The CD11/CD18 (beta2) integrins modulate neutrophil caspase activation and survival following TNF-alpha or endotoxin induced transendothelial migration

Deletion of Tmem268 in mice suppresses anti-infectious immune responses by downregulating CD11b signaling

Transmembrane protein 268 (TMEM268) is a novel, tumor growth-related protein first reported by our laboratory. It interacts with the integrin subunit β4 (ITGB4) and plays a positive role in the regulation of the ITGB4/PLEC signaling pathway. Here, we investigated the effects and mechanism of TMEM268 in anti-infectious immune response in mice. Tmem268 knockout in mice aggravated cecal ligation and puncture-induced sepsis, as evidenced by higher bacterial burden in various tissues and organs, congestion, and apoptosis. Moreover, Tmem268 deficiency in mice inhibited phagocyte adhesion and migration, thus decreasing phagocyte infiltration at the site of infection and complement-dependent phagocytosis. Further findings indicated that TMEM268 interacts with CD11b and inhibits its degradation via the endosome-lysosome pathway. Our results reveal a positive regulatory role of TMEM268 in β2 integrin-associated anti-infectious immune responses and signify the potential value of targeting the TMEM268-CD11b signaling axis for the maintenance of immune homeostasis and immunotherapy for sepsis and related immune disorders.

Clinical relevance of neutrophil/lymphocyte ratio combined with APACHEII for prognosis of severe heatstroke

We evaluated clinical implication of neutrophil-lymphocyte ratio (NLR) for severe heatstroke and predictive value of combined acute physiology and chronic health evaluation (APACHEII) score for prognosis of severe heatstroke. Retrospectively, we studied 185 individuals that have been admitted at emergency department for severe heatstroke. On the basis of their prognosis, we sorted the patients into two categories, namely non-survival (n = 43) and survival groups (n = 142). The primary outcome was 30-day mortality. A considerably higher NLR was observed among the non-survivors compared to survivors (P < 0.05). After correction for confounders, statistical analysis using multi-variable Cox regression indicated NLR as an independent risk factor for patient death (HR = 1.167, 95%CI = 1.110-1.226, P < 0.001). Through receiver-operating characteristics (ROC) curve, we estimated area-under the curve (AUC) of NLR to be 0.7720 (95% CI [0.6953, 0.8488]). Also, transformation of NLR into a profile type analysis showed that the marker remained a risk factor for death, which showed trend variation (P for trend <0.001). Subgroup forest plot analysis showed robustness in the predictive ability of NLR after exclusion of confounders. Besides, we demonstrated through Kaplan-Meier (KM) survival analysis curve that high risk NLR mortality substantially exceeded low risk NLR. The combined prediction of NLR and APACHEII achieved higher efficacy than NLR and APACHEII alone (AUC = 0.880, 95% CI [0.8280, 0.9290]). Additionally, Delong test indicated that the combined prediction demonstrated a significantly greater ROC than NLR and APACHEII alone, while DCA showed a considerably higher clinical net benefit rate. Increased NLR is a high risk factor and has predictive value for death in individuals with severe heatstroke. Suggestively, combination of NLR and APACHEII have greater predictive value.

Neutrophil-Specific Knockdown of β2 Integrins Impairs Antifungal Effector Functions and Aggravates the Course of Invasive Pulmonal Aspergillosis

β2-integrins are heterodimeric surface receptors that are expressed specifically by leukocytes and consist of a variable α (CD11a-d) and a common β-subunit (CD18). Functional impairment of CD18, which causes leukocyte adhesion deficiency type-1 results in an immunocompromised state characterized by severe infections, such as invasive pulmonary aspergillosis (IPA). The underlying immune defects have largely been attributed to an impaired migratory and phagocytic activity of polymorphonuclear granulocytes (PMN). However, the exact contribution of β2-integrins for PMN functions in-vivo has not been elucidated yet, since the mouse models available so far display a constitutive CD18 knockout (CD18^-/- or CD18^hypo). To determine the PMN-specific role of β2-integrins for innate effector functions and pathogen control, we generated a mouse line with a Ly6G-specific knockdown of the common β-subunit (CD18^Ly6G cKO). We characterized CD18^Ly6G cKO mice in-vitro to confirm the PMN-specific knockdown of β2-integrins. Next, we investigated the clinical course of IPA in A. fumigatus infected CD18^Ly6G cKO mice with regard to the fungal burden, pulmonary inflammation and PMN response towards A. fumigatus. Our results revealed that the β2-integrin knockdown was restricted to PMN and that CD18^Ly6G cKO mice showed an aggravated course of IPA. In accordance, we observed a higher fungal burden and lower levels of proinflammatory innate cytokines, such as TNF-α, in lungs of IPA-infected CD18^Ly6G cKO mice. Bronchoalveolar lavage revealed higher levels of CXCL1, a stronger PMN-infiltration, but concomitantly elevated apoptosis of PMN in lungs of CD18^Ly6G cKO mice. Ex-vivo analysis further unveiled a strong impairment of PMN effector function, as reflected by an attenuated phagocytic activity, and a diminished generation of reactive oxygen species (ROS) and neutrophil-extracellular traps (NET) in CD18-deficient PMN. Overall, our study demonstrates that β2-integrins are required specifically for PMN effector functions and contribute to the clearance of A. fumigatus by infiltrating PMN, and the establishment of an inflammatory microenvironment in infected lungs.

β2 Integrin Regulation of Neutrophil Functional Plasticity and Fate in the Resolution of Inflammation

Neutrophils act as the first line of cellular defense against invading pathogens or tissue injury. Their rapid recruitment into inflamed tissues is critical for the elimination of invading microorganisms and tissue repair, but is also capable of inflicting damage to neighboring tissues. The β₂ integrins and Mac-1 (CD11b/CD18, α_Mβ₂ or complement receptor 3) in particular, are best known for mediating neutrophil adhesion and transmigration across the endothelium and phagocytosis of microbes. However, Mac-1 has a broad ligand recognition property that contributes to the functional versatility of the neutrophil population far beyond their antimicrobial function. Accumulating evidence over the past decade has demonstrated roles for Mac-1 ligands in regulating reverse neutrophil transmigration, lifespan, phagocytosis-induced cell death, release of neutrophil extracellular traps and efferocytosis, hence extending the traditional β₂ integrin repertoire in shaping innate and adaptive immune responses. Understanding the functions of β₂ integrins may partly explain neutrophil heterogeneity and may be instrumental to develop novel therapies specifically targeting Mac-1-mediated pro-resolution actions without compromising immunity. Thus, this review details novel insights on outside-in signaling through β₂ integrins and neutrophil functional heterogeneity pertinent to the resolution of inflammation.

Network mapping of primary CD34+ cells by Ampliseq based whole transcriptome targeted resequencing identifies unexplored differentiation regulatory relationships

With the exception of a few master transcription factors, regulators of neutrophil maturation are poorly annotated in the intermediate phenotypes between the granulocyte-macrophage progenitor (GMP) and the mature neutrophil phenotype. Additional challenges in identifying gene expression regulators in differentiation pathways relate to challenges wherein starting cell populations are heterogeneous in lineage potential and development, are spread across various states of quiescence, as well as sample quality and input limitations. These factors contribute to data variability make it difficult to draw simple regulatory inferences. In response we have applied a multi-omics approach using primary blood progenitor cells primed for homogeneous proliferation and granulocyte differentiation states which combines whole transcriptome resequencing (Ampliseq RNA) supported by droplet digital PCR (ddPCR) validation and mass spectrometry-based proteomics in a hypothesis-generation study of neutrophil differentiation pathways. Primary CD34+ cells isolated from human cord blood were first precultured in non-lineage driving medium to achieve an active, proliferating phenotype from which a neutrophil primed progenitor was isolated and cultured in neutrophil lineage supportive medium. Samples were then taken at 24-hour intervals over 9 days and analysed by Ampliseq RNA and mass spectrometry. The Ampliseq dataset depth, breadth and quality allowed for several unexplored transcriptional regulators and ncRNAs to be identified using a combinatorial approach of hierarchical clustering, enriched transcription factor binding motifs, and network mapping. Network mapping in particular increased comprehension of neutrophil differentiation regulatory relationships by implicating ARNT, NHLH1, PLAG1, and 6 non-coding RNAs associated with PU.1 regulation as cell-engineering targets with the potential to increase total neutrophil culture output. Overall, this study develops and demonstrates an effective new hypothesis generation methodology for transcriptome profiling during differentiation, thereby enabling identification of novel gene targets for editing interventions.

CD11b Regulates Fungal Outgrowth but Not Neutrophil Recruitment in a Mouse Model of Invasive Pulmonary Aspergillosis

ß2 integrin receptors consist of an alpha subunit (CD11a-CD11d) and CD18 as the common beta subunit, and are differentially expressed by leukocytes. ß2 integrins are required for cell-cell interaction, transendothelial migration, uptake of opsonized pathogens, and cell signaling processes. Functional loss of CD18—termed leukocyte-adhesion deficiency type 1 (LAD1)—results in an immunocompromised state characterized by frequent occurrence of severe infections. In immunosuppressed individuals Aspergillus fumigatus is a frequent cause of invasive pulmonary fungal infection, and often occurs in patients suffering from LAD1. Here, we asked for the importance of CD11b/CD18 also termed MAC-1 which is required for phagocytosis of opsonized A. fumigatus conidia by polymorphonuclear neutrophils (PMN) for control of pulmonary A. fumigatus infection. We show that CD11b^−/− mice infected with A. fumigatus were unaffected in long term survival, similar to wild type (WT) mice. However, bronchoalveolar lavage (BAL) performed 1 day after infection revealed a higher lung infiltration of PMN in case of infected CD11b^−/− mice than observed for WT mice. BAL derived from infected CD11b^−/− mice also contained a higher amount of leukocyte-attracting CCL5 chemokine, but lower amounts of proinflammatory innate cytokines. In accordance, lung tissue of A. fumigatus infected CD11b^−/− mice was characterized by lower cellular inflammation, and a higher fungal burden. In agreement, CD11b^−/−PMN exerted lower phagocytic activity on serum-opsonized A. fumigatus conidia than WT PMN in vitro. Our study shows that MAC-1 is required for effective clearance of A. fumigatus by infiltrating PMN, and the establishment of an inflammatory microenvironment in infected lung. Enhanced infiltration of CD11b^−/− PMN may serve to compensate impaired PMN function.

Effects of spermine on liver barrier function, amino acid transporters, immune status, and apoptosis in piglets

This study investigated the effects of spermine supplementation and its extended duration on amino acid transporters, immune status, barrier function, and apoptosis in the liver.

Targeting junctional adhesion molecule-C ameliorates sepsis-induced acute lung injury by decreasing CXCR4+ aged neutrophils

Sepsis is a severe inflammatory condition associated with high mortality. Transmigration of neutrophils into tissues increases their lifespan to promote deleterious function. Junctional adhesion molecule-C (JAM-C) plays a pivotal role in neutrophil transmigration into tissues. We aim to study the role of JAM-C on the aging of neutrophils to cause sepsis-induced acute lung injury (ALI). Sepsis was induced in C57BL/6J mice by cecal ligation and puncture (CLP) and JAM-C expression in serum was assessed. Bone marrow-derived neutrophils (BMDN) were treated with recombinant mouse JAM-C (rmJAM-C) ex vivo and their viability was assessed. CLP-operated animals were administrated with either isotype IgG or anti-JAM-C Ab at a concentration of 3 mg/kg and after 20 h, aged neutrophils (CXCR4⁺ ) were assessed in blood and lungs and correlated with systemic injury and inflammatory markers. Soluble JAM-C level in serum was up-regulated during sepsis. Treatment with rmJAM-C inhibited BMDN apoptosis, thereby increasing their lifespan. CLP increased the frequencies of CXCR4⁺ neutrophils in blood and lungs, while treatment with anti-JAM-C Ab significantly reduced the frequencies of CXCR4⁺ aged neutrophils. Treatment with anti-JAM-C Ab significantly reduced systemic injury markers (alanine aminotransferase, aspartate aminotransferase, and lactate dehydrogenase) as well as systemic and lung inflammatory cytokines (IL-6 and IL-1β) and chemokine (macrophage inflammatory protein-2). The blockade of JAM-C improved lung histology and reduced neutrophil contents in lungs of septic mice. Thus, reduction of the pro-inflammatory aged neutrophils by blockade of JAM-C has a novel therapeutic potential in sepsis-induced ALI.

Role of LFA-1 and ICAM-1 in Cancer

The lymphocyte function-associated antigen-1 (LFA-1) (also known as CD11a/CD18 and α_Lβ₂), is just one of many integrins in the human body, but its significance is derived from its exclusive presence in leukocytes. In this review, we summarize the studies relating LFA-1 and its major ligand ICAM-1 (or CD54) with cancer, through the function of lymphocytes and myeloid cells on tumor cells. We consider how LFA-1 mediates the interaction of leukocytes with tumors and the role of ICAM-1 in tumor dynamics, which can be independent of its interaction with LFA-1. We also offer a more detailed examination of the role of LFA-1 within B-cell chronic lymphocytic leukemia. Finally, we discuss the role that exosomes harboring LFA-1 play in tumor growth and metastasis.

Alteration in Leukocyte Subsets and Expressions of FcγR and Complement Receptors among Female Ragpickers in Eastern India

Background

There are a million ragpickers in India who gather and trade recyclable municipal solid wastes materials for a living. The objective of this study was to examine whether their occupation adversely affects their immunity.

Methods

Seventy-four women ragpickers (median age, 30 years) and 65 age-matched control housemaids were enrolled. Flow cytometry was used to measure leukocyte subsets, and leukocyte expressions of Fcγ receptor I (CD64), FcγRIII (CD16), complement receptor 1 (CD35) and CR3 (CD11b/CD18), and CD14. Serum total immunoglobulin-E was estimated with enzyme-linked immunosorbent assay.

Results

Compared with the controls, ragpickers had significantly (p < 0.0001) higher levels of CD8+T-cytotoxic, CD16+CD56+natural killer, and CD4+CD45RO+memory T-cells, but depleted levels of CD19+B-cells. The percentage of CD4+T-helper-cells was lower than the control group (p < 0.0001), but their absolute number was relatively unchanged (p = 0.42) due to 11% higher lymphocyte counts in ragpickers. In ragpickers, the percentages of CD14+CD16+intermediate and CD14dim CD16+nonclassical monocyte subsets were elevated with a decline in CD14+CD16-classical monocytes. The expressions of CD64, CD16, CD35, and CD11b/CD18 on both monocytes and neutrophils, and CD14 on monocytes were significantly higher in ragpickers. In addition, ragpickers had 2.7-times more serum immunoglobulin-E than the controls (p < 0.0001). After controlling potential confounders, the profession of ragpicking was positively associated with the changes.

Conclusion

Ragpicking is associated with alterations in both innate (neutrophils, monocytes, and natural killer cell numbers and expression of complement and Fcγ receptors) and adaptive immunity (numbers of circulating B cells, helper, cytotoxic, and memory T cells).

A novel microfluidic assay reveals a key role for protein kinase C δ in regulating human neutrophil-endothelium interaction

A key step in neutrophil-mediated tissue damage is the migration of activated neutrophils across the vascular endothelium. Previously, we identified protein kinase C δ as a critical regulator of neutrophil migration in sepsis but did not identify specific steps in migration. In this study, we used our novel biomimetic microfluidic assay to delineate systematically the mechanism by which protein kinase C δ regulates individual steps in human neutrophil-endothelial interaction during inflammation. The biomimetic microfluidic assay includes a network of vascular channels, produced from in vivo images connected to a tissue compartment through a porous barrier. HUVECs cultured in vascular channels formed a complete lumen under physiologic shear flow. HUVECs were pretreated with TNF-α ± a protein kinase C δ inhibitor, and the tissue compartment was filled with a chemoattractant (fMLP or IL-8). Under physiologic shear flow, the role of protein kinase C δ on spatial and temporal neutrophil adherence/migration was quantified. Protein kinase C δ inhibition significantly reduced neutrophil adhesion in response to fMLP and IL-8 only under low shear rate and near bifurcations. Protein kinase C δ inhibition also decreased adherence to nonactivated HUVECs in response to fMLP or IL-8. Protein kinase C δ inhibition reduced neutrophil migration into the tissue compartment in response to fMLP and to a lesser degree, to IL-8. Antibody-coated microparticles demonstrated that protein kinase C δ inhibition down-regulated E-selectin and ICAM-1 but not VCAM-1 expression. With the use of a physiologically relevant in vitro model system, we demonstrate that protein kinase C δ plays an important role in the regulation of neutrophil adherence/migration during inflammation and identifies key steps regulated by protein kinase C δ in neutrophil-endothelial interactions.

Hepatocytes: a key cell type for innate immunity

Hepatocytes, the major parenchymal cells in the liver, play pivotal roles in metabolism, detoxification, and protein synthesis. Hepatocytes also activate innate immunity against invading microorganisms by secreting innate immunity proteins. These proteins include bactericidal proteins that directly kill bacteria, opsonins that assist in the phagocytosis of foreign bacteria, iron-sequestering proteins that block iron uptake by bacteria, several soluble factors that regulate lipopolysaccharide signaling, and the coagulation factor fibrinogen that activates innate immunity. In this review, we summarize the wide variety of innate immunity proteins produced by hepatocytes and discuss liver-enriched transcription factors (e.g. hepatocyte nuclear factors and CCAAT/enhancer-binding proteins), pro-inflammatory mediators (e.g. interleukin (IL)-6, IL-22, IL-1β and tumor necrosis factor-α), and downstream signaling pathways (e.g. signal transducer and activator of transcription factor 3 and nuclear factor-κB) that regulate the expression of these innate immunity proteins. We also briefly discuss the dysregulation of these innate immunity proteins in chronic liver disease, which may contribute to an increased susceptibility to bacterial infection in patients with cirrhosis.

Emerging understanding of roles for arterioles in inflammation

Arterioles, capillaries, and venules all actively change their cellular functions and phenotypes during inflammation in ways that are essential for maintenance of homeostasis and self-defense, and are also associated with many inflammatory disorders. ECs, together with pericytes and ECM proteins, can regulate blood flow, the coagulation cascade, fluid and solute exchange, and leukocyte trafficking. While capillary and venular functions in inflammation are well characterized, the arteriolar contribution to inflammation has only recently come into focus. Arterioles differ from venules in structure, EC morphology, shear environment, expression, and distribution of surface ligands; hence, regulation and function of arteriolar wall cells during inflammation may also be distinct from venules. Recent work indicates that in response to proinflammatory stimuli, arterioles alter barrier function, and support leukocyte and platelet interactions through upregulation of adhesion molecules. This suggests that in addition to their role in blood flow regulation, arterioles may also participate in inflammatory responses. In this review, we will discuss mechanisms that characterize arteriolar responses to proinflammatory stimuli. We will detail how distinct arteriolar features contribute to regulation of barrier function and leukocyte-EC interactions in inflammation, and further highlight the potential priming effects of arteriolar responses on venular function and progression of inflammatory responses.

The role of transforming growth factor-β1 in airway inflammation of childhood asthma

TGF-beta-targeting structural and inflammatory cells has been implicated in the mechanisms leading to the inflammatory and restructuring processes in asthma, suggesting an impact of TGF-beta1 signaling on the development and persistency of this disease. We investigated the potential early involvement of TGF-beta1 activity in the immunological and molecular mechanisms underlying progression of inflammation in childhood asthma. We evaluated the levels of TGF-beta1 in induced sputum supernatants (ISSs) and the expression of small mother cell against decapentaplegic (Smad) 2 and Smad7 proteins in induced sputum cells (ISCs) from children with intermittent asthma (IA), moderate asthma (MA) and control subjects (C). Furthermore, we investigated the regulatory role of TGF-beta1 activity on eosinophil and neutrophil adhesion to epithelial cells using adhesion assay, and on the granulocyte expression of adhesion molecule CD11b/CD18 Macrophage-1 antigen (MAC-1), by flow cytometry. We found that the levels of TGF-beta1 are increased in ISSs of IA and MA in comparison to C, concomitantly to the activation of intracellular signaling TGFbeta/Smads pathway in ISCs. In MA, TGF-beta1 levels correlated with the number of sputum eosinophils and neutrophils. Furthermore, we showed the ability of sputum TGF-beta1 to promote eosinophil and neutrophil adhesion to epithelial cells, and to increase the expression of MAC-1 on the granulocyte surface. This study shows the activation of TGFbeta/Smad signaling pathway in the airways of children with IA and, despite the regular ICS treatment, in children with MA, and provides evidence for the contribution of TGF-beta1 in the regulation of granulocyte activation and trafficking.

Pulmonary endothelial protein kinase C-delta (PKCδ) regulates neutrophil migration in acute lung inflammation

Excessive neutrophil migration across the pulmonary endothelium into the lung and release of oxidants and proteases are key elements in pathogenesis of acute lung injury. Previously, we identified protein kinase C-delta (PKCδ) as an important regulator of proinflammatory signaling in human neutrophils and demonstrated that intratracheal instillation of a TAT-conjugated PKCδ inhibitory peptide (PKCδ-TAT) is lung protective in a rat model of sepsis-induced indirect pulmonary injury (cecal ligation and puncture). In the present study, intratracheal instillation of this PKCδ inhibitor resulted in peptide distribution throughout the lung parenchyma and pulmonary endothelium and decreased neutrophil influx, with concomitant attenuation of sepsis-induced endothelial ICAM-1 and VCAM-1 expression in this model. To further delineate the role of PKCδ in regulating neutrophil migration, we used an in vitro transmigration model with human pulmonary microvascular endothelial cells (PMVECs). Consistent with in vivo findings, inhibition of PMVEC PKCδ decreased IL-1β-mediated neutrophil transmigration. PKCδ regulation was stimulus-dependent; PKCδ was required for transmigration mediated by IL-1β and fMLP (integrin-dependent), but not IL-8 (integrin-independent). PKCδ was essential for IL-1β-mediated neutrophil adherence and NF-κB-dependent expression of ICAM-1 and VCAM-1. In PMVECs, IL-1β-mediated production of ROS and activation of redox-sensitive NF-κB were PKCδ dependent, suggesting an upstream signaling role. Thus, PKCδ has an important role in regulating neutrophil-endothelial cell interactions and recruitment to the inflamed lung.

Modulation of Neutrophil Apoptosis and the Resolution of Inflammation through β2 Integrins

Precise control of the neutrophil death program provides a balance between their defense functions and safe clearance, whereas impaired regulation of neutrophil death is thought to contribute to a wide range of inflammatory pathologies. Apoptosis is essential for neutrophil functional shutdown, removal of emigrated neutrophils, and timely resolution of inflammation. Neutrophils receive survival and pro-apoptosis cues from the inflammatory microenvironment and integrate these signals through surface receptors and common downstream mechanisms. Among these receptors are the leukocyte-specific membrane receptors β2 integrins that are best known for regulating adhesion and phagocytosis. Accumulating evidence indicate that outside-in signaling through the β2 integrin Mac-1 can generate contrasting cues in neutrophils, leading to promotion of their survival or apoptosis. Binding of Mac-1 to its ligands ICAM-1, fibrinogen, or the azurophilic granule enzyme myeloperoxidase suppresses apoptosis, whereas Mac-1-mediated phagocytosis of bacteria evokes apoptotic cell death. Mac-1 signaling is also target for the anti-inflammatory, pro-resolving mediators, including lipoxin A4, aspirin-triggered lipoxin A4, and resolvin E1. This review focuses on molecular mechanisms underlying Mac-1 regulation of neutrophil apoptosis and highlights recent advances how hierarchy of survival and pro-apoptosis signals can be harnessed to facilitate neutrophil apoptosis and the resolution of inflammation.

Immune cells and cardiovascular health in premenopausal women of rural India chronically exposed to biomass smoke during daily household cooking

Changes in cells of the immune system are important indicators of systemic response of the body to air pollution. The aim of this study was to investigate the immunological changes in rural women who have been cooking exclusively with biomass for the past 5 years or more and compare the findings with women cooking exclusively with liquefied petroleum gas (LPG). We conducted a cross-sectional analysis of the associations between indices of indoor air pollution (IAP) and a set of immune assays. Biomass users illustrated marked suppression in the total number of T-helper (CD4+) cells and B (CD19+) cells while appreciable rise was documented in the number of CD8+ T-cytotoxic cells and CD16+CD56+ natural killer (NK) cells. A consistent finding among biomass users was rise in regulatory T (Treg) cells. Among biomass users, peripheral lymphocyte subpopulations, Treg cells, and the number of typical monocytes (CD16-CD64+ cells), antigen presenting types (CD16+CD64- cells) and plasmacytoid cells (CD16-CD64- cells) were found to be significantly altered in those who daily cooked with dung in comparison to wood and crop residue users (p<0.05). Biomass users who cooked in kitchens adjacent to their living areas had significant changes in peripheral lymphocyte subpopulations, typical monocytes (CD16-CD64+) with high phagocytic activity and antigen presenting monocytes (CD16+CD64-) against women who cooked in separate kitchens (p<0.01). This study has shown that women who cooked exclusively with biomass fuel had alterations in immune defense compared with their neighbors who cooked with LPG.

Ketamine reduces inducible superoxide generation in human neutrophils in vitro by modulating the p38 mitogen-activated protein kinase (MAPK)-mediated pathway

Many cellular stresses and inflammatory stimuli can activate p38 mitogen-activated protein kinase (MAPK), a serine/threonine kinase in the MAPK family. The different stimuli act via different receptors or signalling pathways to induce phosphorylation of the cytosolic protein p47(phox), one subunit of the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. Formyl-methionyl-leucyl-phenylalanine (fMLP) has been shown to induce the p38 MAPK phosphorylation during the respiratory burst in human neutrophils. Here, we show that treatment with S(+)-ketamine or R(-)-ketamine at different concentrations (50, 100, 200, 400 microM) reduced fMLP-induced superoxide anion generation and p47(phox) phosphorylation in neutrophils in a concentration-dependent manner (y = -0.093x + 93.35 for S(+)-ketamine and y = -0.0982x + 95.603 for R(-)-ketamine, respectively). While treatment with 50 microM ketamine inhibited fMLP-induced superoxide generation by 10%, treatment with 400 microM S(+)-ketamine and R(-)-ketamine reduced fMLP-induced superoxide generation to 60.5 +/- 8.3% and 60.0 +/- 8.5%, respectively, compared with that in neutrophils treated with fMLP alone. Furthermore, treatment with ketamine down-regulated both fMLP-induced p47(phox) and isoproterenol-induced p38 MAPK phosphorylation and superoxide production. Interestingly, treatment with SB203580, the p38 MAPK inhibitor, also mitigated fMLP-induced superoxide anion generation and p38 MAPK and p47(phox) phosphorylation as well as apoptosis in a concentration-dependent fashion in neutrophils. Therefore, ketamine racemes inhibited fMLP-induced superoxide anion generation and p47(phox) phosphorylation by modulating fMLP-mediated p38 MAPK activation in neutrophils.

Mannose–fucose recognition by DC-SIGN

Dendritic cell-specific ICAM-3-grabbing nonintegrin (DC-SIGN). DC-SIGN is a C-type lectin receptor that recognizes N-linked high-mannose oligosaccharides and branched fucosylated structures. It is now clear that the biological role of DC-SIGN is two-fold. It is primarily expressed by dendritic cells and mediates important functions necessary for the induction of successful immune responses that are essential for the clearance of microbial infections, such as the capture, destruction, and presentation of microbial pathogens to induce successful immune responses. Yet, on the other hand, pathogens may also exploit DC-SIGN to modulate DC functioning thereby skewing the immune response and promoting their own survival. This chapter presents an overview of the structure of DC-SIGN and its expression pattern among immune cells. The current state of knowledge of DC-SIGN-carbohydrate interactions is discussed and how these interactions influence dendritic cell functioning is examined. The molecular aspects that underlie the selectivity of DC-SIGN for mannose-and fucose-containing carbohydrates are detailed. Furthermore, the chapter discusses the role of DC-SIGN in dendritic cell biology and how certain bacterial pathogens exploit DC-SIGN to escape immune surveillance.

Febrile-range hyperthermia accelerates caspase-dependent apoptosis in human neutrophils

Human neutrophilic polymorphonuclear leukocytes (PMNs) are central to innate immunity and are responsible for clearance of pathogens. PMNs undergo a tightly regulated apoptosis program that allows for timely clearance of PMNs without extravasation of toxic intracellular contents. We investigated the rate of spontaneous apoptosis of human peripheral blood PMNs cultured at basal (37 degrees C) and febrile-range (39.5 degrees C) temperatures (FRT). We found that PMN apoptosis is accelerated at FRT, reaching approximately 90% completion by 8 h at 39.5 degrees C vs 18 h at 37 degrees C based on morphologic criteria. Caspase-8 activation peaked within 15 min of PMN exposure to FRT, and subsequent activation of caspase-3 and -9, cleavage of the BH3 (Bcl-2 homology domain 3) only protein Bid, and mitochondrial release of cytochrome c were also greater in FRT-exposed PMNs. Inhibition of caspase-3, -8, and -9 conferred comparable protection from apoptosis in FRT-exposed PMNs. These results demonstrate that exposure to FRT enhances caspase-8 activation and subsequent mitochondrial-dependent and mitochondrial-independent apoptosis pathways. The PMN survival factors G-CSF, GM-CSF, and IL-8 each prolonged PMN survival at 37 degrees C and 39.5 degrees C, but did not reduce the difference in survival at the two temperatures. In a mouse model of intratracheal endotoxin-induced alveolitis, coexposure to FRT (core temperature approximately 39.5 degrees C) doubled the proportion of bronchoalveolar PMNs undergoing apoptosis compared with euthermic mice. This process may play an important role in limiting inflammation and tissue injury during febrile illnesses.

Myeloperoxidase Delays Neutrophil Apoptosis Through CD11b/CD18 Integrins and Prolongs Inflammation

Polymorphonuclear neutrophil granulocytes have a central role in innate immunity and their programmed cell death and removal are critical for efficient resolution of acute inflammation. Myeloperoxidase (MPO), a heme protein abundantly expressed in neutrophils, is generally associated with killing of bacteria and oxidative tissue injury. Because MPO also binds to neutrophils, we investigated whether MPO could affect the lifespan of neutrophils. Here, we report that MPO independent of its catalytic activity through signaling via the adhesion molecule CD11b/CD18 rescued human neutrophils from constitutive apoptosis and prolonged their life span. MPO evoked a transient concurrent activation of extracellular signal-regulated kinase and Akt, leading to phosphorylation of Bad at both Ser112 and Ser136, prevention of mitochondrial dysfunction, and subsequent activation of caspase-3. Consistently, pharmacological inhibition of extracellular signal-regulated kinase, Akt, or caspase-3 reversed the antiapoptosis action of MPO. Acute increases in plasma MPO delayed murine neutrophil apoptosis assayed ex vivo. In a mouse model of self-resolving inflammation, MPO also prolonged the duration of carrageenan-induced acute lung injury, as evidenced by enhanced alveolar permeability and accumulation of neutrophils parallel with suppression of neutrophil apoptosis. Our results indicate that MPO functions as a survival signal for neutrophils and thereby contribute to prolongation of inflammation.

The wild boar (Sus scrofa) lymphocyte function-associated antigen-1 (CD11a/CD18) receptor: cDNA sequencing, structure analysis and comparison with homologues

Background

The most predominant beta2-integrin lymphocyte function-associated antigen-1 (LFA-1, CD11a/CD18, alphaLbeta2), expressed on all leukocytes, is essential for many adhesive functions of the immune system. Interestingly, RTX toxin-producing bacteria specifically target this leukocyte beta2-integrin which exacerbates lesions and disease development.

Results

This study reports the sequencing of the wild boar beta2-integrin CD11a and CD18 cDNAs. Predicted CD11a and CD18 subunits share all the main structural characteristics of their mammalian homologues, with a larger interspecies conservation for the CD18 than the CD11a. Besides these strong overall similarities, wild boar and domestic pig LFA-1 differ by 2 (CD18) and 1 or 3 (CD11a) substitutions, of which one is located in the crucial I-domain (CD11a, E168D).

Conclusion

As most wild boars are seropositive to the RTX toxin-producing bacterium Actinobacillus pleuropneumoniae and because they have sustained continuous natural selection, future studies addressing the functional impact of these polymorphisms could bring interesting new information on the physiopathology of Actinobacillus pleuropneumoniae-associated pneumonia in domestic pigs.

Lymphocyte function-associated antigen-1-dependent inhibition of corneal wound healing

Abrasion of murine corneal epithelium induces neutrophil emigration through limbal vessels into the avascular corneal stroma, peaking within 12 to 18 hours after wounding. A central corneal wound closes within 24 hours by epithelial cell migration and division, and during wound closure corneal epithelial cells express intercellular adhesion molecule (ICAM)-1 (CD54). We investigated the contributions of lymphocyte function-associated antigen (LFA)-1 (CD11a/CD18) and Mac-1 (CD11b/CD18) by analyzing wound closure in mice with targeted deletions of CD11a (CD11a-/-) or CD11b (CD11b-/-). In contrast to CD11a-/- mice, CD11b deficiency revealed a much greater delay in epithelial wound closure with >90% inhibition of epithelial cell division at a time when neutrophil accumulation in the cornea was approximately threefold higher than normal. Treating CD11b-/- mice with anti-CD11a monoclonal antibody at the time of epithelial abrasion resulted in significant reductions in neutrophils and significant increases in corneal epithelial cell division and migration. Treating CD11b-/- mice with anti-ICAM-1 significantly increased measures of healing but marginally reduced neutrophil influx. In conclusion, wound healing after corneal epithelial abrasion is disrupted by the absence of CD11b. The disruption is apparently linked to excessive neutrophil accumulation at a time when epithelial division is essential to wound repair, and neutrophils appear to be detrimental through processes involving LFA-1 and ICAM-1.

Neisseria gonorrhoeae delays the onset of apoptosis in polymorphonuclear leukocytes

Neisseria gonorrhoeae (gonococcus) infection results in recruitment of polymorphonuclear leukocytes (PMNs) to the urethral lumen. Recent work from our laboratory demonstrated that N. gonorrhoeae resists killing and replicates within PMNs. In this study, we examined the effect of gonococci on PMN viability. Using both transmission electron microscopy and light microscopy, we observed nuclear condensation after 6 h in PMNs that were resting or challenged with opsonized zymosan particles (OPZ). In contrast, N. gonorrhoeae delayed nuclear condensation in PMNs for 12 h (13% apoptotic PMNs vs. 90% for resting and 94% for OPZ-stimulated PMNs). Additionally, DNA fragmentation was reduced in PMNs challenged with gonococci for 12 h (28% apoptosis vs. 52% for resting and 98% for OPZ-stimulated PMNs). However, 74% of PMNs challenged with gonococci had condensed nuclei and 67% had fragmented DNA after 24 h. Caspase activity (total caspase, caspase-3/7, caspase-9) was reduced at 4 h and mitochondrial integrity was preserved at 2 h in PMNs challenged with N. gonorrhoeae. Quantitative reverse transcription polymerase chain reaction demonstrated that mRNA levels of X-IAP and cIAP-2 remained high after challenge with gonococci, but were downregulated in OPZ-stimulated PMNs. Collectively, these findings demonstrate that N. gonorrhoeae delayed apoptosis in PMNs, perhaps as a strategy to allow intracellular replication.

Fibrinogen-neutrophil interactions in response to fMLP and Porphyromonas gingivalis fimbrial peptides

Porphyromonas gingivalis (P.g) is the primary bacterial agent in many forms of chronic periodontitis. Since polymorphonuclear leukocytes (PMNs) are first-line responders to P.g.- induced inflammation, and fibrinogen is important for in vivo PMN in this disease, we have studied the effect of N-formyl-methionyl-leucyl-phenylalanine (fMLP) (an inflammatory stimulus), P.g. fimbriae and fimbrial peptides (based on FimA, the main structural protein of P.g. fimbriae) on PMN-fibrinogen interactions. Freshly isolated human PMNs were allowed to react with FITC-Fibrinogen and various fimbrial peptides (denoted as FimA followed by amino acid number within whole FimA protein), and FITC-Fibrinogen binding was measured using flow cytometry. Freshly isolated neutrophils were also challenged with Fibrinogen and/or fimbrial peptides to measure IL-8 secretion using ELISA. Our studies show that fibrinogen binding to PMNs is enhanced (p < 0.01) in response to fMLP as well as fimbrial peptides (FimA 61-80) containing the motif LTTE (p < 0.01) in a dose dependent manner but not in response to peptides without that motif. We also observed that fMLP and FimA 61-80 have an additive effect on fibrinogen binding to PMNs (p < 0.05), and fMLP and FimA 171-185 significantly inhibit fMLP-induced fibrinogen binding (p < 0.01). To determine of the role of inflammatory cytokines, we examined IL-8 release from PMNs in response to combinations of P. gingivalis fimbriae, fMLP and fibrinogen. In all cases, IL-8 release increased in a dose-dependent manner (p < 0.05). fMLP-fibrinogen effect on IL-8 release from PMNs was synergistic while fimbriae-fibrinogen effect was additive. In summary, PMN priming by fimbrial peptides facilitates fibrinogen-PMN interaction and may increase inflammation.

Human microvascular endothelial cell activation by IL-1 and TNF-alpha stimulates the adhesion and transendothelial migration of circulating human CD14+ monocytes that develop with RANKL into functional osteoclasts

Circulating pre-OCs may be recruited to locally inflamed sites through specific interactions with activated microvasculature. We found that HMVECs stimulated the adhesion and TEM of circulating pre-OCs, in an ICAM-1- and CD44-dependent manner, leading to greater RANKL-induced OC formation and bone pit resorption.

INTRODUCTION

Inflammation is critical for healing processes but causes severe tissue destruction when chronic. Local osteoclast (OC) formation and bone resorption may increase at inflammatory sites through multiple mechanisms, including direct stimulation by inflamed microvasculature of circulating OC precursor (pre-OC) migration through a blood vessel barrier into bone or joint tissue. How this might occur is not yet well understood.

MATERIALS AND METHODS

Cytokine-activated human microvascular endothelial cell (HMVEC) monolayers, with or without IL-1 and TNF-alpha preactivation (24 h), were incubated in adhesion (1-3 h) or porous transwell transendothelial migration (TEM; 3 h) assays with human peripheral blood mononuclear cells (hPBMCs) or CD14+ monocyte or CD14- lymphocyte subsets. The number of cells that adhered or transmigrated, and their ability to thereafter develop with macrophage-colony stimulating factor (M-CSF) + RANKL into bone pit-resorbing OCs, were analyzed. Immunostaining and neutralizing antibodies to key cell adhesion molecules were used to determine their potential involvement in stimulated CD14+ monocyte TEM.

RESULTS

M-CSF + RANKL caused OC and bone pit formation only from hPBMCs and CD14+ cells but not CD14- cells. Adhesion of hPBMCs or CD14+ cells but not CD14- cells was stimulated by cytokine preactivation of HMVECs and led to the full capture of all circulating pre-OCs capable of developing into OCs. Cytokine-preactivated HMVECs also promoted the postadhesion TEM of hPBMCs and CD14+ populations, resulting in markedly greater OC formation and bone pit resorption by transmigrated cells. Immunodetectable vascular cell adhesion molecule (VCAM-1), intercellular adhesion molecule (ICAM-1), and CD44 levels increased on cytokine-treated HMVEC surfaces, and neutralizing antibodies to ICAM-1 or CD44, but not VCAM-1 or platelet endothelial cell adhesion molecule (PECAM-1), inhibited stimulated CD14+ cell TEM through activated HMVECs.

CONCLUSIONS

This is the first demonstration that cytokine-activated HMVECs efficiently capture and promote the TEM of circulating pre-OCs capable of differentiating into bone-resorbing OCs. Thus, direct pre-OC recruitment by activated microvasculature at inflammatory sites may significantly contribute to normal OC bone remodeling during fracture healing or exacerbate pathological bone loss in various chronic inflammatory disorders.

A small molecule alpha 4 beta 1 antagonist prevents development of murine Lyme arthritis without affecting protective immunity

After infection with Borrelia burgdorferi, humans and mice under certain conditions develop arthritis. Initiation of inflammation is dependent on the migration of innate immune cells to the site of infection, controlled by interactions of a variety of adhesion molecules. In this study, we used the newly synthesized compound S18407, which is a prodrug of the active drug S16197, to analyze the functional importance of alpha4beta1-dependent cell adhesion for the development of arthritis and for the antibacterial immune response. S16197 is shown to interfere specifically with the binding of alpha4beta(1 integrin to its ligands VCAM-1 and fibronectin in vitro. Treatment of B. burgdorferi-infected C3H/HeJ mice with the alpha4beta1 antagonist significantly ameliorated the outcome of clinical arthritis and the influx of neutrophilic granulocytes into ankle joints. Furthermore, local mRNA up-regulation of the proinflammatory mediators IL-1, IL-6, and cyclooxygenase-2 was largely abolished. Neither the synthesis of spirochete-specific Igs nor the development of a Th1-dominated immune response was altered by the treatment. Importantly, the drug also did not interfere with Ab-mediated control of spirochete load in the tissues. These findings demonstrate that the pathogenesis, but not the protective immune response, in Lyme arthritis is dependent on the alpha4beta1-mediated influx of inflammatory cells. The onset of inflammation can be successfully targeted by treatment with S18407.

Integrins as a distinct subtype of dependence receptors

In the absence of their cognate ligand, dependence receptors trigger programmed cell death. This function is the defining feature of dependence receptors, which include members of several different protein families. The integrins are a family of heterodimeric receptors for extracellular matrix (ECM) proteins, mediating cell anchorage and migration. Integrins share characteristics with dependence receptors, and integrin binding to substrate ECM ligands is essential for cell survival. Although integrins do not conform in all characteristics to the established definitions of dependence receptors, alterations in the expression of integrins and their ligands during physiological and pathological events, such as wound healing, angiogenesis and tumorigenesis, do regulate cell fate in a ligand-dependent manner. This biosensory function of integrins fits well with our current concept of dependence receptor action, and thus integrins may rightly be considered to comprise a distinct subclass of dependence receptor.

Albumin attenuates neutrophil activation induced by stimulators including antibodies against neutrophil-specific antigens

As neutrophil activation is related to several adverse transfusion reactions, we studied about the activation induced by anti-neutrophil antibodies and the stabilizing effects of albumin pretreatment by means of flow cytometry. Anti-neutrophil monoclonal antibody (anti-HNA-1a, 1b, 2a) alone induced CD11b expression and shedding of L-selectin, and anti-HNA-1a reinforced reactive oxygen species (ROS) production. Albumin pretreatment significantly reduced CD11b expression and L-selectin shedding induced by fMLP and ROS production induced by PMA, G-CSF combined with PMA or LPS-fMLP, or anti-HNA-1a combined with PMA. These findings suggest that anti-HNA-1a is related to adverse reactions and albumin has a regulating effect on neutrophil activation.

Molecular characterisation of the caprine (Capra hircus) lymphocyte function-associated antigen-1 alpha subunit-encoding cDNA

Background

Lymphocyte function-associated antigen-1 (LFA-1, CD11a/CD18, alpha L beta 2) is required for many cellular adhesive interactions during the immune response.

Results

The Capra hircus CD11a-encoding cDNA was sequenced and compared with its human, murine, rat, bovine and ovine counterparts. Despite some focal differences, it shares all the main characteristics of its known mammalian homologues.

Conclusion

Therefore, along with the caprine CD18-encoding cDNA, which has been available for a few months, the sequence data revealed here will allow the Capra hircus LFA-1 expression in vitro as a tool to explore the specificities of inflammation in the caprine species.

Interleukin-15 increases neutrophil adhesion onto human respiratory epithelial A549 cells and attracts neutrophils in vivo

Interleukin-15 (IL-15) is a neutrophil agonist that plays a role in inflammatory disorders, including a variety of pulmonary diseases. Adhesion of neutrophils onto pulmonary cells is a major event leading to development of inflammation. Recently, elevated levels of IL-15 have been associated with different pulmonary diseases. There is no clear evidence that IL-15 modulates cell surface expression of adhesion molecules in neutrophils, or that IL-15 is involved in neutrophil adhesion onto pulmonary cells. Also, it is not clear if IL-15 induces a neutrophilic inflammation in vivo. This study was aimed at elucidation of these issues. Neutrophils were treated with IL-15 and cell surface expression of CD11a, CD11b, CD11c and CD18 was monitored by flow cytometry. The human respiratory epithelial A549 cell line was used as a substrate for the neutrophil adhesion assay and cell surface expression of CD50, CD54 and CD106 was monitored in IL-15-induced A549 cells. The murine air pouch model was used for investigating potential neutrophilic inflammation induced by IL-15 in vivo. IL-15 significantly increased neutrophil cell surface expression of CD11b and CD18 and up-regulated A549 cell surface expression of CD54. Moreover, A549 cells were found to express IL-15R components and adhesion of neutrophils onto A549 cells was increased when neutrophils or A549 cells were treated with IL-15. Finally, IL-15 induced neutrophilic inflammation in vivo and concentrations of IL-6 and CXCL2/MIP-2 were increased in IL-15-induced pouches. IL-15 might participate in inflammatory pulmonary diseases by attracting neutrophils, modulating cell surface expression molecules and increasing neutrophil adhesion onto pulmonary cells.