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Neutrophil migration and respiratory burst are the prerequisite for efficient first line defense against invading microorganisms. However, migration and respiratory burst can be compromised in adults and especially in newborn infants, where sustained neutrophil accumulation, uncontrolled burst and reduced scavenging of ROS might cause inadvertent tissue damage due to uncontrolled inflammation. The aim of this study was to investigate the modulatory effect of the chemoattractants formyl-methionyl-leucyl-phenylalanine ( fMLP) and IL-8 on respiratory burst in neutrophils from term newborn infants and adults. Whole blood from the umbilical cord of 17 healthy term newborn infants delivered by caesarean section and from 17 healthy adults as reference was preincubated with fMLP or IL-8 and stimulated with PMA or Escherichia coli bacteria. Respiratory burst was quantified by flow cytometry analysis of dihydrorhodamine 123 fluorescence. fMLP reduced the PMA-induced respiratory burst of neutrophils from newborn infants and adults by 12% and 21%, respectively ( P < 0.05). E. coli-induced burst was also reduced by fMLP in neutrophils from newborn infants (10%; P < 0.01) and adults (6%; P < 0.05). No such changes were observed with IL-8. Similar respiratory burst in response to single stimulus with PMA or E. coli was observed in both newborn infants and adults. fMLP reduced PMA- and E. coli-induced respiratory burst of neutrophils in whole blood from term newborn infants as well as in adults. The reduced respiratory burst by fMLP might be a mechanism to reduce the detrimental effects of uncontrolled inflammation during neutrophil migration. [ABSTRACT FROM AUTHOR]

Background and Aims: The pronounced neutrophilia observed in patients with coronavirus disease 2019 (COVID-19) infections suggests a role for these leukocytes in the pathology of the disease. Monocyte and neutrophil expression of CD64 and CD11b have been reported as early biomarkers to detect infections. The aim of this study was to study the expression of receptors for IgG (CD64) and adhesion molecules (CD11b, CD15s, CD65, CD162, CD66b) on neutrophils and monocytes in patients with severe COVID-19 after admission to an intensive care unit (ICU)., Methods: The expression of receptors was analyzed using flow cytometry. EDTA blood from 23 patients with confirmed COVID-19 infection was sampled within 48 h of admission to the ICU. Leukocytes were labeled with antibodies to CD11b, CD15s, CD65s, CD162, CD64, and CD66b. Expression of receptors was reported as mean fluorescence intensity (MFI) or the percentage of cells expressing receptors., Results: Results are presented as comparison of COVID-19 patients with the healthy group and the receptor expression as MFI. Neutrophil receptors CD64 (2.5 versus 0.5) and CD66b (44.5 versus 34) were increased and CD15 decreased (21.6 versus 28.3) when CD65 (6.6 versus 4.4), CD162 (21.3 versus 21.1) and CD11b (10.5 versus 12) were in the same range. Monocytes receptors CD64 (30.5 versus 16.6), CD11b (18.7 versus 9.8), and CD162 (38.6 versus 36.5) were increased and CD15 decreased (10.3 versus 17.9); CD65 were in the same range (2.3 versus 1.96)., Conclusion: Monocytes and neutrophils are activated during severe COVID-19 infection as shown by strong upregulation of CD64. High monocyte and neutrophil CD64 can be an indicator of a severe form of COVID19. The adhesion molecules (CD11b, CD162, CD65, and CD15) are not upregulated on otherwise activated neutrophils, which might lead to relative impairment of tissue migration. Low adhesion profile of neutrophils suggests immune dysfunction of neutrophils. Monocytes maintain upregulation of some adhesion molecules (CD11b, CD162) suggesting the persistence of an increased ability to migrate into tissues, even during a severe stage of COVID-19. Future research should focus on CD64 and CD11b kinetics in the context of prognosis., Competing Interests: Conflict of interest statement: The authors declare that there is no conflict of interest., (© The Author(s), 2021.)

Objectives: The distinction between bacterial and viral causes of acute infections is a major clinical challenge. In this report we investigate the diagnostic performance in this regard of nine candidate biomarkers together with HNL (Human Neutrophil Lipocalin)., Methods: Blood was obtained from patients with symptoms of infectious (n = 581). HNL was measured in whole blood (B-HNL) after pre-activation with the neutrophil activator fMLP or in plasma (P-HNL). Azurocidin also known as heparin-binding protein (HBP), Calprotectin, PMN-CD64, CRP (C-reactive protein), IP-10 (Interferon γ-induced Protein 10 kDa), PCT (Procalcitonin), TK1 (Thymidine kinase 1), TRAIL (TNF-related apoptosis-inducing ligand) were measured in plasma/serum. Area under the ROC (receiver operating characteristics) curve (AuROC) was used for the evaluation of the clinical performance of the biomarkers., Results: Side-by-side comparisons of the ten biomarkers showed large difference in the AuROC with B-HNL being the superior biomarker (0.91, 95% CI 0.86-0.95) and with the other nine biomarkers varying from AuROC of 0.63-0.79. The combination of B-HNL with IP-10 and/or TRAIL increased the diagnostic performance further to AuROCs of 0.94-0.97. The AuROCs of the combination of CRP with IP-10 and/or TRAIL were significantly lower than combinations with B-HNL 0.87 (95% CI 0.83-0.91)., Conclusion: The diagnostic performance of whole blood activated HNL was superior in the distinction between bacterial or viral infections. The addition of IP-10 and/or TRAIL to the diagnostic algorithm increased the performance of B-HNL further. The rapid analysis of HNL, reflecting bacterial infections, together with biomarkers reflecting viral infections may be the ideal combination of diagnostic biomarkers of acute infections., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The distinction between bacterial and viral causes of infections of the respiratory tract is a major but important clinical challenge. We investigated the diagnostic performance of human neutrophil lipocalin (HNL) in respiratory tract infections compared to those of C-reactive protein (CRP) and procalcitonin (PCT). Patients were recruited from the emergency department and from a primary care unit ( n = 162). The clinical diagnosis with regard to bacterial or viral cause of infection was complemented with objective microbiological/serological testing. HNL was measured in whole blood after preactivation with the neutrophil activator formyl-methionine-leucine-phenylalanine (fMLP) (B-HNL), and CRP and PCT were measured in plasma. Head-to-head comparisons of the three biomarkers showed that B-HNL was a superior diagnostic means to distinguish between causes of infections, with areas under the concentration-time curve (AUCs) of receiver operating characteristic (ROC) analysis for HNL of 0.91 (95% confidence interval [CI], 0.83 to 0.96) and 0.92 (95% CI, 0.82 to 0.97) for all respiratory infections and for upper respiratory infections, respectively, compared to 0.72 (95% CI, 0.63 to 0.80) and 0.68 (95% CI, 0.56 to 0.79) for CRP, respectively ( P = 0.001). In relation to major clinical symptoms of respiratory tract infections (cough, sore throat, stuffy nose, and signs of sinusitis), AUCs varied between 0.88 and 0.93 in those patients with likely etiology (i.e., etiology is likely determined) of infection, compared to 0.63 and 0.71 for CRP, respectively, and nonsignificant AUCs for PCT. The diagnostic performance of B-HNL is superior to that of plasma CRP (P-CRP) and plasma PCT (P-PCT) in respiratory tract infections, and the activity specifically reflects bacterial challenge in the body. The rapid and accurate analysis of HNL by point-of-care technologies should be a major advancement in the diagnosis and management of respiratory infections with respect to antibiotic treatment., (Copyright © 2017 Venge et al.)

Background: A prerequisite for an effective innate immunity is the migrative ability of neutrophils to respond to inflammatory and infectious agents such as the intermediate interleukin (IL)-8 and the end-target formyl-methionyl-leucyl-phenylalanine (fMLP) chemoattractants. The aim was to study the chemotactic capacity of neutrophils from newborn infants and adults in response to IL-8 and the bacterial peptide fMLP., Methods: In the under-agarose cell migration assay, isolated leukocytes from healthy adults and from cord blood of healthy term newborn infants were studied with dose responses towards IL-8 and fMLP. The same number of leukocytes (1 × 10 5 cells), with the same distribution of neutrophils and monocytes, were analyzed in neonates and adults. Chemotaxis was distinguished from randomly migrating neutrophils, and the neutrophil pattern of migration, i.e. the migration distance and the number of migrating neutrophils per distance, was evaluated., Results: In comparison to adults, fewer neutrophils from newborn infants migrated towards IL-8 and for a shorter distance (P < .01, respectively). The number of neutrophils migrating to different gradients of fMLP, the distance they migrated, and the correlation between the number and the distance were the same for neonates and adults. Random migration did not differ in any instance., Conclusion: Chemotaxis of neutrophils from newborn infants was as co-ordinated as neutrophils from adults in response to fMLP, whereas the response to IL-8 was reduced. The differential response of neutrophils from neonates to intermediate and end-target chemoattractants could indicate a reduced infectious response.

Objective: To evaluate the Trillium Diagnostics Leuko64(™) assay on Abbott Celldyn Sapphire haematology analyser compared to two flow cytometry protocols on Beckman Coulter EPICS MCL flow cytometer., Materials and Methods: CD64 expression on neutrophils was determined by two flow cytometry protocols and by a commercial assay on an automatic haematology analyser. The inclusion of study subjects was based on elevated procalcitonin (PCT) values, identifying patients where a systemic infection was suspected. Healthy blood donors were used as a reference group., Results: Statistically significant correlations between the Trillium Diagnostics Leuko64(™) assay and the flow cytometry methods were found when measuring neutrophil CD64 expression., Conclusions: The good correlation between a reference method and an automated haematology analyser method for CD64 expression on neutrophils supports introduction of the latter assay for routine use as an independent biomarker of bacterial infection and inflammation.

The distinction between causes of acute infections is a major clinical challenge. Current biomarkers, however, are not sufficiently accurate. Human neutrophil lipocalin (HNL) concentrations in serum or whole blood activated by formyl-methionine-leucine-phenylalanine (fMLP) were shown to distinguish acute infections of bacterial or viral cause with high accuracy. The aim was therefore to compare the clinical performance of HNL with currently used biomarkers. Seven hundred twenty-five subjects (144 healthy controls and 581 patients with signs and symptoms of acute infections) were included in the study. C-reactive protein (CRP), the expression of CD64 on neutrophils, procalcitonin (PCT), and blood neutrophil counts were measured by established techniques, and HNL concentrations were measured in whole-blood samples after activation with fMLP. All tested biomarkers were elevated in bacterial as opposed to viral infections (P < 0.001). CRP, PCT, and CD64 expression in neutrophils was elevated in viral infections compared to healthy controls (P < 0.001). In the distinction between healthy controls and patients with bacterial infections, the areas under the receiver operating characteristic (ROC) curves were >0.85 for all biomarkers, whereas for the distinction between bacterial and viral infections, only HNL concentration in fMLP-activated whole blood showed an area under the ROC curve (AUROC) of >0.90 and superior clinical performance. The clinical performance of HNL in fMLP-activated whole blood was superior to current biomarkers and similar to previous results of HNL in serum. The procedure can be adopted for point-of-care testing with response times of <15 min., (Copyright © 2015, Venge et al.)

Objectives: During extracorporeal circulation (ECC), a mechanical pump and an oxygenator replace the functions of the heart and lungs. The aim of this study is to test the effect of the nitric oxide donor glyceryl-tri-nitrate on activation markers of the innate immune system during simulated ECC., Design: Whole blood concentrations of selected leukocyte adhesion molecules, complement system components and myeloperoxidase (MPO) were measured in an in vitro system of simulated ECC., Results: Simulated ECC stimulated the expression of monocyte LPS-receptor CD14 and C3b-receptor CD35. Glyceryl-tri-nitrate significantly reduced the expression of leukocyte Fcγ receptor CD32 over time, compared to control. Simulated ECC increased the concentrations of MPO, terminal complement complex, and complement component C3a. Addition of glyceryl-tri-nitrate did not significantly affect these changes., Conclusions: Simulated ECC induces the increased expression of some leukocyte markers. Glyceryl-tri-nitrate addition significantly reduces the expression of some leukocyte activation markers.

Human phospholipase B-precursor (PLB-P) is a newly identified and purified protein from human neutrophils. The precise function of PLB-P in vivo is not yet known. Its existence in neutrophils and the enzymatic activity against phospholipids imply a role in the defence against invading microorganisms and in the generation of lipid mediators of inflammation. We describe here the generation of specific antibodies against PLB-P, the tissue localizations of PLB-P and the establishment of an accurate, specific, and reproducible radioimmunoassay (RIA). A survey of normal and malignant tissues showed strong immunostaining of PLB-P in neuronal and myeloid cells and in adrenal glands. Elevated levels were found in sera of patients with influenza A infection i.e. >1 microg/L and in gut fluids of patients with inflammatory bowel disease i.e. >20 microg/L. The levels correlated to markers of neutrophil activation, suggesting a neutrophil origin of PLB-P in these conditions. The antibodies and the assay will be useful in the future basic and clinical investigations of PLB-P., (2010 Elsevier B.V. All rights reserved.)

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.