45, also NFATc2 was found upregulated in PBMCs and peripheral blood cells from asthmatic children and adults with allergic asthma. Moreover, NFATc1 directly correlated with lymphocytes number whereas NFATc2 correlated with peripheral eosinophilia in asthma. CONCLUSIONS: In addition to NFATc1 and NIP45, NFATc2 was found upregulated in asthma. Moreover, NFATc1 mRNA correlated with lymphocytes both in control and asthma, and NFATC1 and NFATc2 mRNA showed a direct correlation with eosinophils in controls but not in asthma, indicating that NFATc1 is associated with lymphocytes and not eosinophils in asthma. CLINICAL SIGNIFICANCE: Targeting NFATc2 in T lymphocytes might ameliorate the allergic phenotype in asthmatic subjects.

A novel proangiogenic B cell subset is increased in cancer and chronic inflammation.

B cells contribute to immune responses through the production of immunoglobulins, antigen presentation, and cytokine production. Several B cell subsets with distinct functions and polarized cytokine profiles have been reported. In this study, we used transcriptomics analysis of immortalized B cell clones to identify an IgG4+ B cell subset with a unique function. These B cells are characterized by simultaneous expression of proangiogenic cytokines including VEGF, CYR61, ADM, FGF2, PDGFA, and MDK. Consequently, supernatants from these clones efficiently promote endothelial cell tube formation. We identified CD49b and CD73 as surface markers identifying proangiogenic B cells. Circulating CD49b+CD73+ B cells showed significantly increased frequency in patients with melanoma and eosinophilic esophagitis (EoE), two diseases associated with angiogenesis. In addition, tissue-infiltrating IgG4+CD49b+CD73+ B cells expressing proangiogenic cytokines were detected in patients with EoE and melanoma. Our results demonstrate a previously unidentified proangiogenic B cell subset characterized by expression of CD49b, CD73, and proangiogenic cytokines.

In vitro simulation of the early proinflammatory phase in fracture healing reveals strong immunomodulatory effects of CD146-positive mesenchymal stromal cells.

The impact of microenvironmental cues and changes due to injury on the phenotype and fate of mesenchymal stromal cells (MSCs) is poorly understood. Here, we aimed to simulate the microenvironment associated with the early stage of bone healing in vitro and to study the regenerative response of MSCs. We enriched CD146+ MSCs from the human bone marrow. Different physiological and pathological microenvironments were simulated by using conditioned medium (CM) from human endothelial cells and osteoblasts (healthy bone), femoral head-derived bone fragments (injured bone), and activated platelets (platelet-rich plasma [PRP], injury). Cells were incubated in CM and analyzed with respect to proliferation, gene expression, migration, osteogenic differentiation, and their effect on polyclonally induced proliferation of peripheral blood mononuclear cells. CD146+ MSCs showed a specific response to different microenvironments. Cell proliferation was observed in all media with the highest values in PRP-CM and injured bone-CM. Gene expression analysis revealed the upregulation of chemokines, proinflammatory, proangiogenic, and genes involved in immunomodulation in cells stimulated with PRP- and injured bone-CM, suggesting strong paracrine activity. PRP-CM led to pronounced inhibition of lymphocyte proliferation by CD146+MSCs. Our results indicate that a microenvironment simulating bone injury elicits strong immunomodulatory and proangiogenic activity of CD146+ MSCs. This suggests that in the early stage of bone healing, the prime function of MSCs and their CD146+ subpopulation is in regulating the immune response and inducing neovascularization. Future studies will investigate the key components in CM driving this function, which might be potential targets to therapeutically stimulate the regenerative potential of MSCs.

Humoral Factors From Musculoskeletal Polytrauma Patients Impair Antibacterial Responses Of Neutrophils In vitro.

Polytrauma is associated with increased risk of sepsis, but the risk for implant infection is less clear. Neutrophil antibacterial responses are significantly reduced in polytrauma patients (n= 9, ISS≥15) for at least 5 days compared to healthy controls. Reduced neutrophil activity could influence implant infection in addition to sepsis.

Diagnostic challenges and future perspectives in fracture-related infection.

Fracture-related infection (FRI) is one of the most challenging complications in orthopaedic trauma surgery. It has severe consequences for patients and an important socio-economic impact. FRI has distinct properties and needs to be addressed interdisciplinary. Since criteria for the diagnosis of FRI are not standardized, an expert panel recently proposed a definition for FRI. In this review the current diagnostic modalities and an interdisciplinary diagnostic algorithm based on this recently published definition, are presented and future diagnostic techniques discussed. Since to date, there is no single universal diagnostic test available that gives the clinician the definitive diagnosis of FRI, it is mandatory to follow a standardized diagnostic algorithm to correctly diagnose FRI.