Anticoagulant selection influences flow cytometric determination of CD11b upregulation in vivo and ex vivo

Optimization of methods for the accurate characterization of whole blood neutrophils

Neutrophils are the most abundant circulating leukocyte population with critical roles in immune defense, regulation of innate and adaptive immune systems, and disease pathogenesis. Our progress in understanding precise mechanisms of neutrophil activation, recruitment, and function has been hampered by the lack of optimized and standardized methods for the characterization and phenotyping of this readily activated population. By comparing eight methods of neutrophil characterization, we demonstrate that the level of neutrophil activation and degranulation is associated with specific experimental conditions and the number and type of manipulation steps employed. Staining whole blood at 4 °C and removal of remaining unbound antibodies prior to one-step fixation and red blood cell lysis minimizes neutrophil activation, decreases phenotypic alterations during processing, and prevents nonspecific antibody binding. The effects of anticoagulants used for collection, processing delays, and time and temperature during sample analysis on neutrophil phenotype are addressed. The presented data provide a foundation for higher quality standards of neutrophil characterization improving consistency and reproducibility among studies.

Impact of Pre-Analytical and Analytical Variables Associated with Sample Preparation on Flow Cytometric Stainings Obtained with EuroFlow Panels

Simple Summary

Objective interpretation of flow cytometry may be hampered by a lack of standardized sample preparation procedures. The EuroFlow consortium conducted a series of experiments to determine the potential impact of different pre-analytical and analytical factors on the variability of results in terms of relative cell populations distribution and marker expression levels. The experiments were performed on healthy donors and patients with different hematological malignancies (e.g., acute leukemia, lymphoma, multiple myeloma, and myelodysplastic syndrome) to mimic real-world clinical settings. Overall, the results showed that sample storage conditions, anticoagulant use, and sample processing protocol might need to be tailored for sample and cell type(s), as well as to the specific markers evaluated. However, defining of well-balanced boundaries for storage time to 24 h, staining-acquisition delay to 3 h, and choosing a washing buffer of pH within the range of 7.2 to 7.8 would be a valid recommendation for most applications and circumstances described herein.

Abstract

Objective interpretation of FC results may still be hampered by limited technical standardization. The EuroFlow consortium conducted a series of experiments to determine the impact of different variables on the relative distribution and the median fluorescence intensity (MFI) of markers stained on different cell populations, from both healthy donors and patients’ samples with distinct hematological malignancies. The use of different anticoagulants; the time interval between sample collection, preparation, and acquisition; pH of washing buffers; and the use of cell surface membrane-only (SM) vs. cell surface plus intracytoplasmic (SM+CY) staining protocols, were evaluated. Our results showed that only monocytes were represented at higher percentages in EDTA- vs. heparin-anticoagulated samples. Application of SM or SM+CY protocols resulted in slight differences in the percentage of neutrophils and debris determined only with particular antibody combinations. In turn, storage of samples for 24 h at RT was associated with greater percentage of debris and cell doublets when the plasma cell disorder panel was used. Furthermore, 24 h storage of stained cells at RT was selectively detrimental for MFI levels of CD19 and CD45 on mature B- and T-cells (but not on leukemic blasts, clonal B- and plasma cells, neutrophils, and NK cells). The obtained results showed that the variables evaluated might need to be tailored for sample and cell type(s) as well as to the specific markers compared; however, defining of well-balanced boundaries for storage time, staining-to-acquisition delay, and pH of washing buffer would be a valid recommendation for most applications and circumstances described herein.

Analysis of platelet-activating factors in severe sepsis by flow cytometry and its correlation with clinical sepsis scoring system: A pilot study

Background

Sepsis is a major global healthcare concern. Platelets and leucocytes play a key role in sepsis. Whole blood flow cytometry (FCM) is a powerful new technique for the assessment of leucocyte and platelet parameters and their functional state. In the present study, we have used FCM to examine platelet and leucocyte functions and parameters in sepsis patients.

Methods

Prospective, non-interventional cohorts of all adult patients with sepsis and history of intensive care unit stay for more than 24 h at mixed surgical- medical ICU were evaluated. The Simplified Acute Physiology Score-3 (SAPS 3) admission score was obtained, and whole blood FCM analysis of select platelets and leukocyte parameters were performed using a combination of monoclonal antibodies in a predefined panel. We also evaluated the correlation between these parameters and the severity of the illness, based on SAPS 3 admission score.

Results

Total leucocyte count (TLC) was statistically and significantly different between all the study samples, but platelet count was not. SAPS 3 acted as the best discriminant between the study groups. With a cut-off score of 55.5, SAPS 3 score predicted hospital mortality with a sensitivity of 82.8% and a specificity of 83.9%, with an area under receiver operating curves (AUROC) of 0.888 (95% CI = 0.807-0.969, p < 0.000). Parameters for CD62P, platelet-leucocyte aggregates (PLAs) and CD11b showed statistically significant differences between the patients and healthy volunteers. CD62P expression was positively correlated to PLA variables in severe sepsis patients. The median fluorescence intensity was found to be more informative than mean fluorescence intensity. New "62P adhesion index (62P AI)" and "PLA adhesion index" are proposed and is likely to be more informative.

Conclusion

SAPS 3 score was the most robust of the parameters evaluated. Our study suggest the idea that the incorporation of platelet and leucocyte activation parameters, rather than mere static counts, will add the existing prognostic model though we could not conclusively prove the same in this study.

Characterization of a whole blood assay for quantifying myeloid-derived suppressor cells

Background

Myeloid-derived suppressor cells (MDSC) have been found to play an important role in limiting immune responses in cancer. Higher circulating MDSC levels have been associated with greater tumor burden, poorer response to immunotherapy, and poorer survival. Optimal measurement of MDSC levels could provide clinicians with a useful prognostic and/or management tool.

Methods

A whole blood (WB) nine color, 11 parameter flow cytometric assay was designed, utilizing fluorescently-labeled antibodies against CD45, CD3, CD19, CD20, CD56, CD16, HLA-DR, CD33, CD11b, CD14 and CD15, and BD Trucount beads for quantitation. Total MDSC were defined as CD45 + CD3⁻CD19⁻CD20⁻CD56⁻CD16⁻HLA-DR⁻CD33 + CD11b + cells, while the monocytic (M-MDSC) and polymorphonuclear subsets were defined as CD14+ or CD15+, respectively.

Results

A novel gating strategy was devised to eliminate granulocytes and improve consistency in gating. Several pre-analytical variables were found to significantly affect MDSC quantitation, including collection tube type and time elapsed between blood collection and testing. Total and M-MDSC levels were a mean of 63% and 73% greater, respectively, with K₂EDTA compared to Na⁺heparin collection tubes (N = 5). In addition, time elapsed at room temperature prior to cell labeling affected MDSC quantitation; by 24 h after blood collection, total and M-MDSC levels were a mean of 26% and 57% lower compared to testing as soon as possible after collection (N = 6). Refrigeration of samples at 4 °C ameliorated time-dependent effects at both 4 and 8 h, but not 24 h after blood collection. To establish normal ranges for this assay, MDSC levels were quantified in 67 healthy subjects (30 male, 37 female) ages 20–93. No significant differences in total or M-MDSC levels were detected for ages ≤60 compared to > 60 (p = 0.5 and p = 0.8, respectively). Finally, assay results demonstrated significantly higher MDSC levels among patients with hepatocellular carcinoma (N = 55) compared to age-matched healthy controls (N = 27) for total and M-MDSC (p = 0.006 and 0.004, respectively).

Conclusions

MDSC are a heterogenous group of cells, and their quantitation in WB can be affected by a number of pre-analytical variables. Consideration of these factors, and measurement using a material type that has not been manipulated, such as whole blood, is likely to yield the most accurate results.

Electronic supplementary material

The online version of this article (10.1186/s40425-019-0674-1) contains supplementary material, which is available to authorized users.

Comparison Between K3EDTA and Lithium Heparin as Anticoagulant to Isolate Bovine Granulocytes From Blood

Granulocytes play a key role in the defense against invading pathogens. To study granulocyte functions, the isolation of a pure and active cell population from fresh blood is required. Anticoagulants and red blood cells (RBCs) lysis used in the isolation procedure may influence cell harvest, cell marker expression, and pre-activation of cells. In this study, the influence of the anticoagulants K₃EDTA or lithium heparin and the effect of different RBCs lysis methods on bovine granulocyte population from fresh blood of healthy cows after density gradient centrifugation were investigated. Venous blood from healthy cows was collected in K₃EDTA and lithium heparin tubes. Density gradient centrifugation to separate granulocytes from other cells was conducted using Biocoll. Then, RBCs were lysed with hypotonic water or 0.2% sodium chloride (NaCl). Immediately after isolation, harvest, viability, size, granularity, purity, and CD11b expression as a marker for granulocytes was analyzed by flow cytometry. In addition, as a marker for activation and reactivity of the granulocytes, we stimulated cells with phorbol-myristate-acetate to evaluate the release of reactive oxygen species. Furthermore, extracellular trap (ET) formation was investigated by confocal immunofluorescence microscopy in untreated control cells and cells treated with the cholesterol-depleting agent methyl-β-cyclodextrin. We did not find a significant difference in percentage of dead cells when comparing the two anticoagulants or the different RBCs lysis methods. However, the percentage of granulocytes in the harvested population was significantly less using lithium heparin blood as anticoagulant compared to K₃EDTA. The granulocytes harvested from lithium heparin blood and water lysis exhibited higher clumping and pre-activation of unstimulated control cells as indicated by isolation of doublet cells, increased CD11b expression, and increased oxidative burst and higher amount of ET-releasing cells. Furthermore, the combination of K₃EDTA as anticoagulant and NaCl as RBCs lysis method revealed the lowest variability and highest difference between untreated and methyl-β-cyclodextrin-treated cells when quantifying ET formation. In conclusion, density gradient centrifugation of K₃EDTA blood resulted in higher purity of bovine granulocytes compared to lithium heparin blood. In contrast to water lysis, NaCl lysis method is recommended to avoid pre-activation of cells which may occur during hypotonic water lysis.

The impact of delayed sample handling and type of anticoagulant on the interpretation of dysplastic signs detected by flow cytometry

Introduction

A growing body of evidence supports the usefulness of dysplastic signs detected by flow cytometry in the diagnosis of myelodysplastic syndromes (MDS). Our aim was to assess the impact of pre-analytical variables (delayed sample handling, type of anticoagulant, and different clones of antibody) in the interpretation of flow cytometric results.

Material and methods

Bone marrow samples were labelled and analysed immediately after aspiration and on two consecutive days. The effect of anticoagulant type was evaluated in 16 bone marrow samples. Thirty-seven different immunophenotypic variables were recorded after eight-colour staining. Furthermore, 8 normal peripheral blood samples collected in K₃-EDTA and Na-heparin were examined with different clones of CD11b antibodies and four parameters were recorded with both anticoagulants on two consecutive days.

Results

Fourteen significant differences were detected in the initial immunophenotype of fresh samples collected in K₃-EDTA and Na-heparin. Regardless of the anticoagulant type, eleven parameters remained stable despite delayed sample handling. Due to delayed sample processing, more alterations were detected in the samples collected in K₃-EDTA than in the samples collected in Na-heparin. The type of CD11b clone influenced the reduction of fluorescence intensity only in samples collected in K₃-EDTA, where the alterations were contrary to the changes observed in Na-heparin.

Conclusions

Delayed sample processing causes considerable immunohenotypic alterations, which can lead to false interpretation of the results. If delayed sample evaluation is unavoidable, markers that remain more stable over time should be considered with more weight in the diagnosis of MDS.

Detection of muramyl dipeptide-sensing pathway defects in monocytes of patients with Crohn's disease using phospho-specific whole blood flow cytometry

Peripheral blood mononuclear cells of Crohn's disease (CD) patients with the common 1007fs mutation of the caspase recruitment domain-containing 15/nucleotide-binding oligomerization domain-containing 2 (CARD15/NOD2) gene show impaired nuclear factor kappa B (NF-κB) activation in response to muramyl dipeptide (MDP), as determined by Western blotting. We applied phospho-specific flow cytometry to examine NF-κB and p38 activation in whole blood monocytes of 16 CD patients with or without the 1007fs and previously described rare mutations of the CARD15 gene, and healthy reference subjects. Aliquots of whole blood were supplemented with MDP (0-1000 ng/mL), incubated for 10-40 min and processed for flow cytometry. Bacterial lipopolysaccharide (LPS) was used as a positive control agonist. We found that NF-κB and p38 phosphorylation induced by MDP was not detectable in monocytes of patients homozygous for the CARD15 1007fs mutation, while those induced by LPS were normal. We also determined MDP-induced NF-κB phosphorylation levels in nuclear extracts of mononuclear cells separated from blood using enzyme-linked immunosorbent assay (ELISA), and observed that the levels decreased in a 1007fs mutation-dose dependent manner. We conclude that phospho-specific whole blood flow cytometry provides a means to study phosphorylation of NF-κB and p38 in clinical samples and can be applied to screening of CD patients homozygous for the CARD15 1007fs mutation.

Patients with acute pancreatitis complicated by organ dysfunction show abnormal peripheral blood polymorphonuclear leukocyte signaling

BACKGROUND/OBJECTIVES

Circulating polymorphonuclear leukocytes (PMNLs) may contribute to development of organ dysfunction in acute pancreatitis (AP). We outlined aberrations in PMNL signaling profiles in patients with AP complicated by organ dysfunction and immune suppression.

METHODS

Study comprised 13 patients treated at intensive care unit due to severe AP complicated by vital organ dysfunction. Mean proportion (SEM) of HLA-DR-positive monocytes was 55.0% (4.1%). 13 healthy volunteers served as reference subjects. Phosphorylation of PMNL NFκB, p38, ERK1/2 and STAT3, -5 and -6 was determined using whole blood flow cytometry. Transmigration of PMNLs was studied using endothelial EA-HY cell monolayer.

RESULTS

Proportions of NFκB phosphorylation-positive PMNLs were lower in the patients' than in reference subjects' blood samples supplemented with tumor necrosis factor. p38 phosphorylation was normal while ERK1/2 phosphorylation was decreased. STAT3 was constitutively activated in five patients. Proportion of patients' pSTAT6-positive cells was normal while fluorescence intensity was decreased. STAT5 phosphorylation was normal. Transmigration of patients' PMNLs was increased.

CONCLUSIONS

In patients with AP complicated by organ dysfunction proportion of pNFκB-positive PMNLs is decreased. This impairs patients' defense mechanisms against infection. Despite immune suppression, PMNL transmigration was increased and p38 phosphorylation capacity was not depressed, which may contribute to end organ inflammation and dysfunction.

Use of 111-Indium-labeled autologous eosinophils to establish the in vivo kinetics of human eosinophils in healthy subjects

Eosinophils are the major cellular effectors of allergic inflammation and represent an important therapeutic target. Although the genesis and activation of eosinophils have been extensively explored, little is known about their intravascular kinetics or physiological fate. This study was designed to determine the intravascular life span of eosinophils, their partitioning between circulating and marginated pools, and sites of disposal in healthy persons. Using autologous, minimally manipulated 111-Indium-labeled leukocytes with blood sampling, we measured the eosinophil intravascular residence time as 25.2 hours (compared with 10.3 hours for neutrophils) and demonstrated a substantial marginated eosinophil pool. γ camera imaging studies using purified eosinophils demonstrated initial retention in the lungs, with early redistribution to the liver and spleen, and evidence of recirculation from a hepatic pool. This work provides the first in vivo measurements of eosinophil kinetics in healthy volunteers and shows that 111-Indium-labeled eosinophils can be used to monitor the fate of eosinophils noninvasively.

Analysis of the temperature affects on leukocyte surface antigen expression

Flow cytometric analysis of leukocyte surface antigens has been used to characterize infectious and septic processes in patients. We wanted to investigate how the sampling and processing temperature, the anticoagulant used, and the storage of the sample influence leukocyte immunophenotyping. Four blood samples, two using acid citrate dextrose and two using heparin as an anticoagulant, were taken from five intensive-care unit patients with severe sepsis and five healthy volunteers. The samples were collected, stored, and processed either at +4°C or at room temperature (RT). The samples were processed for flow cytometric analysis within 1  hr of collection or after 6 or 24  hr storage. The surface antigens of interest were neutrophilic CD11b and CD64, monocytic CD11b, CD14, CD40, CD64, CD80 and HLA-DR, and lymphocytic CD69 (separately in CD4+ and CD8+ T cells, B cells, and natural killer cells). The fluorescence intensities were higher at RT than at +4°C. During storage the intensities increased at RT, but at +4°C there were only minor changes. The effects were similar with both anticoagulants studied. According to our results, flow cytometric analysis of leukocyte surface antigen expressions should be performed using +4°C temperature throughout the process and within 6  hr.

Patients with acute pancreatitis complicated by organ failure show highly aberrant monocyte signaling profiles assessed by phospho-specific flow cytometry

OBJECTIVES

To outline signaling profiles and transmigration capacity of monocytes of patients with severe acute pancreatitis.

DESIGN

Prospective study.

SETTING

University hospital intensive care unit.

PATIENTS

Thirteen patients with severe acute pancreatitis. All patients had organ dysfunction (acute respiratory distress syndrome in 12, renal dysfunction in eight). Healthy volunteers served as reference subjects.

INTERVENTIONS

Blood samples were collected after admission to the intensive care unit.

MEASUREMENTS AND MAIN RESULTS

Phosphorylation of nuclear factor-kappaB and p38, signal transducers and activators of transcription (STATs) 1, 3, 5, and extracellular signal-regulated kinases 1/2 in appropriately stimulated and nonstimulated samples were studied using phospho-specific whole-blood flow cytometry. Monocyte chemotactic protein-1-induced transmigration of monocytes among mononuclear cells obtained by density gradient centrifugation was studied using Transwell cell culture inserts covered with confluent layer of endothelial EA-HY cells. Phosphorylation levels of nuclear factor-kappaB induced by tumor necrosis factor, bacterial lipopolysaccharide, muramyl dipeptide, Escherichia coli, Staphylococcus aureus, and Staphylococcus epidermidis were significantly lower in patients' monocytes than monocytes of healthy reference subjects, whereas mitogen-activated protein kinase p38 phosphorylation levels were normal. Phosphorylation levels induced by interleukin-6 in STAT1 and STAT3 and by combination of phorbol 12-myristate 13-acetate and calcium ionophore A23187 in extracellular signal-regulated kinases 1/2, members of a mitogen-activated protein kinase family, were depressed in patients' monocytes, whereas phosphorylation levels induced by granulocyte-macrophage colony-stimulating factor in STAT5 was normal. In nonstimulated samples, phosphorylation levels were normal. The transmigration percentage of patients' monocytes was significantly lower than that of reference monocytes.

CONCLUSIONS

In severe acute pancreatitis, monocytes show impaired nuclear factor kappaB and STAT1 activation, which may increase susceptibility to secondary infections. p38 activation is normal and STAT3 activation is depressed, which may contribute to maintenance of systemic inflammation. Extracellular signal-regulated kinases 1/2 activation is impaired, which may depress monocytes' transmigration and may consequently increase risk of infection. Monitoring of monocyte signaling profiles may aid in finding new therapeutic approaches and predictors of outcome of severe acute pancreatitis.

Expression of CD11b/CD18 adhesion molecules on circulating phagocytes-a novel aid to diagnose infection in patients with cancer

GOALS OF WORK

No blood marker available to date is useful for distinguishing infection-related from neoplasm-related fever. We evaluated the expression of the peripheral blood phagocyte CD11b/CD18 adhesion molecule complex for this purpose.

MATERIALS AND METHODS

Neutrophil and monocyte CD11b/CD18 expression was assessed in two cohorts of patients with advanced solid cancer (n = 120) and in healthy controls (n = 63). The cancer series included 89 patients with verified infection, 23 without infection, and eight with neoplastic fever. CD11b/CD18 expression was measured using flow cytometry, and serum C-reactive protein (CRP) concentration was determined with immunoturbidimetric assay.

RESULTS

Cancer patients with infection had higher blood neutrophil and monocyte CD11b/CD18 expression levels than patients with neoplastic fever, those with advanced cancer without infection, or healthy controls (p < 0.01 for all analyses). High CD11b/CD18 values were measured exclusively in individuals diagnosed with infection. Receiver-operating characteristic area under the curve (AUC) for neutrophil and monocyte CD11b/CD18 expression for the discrimination of infection from neoplastic fever was 0.80 (95% CI, 0.70 to 0.88), which was superior (p = 0.039 and p = 0.049, respectively) to serum CRP on admission (AUC 0.51, 0.40 to 0.62).

CONCLUSIONS

Peripheral blood phagocytic cell CD11b/CD18 expression is useful for making a differential diagnosis between infection and neoplasm-related fever in cancer patients.

Isolation and activation of human neutrophils in vitro. The importance of the anticoagulant used during blood collection

OBJECTIVES

To assess the effect of different anticoagulants (EDTA, citrate and heparin) on the isolation procedure of human neutrophils and in the subsequent alterations of calcium levels and respiratory burst induced by phorbol myristate acetate (PMA).

DESIGN AND METHODS

Isolation of human neutrophils from whole blood was performed by the gradient density centrifugation method. PMA-induced neutrophil burst was measured by chemiluminescence. Intracellular calcium ([Ca(2+)](i)) was measured using Fluo-3 AM, a calcium-sensitive dye.

RESULTS

EDTA provided the highest number of isolated neutrophils/mL of blood (1.7x10(6)+/-1.5x10(5)) when compared with citrate (0.46x10(6)+/-0.95x10(5)) and heparin (0.66x10(6)+/-0.15x10(5)). EDTA originated less degree of PMA-induced activation (370+/-30%) relatively to citrate (830+/-98%) and heparin (827+/-77%). [Ca(2+)](i) was lower with EDTA (122+/-11 nM) when compared with citrate and heparin (150+/-13 and 230+/-30 nM).

CONCLUSION

The anticoagulant used during blood collection interfered differently with the yield of isolated neutrophils as well as on their calcium levels and reactivity to PMA.

Comparison of sample fixation and the use of LDS-751 or anti-CD45 for leukocyte identification in mouse whole blood for flow cytometry

Flow cytometry methods used to measure leukocyte function often entail sample preparation procedures that cause artifactual cell activation. To avoid leukocyte activation by isolation techniques, some preparation methods use fluorescent markers to discriminate leukocytes from erythrocytes in whole blood. One of these markers, laser dye styryl-751(LDS-751), has been used to distinguish leukocytes by staining nucleic acid, but has been found to stain other blood cells and dead cells indiscriminately. Thus, LDS-751 may not be an appropriate reagent for leukocyte identification in whole blood. Fixing samples with formaldehydes increases cell permeability and causes surface protein cross-linking that may alter staining of both intra- and extracellular markers. The degree of this sample alteration by formaldehyde fixation, however, remains in question. In addition, little is known about flow cytometry and sample preparation methods in mouse whole blood. The purpose of this study was to determine if labeling leukocytes with a monoclonal antibody specific to leukocyte common antigen (CD45) was superior to labeling with LDS-751 and to determine the effect of sample fixation on a mouse whole blood preparation for flow cytometry. Samples were incubated with CD16/CD32 Fc receptor blocker, and either 10 microg/ml LDS-751 or phosphate buffered saline (PBS). The samples were then fixed with paraformaldehyde or diluted with PBS followed by incubation with 5 microg/ml PerCP-conjugated anti-CD45, 5 microg/ml FITC-conjugated anti-CD11b, or 80 microM dichlorofluorescein diacetate. We found that samples labeled with LDS-751 demonstrated decreased fluorescence intensity for granulocyte CD11b expression and ROS production compared to samples labeled with anti-CD45. In addition, sample fixation decreased mean fluorescence intensity in samples labeled with either LDS-751 or anti-CD45. We conclude that labeling leukocytes with monoclonal antibody CD45 in a mouse whole blood preparation is preferable, as it provides improved measurement of leukocyte indices compared to LDS-751. Also, while sample fixation prior to antibody staining caused a decrease in overall fluorescence; it can be used to successfully identify extra-cellular markers.

In whole blood, LPS, TNF-alpha and GM-CSF increase monocyte uptake of 99mtechnetium stannous colloid but do not affect neutrophil uptake

INTRODUCTION

(99m)Technetium stannous colloid (TcSnC) is used in white cell scanning. It labels neutrophils and monocytes via phagocytosis, with uptake mediated by the phagocytic receptor CD11b/CD18 in neutrophils. Uptake of TcSnC is altered by gram-negative infection, possibly due to the endotoxin component lipopolysaccharide (LPS) or to cytokines released during infection (e.g., TNF-alpha and IFN-gamma). Endotoxemia and increased TNF-alpha levels also occur in inflammatory bowel disease. Another potential confounder in cell labeling is that sepsis patients may be treated with GM-CSF and G-CSF, which alter phagocytic cell function. This study aimed to determine how these factors affect TcSnC cellular uptake.

METHODS

Whole blood from six healthy volunteers was incubated with LPS, TNF-alpha, IFN-gamma, GM-CSF or G-CSF. Samples were then mixed with TcSnC. Blood was separated across density gradients and imaged using a gamma camera. Three radioactive count peaks were observed in each tube: free plasma activity, mononuclear cell uptake and neutrophil uptake.

RESULTS

Compared with controls, significant increases in mononuclear cell uptake were induced by LPS, TNF-alpha and GM-CSF stimulation. It was incidentally noted that exogenous estrogens appear to affect TcSnC labeling and may influence the neutrophil response to stimulation. Neutrophil uptake and plasma activity were not significantly affected. IFN-gamma and G-CSF had no significant effect.

CONCLUSIONS

In whole blood, the effect of LPS on TcSnC monocyte uptake is different to its effect on neutrophils, consistent with previously reported differences in CD11b/CD18 expression. TNF-alpha response parallels LPS response. GM-CSF also increases TcSnC uptake by monocytes. These effects should be considered when using TcSnC for imaging purposes, as they will tend to increase monocyte labeling. Estrogens may also affect TcSnC labeling. Responses to IFN-gamma and G-CSF are consistent with previously reported effects of these cytokines on CD11b/CD18 expression.

Leukocyte depleting filter attenuates myocardial injury during elective coronary artery bypass surgery

BACKGROUND

Ischemia-reperfusion injury secondary to leukocyte activation has been widely recognized as one of the most relevant mechanism leading to postoperative organ dysfunction occurring after a period of ischemia. The aim of the present study was to evaluate in a prospective, randomized study, the value of leukocyte depleting filter in patients undergoing elective coronary artery bypass surgery.

METHODS

Twenty patients scheduled for elective on-pump coronary artery bypass surgery were randomized to undergo cardiopulmonary bypass either with a leukocyte depleting filter incorporated in the extracorporeal circulation arterial line or without a filter.

RESULTS

The main finding of this study was the significantly lower postoperative concentrations of cardiac troponin I in the leukocyte filter group (Tests of between-subjects effects: p = 0.024). There were also slightly better cardiac indices in the leukocyte filter group. A larger amount of blood units was infused intra- and postoperatively in patients undergoing cardiopulmonary bypass with leukocyte filtration (median, 600 [IQR, 0-1200] vs. 0 [IQR, 0-600], p = 0.08). Two patients in the leukocyte filter group underwent reoperation for bleeding but none in the control group (p = 0.48). Intra-and postoperative platelet count was lower in the leukocyte filter group (Tests of between-subjects effects: p = 0.08). Despite a significant increased concentration of C-reactive protein on the first postoperative day in the control group (p = 0.029), repeated-measures analysis failed to show any significant increase during the study period (p = 0.33).

CONCLUSIONS

The results of this study suggest a myocardial protective effect of leukocyte filter in the setting of elective coronary artery bypass surgery.

Onset of mechanical ventilation is associated with rapid activation of circulating phagocytes in preterm infants

OBJECTIVE

In preterm infants with respiratory distress syndrome (RDS), circulating neutrophils are activated. Kinetics and effects of surfactant therapy on this activation are unknown. Therefore, we studied activation of circulating neutrophils and monocytes in newborn preterm infants with and without RDS.

PATIENTS AND METHODS

Preterm infants with RDS who were mechanically ventilated and received surfactant ("ventilated infants": n = 38; mean gestational age +/- SD: 28.3 +/- 2.2 weeks; mean birth weight +/- SD: 1086 +/- 353 g) and preterm infants who received nasal continuous positive airway pressure (n = 8) or no ventilatory support (n = 17) ("control infants": mean gestational age +/- SD: 32.1 +/- 1.2 weeks; mean birth weight +/- SD: 1787 +/- 457 g) were recruited. Blood samples were taken from ventilated infants at birth, before surfactant treatment, at 1 and 2 hours after surfactant, and at 12 to 24 hours of age. Blood samples were taken from control infants at birth, at 2 to 6 hours, and at 12 to 24 hours of age. Phagocyte CD11b expression was analyzed by flow cytometry.

RESULTS

In ventilated infants, phagocyte CD11b expression increased from birth to the first postnatal samples. It increased further by 12 to 24 hours of age. Control infants with or without nasal continuous positive airway pressure showed no significant increase after birth. At 12 to 24 hours of age, phagocyte CD11b expression was higher in ventilated infants than in control infants. In ventilated infants, neutrophil CD11b expression at 1 and 2 hours after surfactant correlated positively with gestational age.

CONCLUSIONS

In preterm infants with RDS, significant activation of circulating phagocytes occurs within 1 to 3 hours of the onset of mechanical ventilation, independent of surfactant administration, which indicates that mechanical ventilation may be the inducer of this systemic inflammatory response.

Graft protein C entrapment is associated with reduced phagocyte activation during reperfusion in human liver transplantation

OBJECTIVE

To explore the potential anti-inflammatory role of protein C pathway in ischemia-reperfusion injury during liver transplantation.

DESIGN

Prospective, observational clinical study.

SETTING

Tertiary teaching hospital.

PATIENTS

Fifty adult patients undergoing liver transplantation for acute liver failure or chronic liver disease.

INTERVENTIONS

To assess changes occurring across the transplanted liver, samples of blood entering and leaving the graft were obtained simultaneously from portal and hepatic veins. Plasma protein C and activated protein C levels, neutrophil and monocyte CD11b and L-selectin expression, and leukocyte differential counts were measured. Postoperative liver function and outcome of transplantation were recorded.

MEASUREMENTS AND MAIN RESULTS

During reperfusion, protein C became entrapped within the graft (portal vein 49% [20-96%]; graft caval effluent 25% [12-76%], p < .001), without concomitant activated protein C outflow from the graft. Simultaneously, marked neutrophil and monocyte activation occurred within the graft. Enhanced hepatic protein C entrapment was associated with reduced neutrophil and monocyte activation (R = .377, p = .011; R = .389, p = .008, respectively) during reperfusion.

CONCLUSIONS

Protein C entrapment occurs immediately during reperfusion in the graft without concomitant activated protein C release, suggesting a shortage of activated protein C in the reperfused graft. The ongoing inflammatory response during reperfusion may lead to protein C and activated protein C utilization within the graft. Indeed, hepatic protein C entrapment is associated with reduced hepatic phagocyte activation, suggesting a regulatory role for protein C pathway in hepatic reperfusion in human liver transplantation.

Neutrophil gene expression in rheumatoid arthritis

There is now a growing awareness that infiltrating neutrophils play an important role in the molecular pathology of rheumatoid arthritis. In part, this arises from the fact that neutrophils have potent cytotoxic activity, but additionally from the fact that inflammatory neutrophils can generate a number of cytokines and chemokines that can have a direct influence on the progress of an inflammatory episode. Furthermore, the molecular properties of inflammatory neutrophils are quite different from those normally found in the circulation. For example, inflammatory neutrophils, but not blood neutrophils, can express cell surface receptors (such as MHC Class II molecules and FcgammaRI) that dramatically alter the way in which these cells can interact with ligands to modulate immune function. Cytokine/chemokine expression and surface expression of these novel cell surface receptors is dependent upon the neutrophil responding to local environmental factors to selectively up-regulate the expression of key cellular components via signalling pathways coupled to transcriptional activation. However, major changes in the expression levels of some proteins are also regulated by post-translational modifications that alter rates of proteolysis, and hence changes in the steady-state levels of these molecules.

Activated protein C reduces graft neutrophil activation in clinical renal transplantation

We studied the role of endogenous activated protein C (APC), the major physiological anti-coagulant with concomitant anti-inflammatory properties, on ischemia/reperfusion (I/R) in 45 patients participating in a larger trial comparing three immunosuppressive protocols in cadaveric renal transplantation: perioperative anti-thymocyte globulin (ATG, Fresenius AG, Bad Homburg, Germany), perioperative basiliximab and conventional triple therapy. Blood samples for assessing plasma APC, protein C, and lactoferrin concentrations, neutrophil CD11b and L-selectin expressions and blood leukocyte differential counts were obtained preoperatively and before reperfusion from central venous cannula, complemented with simultaneous samples from iliac artery and graft vein for calculation of transrenal differences (Delta) of study parameters at 1 and 5 min after reperfusion. Unlike basiliximab or conventional therapy groups, ATG infusion induced a substantial increase in plasma APC concentration (119 [88-144]% before infusion vs. 232 [85-1246]% after infusion, p<0.001), resulting in renal graft sequestration of APC at 1 min after reperfusion (Delta=-72 [-567 to 12]%, p<0.001). Graft APC consumption was associated with transrenal reduction of neutrophil activation markers (L-selectin r=0.7, p=0.01; lactoferrin r=-0.6, p=0.02; CD11b r=-0.8, p=0.001), and with both warm (r=0.6, p=0.01) and cold ischemia time (r=0.6, p=0.02) and donor age (r=0.6, p=0.01). These findings suggest that APC has an anti-inflammatory role in I/R injury in clinical renal transplantation.

Breed and age affect baseline immune traits, cortisol, and performance in growing pigs1

It was hypothesized in these studies that differences would exist in baseline immune and performance measures among different breeds of pigs, and that these differences would be affected by age of the pig. Baseline immune, plasma cortisol (CORT) concentrations, and performance measures were determined among Berkshire (n = 36), Duroc (n = 18), Meishan (n = 54), Landrace x Yorkshire (White X; n = 36), and Yorkshire (n = 36) pigs at 4, 8, and 12 wk of age. All piglets were weaned at 17 to 21 d of age and moved to a common nursery environment. Total white blood cell (WBC), leukocyte differential, plasma CORT, immunoglobulin G (IgG) concentrations, natural killer cytotoxicity, neutrophil phagocytosis (PHAGO), and chemotaxis (CHTX) were evaluated. At all ages, plasma CORT was greatest in Meishan pigs, and least in Yorkshires (P < 0.05). Plasma IgG increased with age for all breeds (age: P < 0.01; breed x age: P < 0.005), except that in Meishans, IgG decreased. Natural killer cytotoxicity was greatest (P < 0.05) among Meishan pigs. There were breed x age interactions for neutrophil PHAGO (P < 0.001) and CHTX (P < 0.001). Overall, Yorkshire pigs showed the greatest (P < 0.05) percentage of PHAGO but the least (P < 0.05) CHTX. White X pigs had the greatest (P < 0.05) CHTX response. Berkshire pigs had the greatest (P < 0.001) numbers of neutrophils. At 12 wk of age, Meishan pigs had the least BW gain (P < 0.001), and Durocs had the greatest G:F (P < 0.001). There were no significant sex differences for immune (P > or = 0.15), performance (P > or = 0.20), or CORT (P = 0.70) measures. Pig breed and age influenced both baseline immune measures and plasma CORT in growing pigs, suggesting that pig breed and age are important factors influencing the response to various stressors or infectious challenges.

Impact of preanalytical variables on granulocytic surface antigen expression: a review

BACKGROUND

There is a gradual but steady increase in the use of granulocytic surface marker studies to diagnose several inherited and acquired blood and bone marrow disorders. Diagnosis and follow-up of patients with inflammation and infection are other areas of quantitative flow cytometric application. Despite the increased use of flow cytometry to study granulocytes, there seems to be no well-established standards regarding specimen handling for these studies.

METHODS

This review summarizes the effect of preanalytical variables on granulocytic surface markers.

RESULTS AND CONCLUSIONS

Storing specimens in sodium heparin at room temperature for up to 72 h seems satisfactory. Other anticoagulants, although acceptable, may have a shorter storage time. Storage time could be prolonged further with the use of some preservation media. Lysed whole blood is the preferred technique. Techniques should avoid major temperature change and excessive manipulation and should maintain storage and methodologic temperature with minimal fluctuation. Fixation before staining with the antibody may result in decreased expression of some surface antigens.

Increased CD11b-density on circulating phagocytes as an early sign of late-onset sepsis in extremely low-birth-weight infants

Late-onset hospital-acquired sepsis is common in extremely low birth-weight (<1000 g) (ELBW) infants. The diagnosis is difficult since, at early stages of sepsis, routine laboratory tests are neither specific nor sensitive. In term infants with sepsis neutrophil surface expression of CD11b/CD18, a beta2-integrin, is significantly increased. Here we studied whether increased CD11b/CD18 density on blood neutrophils and monocytes serves as an early sepsis marker in ELBW infants. Blood samples were obtained from 30 ELBW infants on a daily basis for 3-4 postnatal weeks, and neutrophil and monocyte CD11b/CD18 expression was determined by flow-cytometry. Patients were assigned one of 3 groups: 1) an infected group, comprised of infants who had blood culture-positive sepsis and/or necrotizing enterocolitis, 2) a non-infected group, and 3) a potentially infected group, comprised of infants in whom infection was suspected but could not be confirmed microbiologically. One patient had blood culture contamination and was excluded from the analysis. In the infected group, CD11b expression gradually increased during the three days preceding sampling for blood culture. At the day of sampling, median expression of CD11b in neutrophils and monocytes was higher in the infected group than in the control group. For neutrophils the sensitivity and specificity were 1.00 and 0.56, respectively, and for monocytes, 0.86 and 0.94, respectively. From these data, we conclude that determination of CD11b/CD18 density on neutrophils and monocytes may improve diagnosis of late-onset sepsis in ELBW infants.

Chemiluminescence: comparison of whole blood with isolated polymorphonuclear leukocytes after major trauma

INTRODUCTION

Neutrophil (PMN) mediated tissue injury is central to the development of post-traumatic ARDS/MOF. Changes in activity caused by PMN isolation may be avoided by studying respiratory burst activity using whole blood chemiluminescence (WBCL).

METHODS

WBCL and PMNCL were measured in 5 normal laboratory volunteers (NLV) and 9 patients sustaining major trauma, within 2 hours of admission. Receptor mediated (STZ) and independent (PMA) activating agents were used.

RESULTS

PMA activation confirmed significant priming both in WBCL and PMNCL after major trauma. With STZ, priming was confirmed in the WBCL study, but the trauma patient PMNCL showed no difference in response to those of NLV. Although the study population was small, those patients later developing ARDS demonstrated significantly greater STZ activated WBCL, 8 hours after admission.

CONCLUSION

PMN isolation alters behavior in vitro. This may lead to important differences of in vivo PMN function being obscured when studied in the laboratory setting. Further study of CL response and surface receptor expression is clearly warranted, both in WB and PMN preparations.

Association of graft neutrophil sequestration with delayed graft function in clinical renal transplantation

BACKGROUND

The authors studied the impact of neutrophil activation, detected in experimental models, on reperfusion injury in clinical renal transplantation.

METHODS

Forty-five patients from a larger trial comparing three immunosuppressive protocols were recruited: perioperative antithymocyte globulin (ATG) with low initial cyclosporine A (CsA) triple therapy (group A, n=15); two-dose basiliximab with low initial CsA triple therapy (group B, n=16); and conventional triple therapy (group C, n=14). Blood samples were obtained preoperatively, before reperfusion, and at 1 and 5 min after reperfusion. During reperfusion, samples were collected from the iliac artery and the graft vein for calculation of transrenal differences (Delta) of study parameters. Leukocyte differential counts, plasma lactoferrin concentration, and neutrophil CD11b and L-selectin expressions were assessed. Graft blood flow was measured at 2 and 30 min after reperfusion.

RESULTS

ATG induced neutrophil activation already before reperfusion. Thus, group A was excluded, but groups B and C were pooled for analysis of reperfusion-induced neutrophil activation. At 1 min after reperfusion, lactoferrin concentration was higher in graft vein than iliac artery, yielding Delta=15 microg/L (P<0.05). Concomitantly, Delta neutrophil count correlated with both Delta L-selectin expression (R=0.49, P=0.012) and graft blood flow at 2 min (R=0.51, P=0.007). At 5 min after reperfusion, 0.17 (-1.0-0.24)x10 cells/L neutrophils were sequestered in the graft (P<0.001). This sequestration correlated with graft blood flow at 30 min (R=0.53, P=0.005) and was stronger in patients with delayed graft function (DGF) (Delta = -0.38 [-1.45 to -0.2]) than those without (Delta = -0.12 [-0.41-0.24], P<0.001). In multiple regression analysis, sequestration was the most important parameter associated with DGF.

CONCLUSIONS

Neutrophils are activated and sequestered in the reperfused graft during clinical renal transplantation. Neutrophil sequestration is a powerful independent factor explaining the incidence of DGF.

A standardized procedure for quantitation of CD11b on polymorphonuclear neutrophil by flow cytometry: potential application in infectious diseases

An up-regulation of the surface marker CD11b has been demonstrated during polymorphonuclear (PMN) cell activation. CD11b over-expression is often associated with inflammation and is considered as an early marker of infection. However, the absence of standardized assay and the variability of preanalytical settings leading to PMN artifactual activation have compromised the interest of this marker. In the present study a standardized quantitative flow cytometry assay directly performed in whole blood has been used to determine CD11b expression on PMN cells. The results indicate that quantitative flow cytometry can provide consistent CD11b density values between laboratories provided that a calibration system is used including specific calibrators, reagents and protocols. This method allowed us to evidence an up-regulation of CD11b expression for infected patients. This quantitation is a standardized and potentially useful method in clinical situations implying quantitative CD11b expression variations.

M1/70 attenuates blood-borne neutrophil oxidants, activation, and myofiber damage following stretch injury

The purpose of this study was to determine the role of the CD11b-dependent respiratory burst in neutrophil oxidant generation and activation, interleukin-8 (IL-8) production, and myofiber damage after muscle stretch injury by using the monoclonal antibody M1/70 to block this pathway. Twelve male New Zealand White rabbits were randomly assigned to a treatment group: M1/70 (n = 6), IgG isotype control (n = 3), or saline control (n = 3). After intravenous injection of the assigned agent under gas anesthesia, a standardized single-stretch injury was created in the right tibialis anterior, whereas the left tibialis anterior underwent a sham surgery. Blood-borne neutrophil oxidant generation and CD11b receptor density and plasma IL-8 levels were measured pre- and 24 h postinjury. Damage was assessed histologically at the hematoma site by counting torn myofibers. M1/70 group demonstrated decreased blood-borne neutrophil oxidant generation (P < 0.05) and CD11b receptor density (P < 0.05), an increase in plasma IL-8 concentration (P < 0.01), and less torn myofibers (P < 0.01) compared with IgG isotype or saline control groups. These data indicate that 1). CD11b-dependent respiratory burst is a major source of oxidants produced by the neutrophil, and that treatment with M1/70 2). attenuates neutrophil activation status, 3). increases plasma IL-8 concentration, and 4). minimizes myofiber damage 24 h postmuscle stretch injury.

Activation of protein C during reperfusion in clinical liver transplantation

BACKGROUND

Activated protein C (APC) exhibits anticoagulant and antiinflammatory properties. We studied the kinetics and magnitude of protein C activation in clinical liver transplantation and the interaction of this activation with neutrophil and monocyte activation.

METHODS

In 10 patients undergoing liver transplantation, we measured plasma protein C and APC levels, neutrophil and monocyte CD11b and L-selectin expression, and leukocyte differential counts pre-, intra-, and postoperatively. Samples of blood entering and leaving the liver were obtained simultaneously to assess changes across the liver.

RESULTS

Protein C level was low preoperatively (65%, range 39%-141%) and remained low throughout surgery. Compared with the preoperative level (107%, range 78%-161%), APC level increased during liver reperfusion (471%, range 183%-917%, P=0.05). A transhepatic decrease in protein C level (-16%, range -45%-5%, P=0.007), but not in APC level, occurred during initial liver reperfusion. At the same time, neutrophil and monocyte activation took place in the liver.

CONCLUSIONS

Despite protein C deficiency, patients with liver insufficiency are able to maintain normal APC levels. During reperfusion, protein C consumption occurs in the liver without concomitant hepatic release of APC, indicating a shortage of APC in the reperfused liver. The process consuming protein C and APC may be related to the simultaneous ongoing neutrophil and monocyte activation within the liver graft, indicating a regulatory role for APC in inflammation.

Delay in processing porcine whole blood affects cytokine expression

Quantification of cytokine messenger ribonucleic acid (mRNA) in blood samples has become an important tool in the investigation of immune cell activation in a variety of clinical settings. It has been shown that the method of sample collection and processing influences the levels of several cytokine mRNAs. Therefore, it is generally accepted that blood samples for analysis of cytokine expression be processed as soon as possible and under standardised conditions. Since immediate sample processing is not always possible, we investigated the effect of different storage conditions (room temperature (Rt) and 4 degrees C) and storage times (1, 2, 4, 6 and 24 h) on the mRNA level of different cytokines (IL-1alpha, IL-2, IL-6, IL-8, IL-10, IFN-gamma), as well as the IL-2 receptor (IL-2R) in porcine whole blood samples (n=8). Quantification of cytokine expression was performed using simultaneous reverse transcription PCR (RT-PCR) combined with the expression of the housekeeping gene glyceraldehyde-3-phosphate dehydrogenase (GAPDH) as a reference. Our data demonstrate that delays in sample processing longer than 1 h result in significant changes of the mRNA levels of individual cytokines. Expression of the monokines IL-1alpha, IL-6 and IL-10 were increased by storage at both room temperature and 4 degrees C. Expression of IL-8 was increased only in the samples stored at room temperature, and expression of IFN-gamma was raised exclusively in the samples stored at 4 degrees C. We conclude that porcine blood samples should be processed within 2 h to prevent undesired stimulatory effects on the cytokine expression pattern. However, if only selected cytokines are investigated, the undesired effects of prolonged storage can be selectively suppressed by choosing the appropriate temperature of sample storage.

Ethylenediaminetetraacetic acid plus citrate-theophylline-adenosine-dipyridamole (EDTA-CTAD): a novel anticoagulant for the flow cytometric assessment of platelet and neutrophil activation ex vivo in whole blood

Ethylenediaminetetraacetic acid (EDTA) is the anticoagulant recommended for full blood counts, citrate is recommended for coagulation and platelet studies, and citrate-theophylline-adenosine-dipyridamole (CTAD) inhibits platelet activation. Because the combination of EDTA and CTAD (E/C) is better than EDTA or CTAD alone for measuring platelet parameters on the ADVIA 120 Haematology System, we investigated whether it also offers advantages for the flow cytometric assessment of platelet and/or neutrophil activation and platelet-leucocyte aggregate formation ex vivo. Blood from healthy subjects was collected into E/C or citrate, kept at room temperature or at 4 degrees C, and analysed 0 to 360 min later in the ADVIA 120 and by immunofluorescent flow cytometry. Platelet count, mean platelet volume, number of platelet clumps, mean platelet component, numbers of CD62P(+) platelets and platelet-leucocyte aggregates, and expression of CD11b on neutrophils changed little over 360 min in blood with E/C kept at 4 degrees C. In contrast, one or more parameter changed when blood was kept with E/C at ambient temperature or with citrate at either temperature. The use of E/C in in vitro and in vivo studies is illustrated. Platelet and neutrophil activation status ex vivo can be reliably assessed if blood is collected into E/C, held at 4 degrees C, and analysed within 6 h.

Macrophage-dependent regulation of neutrophil mobilization and chemotaxis during development of sterile peritonitis in the rat

Pro-inflammatory cytokines attract leukocytes to inflamed tissues and activate them. Few attempts have been made to identify the sources of cytokines in vivo. We examined the importance of peritoneal macrophages in the mobilization and homing of neutrophils to a sterile peritonitis in the rat, with emphasis on their cytokine production. Macrophages, present in virtually all tissues, are known to be easily activated and to serve as an important source of cytokines. Flow cytometric analysis of cells stained intracellularly with tagged antibodies against various cytokines revealed that the peritoneal macrophages were stimulated to produce the following cytokines: interleukin (IL)-1beta, macrophage inflammatory protein-2 (MIP-2), and keratinocyte-derived cytokine (KC). High numbers of neutrophils, activated on arrival into the peritoneal cavity, also produced IL-1beta, whereas lower numbers contained interleukin-6, tumor necrosis factor-alpha, MIP-2, KC, and MIP-1alpha. This marked activation of peritoneal neutrophils was also reflected by increased surface expression of CD11b. On the other hand, peritoneal macrophages expressed high basal levels of CD11b, which were reduced 24 h after the onset of inflammation. In rats selectively depleted of macrophages by i.p. injection of liposome-containing clodronate, the massive influx of neutrophils to the peritoneal cavity was markedly reduced, as was the rapid mobilization of mature bone marrow neutrophils. Local macrophages are important both for the accumulation of neutrophils in the inflamed peritoneal cavity and for the early mobilization of neutrophils from the bone marrow. Macrophage-derived IL-1beta, MIP-2, and KC are possible mediators of neutrophil homing to inflamed tissues.

Neutrophil activation in preterm infants who have respiratory distress syndrome

OBJECTIVE

To study neutrophil activation in circulation as a sign of systemic inflammation in preterm infants with respiratory distress syndrome.

METHODS

The study comprised very low birth weight preterm infants who had respiratory distress syndrome and required intubation and mechanical ventilation (n = 51), 1-day-old preterm infants who had no need for mechanical ventilation (n = 12), term infants (n = 47), and adult volunteers (n = 25). Neutrophil surface expression of CD11b was quantified with flow cytometry.

RESULTS

In preterm infants with respiratory distress syndrome, neutrophil CD11b expression during the first day of life was higher than in cord blood (mean: 165 relative fluorescence units [RFU] [standard deviation [SD]: 53], n = 29 vs 83 RFU [SD: 21], n = 11; 95% confidence interval [CI] for difference: 59-106) or in preterm infants without mechanical ventilation (106 RFU [SD: 33], n = 12; 95% CI for difference: 17-90). CD11b expression decreased by age of 10 days. CD11b expression was lower in preterm cord than in term cord blood (95% CI for difference: 5-53). However, in preterm infants with respiratory distress syndrome aged 2 to 5 days, it was higher than in term infants of that age.

CONCLUSIONS

The observations demonstrate an early transient postnatal neutrophil activation indicative of systemic inflammation that may contribute to the tissue injury in preterm infants with respiratory distress syndrome.

Extracellular release of bactericidal/permeability-increasing protein in newborn infants

Upon activation, polymorphonuclear leucocytes (PMN) release bactericidal/permeability-increasing protein, (BPI) from their azurophil granules. BPI selectively binds to the lipopolysaccharide (LPS) on gram-negative bacteria and induces their death. This study examined plasma BPI concentration levels in healthy newborns and in newborns with clinical sepsis, and the ability of PMN from preterm and term infants to release BPI. We also studied the release of myeloperoxidase (MPO), and the surface expression of adhesion molecule CD11b on PMN. In infants with clinical sepsis, plasma BPI concentration was higher, 27.8 microg/L [8.6-883; median (range)] (n = 11), than in healthy term infants 8.9 microg/L (3.9-179) (n = 17), and in adults 7.3 microg/L (0.7 -18.4) (n = 15); p = 0.014, Kruskal-Wallis. In preterm infants (n = 8), the ability of PMN to release BPI in vitro after stimulation with PMA was 8.8, in term infants it was 15.9 (n = 29; p > 0.05 vs. preterm infants) and in adults 23.4 ng/10(6) PMN (n = 15; p = 0.024 and p > 0.05 vs. preterm and term infants, respectively). The corresponding values of MPO were 20.0 ng/10(6) (11.3-46.7) in preterms, 19.0 ng/10(6) (2.2-223.7) in terms, and 27.8 ng/10(6) (9.1-80.7) in adults; p = 0.67 between groups. In infants with clinical sepsis, CD11b level was higher, 292 RFU (234-403) than the basal CD11b expression levels in healthy newborn infants, 116 RFU (76-145); P = 0.0001. FMLP-stimulated PMN CD11b expressions in preterm cord blood, 1071 RFU (552-1286) and in term cord blood, 918 (567-1472) were on the same level, but lower than that in adult blood, 1592 (973-1946); p < 0.001, ANOVA. Our findings suggest that in preterm infants the ability to release BPI is lower than in adults and term infants. These findings suggest that premature neonates have an impaired ability to mobilize BPI, possibly contributing to their marked susceptibility to infections with Gram-negative bacteria.

Omeprazole treatment diminishes intra- and extracellular neutrophil reactive oxygen production and bactericidal activity

OBJECTIVE

Neutrophils play a crucial role in host defense against infectious disease. The objective was to analyze the effect of omeprazole treatment on indexes of neutrophil function in healthy subjects.

DESIGN

Open.

SETTING

University hospital.

SUBJECTS

Ten healthy subjects.

INTERVENTION

Analysis of blood samples before and after omeprazole administration.

MEASUREMENTS AND MAIN RESULTS

Neutrophil Escherichia coli phagocytosis was assessed by microscopy and flow cytometry. Intracellular production of reactive oxygen intermediates was measured by flow cytometry. Extracellular reactive oxygen intermediate production was assessed with a cytochrome c reduction assay. Neutrophil bactericidal capacity and intracellular concentrations of Ca2+ were determined by fluorometry. Four hours after a single 40-mg dose of omeprazole, intra- and extracellular reactive oxygen intermediate production by neutrophils was significantly reduced compared with pretreatment values: -30% (24% to 42%) (median and range) and -22% (21% to 68%; p <.05 for both). The intracellular Ca2+ concentrations in resting neutrophils were significantly increased (+33%, 21% to 39%, compared with pretreatment concentrations, p <.001) and neutrophilic bactericidal activity was decreased (-30%, 19% to 47%, compared with pretreatment concentrations, p <.0001). Intracellular Ca2+ concentrations correlated with intracellular reactive oxygen intermediate production and neutrophilic bactericidal capacity (r =.730 and r =.618, p <.05 for both, respectively). In contrast, phagocytosis rates were not impaired by omeprazole.

CONCLUSIONS

Our results imply that omeprazole impairs production of reactive oxygen intermediates by neutrophils. Whether specific impairments of neutrophil host defenses occur in vivo remains uncertain. Reduced bactericidal activity is associated with an increase of intracellular Ca2+ concentrations in resting neutrophils.

Effects of magnetic cell separation on monocyte adhesion to endothelial cells under flow

Studies on monocyte adhesion are frequently limited by spontaneous changes of CD11b and CD62L during cell purification. Most isolation protocols for flow cytometric analysis that overcome this problem cannot be used when large numbers of living cells are needed for functional adhesion assays. This study investigated whether magnetic cell separation of monocytes with a paramagnetic bead against CD33 is a feasible method combining high yield with a low degree of spontaneous activation. As determined by flow cytometry, isolation of magnetically tagged monocytes at 4 degrees C did not alter the expression of CD11b and CD62L when compared to whole blood controls. Warming the cells slowly to room temperature immediately before starting the adhesion assay in a parallel plate flow chamber at 37 degrees C prevented further upregulation of adhesion molecules due to rewarming. When adhesion of magnetically tagged monocytes was compared with untouched monocytes that had been isolated via depletion of contaminating leukocytes, videomicroscopy showed that labelling CD33 neither affected rolling nor firm adhesion to human umbilical venous endothelial cells under flow. Finally, the subsequent upregulation of tissue factor expression on adherent monocytes indicates that magnetically separated monocytes responded properly to activating stimuli during cell adhesion. We conclude that magnetic cell separation via CD33 represents a feasible method for cell separation whenever large numbers of non-activated monocytes are needed for adhesion assays under flow.

Neutrophil CD11b expression and circulating interleukin-8 as diagnostic markers for early-onset neonatal sepsis

OBJECTIVE

To assess neutrophil CD11b and circulating interleukin 8 (IL-8) as markers of early-onset infection in neonates.

METHODS

The study comprised 39 neonates, with a gestational age of 29 to 41 weeks, suspected of infection within 48 hours of life. Neutrophil surface expression of CD11b was quantified with flow cytometry and plasma IL-8 with an enzyme-linked immunosorbent assay. Both data were available from 35 of 39 neonates. Serum C-reactive protein was determined at initial evaluation and, later, on the basis of the clinical picture. Neonates were allocated retrospectively into 2 groups. In the sepsis group (N = 22), 4 had culture-proven sepsis, and 14 had an antenatal risk factor for infection. In the possible-infection group (N = 13), each neonate had a noninfective disorder, but co-occurring infection remained a possibility. Twelve healthy term infants served as controls.

RESULTS

CD11b expression and IL-8 levels both increased in order of sepsis > possible infection > healthy. Sensitivity and specificity by the CD11b test for sepsis were equal, at 1.00, and those by the IL-8 test 0.91 and 1.00, respectively; 6 (17.1%) of the 35 neonates had CD11b and IL-8 below cutoff levels.

CONCLUSIONS

Measuring neutrophil CD11b expression and circulating IL-8 provides a means to identify early-onset neonatal sepsis. The findings may be helpful in planning strategies to safely reduce the use of antimicrobials in neonates.

Effect of vitamin C on neutrophil function after high-intensity exercise

High-intensity exercise leads to an increased risk of upper respiratory tract infections in athletes, which had been related to an exercise-induced impairment of neutrophil function. In this study, several indices of neutrophil function were analysed before and after a biathlon and the effect of oral vitamin C on neutrophil function was determined. Six athletes took 2 g vitamin C daily for 1 week prior to a biathlon and four athletes did not take any supplementation. Neutrophil phagocytosis was analysed by fluorescence microscopy and flow cytometry. Cytosolic calcium kinetics were assessed fluorometrically and neutrophil bactericidal ability was assessed by fluorescence microscopy. Reactive oxygen production was analysed by flow cytometry. Catecholamines were analysed by high-performance liquid chromatography. After high-intensity exercise there were significant reductions in the number of phagocytosed Escherichia coli per neutrophil and in neutrophil bactericidal ability. There was a significant exercise-dependent increase of catecholamines. There was no difference between the two groups of athletes. These results do not support the concept that vitamin C supplementation corrects neutrophil dysfunction after strenuous exercise.

Assessment of neutrophil function in patients with septic shock: comparison of methods

Patients with septic shock are shown to have decreased neutrophil phagocytic function by multiple assays, and their assessment by whole-blood assays (fluorescence-activated cell sorter analysis) correlates with assays requiring isolated neutrophils (microscopic and spectrophotometric assays). For patients with similar underlying conditions but without septic shock, this correlation does not occur.

The use of flow cytometry to measure neutrophil function

Neutrophils are important professional phagocytic cells that provide the host with a first line of defense against acute bacterial and fungal diseases and recurrent, severe or unusual infections are associated with inherited defects of neutrophil function. Furthermore, abundant evidence links inappropriate neutrophil-mediated tissue damage to the pathogenesis of conditions such as acute respiratory distress syndrome, septicemia with multiorgan failure, ischemia-reperfusion injury and rheumatoid arthritis. Flow cytometry has been increasingly used to evaluate the functional capabilities of neutrophils. In this review, we discuss the use of flow cytometry to assess neutrophil functional responses including calcium mobilization, F-actin assembly, adhesion, aggregation, degranulation, phagocytosis and reactive oxygen species (ROS) production. The use of flow cytometry to identify neutrophil priming is also discussed. The advantage of flow cytometry is that the majority of neutrophil functions can be measured using a small volume of whole blood that reduces artifactual changes in function caused by purification procedures. The advent of numerous new fluorochromes and multiparametric analysis allows the simultaneous measurement of several neutrophil functions in the same population of cells. Flow cytometric analysis provides a rapid screen for abnormalities of neutrophil function and reflects more accurately their behavior in vivo.

Anti-ICAM-1 Monoclonal Antibody R6.5 (Enlimomab) Promotes Activation of Neutrophils in Whole Blood

R6.5 (BIRR-1, Enlimomab), a murine IgG2a mAb to the human ICAM-1, inhibits leukocyte adhesion to the vascular endothelium, thereby decreasing leukocyte extravasation and inflammatory tissue injury. In initial clinical trials, R6.5 proved to be beneficial in reducing both disease activity in refractory rheumatoid arthritis and the incidence of acute rejection after kidney and liver allograft transplantations. However, adverse effects such as fever, leukopenia, or cutaneous reactions were not infrequent. We studied the effects of R6.5 on neutrophil function in whole blood samples ex vivo. Surprisingly, at the concentrations achieved in clinical trials, R6.5 activated neutrophilic granulocytes, as indicated by a significant increase in expression of the adhesion molecule β2-integrin CD11b, a concurrent decrease in L-selectin expression, and an enhancement of the oxidative burst activity. Neutrophil activation was not exerted by an anti-ICAM-1 mAb of the IgG1 isotype, by isotype-matched, irrelevant anti-2-phenyloxazolone mAb, or by F(ab′)2 fragments of R6.5. Neutrophil activation was completely inhibited by soluble complement receptor type 1. We conclude that in whole blood, R6.5 activates resting neutrophils in a complement-dependent manner. This finding can explain, at least in part, the side effects associated with R6.5 therapy.

PGG-glucan, a soluble beta-(1,3)-glucan, enhances the oxidative burst response, microbicidal activity, and activates an NF-kappa B-like factor in human PMN: evidence for a glycosphingolipid beta-(1,3)-glucan receptor

PGG-Glucan, a soluble beta-(1,6)-branched beta-(1,3)-linked glucose homopolymer derived from the cell wall of the yeast Saccharomyces cerevisiae, is an immunomodulator which enhances leukocyte anti-infective activity and enhances myeloid and megakaryocyte progenitor proliferation. Incubation of human whole blood with PGG-Glucan significantly enhanced the oxidative burst response of subsequently isolated blood leukocytes to both soluble and particulate activators in a dose-dependent manner, and increased leukocyte microbicidal activity. No evidence for inflammatory cytokine production was obtained under these conditions. Electrophoretic mobility shift assays demonstrated that PGG-Glucan induced the activation of an NF-kappaB-like nuclear transcription factor in purified human neutrophils. The binding of 3H-PGG-Glucan to human leukocyte membranes was specific, concentration-dependent, saturable, and high affinity (Kd approximately 6 nM). A monoclonal antibody specific to the glycosphingolipid lactosylceramide was able to inhibit activation of the NF-kappaB-like factor by PGG-Glucan, and ligand binding data, including polysaccharide specificity, suggested that the PGG-Glucan binding moiety was lactosylceramide. These results indicate that PGG-Glucan enhances neutrophil anti-microbial functions and that interaction between this beta-glucan and human neutrophils is mediated by the glycosphingolipid lactosylceramide present at the cell surface.

Lactosylceramide stimulates human neutrophils to upregulate Mac-1, adhere to endothelium, and generate reactive oxygen metabolites in vitro

Glycosphingolipids (GSLs) and their metabolites play important roles in a variety of biological processes. We have previously reported that lactosylceramide (LacCer), a ubiquitous GSL, stimulates NADPH oxidase-dependent superoxide generation by aortic smooth muscle cells and their consequent proliferation. We postulated that LacCer may upregulate adhesion molecules on human polymorphonuclear leukocytes (hPMNs), perhaps also via NADPH oxidase-dependent reactive oxygen metabolite (ROM) generation. Incubation of hPMNs with LacCer upregulated CD11b/CD18 (Mac-1) and CD11c/CD18, as determined by fluorescence-automated cell sorting. LacCer also stimulated these hPMNs to generate superoxide via NADPH oxidase, as determined by lucigenin-enhanced chemiluminescence. However, the upregulation of Mac-1 by LacCer did not itself appear to be mediated by ROMs, since neither an antioxidant nor an NADPH oxidase inhibitor substantially inhibited the Mac-1 upregulation. However, this Mac-1 upregulation was significantly inhibited by two disparate phospholipase A2 (PLA2) inhibitors. Moreover, LacCer induced arachidonic acid metabolism, which was inhibited by the PLA2 inhibitors, but not by an NADPH oxidase inhibitor. To evaluate the effect of LacCer on hPMN adhesion to endothelium, hPMNs stimulated with LacCer were allowed to adhere to unstimulated human endothelial cell monolayers. LacCer stimulated hPMN adhesion to endothelial cells, which was blocked by anti-CD18 and by the PLA2 inhibitors. We conclude that LacCer stimulates both Mac-1 upregulation and superoxide generation in hPMNs but that ROMs are not the upstream signal for Mac-1 upregulation. This mechanism may well be relevant to acute endothelial injury in inflammation and other pathological conditions.