Neutrophils in innate and adaptive immunity

The Inflammatory Cytokine IL-21 is Expressed by Splenic Neutrophils in Response to Transplantation of Allogeneic Cells

We have previously reported that GR-1 neutrophil/monocytes rose dramatically in the spleen, peaked by day 7 and declined through day 14. This period corresponded to the peak of acute Graft-Versus-Host Disease (aGVHD) in BALB/c mice transplanted with allogeneic donor cells. We now asked: what cytokines did these splenic neutrophil/monocytes express on day 7 and 14 post transplant? BALB/c mice were transplanted with allogeneic B6 or syngeneic BALB/c donor cells. Long term survival was recorded through day 31. Other groups were sacrificed on days 3, 5, 7, 14, 21 and 31 days post transplant to record the total number of cells in the spleens and their phenotypes. Neutrophils were isolated from the spleens of mice transplanted with B6 and BALB/c cells on days 7 and 14. Daily body weight demonstrated a transient drop in the syngeneic transplants on day 2 but a much greater drop with its nadir at day 7 and never fully recovering through 31 days. CD8/CD4 T lymphocytes peaked in the spleen on day 5 and were followed on day 7 by GR-I cells in all of the allogeneic transplants. In syngeneic transplants this early rise in lymphocytes did not occur and GR-1 cells peaked on day 14. Highly purified neutrophils were isolated in two separate experiments from the spleens on days 7 and 14 post transplant. In both experiments day 7 allogeneic neutrophils expressed significantly elevated levels of Interleukin-21 (IL-21) mRNA whereas the day 7 and 14 syngeneic cells expressed lower but significant levels of TNFα. Intracellular IL-21 was demonstrated in the allogeneic neutrophils on day 7 before and after in vitro stimulation. In conclusion Purified neutrophils isolated from the spleen on day 7, the early peak of allogeneic transplantation a GVHD, express high levels of IL-21 message and intracellular IL-21.

Multifaceted effects of Francisella tularensis on human neutrophil function and lifespan

Francisella tularensis in an intracellular bacterial pathogen that causes a potentially lethal disease called tularemia. Studies performed nearly 100 years ago revealed that neutrophil accumulation in infected tissues correlates directly with the extent of necrotic damage during F. tularensis infection. However, the dynamics and details of bacteria-neutrophil interactions have only recently been studied in detail. Herein, we review current understanding regarding the mechanisms that recruit neutrophils to F. tularensis-infected lungs, opsonization and phagocytosis, evasion and inhibition of neutrophil defense mechanisms, as well as the ability of F. tularensis to prolong neutrophil lifespan. In addition, we discuss distinctive features of the bacterium, including its ability to act at a distance to alter overall neutrophil responsiveness to exogenous stimuli, and the evidence which suggests that macrophages and neutrophils play distinct roles in tularemia pathogenesis, such that macrophages are major vehicles for intracellular growth and dissemination, whereas neutrophils drive tissue destruction by dysregulation of the inflammatory response.

Impaired Blood Neutrophil Function in the Frequent Exacerbator of Chronic Obstructive Pulmonary Disease: A Proof-of-Concept Study

PURPOSE

The underlying biological mechanisms of the frequent exacerbator phenotype of COPD remain unclear. We compared systemic neutrophil function in COPD patients with or without frequent exacerbations.

METHODS

Whole blood from COPD frequent exacerbators (defined as ≥2 moderate-severe exacerbations in the previous 2 years) and non-exacerbators (no exacerbations in the preceding 2 years) was assayed for neutrophil function. Neutrophil function in healthy ex-smoking volunteers was also measured as a control (reference) group.

RESULTS

A total of 52 subjects were included in this study: 26 frequent exacerbators, 18 non-exacerbators and 8 healthy controls. COPD frequent exacerbators had blunted blood neutrophil fMLP-stimulated oxidative burst compared to both non-exacerbators (p < 0.01) and healthy controls (p < 0.001). There were no differences between COPD frequent exacerbators and non-exacerbators in blood neutrophil PMA-stimulated oxidative burst, but both COPD groups had reduced responses compared to healthy controls (p < 0.001). Bacterial-stimulated neutrophil degranulation was greater in frequent exacerbators than non-exacerbators (p < 0.05).

CONCLUSION

This study is the first to report aberrant receptor-mediated blood neutrophil function in the frequent exacerbator of COPD.

Neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) were associated with disease activity in patients with systemic lupus erythematosus

OBJECTIVE

Neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) have recently been investigated as two new inflammatory markers used in the assessment of systemic inflammation in many diseases. The purpose of the study was to investigate their relation with disease activity in newly diagnosed SLE patients.

METHODS

The study population consisted of 116 SLE patients who did not receive any treatment and 136 healthy controls. We divided the patients into two groups according to the SLE Disease Activity Index 2000 (SLEDAI-2K) system. Group 1 included patients with a score of 9 and lower (patients with mild disease activity), and Group 2 included patients with a score of >9 (patients with severe disease activity). Correlations between NLR, PLR and disease activity were analyzed.

RESULTS

The NLR and PLR of SLE patients were significantly higher compared to those of the controls (both P<0.001). There was a statistically significant difference in NLR and PLR between Group 1 and Group 2 (both P<0.05). SLEDAI scores positively correlated with NLR (r=0.312, P<0.001) and PLR (r=0.298, P<0.001). Furthermore, SLE patients with nephritis had higher NLR levels than those without nephritis (P=0.027). Based on the ROC curve, the best NLR cut-off value to predict SLE patients with severe disease activity was 2.26, with 75% sensitivity and 50% specificity, whereas the best PLR cut-off value was 203.85, with 42.3% sensitivity and 83.9% specificity.

CONCLUSION

NLR and PLR were two useful inflammatory markers for assessment of disease activity in patients with SLE.

The immune network in thyroid cancer

The immune system plays critical roles in tumor prevention, but also in its initiation and progression. Tumors are subjected to immunosurveillance, but cancer cells generate an immunosuppressive microenvironment that favors their escape from immune-mediated elimination. During chronic inflammation, immune cells can contribute to the formation and progression of tumors by producing mitogenic, prosurvival, proangiogenic and lymphangiogenic factors. Thyroid cancer is the most frequent type of endocrine neoplasia and is the most rapidly increasing cancer in the US. In this review, we discuss recent findings on how different immune cells and mediators can contribute to thyroid cancer development and progression.

Moraxella catarrhalis induces CEACAM3-Syk-CARD9-dependent activation of human granulocytes

The human restricted pathogen Moraxella catarrhalis is an important causal agent for exacerbations in chronic obstructive lung disease in adults. In such patients, increased numbers of granulocytes are present in the airways, which correlate with bacteria-induced exacerbations and severity of the disease. Our study investigated whether the interaction of M. catarrhalis with the human granulocyte-specific carcinoembryonic antigen-related cell adhesion molecule (CEACAM)-3 is linked to NF-κB activation, resulting in chemokine production. Granulocytes from healthy donors and NB4 cells were infected with M. catarrhalis in the presence of different inhibitors, blocking antibodies and siRNA. The supernatants were analysed by enzyme-linked immunosorbent assay for chemokines. NF-κB activation was determined using a luciferase reporter gene assay and chromatin-immunoprecipitation. We found evidence that the specific engagement of CEACAM3 by M. catarrhalis ubiquitous surface protein A1 (UspA1) results in the activation of pro-inflammatory events, such as degranulation of neutrophils, ROS production and chemokine secretion. The interaction of UspA1 with CEACAM3 induced the activation of the NF-κB pathway via Syk and the CARD9 pathway and was dependent on the phosphorylation of the CEACAM3 ITAM-like motif. These findings suggest that the CEACAM3 signalling in neutrophils is able to specifically modulate airway inflammation caused by infection with M. catarrhalis.

Epigenetic regulation of neutrophil development and function

In addition to performing well-defined effector functions, neutrophils are now recognized as versatile and sophisticated cells with critical immunoregulatory roles. These include the release of a variety of proinflammatory or immunosuppressive cytokines, as well as the expression of genes with regulatory functions. Neutrophils share broad transcriptional features with monocytes, in keeping with the close developmental relation between the two cell types. However, neutrophil-specific gene expression patterns conferring cell type-specific responses to bacterial, viral or fungal components have been identified. Accumulating evidence suggest that these differences reflect the peculiar epigenomic and regulatory landscapes of neutrophils and monocytes, in turn controlled by the specific lineage-determining transcription factors shaping their identity. In this review, we will describe current knowledge on how neutrophil identity and function are controlled at the molecular level, focusing on transcriptional and chromatin regulation of neutrophil development and activation in response to inflammatory stimuli.

Neutrophil-derived chemokines on the road to immunity

During recent years, it has become clear that polymorphonuclear neutrophils are remarkably versatile cells, whose functions go far beyond phagocytosis and killing. In fact, besides being involved in primary defense against infections-mainly through phagocytosis, generation of toxic molecules, release of toxic enzymes and formation of extracellular traps-neutrophils have been shown to play a role in finely regulating the development and the evolution of inflammatory and immune responses. These latter neutrophil-mediated functions occur by a variety of mechanisms, including the production of newly manufactured cytokines. Herein, we provide a general overview of the chemotactic cytokines/chemokines that neutrophils can potentially produce, either under inflammatory/immune reactions or during their activation in more prolonged processes, such as in tumors. We highlight recent observations generated from studying human or rodent neutrophils in vitro and in vivo models. We also discuss the biological significance of neutrophil-derived chemokines in the context of infectious, neoplastic and immune-mediated diseases. The picture that is emerging is that, given their capacity to produce and release chemokines, neutrophils exert essential functions in recruiting, activating and modulating the activities of different leukocyte populations.

Fluid phase recognition molecules in neutrophil-dependent immune responses

The innate immune system comprises both a cellular and a humoral arm. Neutrophils are key effector cells of the immune and inflammatory responses and have emerged as a major source of humoral pattern recognition molecules (PRMs). These molecules, which include collectins, ficolins, and pentraxins, are specialised in the discrimination of self versus non-self and modified-self and share basic multifunctional properties including recognition and opsonisation of pathogens and apoptotic cells, activation and regulation of the complement cascade and tuning of inflammation. Neutrophils act as a reservoir of ready-made soluble PRMs, such as the long pentraxin PTX3, the peptidoglycan recognition protein PGRP-S, properdin and M-ficolin, which are stored in neutrophil granules and are involved in neutrophil effector functions. In addition, other soluble PRMs, such as members of the collectin family, are not expressed in neutrophils but can modulate neutrophil-dependent immune responses. Therefore, soluble PRMs are an essential part of the innate immune response and retain antibody-like effector functions. Here, we will review the expression and general function of soluble PRMs, focusing our attention on molecules involved in neutrophil effector functions.

Occurrence and significance of tumor-associated neutrophils in patients with colorectal cancer

Inflammatory cells are an essential component of the tumor microenvironment. Neutrophils have emerged as important players in the orchestration and effector phase of innate and adaptive immunity. The significance of tumor-associated neutrophils (TAN) in colorectal cancer (CRC) has been the subject of conflicting reports and the present study was designed to set up a reliable methodology to assess TAN infiltration in CRC and to evaluate their clinical significance. CD66b and myeloperoxidase (MPO) were assessed as candidate neutrophil markers in CRC using immunohistochemistry. CD66b was found to be a reliable marker to identify TAN in CRC tissues, whereas MPO also identified a subset of CD68(+) macrophages. CRC patients (n = 271) (Stages I-IV) were investigated retrospectively by computer-assisted imaging on whole tumor sections. TAN density dramatically decreases in Stage IV patients as compared to Stage I-III. At Cox analysis, higher TAN density was associated with better prognosis. Importantly, multivariate analysis showed that prognostic significance of TAN can be influenced by clinical stage and 5-fluorouracil(5-FU)-based chemotherapy. On separate analysis of Stage III patients (n = 178), TAN density had a dual clinical significance depending on the use of 5-FU-based chemotherapy. Unexpectedly, higher TAN density was associated with better response to 5-FU-based chemotherapy. Thus, TAN are an important component of the immune cell infiltrate in CRC and assessment of TAN infiltration may help identify patients likely to benefit from 5-FU-based chemotherapy. These results call for a reassessment of the role of neutrophils in cancer using rigorous quantitative methodology.

Neutrophils: Critical components in experimental animal models of cancer

Neutrophils have a crucial role in tumor development and metastatic progression. The contribution of neutrophils in tumor development is multifaceted and contradictory. On the one hand, neutrophils prompt tumor inception, promote tumor development by mediating the initial angiogenic switch and facilitate colonization of circulating tumor cells, and on the other hand, have cytotoxic and anti-metastatic capabilities. Our understanding of the role of neutrophils in tumor development has greatly depended on different experimental animal models of cancer. In this review we cover important findings that have been made about neutrophils in experimental animal models of cancer, point to their advantages and limitations, and discuss novel techniques that can be used to expand our knowledge of how neutrophils influence tumor progression.

Neutrophils in type 1 diabetes

Type 1 diabetes is an autoimmune disease that afflicts millions of people worldwide. It occurs as the consequence of destruction of insulin-producing pancreatic β-cells triggered by genetic and environmental factors. The initiation and progression of the disease involves a complicated interaction between β-cells and immune cells of both innate and adaptive systems. Immune cells, such as T cells, macrophages and dendritic cells, have been well documented to play crucial roles in type 1 diabetes pathogenesis. However, the particular actions of neutrophils, which are the most plentiful immune cell type and the first immune cells responding to inflammation, in the etiology of this disease might indeed be unfairly ignored. Progress over the past decades shows that neutrophils might have essential effects on the onset and perpetuation of type 1 diabetes. Neutrophil-derived cytotoxic substances, including degranulation products, cytokines, reactive oxygen species and extracellular traps that are released during the process of neutrophil maturation or activation, could cause destruction to islet cells. In addition, these cells can initiate diabetogenic T cell response and promote type 1 diabetes development through cell-cell interactions with other immune and non-immune cells. Furthermore, relevant antineutrophil therapies have been shown to delay and dampen the progression of insulitis and autoimmune diabetes. Here, we discuss the relationship between neutrophils and autoimmune type 1 diabetes from the aforementioned aspects to better understand the roles of these cells in the initiation and development of type 1 diabetes.

Interplay between Cellular and Molecular Inflammatory Mediators in Lung Cancer

Inflammation is a component of the tumor microenvironment and represents the 7th hallmark of cancer. Chronic inflammation plays a critical role in tumorigenesis. Tumor infiltrating inflammatory cells mediate processes associated with progression, immune suppression, promotion of neoangiogenesis and lymphangiogenesis, remodeling of extracellular matrix, invasion and metastasis, and, lastly, the inhibition of vaccine-induced antitumor T cell response. Accumulating evidence indicates a critical role of myeloid cells in the pathophysiology of human cancers. In contrast to the well-characterized tumor-associated macrophages (TAMs), the significance of granulocytes in cancer has only recently begun to emerge with the characterization of tumor-associated neutrophils (TANs). Recent studies show the importance of CD47 in the interaction with macrophages inhibiting phagocytosis and promoting the migration of neutrophils, increasing inflammation which can lead to recurrence and progression in lung cancer. Currently, therapies are targeted towards blocking CD47 and enhancing macrophage-mediated phagocytosis. However, antibody-based therapies may have adverse effects that limit its use.

Blood Genome-Wide Transcriptional Profiles of HER2 Negative Breast Cancers Patients

Tumors act systemically to sustain cancer progression, affecting the physiological processes in the host and triggering responses in the blood circulating cells. In this study, we explored blood transcriptional patterns of patients with two subtypes of HER2 negative breast cancers, with different prognosis and therapeutic outcome. Peripheral blood samples from seven healthy female donors and 29 women with breast cancer including 14 triple-negative breast cancers and 15 hormone-dependent breast cancers were evaluated by microarray. We also evaluated the stroma in primary tumors. Transcriptional analysis revealed distinct molecular signatures in the blood of HER2− breast cancer patients according to ER/PR status. Our data showed the implication of immune signaling in both breast cancer subtypes with an enrichment of these processes in the blood of TNBC patients. We observed a significant alteration of “chemokine signaling,” “IL-8 signaling,” and “communication between innate and adaptive immune cells” pathways in the blood of TNBC patients correlated with an increased inflammation and necrosis in their primary tumors. Overall, our data indicate that the presence of triple-negative breast cancer is associated with an enrichment of altered systemic immune-related pathways, suggesting that immunotherapy could possibly be synergistic to the chemotherapy, to improve the clinical outcome of these patients.

A Common Genetic Variant in TLR1 Enhances Human Neutrophil Priming and Impacts Length of Intensive Care Stay in Pediatric Sepsis

Polymorphonuclear leukocytes (PMN) achieve an intermediate or primed state of activation following stimulation with certain agonists. Primed PMN have enhanced responsiveness to subsequent stimuli, which can be beneficial in eliminating microbes but may cause host tissue damage in certain disease contexts, including sepsis. As PMN priming by TLR4 agonists is well described, we hypothesized that ligation of TLR2/1 or TLR2/6 would prime PMN. Surprisingly, PMN from only a subset of donors were primed in response to the TLR2/1 agonist, Pam3CSK4, although PMN from all donors were primed by the TLR2/6 agonist, FSL-1. Priming responses included generation of intracellular and extracellular reactive oxygen species, MAPK phosphorylation, integrin activation, secondary granule exocytosis, and cytokine secretion. Genotyping studies revealed that PMN responsiveness to Pam3CSK4 was enhanced by a common single-nucleotide polymorphism (SNP) in TLR1 (rs5743618). Notably, PMN from donors with the SNP had higher surface levels of TLR1 and were demonstrated to have enhanced association of TLR1 with the endoplasmic reticulum chaperone gp96. We analyzed TLR1 genotypes in a pediatric sepsis database and found that patients with sepsis or septic shock who had a positive blood culture and were homozygous for the SNP associated with neutrophil priming had prolonged pediatric intensive care unit length of stay. We conclude that this TLR1 SNP leads to excessive PMN priming in response to cell stimulation. Based on our finding that septic children with this SNP had longer pediatric intensive care unit stays, we speculate that this SNP results in hyperinflammation in diseases such as sepsis.

From neutrophils to macrophages: differences in regional adipose tissue depots

Currently, we do not fully understand the underlying mechanisms of how regional adiposity promotes metabolic dysregulation. As adipose tissue expands, there is an increase in chronic systemic low-grade inflammation due to greater infiltration of immune cells and production of cytokines. This chronic inflammation is thought to play a major role in the development of metabolic complications and disease such as insulin resistance and diabetes. We know that different adipose tissue depots contribute differently to the risk of metabolic disease. People who have an upper body fat distribution around the abdomen are at greater risk of disease than those who tend to store fat in their lower body around the hips and thighs. Thus, it is conceivable that adipose tissue depots contribute differently to the inflammatory milieu as a result of varied infiltration of immune cell types. In this review, we describe the role and function of major resident immune cells in the development of adipose tissue inflammation and discuss their regional differences in the context of metabolic disease risk. We find that although initial studies have found regional differences, a more comprehensive understanding of how immune cells interrupt adipose tissue homeostasis is needed.

Streptolysin O Rapidly Impairs Neutrophil Oxidative Burst and Antibacterial Responses to Group A Streptococcus

Group A Streptococcus (GAS) causes a wide range of human infections, ranging from simple pharyngitis to life-threatening necrotizing fasciitis and toxic shock syndrome. A globally disseminated clone of M1T1 GAS has been associated with an increase in severe, invasive GAS infections in recent decades. The secreted GAS pore-forming toxin streptolysin O (SLO), which induces eukaryotic cell lysis in a cholesterol-dependent manner, is highly upregulated in the GAS M1T1 clone during bloodstream dissemination. SLO is known to promote GAS resistance to phagocytic clearance by neutrophils, a critical first element of host defense against invasive bacterial infection. Here, we examine the role of SLO in modulating specific neutrophil functions during their early interaction with GAS. We find that SLO at subcytotoxic concentrations and early time points is necessary and sufficient to suppress neutrophil oxidative burst, in a manner reversed by free cholesterol and anti-SLO blocking antibodies. In addition, SLO at subcytotoxic concentrations blocked neutrophil degranulation, interleukin-8 secretion and responsiveness, and elaboration of DNA-based neutrophil extracellular traps, cumulatively supporting a key role for SLO in GAS resistance to immediate neutrophil killing. A non-toxic SLO derivate elicits protective immunity against lethal GAS challenge in a murine infection model. We conclude that SLO exerts a novel cytotoxic-independent function at early stages of invasive infections (<30 min), contributing to GAS escape from neutrophil clearance.

ROS production, intracellular HSP70 levels and their relationship in human neutrophils: effects of age

ROS production and intracellular HSP70 levels were measured in human neutrophils for three age groups: young (20-59 years), elders (60-89 years) and nonagenarians (90 years and older). Elders showed higher levels of spontaneous intracellular ROS content compared with young and nonagenarian groups, which had similar intracellular ROS levels. Zymosan-induced (non-spontaneous) extracellular ROS levels were also similar for young and nonagenarians but were lower in elders. However, spontaneous extracellular ROS production increased continuously with age. Correlation analysis revealed positive relationships between HSP70 levels and zymosan-stimulated ROS production in the elder group. This was consistent with a promoting role for HSP70 in ROS-associated neutrophils response to pathogens. No positive correlation between ROS production and intracellular HSP70 levels was found for groups of young people and nonagenarians. In contrast, significant negative correlations of some ROS and HSP70 characteriscics were found for neutrophils from young people and nonagenarians. The observed difference in ROS and HSP70 correlations in elders and nonagenarians might be associated with an increased risk of mortality in older individuals less than 90 years old.

Update on Pediatric Cough

Despite the high prevalence of cough in children, the topic has been poorly researched. Although pediatricians recognize that chronic cough in children is different from that in adults, this difference seems less recognizable to other health professionals. During childhood, the respiratory tract and nervous system undergo a series of anatomical and physiological maturation processes that influence the cough reflex. Additionally, immunological responses undergo developmental and memorial processes that make infection and congenital abnormalities the overwhelming cause of cough in children. The lack of comprehensive clinical data regarding chronic cough in children has initially required pediatricians to adopt an adult approach to the problem. In the last 10 years, however, research has led to the reconsideration of the etiology of chronic cough in children. Currently, attention has focused on protracted bacterial bronchitis as a major cause of chronic cough in preschool-aged children and as a possible precursor of bronchiectasis. New research horizons are emerging for both the treatment and prevention of particular causes of chronic cough in children.

Neutrophil Extracellular Traps in Periodontitis: A Web of Intrigue

Neutrophil extracellular traps (NETs) represent a novel paradigm in neutrophil-mediated immunity. NETs are believed to constitute a highly conserved antimicrobial strategy comprising decondensed nuclear DNA and associated histones that are extruded into the extracellular space. Associated with the web-like strands of DNA is an array of antimicrobial peptides (AMPs), which facilitate the extracellular destruction of microorganisms that become entrapped within the NETs. NETs can be released by cells that remain viable or following a unique form of programmed cell death known as NETosis, which is dependent on the production of reactive oxygen species (ROS) and the decondensing of the nuclear DNA catalyzed by peptidyl arginine deiminase-4. NETs are produced in response to a range of pathogens, including bacteria, viruses, fungi, and protozoa, as well as host-derived mediators. NET release is, however, not without cost, as the concomitant release of cytotoxic molecules can also cause host tissue damage. This is evidenced by a number of immune-mediated diseases, in which excess or dysfunctional NET production, bacterial NET evasion, and decreased NET removal are associated with disease pathogenesis. Periodontitis is the most prevalent infectious-inflammatory disease of humans, characterized by a dysregulated neutrophilic response to specific bacterial species within the subgingival plaque biofilm. Neutrophils are the predominant inflammatory cell involved in periodontitis and have previously been found to exhibit hyperactivity and hyperreactivity in terms of ROS production in chronic periodontitis patients. However, the contribution of ROS-dependent NET formation to periodontal health or disease remains unclear. In this focused review, we discuss the mechanisms, stimuli, and requirements for NET production; the ability of NET-DNA and NET-associated AMPs to entrap and kill pathogens; and the potential immunogenicity of NETs in disease. We also speculate on the potential role of NETs in the pathogenesis of periodontitis.

Oral TNFα Modulation Alters Neutrophil Infiltration, Improves Cognition and Diminishes Tau and Amyloid Pathology in the 3xTgAD Mouse Model

Cytokines such as TNFα can polarize microglia/macrophages into different neuroinflammatory types. Skewing of the phenotype towards a cytotoxic state is thought to impair phagocytosis and has been described in Alzheimer’s Disease (AD). Neuroinflammation can be perpetuated by a cycle of increasing cytokine production and maintenance of a polarized activation state that contributes to AD progression. In this study, 3xTgAD mice, age 6 months, were treated orally with 3 doses of the TNFα modulating compound isoindolin-1,3 dithione (IDT) for 10 months. We demonstrate that IDT is a TNFα modulating compound both in vitro and in vivo. Following long-term IDT administration, mice were assessed for learning & memory and tissue and serum were collected for analysis. Results demonstrate that IDT is safe for long-term treatment and significantly improves learning and memory in the 3xTgAD mouse model. IDT significantly reduced paired helical filament tau and fibrillar amyloid accumulation. Flow cytometry of brain cell populations revealed that IDT increased the infiltrating neutrophil population while reducing TNFα expression in this population. IDT is a safe and effective TNFα and innate immune system modulator. Thus small molecule, orally bioavailable modulators are promising therapeutics for Alzheimer’s disease.

Anti-Inflammatory Effects of IL-27 in Zymosan-Induced Peritonitis: Inhibition of Neutrophil Recruitment Partially Explained by Impaired Mobilization from Bone Marrow and Reduced Chemokine Levels

Rapid activation of the innate immune system is critical for an efficient host response to invading pathogens. However, the inflammatory reaction has to be strictly controlled to minimize harmful immunopathology. A number of mediators including the cytokine interleukin-27 (IL-27) appear to be responsible for limitation and resolution of inflammation. Despite increasing knowledge of its suppressive effects on T cells, the influence on neutrophils and macrophages is poorly understood. To determine the role of IL-27 in innate immune responses we analysed the effect of IL-27 in a T cell independent model of zymosan-induced peritonitis. Early administration of recombinant IL-27 strongly reduced the number of neutrophils recruited to the peritoneal cavity after zymosan application as well as the neutrophil frequency in the blood. Simultaneously, IL-27 reduced the release of neutrophils from the bone marrow upon inflammation. Although cytokine levels were not affected by IL-27 treatment, the levels of the chemokines KC, MCP-1 and MIP-1α in the peritoneal fluid were strongly decreased. These findings demonstrate that IL-27 is able to control mobilisation and recruitment of neutrophils into the peritoneal cavity and identify a novel mechanism to limit inflammation caused by innate immune cells.

Role of the Yersinia YopJ protein in suppressing interleukin-8 secretion by human polymorphonuclear leukocytes

Polymorphonuclear leukocytes, in addition to their direct bactericidal activities, produce cytokines involved in the activation and regulation of the innate and adaptive immune response to infection. In this study we evaluated the cytokine response of human PMNs following incubation with the pathogenic Yersinia species. Yersinia pestis strains with the pCD1 virulence plasmid, which encodes cytotoxic Yop proteins that are translocated into host cells, stimulated little or no cytokine production compared to pCD1-negative strains. In particular, PMNs incubated with pCD1-negative Y. pestis secreted 1000-fold higher levels of interleukin-8 (IL-8 or CXCL8), a proinflammatory chemokine important for PMN recruitment and activation. Deletion of yopE, -H, -T, -M or ypkA had no effect on pCD1-dependent inhibition, whereas deletion of yopJ resulted in significantly increased IL-8 production. Like Y. pestis, the enteropathogenic Yersinia species inhibited IL-8 secretion by PMNs, and strains lacking the virulence plasmid induced high levels of IL-8. Our results show that virulence plasmid-encoded effector Yops, particularly YopJ, prevent IL-8 secretion by human PMNs. Suppression of the chemotactic IL-8 response by Y. pestis may contribute to the delayed PMN recruitment to the infected lymph node that typifies bubonic plague.

Cathelicidin impact on inflammatory cells

Cathelicidins, like other antimicrobial peptides, exhibit direct antimicrobial activities against a broad spectrum of microbes, including both Gram-positive and Gram-negative bacteria, enveloped viruses, and fungi. These host-derived peptides kill the invaded pathogens by perturbing their cell membranes and can neutralize biological activities of endotoxin. Nowadays, more and more data indicate that these peptides, in addition to their antimicrobial properties, possess various immunomodulatory activities. Cathelicidins have the potential to influence and modulate, both directly and indirectly, the activity of various cell populations involved in inflammatory processes and in host defense against invading pathogens. They induce migration of neutrophils, monocytes/macrophages, eosinophils, and mast cells and prolong the lifespan of neutrophils. These peptides directly activate inflammatory cells to production and release of different pro-inflammatory and immunoregulatory mediators, cytokines, and chemokines, however cathelicidins might mediate the generation of anti-inflammatory cytokines as well. Cathelicidins also modulate epithelial cell/keratinocyte responses to infecting pathogens. What is more, they affect activity of monocytes, dendritic cells, keratinocytes, or epithelial cells acting in synergy with cytokines or β-defensins. In addition, these peptides indirectly balance TLR-mediated responses of monocytes, macrophages, dendritic cells, epithelial cells, and keratinocytes. This review discusses the role and significance of cathelicidins in inflammation and innate immunity against pathogens.

Role of PTEN in neutrophil extracellular trap formation

NETosis has been associated with a particular mode of cell death although it is still controversial as to what extent autophagy is involved in NETosis. Class I/AKT/mTOR pathway is a key regulator of autophagy. PTEN tumor suppressor gene encodes a dual specificity phosphatase that antagonizes the phosphatidylinositol 3-kinase in class the I/AKT/mTOR pathway. In this study, we investigated the effects of PTEN down-regulation as well as overexpression on NETosis. Our results show that 35% of HL-60 differentiated neutrophil-like cells generated NETs by PMA. The portion of the population that produced NETs in PTEN knockdown HL-60 differentiated neutrophils was 9% and in PTEN overexpressed HL-60 differentiated neutrophils, it was 56%. Our results show that increasing PTEN expression increases NETs formation in neutrophils, and its suppression reduces NETs.

Two new inflammatory markers associated with Disease Activity Score-28 in patients with rheumatoid arthritis: neutrophil-lymphocyte ratio and platelet-lymphocyte ratio

AIM

Rheumatoid arthritis (RA) is an inflammatory autoimmune disease with unknown etiology and systemic involvement. Neutrophil-lymphocyte ratio (NLR) and platelet-lymphocyte ratio (PLR) are two new inflammatory markers used in the assessment of systemic inflammation. The aim here is to study NLR and PLR in patients with RA to investigate their relation with Disease Activity Score of 28 joints (DAS-28).

METHODS

The study included 104 patients with RA and a control group of 51 age- and gender-matched healthy subjects. We divided the patients into two groups according to the DAS-28 score. Group 1 included patients with a score of lower than 2.6 by the DAS-28 (patients in remission) and Group 2 included patients with a score of 2.6 and higher (patients with active disease).

RESULTS

NLR was 2.12 ± 0.83 in the patient group and 1.58 ± 0.57 in the control group. PLR was 136.50 ± 53.52 in the patient group and 114.84 ± 29.41 in the control group. There was a statistically significant difference in NLR and PLR between the patient and control groups (P ≤ 0.0001 and P = 0.001, respectively). Patients in Group 1 had an NLR of 1.84 ± 0.61 and a PLR of 119.25 ± 41.77. Patients in Group 2 had an NLR of 2.29 ± 0.90 and a PLR of 147.28 ± 56.96. There was a statistically significant difference in NLR and PLR between the two groups (P = 0.003 and P = 0.005 respectively). A correlation was observed between NLR and PLR by DAS-28 (r = 0.345, P ≤ 0.0001 and r = 0.352, P ≤ 0.0001, respectively).

CONCLUSIONS

The present study showed us that NLR and PLR were two new inflammatory markers which could be used to assess disease activity in patients with RA.

Inhibition of connexin 43 hemichannel-mediated ATP release attenuates early inflammation during the foreign body response

BACKGROUND

In the last 50 years, the use of medical implants has increased dramatically. Failure of implanted devices and biomaterials is a significant source of morbidity and increasing healthcare expenditures. An important cause of implant failure is the host inflammatory response. Recent evidence implicates extracellular ATP as an important inflammatory signaling molecule. A major pathway for release of cytoplasmic ATP into the extracellular space is through connexin hemichannels, which are the unpaired constituents of gap junction intercellular channels. Blockade of hemichannels of the connexin 43 (Cx43) isoform has been shown to reduce inflammation and improve healing. We have developed a Cx43 mimetic peptide (JM2) that targets the microtubule-binding domain of Cx43. The following report investigates the role of the Cx43 microtubule-binding domain in extracellular ATP release by Cx43 hemichannels and how this impacts early inflammatory events of the foreign body reaction.

METHODS

In vitro Cx43 hemichannel-mediated ATP release by cultured human microvascular endothelial cells subjected to hypocalcemic and normocalcemic conditions was measured after application of JM2 and the known hemichannel blocker, flufenamic acid. A submuscular silicone implant model was used to investigate in vivo ATP signaling during the early foreign body response. Implants were coated with control pluronic vehicle or pluronic carrying JM2, ATP, JM2+ATP, or known hemichannel blockers and harvested at 24 h for analysis.

RESULTS

JM2 significantly inhibited connexin hemichannel-mediated ATP release from cultured endothelial cells. Importantly, the early inflammatory response to submuscular silicone implants was inhibited by JM2. The reduction in inflammation by JM2 was reversed by the addition of exogenous ATP to the pluronic vehicle.

CONCLUSIONS

These data indicate that ATP released through Cx43 hemichannels into the vasculature is an important signal driving the early inflammatory response to implanted devices. A vital aspect of this work is that it demonstrates that targeted molecular therapeutics, such as JM2, provide the capacity to regulate inflammation in a clinically relevant system.

Inflammation and prostate cancer: friends or foe?

INTRODUCTION

Prostate cancer is the most common non-cutaneous malignancy diagnosed in men. Moving from histological observations since a long time, it has been recognized that innate and adaptive immunity actively participates in the pathogenesis, surveillance, and progression of prostate cancer.

MATERIALS AND METHODS

A PubMed and Web of Science databases search was performed for studies providing evidence on the roles of the innate and adaptive immunity during the development and progression of prostate cancer.

CONCLUSIONS

There are growing evidences that chronic inflammation is involved in the regulation of cellular events in prostate carcinogenesis, including disruption of the immune response and regulation of the tumor microenvironment. This review discusses the role played by the innate and adaptive immune system in the local progression of prostate cancer, and the prognostic information that we can currently understand and exploit.

Altered neutrophil functions in elderly patients during a 6-month follow-up period after a hip fracture

BACKGROUND

Fracture of the hip (HF) is a significant cause of morbidity and mortality in elderly individuals. HF is an acute stress that triggers a state of inflammation which may affect immune responses and physical recovery.

METHODS

Longitudinal study of the impact of HF on the functions of polymorphonuclear neutrophils (PMNs) in elderly subjects. Data were recorded prior to surgery, 6weeks and 6months later.

RESULTS

PMN functions were severely impaired shortly after HF (chemotaxis, phagocytosis, superoxide production) but there was a time-related recovery of some PMN functions (chemotaxis, phagocytosis) over time, except in the case of superoxide production. Whereas FcγRII (CD32) expression remained unchanged, FcγRIII (CD16) increased from low values before surgery to levels of controls 6months post-surgery. This was also the case for the C5a complement receptor and CD11b. TLR2 and TLR4 expressions were unchanged. Cytokine and chemokine secretions by stimulated PMN were altered. TNFα and IL-10 secretions were increased following HF but IL-8 secretion was decreased. Impaired PMN functions prior to surgery were related to alterations in PI3K and NF-κB signaling pathways. Recovery of these functions paralleled increased PI3K activity, although superoxide production remained low. Sustained activation of the NF-κB pathway by TNFα has been reported to involve upregulation of IKKβ kinase activity. Activated IKKβ kinase inhibits ERK1/2 and results in concomitant downstream inhibition of NADPH oxidase complex which can account for sustained impaired production of ROS in HF patients.

CONCLUSION

Our data showed that the stress caused by HF negatively affects initial PMN responses shortly after the event and that may negatively influence clinical outcomes such as resolving long-term inflammation and recovery, as well as explaining susceptibility to opportunistic infections.

The role of formylated peptides and formyl peptide receptor 1 in governing neutrophil function during acute inflammation

Neutrophil migration to sites of inflammation and the subsequent execution of multiple functions are designed to contain and kill invading pathogens. These highly regulated and orchestrated processes are controlled by interactions between numerous receptors and their cognate ligands. Unraveling and identifying those that are central to inflammatory processes may represent novel therapeutic targets for the treatment of neutrophil-dominant inflammatory disorders in which dysregulated neutrophil recruitment, function, and elimination serve to potentiate rather than resolve an initial inflammatory insult. The first G protein-coupled receptor to be described on human neutrophils, formyl peptide receptor 1 (FPR1), is one such receptor that plays a significant role in the execution of these functions through multiple intracellular signaling pathways. Recent work has highlighted important observations with regard to both receptor function and the importance and functional relevance of FPR1 in the pathogenesis of a range of both sterile and infective inflammatory conditions. In this review, we explore the multiple components of neutrophil migration and function in both health and disease, with a focus on the role of FPR1 in these processes. The current understanding of FPR1 structure, function, and signaling is examined, alongside discussion of the potential importance of FPR1 in inflammatory diseases suggesting that FPR1 is a key regulator of the inflammatory environment.

Influence of 4 weeks of bovine colostrum supplementation on neutrophil and mucosal immune responses to prolonged cycling

Bovine colostrum (COL) has been advocated as a nutritional countermeasure to exercise-induced immune dysfunction. The aims of this study were to identify the effects of 4 weeks of COL supplementation on neutrophil responses and mucosal immunity following prolonged exercise. In a randomized double-blind, parallel group design, participants [age 28 ± 8 years; body mass 79 ± 7 kg; height 182 ± 6 cm; maximal oxygen uptake (V̇O2max) 55 ± 9 mL/kg/min] were assigned to 20 g per day of COL (n = 10) or an isoenergetic/isomacronutrient placebo (PLA; n = 10) for 4 weeks. Venous blood and unstimulated saliva samples were obtained before and after 2.5 h of cycling at 15% Δ (∼55-60% V̇O2max). A significantly greater formyl-methionyl-leucyl phenylalanine-stimulated oxidative burst was observed in the COL group compared with PLA group (P < 0.05) and a trend toward a time × group interaction (P = 0.06). However, there was no effect of COL on leukocyte trafficking, phorbol-12-myristate-13-acetate-stimulated oxidative burst, bacterial-stimulated neutrophil degranulation, salivary secretory IgA, lactoferrin or lysozyme (P > 0.05). These findings provide further evidence of the beneficial effects of COL on receptor-mediated stimulation of neutrophil oxidative burst in a model of exercise-induced immune dysfunction.

Fucoidan from Macrocystis pyrifera has powerful immune-modulatory effects compared to three other fucoidans

Fucoidan, a sulfated polysaccharide purified from brown algae, has a variety of immune-modulation effects, such as promoting activation of dendritic cells (DCs), natural killer (NK) cells and T cells, and enhancing anti-viral and anti-tumor responses. However, the immune-modulatory effect of fucoidan from different seaweed extracts has not been thoroughly analyzed and compared. We analyzed fucoidans obtained from Ascophyllum nodosum (A. nodosum), Macrocystis pyrifera (M. pyrifera), Undaria pinnatifida (U. pinnatifida) and Fucus vesiculosus (F. vesiculosus) for their effect on the apoptosis of human neutrophils, activation of mouse NK cells, maturation of spleen DCs, proliferation and activation of T cells, and the adjuvant effect in vivo. Fucoidans from M. pyrifera and U. pinnatifida strongly delayed human neutrophil apoptosis at low concentration, whereas fucoidans from A. nodosum and F. vesiculosus delayed human neutrophil apoptosis at higher concentration. Moreover, fucoidan from M. pyrifera promoted NK cell activation and cytotoxic activity against YAC-1 cells. In addition, M. pyrifera fucoidan induced the strongest activation of spleen DCs and T cells and ovalbumin (OVA) specific immune responses compared to other fucoidans. These data suggest that fucoidan from M. pyrifera can be potentially useful as a therapeutic agent for infectious diseases, cancer and an effective adjuvant for vaccine.

Neutrophil recruitment to the brain in mouse and human ischemic stroke

Neutrophils are rapidly recruited in response to local tissue infection or inflammation. Stroke triggers a strong inflammatory reaction but the relevance of neutrophils in the ischemic brain is not fully understood, particularly in the absence of reperfusion. We investigated brain neutrophil recruitment in two murine models of permanent ischemia induced by either cauterization of the distal portion of the middle cerebral artery (c-MCAo) or intraluminal MCA occlusion (il-MCAo), and three fatal cases of human ischemic stroke. Flow cytometry analyses revealed progressive neutrophil recruitment after c-MCAo, lesser neutrophil recruitment following il-MCAo, and absence of neutrophils after sham operation. Confocal microscopy identified neutrophils in the leptomeninges from 6 h after the occlusion, in the cortical basal lamina and cortical Virchow-Robin spaces from 15 h, and also in the cortical brain parenchyma at 24 h. Neutrophils showed signs of activation including histone-3 citrullination, chromatin decondensation, and extracellular projection of DNA and histones suggestive of extracellular trap formation. Perivascular neutrophils were identified within the entire cortical infarction following c-MCAo. After il-MCAo, neutrophils prevailed in the margins but not the center of the cortical infarct, and were intraluminal and less abundant in the striatum. The lack of collaterals to the striatum and a collapsed pial anastomotic network due to brain edema in large hemispheric infarctions could impair neutrophil trafficking in this model. Neutrophil extravasation at the leptomeninges was also detected in the human tissue. We concluded that neutrophils extravasate from the leptomeningeal vessels and can eventually reach the brain in experimental animal models and humans with prolonged arterial occlusion.

Production of inflammatory mediators and extracellular traps by carp macrophages and neutrophils in response to lipopolysaccharide and/or interferon-γ2

Neutrophilic granulocytes and macrophages are crucial for the innate immune response against infections. They migrate into the focus of inflammation, where they efficiently bind, engulf and kill bacteria by proteolytic enzymes, antimicrobial peptides, reactive oxygen (ROS) and nitrogen (RNS) species. Moreover, activated neutrophils and macrophages can form extracellular traps (ETs). Fish neutrophils and macrophages are morphologically, histochemically, and functionally similar to their mammalian counterparts, but their significance for regulation of inflammatory responses and pathogen killing needs further elucidation. We compared the activity of head kidney monocytes/macrophages and neutrophilic granulocytes of common carp and established that upon lipopolysaccharide stimulation, not only neutrophils, but also carp monocytes/macrophages release extracellular DNA and are capable to form macrophage extracellular traps (METs). To clarify whether many specific LPS functions reported for piscine phagocytes might be due to impurities in the commonly used LPS preparations we studied expression of inflammatory mediators, release of DNA, ROS and RNS in cells stimulated with LPS or its highly purified form (pLPS). Also IFN-γ2 stimulation and its synergism with LPS/pLPS in stimulating expression of pro-inflammatory mediators was studied. Results substantiate that a classical stimulation of TLR4 by LPS may indeed be absent in carp as most of the classically reported LPS effects are abolished or diminished when pLPS is used. Interestingly, we also observed a potent IL-10 expression in neutrophilic granulocytes upon LPS stimulation, which, apart from their pro-inflammatory function, clearly indicates a role in restrictive control of the inflammatory reaction.

Selenium deficiency influences the gene expressions of heat shock proteins and nitric oxide levels in neutrophils of broilers

The aim of the present study was to investigate the effects of selenium (Se) deficiency on the expressions of heat shock proteins (Hsp90, 70, 60, 40, and 27) and nitric oxide (NO) levels in neutrophils of broilers. One hundred eighty 1-day-old broilers were randomly assigned into two groups and were fed on a low-Se diet (0.008 mg/kg Se) or a control diet (0.2 mg/kg Se), respectively. Then, the messenger RNA (mRNA) levels of Hsp90, 70, 60, 40, and 27, induced nitric oxide synthase (iNOS), and NO levels were examined. The results showed that Se deficiency increased the mRNA levels of Hsps and iNOS and induced higher level of NO in chicken neutrophils (P < 0.05). It showed that the expression of Hsp40 increased higher than other Hsps in neutrophils, which indicated that it might play the crucial protective role in neutrophils. In addition, correlation analysis showed that iNOS had the biggest correlation with Hsp60, which indicated that Hsp60 might play an important function in inhibiting the production of NO, and the correlation coefficient between Hsp60 and Hsp70 was over 0.9, which indicated that they might have a synergistic effect. These results suggested that the level of NO and Hsp expression levels in neutrophils can be influenced by Se deficiency. And Hsp40 might play the crucial protective role in neutrophils induced by Se deficiency.

Fucoidan delays apoptosis and induces pro-inflammatory cytokine production in human neutrophils

Although some immune modulatory effects of fucoidan have been elucidated, the effects of fucoidan on the apoptosis and activation of human neutrophils have not been investigated. In this study, we demonstrated that fucoidan purified from the brown seaweed Undaria pinnatifilda delays spontaneous apoptosis of human neutrophils and induces their activation. Fucoidan treatment inhibited apoptotic nuclei changes and phosphatidyl serine (PS) exposure on neutrophils cultured in vitro for 24h. The delay in neutrophil apoptosis mediated by fucoidan was associated with increased levels of the anti-apoptotic protein Mcl-1 and decreased levels of activated caspase-3. Screening of the signaling pathways by specific inhibitors indicated that fucoidan-induced delay in neutrophil apoptosis was dependent on the activation of PI3K/AKT signaling pathway, whereas MAPK signaling pathway was not critical. In addition, fucoidan enhanced the production of IL-6, IL-8 and TNF-α from neutrophils in an AKT-dependent manner. Taken together, these results demonstrated that fucoidan delays human neutrophil apoptosis and induces their production of pro-inflammatory cytokines. This knowledge could facilitate the development of novel therapeutic strategies for infectious diseases and neutropenia by controlling neutrophil homeostasis and function with fucoidan.

Reduced bioenergetics and toll-like receptor 1 function in human polymorphonuclear leukocytes in aging

Aging is associated with a progressive decline in immune function (immunosenescence) resulting in an increased susceptibility to viral and bacterial infections. Here we show reduced expression of Toll-like receptor 1 (TLR1) in polymorphonuclear leukocytes (PMN) and an underlying age-dependent deficiency in PMN bioenergetics. In older (>65 years) adults, stimulation through TLR1 led to lower activation of integrins (CD11b and CD18), lower production of the chemokine IL-8, and lower levels of the phosphorylated signaling intermediate p38 MAP kinase than in PMN from younger donors (21-30 years). In addition, loss of CD62L, a marker of PMN activation, was reduced in PMN of older adults stimulated through multiple pathways. Rescue of PMN from apoptosis by stimulation with TLR1 was reduced in PMN from older adults. In seeking an explanation for effects of aging across multiple pathways, we examined PMN energy utilization and found that glucose uptake after stimulation through TLR1 was dramatically lower in PMN of older adults. Our results demonstrate a reduction in TLR1 expression and TLR1-mediated responses in PMN with aging, and reduced efficiency of bioenergetics in PMN. These changes likely contribute to reduced PMN efficiency in aging through multiple aspects of PMN function and suggest potential therapeutic opportunities.

Neutrophil-derived cytokines: facts beyond expression

Polymorphonuclear neutrophils, besides their involvement in primary defense against infections - mainly through phagocytosis, generation of toxic molecules, release of enzymes, and formation of extracellular traps - are also becoming increasingly important for their contribution to the fine regulation in development of inflammatory and immune responses. These latter functions of neutrophils occur, in part, via their de novo production and release of a large variety of cytokines, including chemotactic cytokines (chemokines). Accordingly, the improvement in technologies for molecular and functional cell analysis, along with concomitant advances in cell purification techniques, have allowed the identification of a continuously growing list of neutrophil-derived cytokines, as well as the characterization of their biological implications in vitro and/or in vivo. This short review summarizes crucial concepts regarding the modalities of expression, release, and regulation of neutrophil-derived cytokines. It also highlights examples illustrating the potential implications of neutrophil-derived cytokines according to recent observations made in humans and/or in experimental animal models.

Intramuscular administration of a synthetic CpG-oligodeoxynucleotide modulates functional responses of neutrophils of neonatal foals

Neutrophils play an important role in protecting against infection. Foals have age-dependent deficiencies in neutrophil function that may contribute to their predisposition to infection. Thus, we investigated the ability of a CpG-ODN formulated with Emulsigen to modulate functional responses of neutrophils in neonatal foals. Eighteen foals were randomly assigned to receive either a CpG-ODN with Emulsigen (N = 9) or saline intramuscularly at ages 1 and 7 days. At ages 1, 3, 9, 14, and 28, blood was collected and neutrophils were isolated from each foal. Neutrophils were assessed for basal and Rhodococcus equi-stimulated mRNA expression of the cytokines interferon-γ (IFN-γ), interleukin (IL)-4, IL-6, and IL-8 using real-time PCR, degranulation by quantifying the amount of β-D glucuronidase activity, and reactive oxygen species (ROS) generation using flow cytometry. In vivo administration of the CpG-ODN formulation on days 1 and 7 resulted in significantly (P<0.05) increased IFN-γ mRNA expression by foal neutrophils on days 3, 9, and 14. Degranulation was significantly (P<0.05) lower for foals in the CpG-ODN-treated group than the control group at days 3 and 14, but not at other days. No effect of treatment on ROS generation was detected. These results indicate that CpG-ODN administration to foals might improve innate and adaptive immune responses that could protect foals against infectious diseases and possibly improve responses to vaccination.

Granule protein processing and regulated secretion in neutrophils

Neutrophils are part of a family of granulocytes that, together with eosinophils and basophils, play an essential role in innate immunity. Neutrophils are the most abundant circulating leukocytes and are vital for rapid immune responses, being recruited to sites of injury or infection within minutes, where they can act as specialized phagocytic cells. However, another prominent function of neutrophils is the release of pro-inflammatory compounds, including cytokines, chemokines, and digestive enzymes, which are stored in intracellular compartments and released through regulated exocytosis. Hence, an important feature that contributes to rapid immune responses is capacity of neutrophils to synthesize and store pre-formed pro-inflammatory mediators in specialized intracellular vesicles and thus no new synthesis is required. This review will focus on advancement in three topics relevant to neutrophil secretion. First, we will examine what is known about basal level pro-inflammatory mediator synthesis, trafficking, and storage in secretory compartments. Second, we will review recent advancements in the mechanisms that control vesicle mobilization and the release of pre-formed mediators. Third, we will examine the upregulation and de novo synthesis of pro-inflammatory mediators by neutrophils engaged at sites of infection.

Global analysis of neutrophil responses to Neisseria gonorrhoeae reveals a self-propagating inflammatory program

An overwhelming neutrophil-driven response causes both acute symptoms and the lasting sequelae that result from infection with Neisseria gonorrhoeae. Neutrophils undergo an aggressive opsonin-independent response to N. gonorrhoeae, driven by the innate decoy receptor CEACAM3. CEACAM3 is exclusively expressed by human neutrophils, and drives a potent binding, phagocytic engulfment and oxidative killing of Opa-expressing bacteria. In this study, we sought to explore the contribution of neutrophils to the pathogenic inflammatory process that typifies gonorrhea. Genome-wide microarray and biochemical profiling of gonococcal-infected neutrophils revealed that CEACAM3 engagement triggers a Syk-, PKCδ- and Tak1-dependent signaling cascade that results in the activation of an NF-κB-dependent transcriptional response, with consequent production of pro-inflammatory cytokines. Using an in vivo model of N. gonorrhoeae infection, we show that human CEACAM-expressing neutrophils have heightened migration toward the site of the infection where they may be further activated upon Opa-dependent binding. Together, this study establishes that the role of CEACAM3 is not restricted to the direct opsonin-independent killing by neutrophils, since it also drives the vigorous inflammatory response that typifies gonorrhea. By carrying the potential to mobilize increasing numbers of neutrophils, CEACAM3 thereby represents the tipping point between protective and pathogenic outcomes of N. gonorrhoeae infection.

Gonorrhea is a sexually transmitted infection caused by the bacteria Neisseria gonorrhoeae. These bacteria have re-emerged as a public health priority due to its acquisition of resistance to multiple antibiotics, leading to fears of untreatable infection. The symptoms of gonorrhea include an intense inflammatory response that may lead to pus discharged from the infected genital tract and scarring of the reproductive tract caused by neutrophils recruited to the site of infection. Past studies have detailed molecular interactions that lead to neutrophil binding and engulfment of N. gonorrhoeae, yet it remains unclear why N. gonorrhoeae elicits such a pathogenic inflammatory response. In this study, we reveal that N. gonorrhoeae binding to the human innate decoy receptor, CEACAM3, elicits a potent intracellular signaling cascade that leads to neutrophil expression of cytokines that actively recruit other neutrophils to the infected tissues. As they encounter the gonococci, the next wave of neutrophils becomes similarly activated, leading to the progressive expansion in phagocytic cell numbers until they overwhelm the infected tissues. While this process promotes a rapid response to a troubling pathogen early during infection, the unrestrained recruitment of neutrophils and their toxic antimicrobial arsenal also lead to the pathogenic consequences associated with gonorrhea.

Dynamics of lung defense in pneumonia: resistance, resilience, and remodeling

Pneumonia is initiated by microbes in the lung, but physiological processes integrating responses across diverse cell types and organ systems dictate the outcome of respiratory infection. Resistance, or actions of the host to eradicate living microbes, in the lungs involves a combination of innate and adaptive immune responses triggered by air-space infection. Resilience, or the ability of the host tissues to withstand the physiologically damaging effects of microbial and immune activities, is equally complex, precisely regulated, and determinative. Both immune resistance and tissue resilience are dynamic and change throughout the lifetime, but we are only beginning to understand such remodeling and how it contributes to the incidence of severe pneumonias, which diminishes as childhood progresses and then increases again among the elderly. Here, we review the concepts of resistance, resilience, and remodeling as they apply to pneumonia, highlighting recent advances and current significant knowledge gaps.

Neutrophils mediate blood-spinal cord barrier disruption in demyelinating neuroinflammatory diseases

Disruption of the blood-brain and blood-spinal cord barriers (BBB and BSCB, respectively) and immune cell infiltration are early pathophysiological hallmarks of multiple sclerosis (MS), its animal model experimental autoimmune encephalomyelitis (EAE), and neuromyelitis optica (NMO). However, their contribution to disease initiation and development remains unclear. In this study, we induced EAE in lys-eGFP-ki mice and performed single, nonterminal intravital imaging to investigate BSCB permeability simultaneously with the kinetics of GFP(+) myeloid cell infiltration. We observed a loss in BSCB integrity within a day of disease onset, which paralleled the infiltration of GFP(+) cells into the CNS and lasted for ∼4 d. Neutrophils accounted for a significant proportion of the circulating and CNS-infiltrating myeloid cells during the preclinical phase of EAE, and their depletion delayed the onset and reduced the severity of EAE while maintaining BSCB integrity. We also show that neutrophils collected from the blood or bone marrow of EAE mice transmigrate more efficiently than do neutrophils of naive animals in a BBB cell culture model. Moreover, using intravital videomicroscopy, we demonstrate that the IL-1R type 1 governs the firm adhesion of neutrophils to the inflamed spinal cord vasculature. Finally, immunostaining of postmortem CNS material obtained from an acutely ill multiple sclerosis patient and two neuromyelitis optica patients revealed instances of infiltrated neutrophils associated with regions of BBB or BSCB leakage. Taken together, our data provide evidence that neutrophils are involved in the initial events that take place during EAE and that they are intimately linked with the status of the BBB/BSCB.

Interleukin-1 receptor but not Toll-like receptor 2 is essential for MyD88-dependent Th17 immunity to Coccidioides infection

Interleukin-17A (IL-17A)-producing CD4(+) T helper (Th17) cells have been shown to be essential for defense against pulmonary infection with Coccidioides species. However, we have just begun to identify the required pattern recognition receptors and understand the signal pathways that lead to Th17 cell activation after fungal infection. We previously reported that Card9(-/-) mice vaccinated with formalin-killed spherules failed to acquire resistance to Coccidioides infection. Here, we report that both MyD88(-/-) and Card9(-/-) mice immunized with a live, attenuated vaccine also fail to acquire protective immunity to this respiratory disease. Like Card9(-/-) mice, vaccinated MyD88(-/-) mice revealed a significant reduction in numbers of both Th17 and Th1 cells in their lungs after Coccidioides infection. Both Toll-like receptor 2 (TLR2) and IL-1 receptor type 1 (IL-1r1) upstream of MyD88 have been implicated in Th17 cell differentiation. Surprisingly, vaccinated TLR2(-/-) and wild-type (WT) mice showed similar outcomes after pulmonary infection with Coccidioides, while vaccinated IL-1r1(-/-) mice revealed a significant reduction in the number of Th17 cells in their infected lungs compared to WT mice. Thus, activation of both IL-1r1/MyD88- and Card9-mediated Th17 immunity is essential for protection against Coccidioides infection. Our data also reveal that the numbers of Th17 cells were reduced in IL-1r1(-/-) mice to a lesser extent than in MyD88(-/-) mice, raising the possibility that other TLRs are involved in MyD88-dependent Th17 immunity to coccidioidomycosis. An antimicrobial action of Th17 cells is to promote early recruitment of neutrophils to infection sites. Our data revealed that neutrophils are required for vaccine immunity to this respiratory disease.

Innate immunity in disease

Cells can innately recognize generic products of viruses, bacteria, fungi, or injured tissue by engagement of pattern recognition receptors. Innate immune cells rapidly respond to this engagement to control commensals, thwart pathogens, and/or prompt repair. Insufficient or excessive activation of the innate immune response results in disease. This review focuses on pattern recognition receptors and cells of the innate immune system that are important for intestinal function. Our improving knowledge pertaining to this important aspect of our immune response is opening potential important new therapeutic opportunities for the treatment of disease.

Transcriptional profiling of Mycobacterium tuberculosis replicating ex vivo in blood from HIV- and HIV+ subjects

Hematogenous dissemination of Mycobacterium tuberculosis (M. tb) occurs during both primary and reactivated tuberculosis (TB). Although hematogenous dissemination occurs in non-HIV TB patients, in ∼80% of these patients, TB manifests exclusively as pulmonary disease. In contrast, extrapulmonary, disseminated, and/or miliary TB is seen in 60–70% of HIV-infected TB patients, suggesting that hematogenous dissemination is likely more common in HIV+ patients. To understand M. tb adaptation to the blood environment during bacteremia, we have studied the transcriptome of M. tb replicating in human whole blood. To investigate if M. tb discriminates between the hematogenous environments of immunocompetent and immunodeficient individuals, we compared the M. tb transcriptional profiles during replication in blood from HIV- and HIV+ donors. Our results demonstrate that M. tb survives and replicates in blood from both HIV- and HIV+ donors and enhances its virulence/pathogenic potential in the hematogenous environment. The M. tb blood-specific transcriptome reflects suppression of dormancy, induction of cell-wall remodeling, alteration in mode of iron acquisition, potential evasion of immune surveillance, and enhanced expression of important virulence factors that drive active M. tb infection and dissemination. These changes are accentuated during bacterial replication in blood from HIV+ patients. Furthermore, the expression of ESAT-6, which participates in dissemination of M. tb from the lungs, is upregulated in M. tb growing in blood, especially during growth in blood from HIV+ patients. Preliminary experiments also demonstrate that ESAT-6 promotes HIV replication in U1 cells. These studies provide evidence, for the first time, that during bacteremia, M. tb can adapt to the blood environment by modifying its transcriptome in a manner indicative of an enhanced-virulence phenotype that favors active infection. Additionally, transcriptional modifications in HIV+ blood may further accentuate M. tb virulence and drive both M. tb and HIV infection.

Innate Immune Responses in the Neutrophils of Community Dwelling and Nursing Home Elders

OBJECTIVE

To evaluate innate immune responses of older disabled nursing home residents that may contribute to infectious disease susceptibility, we compared surface markers and signaling efficiency of neutrophils from nursing home residents and community dwelling elders.

DESIGN

Observational pilot study.

SETTING

Five New Haven, CT area nursing homes and the greater New Haven community.

PARTICIPANTS

15 nursing home residents and 43 community dwelling elders.

MEASUREMENTS

Neutrophils were isolated and Toll-like receptor (TLR) and β2 integrin expression on the surface of unstimulated neutrophils were measured via flow cytometry. Chemokine induction was determined by Quantitative PCR.

RESULTS

Surface expression of TLR4 was elevated among nursing home residents compared to community dwellers (mean percent positive cells 33.91 [SE 2.75] vs. 15.67 [SE 1.58], p<0.001), while expression of the β2 integrins CD11b and CD18 was significantly lower (mean fluorescent intensity 460.8 [SE 49.1] vs. 632.9 [SE 29.5] for CD11b and 59.6 [SE 7.9] vs. 137.6 [SE 4.6] for CD18, p<0.0001). Neutrophils from nursing home residents produced substantially reduced levels of chemokines at baseline and after stimulation.

CONCLUSIONS

Because integrins are an important pathway to phagocyte signaling and contribute to adherence and locomotion of neutrophils, reduced β2 integrin expression may contribute to impaired responses to stimulation and reduced adhesive properties in PMN from nursing home residents. Since integrin CD11b has been shown to negatively regulate TLR4 response, it is plausible that lower levels of CD11b contribute to elevated expression of TLR4.