Expression patterns of the lipopolysaccharide receptor CD14, and the FCgamma receptors CD16 and CD64 on polymorphonuclear neutrophils: data from patients with severe bacterial infections and lipopolysaccharide-exposed cells

Apoptotic Cell-Derived CD14(+) Microparticles Promote the Phagocytic Activity of Neutrophilic Precursor Cells in the Phagocytosis of Apoptotic Cells

Membranous CD14 is crucial in the phagocytic activity of neutrophils. However, the role of CD14(+) microparticles (MPs) derived from apoptotic neutrophils (apo-MP) during the phagocytic process is not clear. All trans-retinoic acid (ATRA) induces acute promyelocytic leukemic NB4 cells along granulocytic differentiation. In this study, we investigated the role of CD14(+)apo-MP in the cell-cell interaction during the phagocytic process of apoptotic cells by viable ATRA-NB4 cells. We firstly demonstrate that CD14 expression and phagocytic activity of NB4 cells were upregulated simultaneously after ATRA treatment in a time-dependent manner, and both were significantly enhanced via concurrent lipopolysaccharide treatment. The phagocytic activity of ATRA-NB4 cells and lipopolysaccharide-treated ATRA-NB4 cells were both significantly attenuated by pre-treating cells with an antibody specific to either CD14 or TLR4. Further flow cytometric analysis demonstrates that apoptotic ATRA-NB4 cells release CD14(+)apo-MP in an idarubicin dosage-dependent manner. Both CD14 expression and the phagocytic activity of viable ATRA-NB4 cells were significantly enhanced after incubation with apo-MP harvested from apoptotic ATRA-NB4 cells, and the apo-MP-enhanced phagocytic activity was significantly attenuated by pre-treating apo-MP with an anti-CD14 antibody before incubation with viable cells. We conclude that CD14(+)apo-MP derived from apoptotic ATRA-NB4 cells promotes the phagocytic activity of viable ATRA-NB4 cells in engulfing apoptotic cells.

Modification of bacterial cells for in vivo remotely guided systems

It was shown recently that bacterial strains, which can act specifically against malignant cells, can be used efficiently in cancer therapy. Many appropriate bacterial strains are either pathogenic or invasive and there is a substantial shortage of methods with which to monitor in vivo the distribution of bacteria used in this way. Here, it is proposed to use a Layer-by-Layer (LbL) approach that can encapsulate individual bacterial cells with fluorescently labeled polyelectrolytes (PE)s and magnetite nanoparticles (NP)s. The NP enable remote direction in vivo to the site in question and the labeled shells in the far-red emission spectra allow non-invasive monitoring of the distribution of bacteria in the body. The magnetic entrapment of the modified bacteria causes the local concentration of the bacteria to increase by a factor of at least 5. The PEs create a strong barrier, and it has been shown in vitro experiments that the division time of bacterial cells coated in this way can be regulated, resulting in control of their invasion into tissues. That animals used in the study survived and did not suffer septic shock, which can be attributed to PE capsules that prevent release of endotoxins from bacterial cells.

Cellular activation status in femoral shaft fracture hematoma following different reaming techniques - A large animal model

The local inflammatory impact of different reaming protocols in intramedullary nailing has been sparsely investigated. We examined the effect of different reaming protocols on fracture hematoma (FH) immunological characteristics in pigs. To do so, a standardized midshaft femur fracture was induced in adult male pigs. Fractures were treated with conventional reamed femoral nailing (group RFN, n = 6); unreamed femoral nailing (group UFN, n = 6); reaming with a Reamer Irrigator Aspirator device (group RIA, n = 12). Animals were observed for 6 h and FH was collected. FH-cell apoptosis and neutrophil receptor expression (Mac-1/CD11b and FcγRIII/CD16) were studied by flow cytometry and local temperature changes were analyzed. The study demonstrates that apoptosis-rates of FH-immune cells were significantly lower in group RIA (3.50 ± 0.53%) when compared with non-RIA groups: (group UFN 12.50 ± 5.22%, p = 0.028 UFN vs. RIA), (group RFN 13.30 ± 3.18%, p < 0.001, RFN vs. RIA). Further, RIA-FH showed lower neutrophil CD11b/CD16 expression when compared with RFN (mean difference of 43.0% median fluorescence intensity (MFI), p = 0.02; and mean difference of 35.3% MFI, p = 0.04, respectively). Finally, RIA induced a transient local hypothermia and hypothermia negatively correlated with both FH-immune cell apoptosis and neutrophil activation. In conclusion, immunologic changes observed in FH appear to be modified by certain reaming techniques. Irrigation during reaming was associated with transient local hypothermia, decreased apoptosis, and reduced neutrophil activation. Further study is warranted to examine whether the rinsing effect of RIA, specific tissue removal by reaming, or thermal effects predominantly determine local inflammatory changes during reaming.

Neutrophil Activation/Maturation Markers in Chronic Heart Failure with Reduced Ejection Fraction

BACKGROUND

Neutrophils are critically involved in the immune response. Inflammatory stimuli alter the expression status of their surface molecule toolset, while inflammation-stimulated granulopoiesis might also influence their maturation status. Data on neutrophil status in heart failure with reduced ejection fraction (HFrEF) are scarce. The present study aims to evaluate the role of neutrophil CD11b, CD66b and CD64 expression in HFrEF.

METHODS

A total of 135 HFrEF patients and 43 controls were recruited. Mean fluorescence intensity of the activation/maturation markers CD11b, CD66b and CD64 was measured on neutrophils by flow cytometry. CD10 (neprilysin) expression was simultaneously determined.

RESULTS

Neutrophil CD64 expression was higher in HFrEF compared with controls, while CD11b/CD66b levels were similar. Neutrophil CD11b and CD66b showed a significant direct correlation to neutrophil CD10 expression (rs = 0.573, p < 0.001 and rs = 0.184, p = 0.033). Neutrophil CD11b and CD66b correlated inversely with heart failure severity reflected by NT-proBNP and NYHA class (NT-proBNP: rs = -0.243, p = 0.005 and rs = -0.250, p = 0.004; NYHA class: p = 0.032 and p = 0.055), whereas no association for CD64 could be found. Outcome analysis did not reveal a significant association between the expression of CD11b, CD66b and CD64 and all-cause mortality (p = ns).

CONCLUSIONS

The results underline the potential role of neutrophils in HFrEF disease pathophysiology and risk stratification and should stimulate further research, characterizing subpopulations of neutrophils and searching for key molecules involved in the downward spiral of inflammation and heart failure.

DEspRhigh neutrophils are associated with critical illness in COVID-19

SARS-CoV-2 infection results in a spectrum of outcomes from no symptoms to widely varying degrees of illness to death. A better understanding of the immune response to SARS-CoV-2 infection and subsequent, often excessive, inflammation may inform treatment decisions and reveal opportunities for therapy. We studied immune cell subpopulations and their associations with clinical parameters in a cohort of 26 patients with COVID-19. Following informed consent, we collected blood samples from hospitalized patients with COVID-19 within 72 h of admission. Flow cytometry was used to analyze white blood cell subpopulations. Plasma levels of cytokines and chemokines were measured using ELISA. Neutrophils undergoing neutrophil extracellular traps (NET) formation were evaluated in blood smears. We examined the immunophenotype of patients with COVID-19 in comparison to that of SARS-CoV-2 negative controls. A novel subset of pro-inflammatory neutrophils expressing a high level of dual endothelin-1 and VEGF signal peptide-activated receptor (DEspR) at the cell surface was found to be associated with elevated circulating CCL23, increased NETosis, and critical-severity COVID-19 illness. The potential to target this subpopulation of neutrophils to reduce secondary tissue damage caused by SARS-CoV-2 infection warrants further investigation.

Ex vivo immune profiling in patient blood enables quantification of innate immune effector functions

The assessment of a patient's immune function is critical in many clinical situations. In complex clinical immune dysfunction like sepsis, which results from a loss of immune homeostasis due to microbial infection, a plethora of pro- and anti-inflammatory stimuli may occur consecutively or simultaneously. Thus, any immunomodulatory therapy would require in-depth knowledge of an individual patient's immune status at a given time. Whereas lab-based immune profiling often relies solely on quantification of cell numbers, we used an ex vivo whole-blood infection model in combination with biomathematical modeling to quantify functional parameters of innate immune cells in blood from patients undergoing cardiac surgery. These patients experience a well-characterized inflammatory insult, which results in mitigation of the pathogen-specific response patterns towards Staphylococcus aureus and Candida albicans that are characteristic of healthy people and our patients at baseline. This not only interferes with the elimination of these pathogens from blood, but also selectively augments the escape of C. albicans from phagocytosis. In summary, our model could serve as a valuable functional immune assay for recording and evaluating innate responses to infection.

Diagnostic value of neutrophil CD64, procalcitonin, and interleukin-6 in sepsis: a meta-analysis

Background

The aim of the study was to conduct a meta-analysis to evaluate the accuracy of neutrophil CD64, procalcitonin (PCT), and interleukin-6 (IL-6) as markers for the diagnosis of sepsis in adult patients.

Methods

Various databases were searched to collect published studies on the diagnosis of sepsis in adult patients using neutrophil CD64, PCT, and IL-6 levels. Utilizing the Stata SE 15.0 software, forest plots and the area under the summary receiver operating characteristic curves were drawn. The pooled sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, diagnostic odds ratio, and area under the curve (AUC) were calculated.

Results

Fifty-four articles were included in the study. The pooled sensitivity, specificity, and AUC of neutrophil CD64 for the diagnosis of sepsis were 0.88 (95% confidence interval [CI], 0.81–0.92), 0.88 (95% CI, 0.83–0.91), and 0.94 (95% CI, 0.91–0.96), respectively. The pooled sensitivity, specificity, and AUC of PCT for the diagnosis of sepsis were 0.82 (95% CI, 0.78–0.85), 0.78 (95% CI, 0.74–0.82), and 0.87 (95% CI, 0.83–0.89), respectively. Subgroup analysis showed that the AUC for PCT diagnosis of intensive care unit (ICU) sepsis was 0.86 (95% CI, 0.83–0.89) and the AUC for PCT diagnosis of non-ICU sepsis was 0.82 (95% CI, 0.78–0.85). The pooled sensitivity, specificity, and AUC of IL-6 for the diagnosis of sepsis were 0.72 (95% CI, 0.65–0.78), 0.70 (95% CI, 0.62–0.76), and 0.77 (95% CI, 0.73–0.80), respectively.

Conclusions

Of the three biomarkers studied, neutrophil CD64 showed the highest diagnostic value for sepsis, followed by PCT, and IL-6. On the other hand, PCT showed a better diagnostic potential for the diagnosis of sepsis in patients with severe conditions compared with that in patients with non-severe conditions.

Effect of High-Density Lipoprotein from Healthy Subjects and Chronic Kidney Disease Patients on the CD14 Expression on Polymorphonuclear Leukocytes

In uremic patients, high-density lipoprotein (HDL) loses its anti-inflammatory features and can even become pro-inflammatory due to an altered protein composition. In chronic kidney disease (CKD), impaired functions of polymorphonuclear leukocytes (PMNLs) contribute to inflammation and an increased risk of cardiovascular disease. This study investigated the effect of HDL from CKD and hemodialysis (HD) patients on the CD14 expression on PMNLs. HDL was isolated using a one-step density gradient centrifugation. Isolation of PMNLs was carried out by discontinuous Ficoll-Hypaque density gradient centrifugation. CD14 surface expression was quantified by flow cytometry. The activity of the small GTPase Rac1 was determined by means of an activation pull-down assay. HDL increased the CD14 surface expression on PMNLs. This effect was more pronounced for HDL isolated from uremic patients. The acute phase protein serum amyloid A (SAA) caused higher CD14 expression, while SAA as part of an HDL particle did not. Lipid raft disruption with methyl-β-cyclodextrin led to a reduced CD14 expression in the absence and presence of HDL. HDL from healthy subjects but not from HD patients decreased the activity of Rac1. Considering the known anti-inflammatory effects of HDL, the finding that even HDL from healthy subjects increased the CD14 expression was unexpected. The pathophysiological relevance of this result needs further investigation.

The Role of TLR2 and TLR4 in Recognition and Uptake of the Apicomplexan Parasite Eimeria bovis and Their Effects on NET Formation

BACKGROUND

Bovine polymorphonuclear neutrophils (PMN) constitutively express the Toll-like receptors (TLRs) TLR2 and TLR4 and have been shown to generate Neutrophil extracellular traps (NETs) upon exposure to Eimeria bovis. The present work investigated the role of TLR2 and TLR4 in the recognition and uptake of E. bovis sporozoites, IL-8 production and neutrophil extracellular trap (NET) formation.

METHODS

TLR expression was performed by flow cytometric analysis on PMN exposed to live carboxyfluorescein succinimidyl ester (CFSE)-stained sporozoites. Supernatants of PMN exposed to different E. bovis sporozoite preparations and antigens in the absence or presence of TLR antibodies were assessed for IL-8 secretion. Cells were exposed to sporozoite preparations and assessed for the activation of transcription factor NF-κB using a luciferase reporter assay. Immunofluorescence analysis was done to investigate TLR2 and TLR4 surface expression and NET formation on bovine PMN exposed to vital sporozoites.

RESULTS

we observed significantly increased TLR2 and TLR4 expression with a mean increase in expression that was greater for TLR2 than TLR4. This upregulation neither inhibited nor promoted sporozoite phagocytosis by bovine PMN. Live sporozoites together with anti-TLR2 mAb resulted in a significant enhancement of IL-8 production. NF-κB activation was more strongly induced in TLR2-HEK cells than in TLR4/MD2-HEK cells exposed to heat-killed sporozoites and antigens. Immunofluorescence analysis showed TLR-positive signals on the surface of PMN and concomitant NET formation.

CONCLUSIONS

This is the first report on E. bovis-induced concomitant TLR2 and TLR4 expression during bovine PMN-derived NETosis.

Neutrophil CD64 a Diagnostic and Prognostic Marker of Sepsis in Adult Critically Ill Patients: A Brief Review

INTRODUCTION

Sepsis is a life-threatening organ dysfunction with increased incidence of morbidity and mortality. Early diagnosis and prompt therapeutic intervention is the cornerstone of sepsis care. Biomarkers play an important role in sepsis having both diagnostic and prognostic implications. Neutrophil CD64 (nCD64) is a useful candidate biomarker for sepsis. Neutrophil CD64 also known as Fc receptor 1 (FcR1), is a high-affinity receptor present on neutrophils for Fc part of immunoglobulin-G (IgG) heavy chain. Its expression gets strongly upregulated in response to proinflammatory cytokines of infection within 4-6 hours. Neutrophil CD64 integrates function involving both innate and adaptive immune responses. The aim of this review is to present literature about nCD64 as a diagnostic and prognostic marker in patients with sepsis/septic shock.

BACKGROUND

The authors searched articles over 13 years, i.e., from 2006 to 2019. They included articles written in English only and further reviewed the reference list of selected articles to obtain potentially relevant articles. Reviews, letters, commentaries, correspondences, case reports, conference abstracts, expert opinions, editorials, and animal experiments were excluded. Articles involving pediatric patients (≤18 years) were also excluded.

REVIEW RESULTS

Several studies have indicated that nCD64 is a highly sensitive and specific marker for the diagnosis of sepsis. Various combinations of biomarkers have been used with nCD64 for a better diagnostic value. Neutrophil CD64 as a prognostic marker in critically ill patients needs to be explored more. Most of the existing literatures have highlighted its prognostic utility based on single value at enrolment. There are limited literatures on prognostic implications of serial trend and kinetics of nCD64.

CONCLUSION

Neutrophil CD64 is a useful diagnostic and prognostic marker of sepsis in critically ill patients. Additional studies are needed on nCD64 in sepsis based on sepsis-3 criteria. Further trials with large sample size are needed to establish prognostic implications of serial nCD64 trend.

HOW TO CITE THIS ARTICLE

Patnaik R, Azim A, Agarwal V. Neutrophil CD64 a Diagnostic and Prognostic Marker of Sepsis in Adult Critically Ill Patients: A Brief Review. Indian J Crit Care Med 2020;24(12):1242-1250.

Effect of lipopolysaccharide structure on functional response of whole blood cells

Lipopolysaccharides (LPSs) induce a wide spectrum of functional activities after interaction with blood cells. Effect of structure of toxic LPS from S- and Re-chemotypes of E. coli and/or non-toxic LPS of Rhodobacter capsulatus PG (R. caps.) on activation of neutrophils and monocytes of human whole blood were studied, particularly, expression of TLR4, CD14 and CD11b receptors, phagocytosis of BioParticles Alexa Fluor 488, synthesis of cytokines and chemokines. A leading role of CD11b receptor in phagocytic activity of neutrophils primed by LPS from various E. coli chemotypes was shown. The non-toxic LPS of R. caps. does not affect the efficiency of phagocytosis activity of the neutrophils. The LPS of R. caps. was shown to induce production of TRIF-dependent cytokine IFN-β in human whole blood leukocytes selectively, without activating MyD88-dependent pathway of pro-inflammatory cytokine synthesis, displaying properties of patrial agonist of TLR4. Structure and biological activity of LPS R. caps. allows considering it as a promising immunity stimulating pharmacological agent.

Persistent Activation of Innate Immunity in Patients with Primary Antibody Deficiencies

Primary antibody deficiencies (PAD) represent a heterogeneous group of disorders, with common variable immunodeficiency being the most common with clinical significance. The main phenotypic defect resides in the inability of B cells to produce antibodies, and the cornerstone of therapy is immunoglobulin replacement treatment in order to fight infections. However, the management of the other inflammatory manifestations is inadequate, reinforcing the hypothesis that a complex genetic background affecting additional cell populations, such as polymorphonuclear cells (PMN) and monocytes, influences the expression of the clinical phenotype of the disease. In this study, we investigated by flow cytometry in different conditions (resting state, and after isolation and incubation, with and without stimuli) the expression pattern of several markers on PMN and monocytes, indicative of their maturation, capacity for chemotaxis, adhesion, opsonization, migration, and phagocytosis in 25 PAD patients, 12 healthy blood donors, and 4 septic patients. In this context, we also analyzed patients before and after the initiation of replacement treatment, as well as an untreated patient in different clinical conditions. Interestingly, we observed that PAD patients exhibit a chronic activation status of the innate immunity compartment, along with several differences in the expression of activation, maturation, and adhesion markers, with respect to different clinical conditions. Moreover, immunoglobulin replacement treatment had a favorable effect on PMN, as it was expressed by a more mature and less activated phenotype on basal state cells, and an enhanced activation capacity after LPS exposure. Thus, we conclude that PAD patients display a persistent innate immune cell activation, which is probably associated with the chronic inflammatory stress, usually observed in these disorders.

FcγRI plays a critical role in patients with ulcerative colitis relapse

Ulcerative colitis (UC) is a disease that frequently relapses and affects more than 0.1% general population; the underlying mechanism is poorly understood. Published data show that polymorphonuclear neutrophils (PMN) contribute to the pathogenesis of UC. This study aims to identify antigen (Ag)-specific PMNs and investigate their role in UC relapse. In this study, the correlation between PMN activities and UC relapse was assessed in a group of UC patients. A UC mouse model was developed to expand the findings of UC patient study. The results showed that a positive correlation was detected between the high PMN activities and the food Ag-specific IgG amounts in colon biopsies of UC patients. UC patient-derived Ag-specific PMNs could be activated upon exposure to food specific Ag. The Ag/FcγRI complexes were detected on the surface of PMNs in UC patients. Re-exposure of sensitized PMNs to specific Ag triggered PMN activation and induced UC-like inflammation in the mouse colon. We conclude that FcγRI plays a critical role in UC relapse. Inhibition of FcγRI can efficiently inhibits experimental UC.

Human Cell Atlas and cell-type authentication for regenerative medicine

In modern biology, the correct identification of cell types is required for the developmental study of tissues and organs and the production of functional cells for cell therapies and disease modeling. For decades, cell types have been defined on the basis of morphological and physiological markers and, more recently, immunological markers and molecular properties. Recent advances in single-cell RNA sequencing have opened new doors for the characterization of cells at the individual and spatiotemporal levels on the basis of their RNA profiles, vastly transforming our understanding of cell types. The objective of this review is to survey the current progress in the field of cell-type identification, starting with the Human Cell Atlas project, which aims to sequence every cell in the human body, to molecular marker databases for individual cell types and other sources that address cell-type identification for regenerative medicine based on cell data guidelines.

Role of FcγRI in Antigen-Dependent Eosinophil Activation in Patients With Allergic Rhinitis

Background

The eosinophil (Eo) activation is a crucial factor evoking allergic rhinitis (AR) attacks; factors; the mechanism of triggering Eo activation remains to be further investigated. The interaction of antigen (Ag) and antibody plays a critical role in evoking allergy attacks. This study aims to elucidate the role of FcγRI, the high affinity receptor of IgG, in the Ag-mediated Eo activation.

Methods

Nasal lavage fluids (NLF) were collected from AR patients and healthy control (HC) subjects. Eos were isolated by flow cytometry cell sorting and analyzed by pertinent immunological approaches.

Results

Eos composed more than 60% of the cellular components in AR NLF. Exposure to specific Ags (sAgs) in the culture triggered Eos to release inflammatory mediators. High levels of FcγRI were detected on the surface of AR NLF Eos. Exposure to lipopolysaccharide markedly increased the FcγRI expression in naive Eos, which could be bound by Ag-specific IgG (sIgG) to form complexes on the surface of Eos; this made Eos at the sensitized status. Eos bore with the sIgG/FcγRI complexes could be activated upon exposure to sIgG in the culture; these Eos can be designated as Ag-specific Eos. Passive transfer of Ag-specific Eos resulted in profound AR response in mice upon sAg challenge. Depletion of FcγRI on Eos efficiently abolished AR response in mice.

Conclusions

AR Eos express high levels FcγRI, that can be bound by sIgG to make Eos sensitized. Re-exposure to specific Ags can activate the sensitized Eos.

Neutrophil and monocyte receptor expression in patients with sepsis: implications for diagnosis and prognosis of sepsis

Understanding the complex immune responses in sepsis is crucial to provide insight into the clinical syndrome. We evaluated the changes in the surface receptors of the cells of innate immunity, neutrophils and monocytes, in patients with sepsis. Since sepsis remains a clinical challenge, we aimed to assess the significance of altered receptor expression in diagnosis and prognosis. Critically ill patients with sepsis (n=31) were investigated for the expression of receptors for IgG heavy chain CD64 and CD16 on neutrophils and CD64 and the lipopolysaccharide receptor CD14 on monocytes by flow cytometry and compared to 23 patients with no sepsis. Patients with sepsis had increased expression of neutrophil CD64. Neutrophil CD64 was specific for discriminating patients with sepsis but showed weak sensitivity. When integrated in a scoring system, neutrophil CD64 in combination with C-reactive protein (CRP) and SOFA score showed a diagnostic accuracy of 0.93 for sepsis and significantly predicted increased mortality risk. While neutrophil CD16 did not discriminate for sepsis, decreased expression was associated with increased mortality risk. In contrast, monocyte CD64 and CD14 expression was unaltered in sepsis and was not associated with mortality risk. Our study demonstrates that unlike monocytes, neutrophil receptor expression is altered in patients with sepsis receiving intensive care. It is promising to apply a combination approach to diagnose sepsis especially in time-limited conditions.

Infection-induced innate antimicrobial response disorders: from signaling pathways and their modulation to selected biomarkers

Severe infections are a major public health problem responsible for about 40-65% of hospitalizations in intensive care units (ICU). The high mortality (30-50%) of persons diagnosed with severe infection is caused by largely unknown mechanisms of sepsis-induced immune system response. Severe infections with dynamic progress are accompanied with SIRS (systemic inflammatory reaction syndrome) and CARS (compensatory anti-inflammatory response syndrome), and require a biological treatment appropriate to the phase of immune response. The mechanisms responsible for severe infection related to immune system response particularly attract extensive interest of non-specific defense mechanisms, including signaling pathways of Toll-like receptors (mainly TLR4 and TLR2) that recognize distinct pathogen-associated molecular patterns (PAMP) and play a critical role in innate immune response. There are attempts of treatment, followed by blocking ligand binding with TLR or modulation of intracellular signaling pathways, to inhibit signal transduction. Moreover, researches regarding new and more efficient diagnostics biomarkers were mostly focused on indicators related to innate response to infection as well as connections of pro-inflammatory response with anti-inflammatory response.According to these studies, in case of ICU septic patients with high-risk of mortality, the solution for the problem will require mainly early immune and genetic diagnostics (e.g. cytokines, microRNA, cluster of differentiation-64 [CD64], triggering receptor expressed on myeloid cells-1 [TREM-1], and high mobility group box 1 protein [HMGB1]).

ABCA7 haplodeficiency disturbs microglial immune responses in the mouse brain

Carrying premature termination codons in 1 allele of the ABCA7 gene is associated with an increased risk for Alzheimer's disease (AD). While the primary function of ABCA7 is to regulate the transport of phospholipids and cholesterol, ABCA7 is also involved in maintaining homeostasis of the immune system. Since inflammatory pathways causatively or consequently participate in AD pathogenesis, we studied the effects of Abca7 haplodeficiency in mice on brain immune responses under acute and chronic conditions. When acute inflammation was induced through peripheral lipopolysaccharide injection in control or heterozygous Abca7 knockout mice, partial ABCA7 deficiency diminished proinflammatory responses by impairing CD14 expression in the brain. On breeding to App ^NL-G-F knockin mice, we observed increased amyloid-β (Aβ) accumulation and abnormal endosomal morphology in microglia. Taken together, our results demonstrate that ABCA7 loss of function may contribute to AD pathogenesis by altering proper microglial responses to acute inflammatory challenges and during the development of amyloid pathology, providing insight into disease mechanisms and possible treatment strategies.

The CD14+HLA-DRlo/neg Monocyte: An Immunosuppressive Phenotype That Restrains Responses to Cancer Immunotherapy

Recent successes in cancer immunotherapy have been tempered by sub-optimal clinical responses in the majority of patients. The impaired anti-tumor immune responses observed in these patients are likely a consequence of immune system dysfunction contributed to by a variety of factors that include, but are not limited to, diminished antigen presentation/detection, leukopenia, a coordinated network of immunosuppressive cell surface proteins, cytokines and cellular mediators. Monocytes that have diminished or no HLA-DR expression, called CD14⁺HLA-DR^lo/neg monocytes, have emerged as important mediators of tumor-induced immunosuppression. These cells have been grouped into a larger class of suppressive cells called myeloid derived suppressor cells (MDSCs) and are commonly referred to as monocytic myeloid derived suppressor cells. CD14⁺HLA-DR^lo/neg monocytes were first characterized in patients with sepsis and were shown to regulate the transition from the inflammatory state to immune suppression, ultimately leading to immune paralysis. These immunosuppressive monocytes have also recently been shown to negatively affect responses to PD-1 and CTLA-4 checkpoint inhibition, CAR-T cell therapy, cancer vaccines, and hematopoietic stem cell transplantation. Ultimately, the goal is to understand the role of these cells in the context of immunosuppression not only to facilitate the development of targeted therapies to circumvent their effects, but also to potentially use them as a biomarker for understanding disparate responses to immunotherapeutic regimens. Practical aspects to be explored for development of CD14⁺HLA-DR^lo/neg monocyte detection in patients are the standardization of flow cytometric gating methods to assess HLA-DR expression, an appropriate quantitation method, test sample type, and processing guidances. Once detection methods are established that yield consistently reproducible results, then further progress can be made toward understanding the role of CD14⁺HLA-DR^lo/neg monocytes in the immunosuppressive state.

Cell Type-Specific Roles of NF-κB Linking Inflammation and Thrombosis

The transcription factor NF-κB is a central mediator of inflammation with multiple links to thrombotic processes. In this review, we focus on the role of NF-κB signaling in cell types within the vasculature and the circulation that are involved in thrombo-inflammatory processes. All these cells express NF-κB, which mediates important functions in cellular interactions, cell survival and differentiation, as well as expression of cytokines, chemokines, and coagulation factors. Even platelets, as anucleated cells, contain NF-κB family members and their corresponding signaling molecules, which are involved in platelet activation, as well as secondary feedback circuits. The response of endothelial cells to inflammation and NF-κB activation is characterized by the induction of adhesion molecules promoting binding and transmigration of leukocytes, while simultaneously increasing their thrombogenic potential. Paracrine signaling from endothelial cells activates NF-κB in vascular smooth muscle cells and causes a phenotypic switch to a “synthetic” state associated with a decrease in contractile proteins. Monocytes react to inflammatory situations with enforced expression of tissue factor and after differentiation to macrophages with altered polarization. Neutrophils respond with an extension of their life span—and upon full activation they can expel their DNA thereby forming so-called neutrophil extracellular traps (NETs), which exert antibacterial functions, but also induce a strong coagulatory response. This may cause formation of microthrombi that are important for the immobilization of pathogens, a process designated as immunothrombosis. However, deregulation of the complex cellular links between inflammation and thrombosis by unrestrained NET formation or the loss of the endothelial layer due to mechanical rupture or erosion can result in rapid activation and aggregation of platelets and the manifestation of thrombo-inflammatory diseases. Sepsis is an important example of such a disorder caused by a dysregulated host response to infection finally leading to severe coagulopathies. NF-κB is critically involved in these pathophysiological processes as it induces both inflammatory and thrombotic responses.

Comparison of the accuracy of neutrophil CD64, procalcitonin, and C-reactive protein for sepsis identification: a systematic review and meta-analysis

Background

Neutrophil CD64 is widely described as an accurate biomarker for the diagnosis of infection in patients with septic syndrome. We performed a systematic review and meta-analysis to evaluate the diagnostic accuracy of neutrophil CD64, comparing it with C-reactive protein (CRP) and procalcitonin (PCT) for the diagnosis of infection in adult patients with septic syndrome, based on sepsis-2 criteria. We searched the PubMed and Embase databases and Google Scholar. Original studies reporting the performance of neutrophil CD64 for sepsis diagnosis in adult patients were retained. The pooled sensitivity, specificity, diagnostic odds ratio (DOR), and hierarchical summary receiver operating characteristic (SROC) curve were calculated.

Results

We included 14 studies (2471 patients) from 2006 to 2017 in the meta-analysis. The pooled sensitivity and specificity of neutrophil CD64 for diagnosing infection in adult patients with septic syndrome were 0.87 (95% CI 0.80–0.92) and 0.89 (95% CI 0.82–0.93), respectively. The area under the SROC curve and the DOR were 0.94 (95% CI 0.92–0.96) and 53 (95% CI 22–128), respectively. There was significant heterogeneity between the studies included. Subgroup analyses showed that this heterogeneity was due to differences in sample size and the proportions of patients with sepsis included in the studies. Six studies (927 patients) compared neutrophil CD64 and CRP determinations, and six studies (744 patients) compared neutrophil CD64 and PCT determinations. The area under the SROC curve was larger for neutrophil CD64 than for CRP (0.89 [95% CI 0.87–0.92] vs. 0.84 [95% CI 0.80–0.88], P < 0.05) or PCT (0.89 [95% CI 0.84–0.95] vs. 0.84 [95% CI 0.79–0.89], P < 0.05).

Conclusions

In adult patients with septic syndrome, neutrophil CD64 levels are an excellent biomarker with moderate accuracy outperforming both CRP and PCT determinations.

Electronic supplementary material

The online version of this article (10.1186/s13613-018-0479-2) contains supplementary material, which is available to authorized users.

The Expression Level of Neutrophil CD64 Is a Useful Marker of Systemic Inflammation Associated with HIV Infection

CD64 is an Fc-gamma-receptor type 1. The expression level of neutrophil CD64 (nCD64) is a known bacterial infection marker, and it also increases in viral infections. We examined the absolute nCD64 before and after the initiation of antiretroviral therapy (ART) to determine its role as an infection and inflammation marker of human immunodeficiency virus (HIV) infection. In this prospective observational study, 94 HIV-infected patients were enrolled and classified into ART (n = 62), ART naive (n = 24), and acute/early phase groups (n = 8). The median nCD64 was 1,430 molecules/cell in the ART group, 2,994 in the ART naive group, 4,625 in the acute/early phase group, and 1,196 in the healthy control group. The nCD64 in the ART group was significantly higher compared with the healthy controls (p = .041), and the nCD64 in the ART naive and acute/early phase groups was significantly higher compared with the ART group (both p < .001). In the ART naive group, nCD64 was significantly higher in patients with than without concomitant infections (3,942 ± 1,519 vs. 2,300 ± 784, p = .004). However, this was influenced by the fact that nCD64 elevated as the stage of HIV infection progressed. nCD64 decreased significantly during the 24 weeks after starting ART (p = .004), although an upward trend in nCD64 was observed at weeks 2 and 4, without symptoms. When immune reconstitution inflammatory syndrome occurred, nCD64 elevated with a wider range than did C-reactive protein. This preliminary study suggests that nCD64 would be useful as a marker of the systemic inflammation of HIV-infected patients.

Molecular aspects of the pathogenesis of periodontitis

The past decade of basic research in periodontology has driven radical changes in our understanding and perceptions of the pathogenic processes that drive periodontal tissue destruction. The core elements of the classical model of disease pathogenesis, developed by Page & Kornman in 1997, remain pertinent today; however, our understanding of the dynamic interactions between the various microbial and host factors has changed significantly. The molecular era has unraveled aspects of genetics, epigenetics, lifestyle and environmental factors that, in combination, influence biofilm composition and the host's inflammatory immune response, creating a heterogenic biological phenotype that we label as 'periodontitis'. In this volume of Periodontology 2000, experts in their respective fields discuss these emerging concepts, such as a health-promoting biofilm being essential for periodontal stability, involving a true symbiosis between resident microbial species and each other and also with the host response to that biofilm. Rather like the gut microbiome, changes in the local environment, which may include inflammatory response mediators or viruses, conspire to drive dysbiosis and create a biofilm that supports pathogenic species capable of propagating disease. The host response is now recognized as the major contributor to periodontal tissue damage in what becomes a dysfunctional, poorly targeted and nonresolving inflammation that only serves to nourish and sustain the dysbiosis. The role of epithelial cells in signaling to the immune system is becoming clearer, as is the role of dendritic cells as transporters of periodontal pathogens to distant sites within the body, namely metastatic infection. The involvement of nontraditional immune cells, such as natural killer cells, is being recognized, and the simple balance between T-helper 1- and T-helper 2-type T-cell populations has become less clear with the emergence of T-regulatory cells, T-helper 17 cells and follicular helper cells. The dominance of the neutrophil has emerged, not only as a potential destructor when poorly regulated but as an equally unpredictable effector cell for specific B-cell immunity. The latter has emerged, in part, from the realization that neutrophils live for 5.4 days in the circulation, rather than for 24 h, and are also schizophrenic in nature, being powerful synthesizers of proinflammatory cytokines but also responding to prostaglandin signals to trigger a switch to a pro-resolving phenotype that appears capable of regenerating the structure and function of healthy tissue. Key to these outcomes are the molecular signaling pathways that dominate at any one time, but even these are influenced by microRNAs capable of 'silencing' certain inflammatory genes. This volume of Periodontology 2000 tries to draw these complex new learnings into a contemporary model of disease pathogenesis, in which inflammation and dysbiosis impact upon whether the outcome is driven toward acute resolution and stability, chronic resolution and repair, or failed resolution and ongoing periodontal tissue destruction.

Emerging infection and sepsis biomarkers: will they change current therapies?

INTRODUCTION

Sepsis is a heterogeneous syndrome characterized by both immune hyperactivity and relative immune suppression. Biomarkers have the potential to improve recognition and management of sepsis through three main applications: diagnosis, monitoring response to treatment, and stratifying patients based on prognosis or underlying biological response.

AREAS COVERED

This review focuses on specific examples of well-studied, evidence-supported biomarkers, and discusses their role in clinical practice with special attention to antibiotic stewardship and cost-effectiveness. Biomarkers were selected based on availability of robust prospective trials and meta-analyses which supported their role as emerging tools to improve the clinical management of sepsis. Expert commentary: Great strides have been made in candidate sepsis biomarker discovery and testing, with the biomarkers in this review showing promise. Yet sepsis remains a dynamic illness with a great degree of biological heterogeneity - heterogeneity which may be further resolved by recently discovered gene expression-based endotypes in septic shock.

CD36 regulates lipopolysaccharide-induced signaling pathways and mediates the internalization of Escherichia coli in cooperation with TLR4 in goat mammary gland epithelial cells

The scavenger receptor CD36 is involved in pathogen recognition, phagocytosis, and pathogen-induced signaling. This study investigated the relationship between CD36 and TLR4 in modifying lipopolysaccharide (LPS)-induced signaling pathways and mediating Escherichia coli (E. coli) endocytosis in primary goat mammary epithelial cells (pGMECs). The manipulation of CD36 expression significantly influenced TLR4 and nuclear factor kappa B (NF-κB) mRNA expression in pGMECs stimulated with LPS for 12 h. NF-κB and activator protein-1 (AP-1) activity was regulated by the manipulation of CD36 expression in LPS-induced pGMECs. However, CD36-mediated AP-1 activation occurred primarily through c-Jun N-terminal kinase (c-JNK). Adaptor proteins and proinflammatory cytokines were also involved in these signaling pathways and acted by regulating CD36 expression in LPS-stimulated cells. Moreover, CD36 cooperated with TLR4 in TLR4-mediated phagocytosis following E. coli simulation, but this complex was not induced by LPS treatment. Our study is the first to illuminate CD36 as a scavenger receptor in ruminants. Additionally, this study indicates that CD36 plays a vital role in the LPS-induced activation of downstream signaling cascades and mediates E. coli phagocytosis via TLR4 in pGMECs, which offers a novel treatment strategy for mastitis.

Role of CD11b/CD18 in priming of human leukocytes by endotoxin glycoforms from Escherichia coli

The primary objective of this study was to determine the role of β2 integrin α-subunit (CD11b) in the mechanism of human polymorphonuclear leukocyte (PML) priming by S or Re endotoxin glycoforms from Escherichia coli for fMLP-induced respiratory burst. Similar priming activity of S and Re endotoxin glycoforms for fMLP-induced reactive oxygen species (ROS) generation from primed PML was found. Anti-CD11b antibodies (clone ICRF 44) as well as isotype-matched immunoglobulin G1 (clone MOPC-21) do not influence the fMLP-induced ROS generation from unprimed PML. Antibodies against CD11b do not change fMLP-induced ROS generation from endotoxin-primed PML as well. The involvement of different isoforms of Fcγ receptors in fMLP-induced ROS generation from activated PML is proposed.

A method for identification and analysis of non-overlapping myeloid immunophenotypes in humans

The development of flow cytometric biomarkers in human studies and clinical trials has been slowed by inconsistent sample processing, use of cell surface markers, and reporting of immunophenotypes. Additionally, the function(s) of distinct cell types as biomarkers cannot be accurately defined without the proper identification of homogeneous populations. As such, we developed a method for the identification and analysis of human leukocyte populations by the use of eight 10-color flow cytometric protocols in combination with novel software analyses. This method utilizes un-manipulated biological sample preparation that allows for the direct quantitation of leukocytes and non-overlapping immunophenotypes. We specifically designed myeloid protocols that enable us to define distinct phenotypes that include mature monocytes, granulocytes, circulating dendritic cells, immature myeloid cells, and myeloid derived suppressor cells (MDSCs). We also identified CD123 as an additional distinguishing marker for the phenotypic characterization of immature LIN^-CD33⁺HLA-DR^- MDSCs. Our approach permits the comprehensive analysis of all peripheral blood leukocytes and yields data that is highly amenable for standardization across inter-laboratory comparisons for human studies.

Recognition of TLR2 N-glycans: critical role in ArtinM immunomodulatory activity

TLR2 plays a critical role in the protection against Paracoccidioides brasiliensis conferred by ArtinM administration. ArtinM, a D-mannose-binding lectin from Artocarpus heterophyllus, induces IL-12 production in macrophages and dendritic cells, which accounts for the T helper1 immunity that results from ArtinM administration. We examined the direct interaction of ArtinM with TLR2using HEK293A cells transfected with TLR2, alone or in combination with TLR1 or TLR6, together with accessory proteins. Stimulation with ArtinM induced NF-κB activation and interleukin (IL)-8 production in cells transfected with TLR2, TLR2/1, or TLR2/6. Murine macrophages that were stimulated with ArtinM had augmented TLR2 mRNA expression. Furthermore, pre-incubation of unstimulated macrophages with an anti-TLR2 antibody reduced the cell labeling with ArtinM. In addition, a microplate assay revealed that ArtinM bound to TLR2 molecules that had been captured by specific antibodies from a macrophages lysate. Notably,ArtinM binding to TLR2 was selectively inhibited when the lectin was pre-incubated with mannotriose. The biological relevance of the direct interaction of ArtinM with TLR2 glycans was assessed using macrophages from TLR2-KOmice, which produced significantly lower levels of IL-12 and IL-10 in response to ArtinM than macrophages from wild-type mice. Pre-treatment of murine macrophages with pharmacological inhibitors of signaling molecules demonstrated the involvement of p38 MAPK and JNK in the IL-12 production induced by ArtinM and the involvement ofPI3K in IL-10 production. Thus, ArtinM interacts directly with TLR2 or TLR2 heterodimers in a carbohydrate recognition-dependent manner and functions as a TLR2 agonist with immunomodulatory properties.

Role of biomarkers in sepsis care

Sepsis is one of the leading causes of mortality and morbidity, even with the current availability of extended-spectrum antibiotics and advanced medical care. Biomarkers offer a tool in facilitating early diagnosis, in identifying patient populations at high risk of complications, and in monitoring progression of the disease, which are critical assessments for appropriate therapy and improvement in patient outcomes. Several biomarkers are already available for clinical use in sepsis; however, their effectiveness in many instances is limited by the lack of specificity and sensitivity to characterize the presence of an infection and the complexity of the inflammatory and immune processes and to stratify patients into homogenous groups for specific treatments. Current advances in molecular techniques have provided new tools facilitating the discovery of novel biomarkers, which can vary from metabolites and chemical products present in body fluids to genes and proteins in circulating blood cells. The purpose of this review was to examine the current status of sepsis biomarkers, with special emphasis on emerging markers, which are undergoing validation and may transition into clinical practice for their informative value in diagnosis, prognosis, or response to therapy. We will also discuss the new concept of combination biomarkers and biomarker risk models, their existing challenges, and their potential use in the daily management of patients with sepsis.

Comparison of Fcγ receptor expression on neutrophils with procalcitonin for the diagnosis of sepsis in critically ill patients

BACKGROUND AND OBJECTIVE

The expression of Fc receptors for IgG (FcγRs) on neutrophils, including CD16, CD32 and CD64, may be modulated in response to sepsis. We investigated the expression of FcγRs on neutrophils and procalcitonin (PCT) as biomarkers of sepsis among critically ill patients.

METHODS

This prospective study was conducted in a 24-bed respiratory intensive care unit between July 2007 and June 2008. Critically ill patients requiring mechanical ventilation were enrolled and categorized into three groups: those with systemic inflammatory response syndrome (SIRS), those with severe sepsis and those with septic shock. Expression of FcγRs on neutrophils was quantitatively measured by flow cytometry immediately after enrolment of the patient. Serum PCT levels were also measured. Receiver operating characteristic (ROC) curves were used to evaluate the performance of FcγR expression and PCT as biomarkers of sepsis.

RESULTS

Sixty-six patients were enrolled, including 11 with SIRS, 31 with severe sepsis and 24 with septic shock. Nineteen healthy volunteers served as normal controls. CD64 was upregulated, CD16 was downregulated and CD32 remained unchanged during sepsis. CD64 expression and the ratio of CD64/CD16 increased significantly with the severity of sepsis. However, serum PCT levels were not significantly different between SIRS and severe sepsis patients. CD64, CD64/CD16 and PCT all significantly predicted sepsis, septic shock and bacteraemia. As assessed using ROC curves, CD64 was better than PCT for differentiating SIRS from severe sepsis and septic shock. CD64 and CD64/CD16 were associated with mortality.

CONCLUSIONS

CD64 and CD16 were differentially modulated by sepsis. CD64, CD64/CD16 and PCT may be biomarkers of sepsis. CD64 was better than PCT for identifying patients who required treatment with antibiotics.

Lipopolysaccharide-induced expression of cell surface receptors and cell activation of neutrophils and monocytes in whole human blood

Lipopolysaccharide (LPS) activates neutrophils and monocytes, inducing a wide array of biological activities. LPS rough (R) and smooth (S) forms signal through Toll-like receptor 4 (TLR4), but differ in their requirement for CD14. Since the R-form LPS can interact with TLR4 independent of CD14 and the differential expression of CD14 on neutrophils and monocytes, we used the S-form LPS from Salmonella abortus equi and the R-form LPS from Salmonella minnesota mutants to evaluate LPS-induced activation of human neutrophils and monocytes in whole blood from healthy volunteers. Expression of cell surface receptors and reactive oxygen species (ROS) and nitric oxide (NO) generation were measured by flow cytometry in whole blood monocytes and neutrophils. The oxidative burst was quantified by measuring the oxidation of 2',7'-dichlorofluorescein diacetate and the NO production was quantified by measuring the oxidation of 4-amino-5-methylamino-2',7'-difluorofluorescein diacetate. A small increase of TLR4 expression by monocytes was observed after 6 h of LPS stimulation. Monocyte CD14 modulation by LPS was biphasic, with an initial 30% increase followed by a 40% decrease in expression after 6 h of incubation. Expression of CD11b was rapidly up-regulated, doubling after 5 min on monocytes, while down-regulation of CXCR2 was observed on neutrophils, reaching a 50% reduction after 6 h. LPS induced low production of ROS and NO. This study shows a complex LPS-induced cell surface receptor modulation on human monocytes and neutrophils, with up- and down-regulation depending on the receptor. R- and S-form LPS activate human neutrophils similarly, despite the low CD14 expression, if the stimulation occurs in whole blood.

Neutrophil CD64 expression as marker of bacterial infection: a systematic review and meta-analysis

OBJECTIVE

We performed a systematic review and meta-analysis of studies to evaluate the diagnostic accuracy of expression of CD64 on polymorphonuclear neutrophils (PMN) as a marker for bacterial infection.

METHODS

The analysis included studies of patients from all age groups that prospectively evaluated CD64 expression on PMNs for the diagnosis of bacterial infection. We evaluated the methodological quality of the studies according to the 25-item criteria developed by the Standards for Reporting of Diagnostic Accuracy (STARD) committee. We calculated a summary receiver operating characteristic (SROC) curve across studies included in the meta-analysis.

RESULTS

The methodological quality score of the 13 included studies ranged from 9 to 16 points (maximum score was 25 points). The pooled sensitivity and specificity for CD64 expression on PMNs were 79% (95% CI: 70-86%) and 91% (95% CI: 85-95%), respectively. The area under curve (AUC) was 0.94.

CONCLUSIONS

On the basis of this meta-analysis, CD64 expression on PMNs could be a useful diagnostic cell-based parameter of bacterial infections. However, published studies about this topic showed a low methodological quality.

A systemic neutrophil response precedes robust CD8(+) T-cell activation during natural respiratory syncytial virus infection in infants

Severe primary respiratory syncytial virus (RSV) infections are characterized by bronchiolitis accompanied by wheezing. Controversy exists as to whether infants suffer from virus-induced lung pathology or from excessive immune responses. Furthermore, detailed knowledge about the development of primary T-cell responses to viral infections in infants is lacking. We studied the dynamics of innate neutrophil and adaptive T-cell responses in peripheral blood in relation to the viral load and parameters of disease in infants admitted to the intensive care unit with severe RSV infection. Analysis of primary T-cell responses showed substantial CD8(+) T-cell activation, which peaked during convalescence. A strong neutrophil response, characterized by mobilization of bone marrow-derived neutrophil precursors, preceded the peak in T-cell activation. The kinetics of this neutrophil response followed the peak of clinical symptoms and the viral load with a 2- to 3-day delay. From the sequence of events, we conclude that CD8(+) T-cell responses, initiated during primary RSV infections, are unlikely to contribute to disease when it is most severe. The mobilization of precursor neutrophils might reflect the strong neutrophil influx into the airways, which is a characteristic feature during RSV infections and might be an integral pathogenic process in the disease.

CD64 index provides simple and predictive testing for detection and monitoring of sepsis and bacterial infection in hospital patients

The rapid diagnosis and management of bacterial infection are heavily dependent upon clinical assessment. Blood culture may take up to 2 days for results and may be suspect. Surface neutrophil CD64 expression has been shown to be upregulated in cases of bacterial infection. Recently, a standardized kit for the CD64 index was used in neonatal intensive care units, showing high sensitivity and specificity for bacterial infections. Our study was designed to confirm and extend these results to adult hospital patients and to determine the impact of this testing on a clinical laboratory's finances and staffing. CD64 indices were performed with peripheral blood drawn in tandem with blood cultures from 109 patients over a 2-month period. We found that a CD64 index of <or=1.19 was predictive of "no growth" blood culture results. An index of >1.19 was predictive of an ultimate clinical and/or culture diagnosis of infection with a sensitivity and specificity of 94.6% and 88.7%, respectively. Positive and negative predictive values were 89.8% and 94%, respectively. The CD64 index was easily performed using our flow cytometer and staff, producing minimal alteration in clinical workflow. A 7-day-a-week testing schedule will result in some additional expense but will be more than offset by the expected cost savings. The CD64 index is a useful and inexpensive test for improving the diagnosis and management of hospital patients with bacterial infection. It can be readily performed by clinical laboratories and could result in considerable savings for the institution.

Neutrophil CD64 expression in the diagnosis of local musculoskeletal infection and the impact of antibiotics

We examined the usefulness of neutrophil CD64 expression in detecting local musculoskeletal infection and the impact of antibiotics on its expression. Of 141 patients suspected of musculoskeletal infection, 46 were confirmed by microbiological culture to be infected and 95 had infection excluded. The median CD64 count of patients with localised infection was 2230 molecules per cell (interquartile range (IQR) 918 to 4592) and that of the patients without infection was 937 molecules per cell (IQR 648 to 1309) (p < 0.001). The level of CD64 correlated with the CRP level in patients with infection, but not in those without infection (r = 0.59, p < 0.01). Receiver operator characteristic curve analysis revealed that CD64 was a good predictor of local infection. When the patients were subdivided into two groups based on the administration of antibiotics at the time of CD64 sampling, the sensitivity for detecting infection was better in those who had not received antibiotics.

These results suggest that measurement of CD64 expression is a useful marker for local musculoskeletal infection.

Cell surface expression of FcγRI (CD64) on neutrophils and monocytes in patients with influenza A, with and without complications

The expression of the Fcgamma-receptor I (FcgammaRI), CD64 on normal neutrophils is up-regulated during bacterial infections. CD64 is a promising diagnostic tool in the diagnosis of acute infections. The aim was to study surface expressions of CD64 on neutrophils and monocytes in patients with influenza A with and without complications and evaluate these as diagnostic tools in comparison with serum levels of HNL (human neutrophil lipocalin). CD64 expression on neutrophils and monocytes was evaluated by flow cytometry. HNL was assayed by a specific radioimmunoassay. 22 patients with influenza A with or without complications were included and the results compared with those of 29 patients with acute bacterial infections and 29 healthy subjects. Neutrophil expression of CD64 was increased in influenza A with raised proportion expressing CD64 in complicated compared to uncomplicated influenza. The expression was significantly higher in bacterial infections compared to both influenza groups. Serum levels of HNL were raised in all infection groups, but significantly more so in the group with bacterial infection. ROC-curve analysis showed that neutrophil expression of CD64 and the serum levels of HNL had similar diagnostic power in the discrimination between acute bacterial infections and influenza A. Monocyte expression of CD64 was raised in all infections with no differences between subgroups. We conclude that neutrophil expression of CD64 and serum levels of HNL are both promising assays in the distinction between infections caused by bacteria or influenza A, whereas CD64 could identify patients with complications of their influenza A infection.

Neutrophil and monocyte receptor expression in uncomplicated and complicated influenza A infection with pneumonia

Following influenza, the elderly and those with chronic heart/lung diseases are often affected by bacterial complications such as pneumonia. Whether neutrophil and monocyte functions are affected differently in patients with or without complications is less well known. Therefore, blood neutrophil and monocyte surface receptor expressions were measured in patients with influenza A, with or without complications, by means of flow cytometry. Neutrophil expressions of the adhesion molecules CD11b and CD66b were increased in influenza A, with the highest expression of CD11b in uncomplicated influenza. Monocyte expressions of CD11b and CD18 were also higher in influenza compared with bacterial infection and healthy controls. Neutrophil expressions of the phagocyte receptors CD64 and CD32 and the complement receptor CD35 were impaired in influenza with and without pneumonia compared with bacterial infection, whereas the expressions in monocytes were increased in all infected groups. The expression of the phagocyte receptor CD16 on neutrophils was impaired in all infected groups. Our results suggest increased recruitment of neutrophils and monocytes to infected areas by up-regulation of adhesion molecules in influenza that may be involved in the inflammatory response during infection. In contrast, depression of phagocyte receptor expression on neutrophils in patients with influenza pneumonia may contribute to increased susceptibility to bacterial infections and impaired clearance of encapsulated bacteria such as pneumococci.

Arginase 2 is expressed by human lung cancer, but it neither induces immune suppression, nor affects disease progression

In human prostate cancer, Arginase 2 (ARG2) and nitric oxide synthase (NOS) are concomitantly expressed by tumor cells, and induce tumor immune escape via peroxynitrite-dependent Tyrosine nitrosylation. Since there were no data regarding this immune suppressive mechanism in other tumor types, and an evaluation of its clinical relevance in human tumors had still to be provided, we have investigated presence and clinical relevance of ARG2 and NOS expression in lung cancer. No evidence of NOS expression was found, no significant NOS enzymatic activity was detected. Instead, ARG2 protein was expressed by tumor cells. In a cohort of 120 patients, the amount of ARG2-positive tumor cells was significantly higher in small cell lung cancers (SCLC) than in non-small cell lung cancers (NSCLC). Large cell undifferentiated carcinomas had twice ARG2 than the other NSCLC subtypes. ARG2 expression was increased in Grade 3 tumors, as compared to Grades 1 and 2. However, no relationship was found with tumor size and stage, and with patient survival. Indeed, the enzyme was active, since the Arginine catabolite Ornithine was produced, but Arginine depletion was not attained. In addition, nitrotyrosine was not found in tumor tissue. Accordingly, when tumor cells isolated from lung cancer were incubated with activated autologous T cells, no inhibition of proliferation was detected. Our results indicate that ARG2 is expressed in lung cancer, but it does not induce tumor immune escape and does not affect disease progression, most probably due to the lack of concomitant NOS expression.

Simultaneous quantitative analysis of FcgammaRI (CD64) expression on neutrophils and monocytes: a new, improved way to detect infections

We performed simultaneous quantitative flow cytometric analysis of neutrophil and monocyte FcgammaRI (CD64) in 289 hospitalized febrile patients. Microbiological evaluation or clinical diagnosis confirmed bacterial (n=89) or viral (n=46) infection in 135 patients. Patient data were compared with data from 60 healthy controls. The average number of FcgammaRI on the surfaces of both neutrophils and monocytes was significantly increased in patients with febrile viral and bacterial infections, compared to healthy controls. Furthermore, we describe a novel marker of febrile infection, designated 'CD64 score point', which incorporates the quantitative analysis of FcgammaRI expressed on both neutrophils and monocytes, with 94% sensitivity and 98% specificity in distinguishing between febrile infections and healthy controls. By contrast, analysis of FcgammaRI expression on neutrophils and monocytes displayed poor sensitivity (73% and 52%) and specificity (65% and 52%) in distinguishing between bacterial and viral infections, and the levels did not differ significantly between systemic (sepsis), local, and clinically diagnosed bacterial infections. In summary, our results clearly show that the increased number of FcgammaRI on neutrophils and monocytes is a useful marker of febrile infection, but cannot be applied for differential diagnosis between bacterial and viral infections or between systemic and local bacterial infections.

[Implant-associated post-traumatic osteomyelitis. Bacterial biofilms and the immune defence as protagonists of the local inflammatory process]

BACKGROUND

Formation of bacterial biofilms on implants is a severe complication following orthopaedic surgery. In the present study we addressed the role of the immune response, particularly with regard to the pathogenesis of the disease.

METHODS

In a prospective study comprising 74 patients with implant-associated post-traumatic osteomyelitis, peripheral blood cells as well as cells recovered from the infected site during surgery were characterised phenotypically and functionally.

RESULTS

We found massive infiltration of polymorphonuclear neutrophils (PMN), which were highly activated, particularly regarding their bactericidal potential, such as increased production of superoxides and upregulation of activation-associated surface receptors.

CONCLUSION

PMN are activated in response to the implant-associated osteomyelitis; they also infiltrate the infected tissue, but cannot control the infection. By release of their cytotoxic entities they could contribute to tissue destruction and eventually to osteolysis.

Anaplasma phagocytophilum infection reduces expression of phagocytosis-related receptors on neutrophils

Anaplasma phagocytophilum is a tick-transmitted obligate intracellular bacterium of neutrophils that causes human granulocytic anaplasmosis. Previous data confirm that in vitro infection by A. phagocytophilum modifies neutrophil functions, including a 50% or greater reduction in phagocytosis and shedding of neutrophil cell surface adhesion molecule receptors. If these receptors are downregulated or shed from the surface of neutrophils with A. phagocytophilum infection, it may prevent neutrophils from effective phagocytosis. We hypothesized that diminished phagocytosis in neutrophils is partly associated with the loss of surface phagocytic receptors. To address this, we assayed the expression of these receptors after 24 h of A. phagocytophilum infection in human neutrophils.