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PubMed1989

Macrophage phagocytosis of aging neutrophils in inflammation. Programmed cell death in the neutrophil leads to its recognition by macrophages.

Mechanisms governing the normal resolution processes of inflammation are poorly understood, yet their elucidation may lead to a greater understanding of the pathogenesis of chronic inflammation. The removal of neutrophils and their potentially histotoxic contents is one prerequisite of resolution. Engulfment by macrophages is an important disposal route, and changes in the senescent neutrophil that are associated with their recognition by macrophages are the subject of this investigation. Over 24 h in culture an increasing proportion of human neutrophils from peripheral blood or acutely inflamed joints underwent morphological changes characteristic of programmed cell death or apoptosis. Time-related chromatin cleavage in an internucleosomal pattern indicative of the endogenous endonuclease activation associated with programmed cell death was also demonstrated. A close correlation was observed between the increasing properties of apoptosis in neutrophils and the degree of macrophage recognition of the aging neutrophil population, and a direct relationship between these parameters was confirmed within aged neutrophil populations separated by counterflow centrifugation into fractions with varying proportions of apoptosis. Macrophages from acutely inflamed joints preferentially ingested apoptotic neutrophils and histological evidence was presented for occurrence of the process in situ. Programmed cell death is a phenomenon of widespread biological importance and has not previously been described in a cell of the myeloid line. Because it leads to recognition of intact senescent neutrophils that have not necessarily disgorged their granule contents, these processes may represent a mechanism for the removal of neutrophils during inflammation that also serves to limit the degree of tissue injury.

Arthritis↗
PubMed1996

Neutrophil-related cytokines and neutrophil products in bronchoalveolar lavage fluid of a patient with ANCA negative Wegener's granulomatosis.

We report a case of Wegener's granulomatosis (WG), with neutrophil accumulation in bronchoalveolar lavage fluid (BALF). Peripheral blood neutrophilia was present but the anti-neutrophil cytoplasmic antibody (ANCA) was negative. The serum and BALF levels of neutrophil-related cytokines, including interleukin (IL)-8, granulocyte colony-stimulating factor (G-CSF) and IL-1 beta, were increased, particularly in BALF. Plasma and BALF levels of neutrophil elastase and defensins, which are released by neutrophils and are potentially toxic to cells, were also elevated. Our findings suggest that neutrophils and neutrophil-related cytokines may play an important role in the pathogenesis of anti-neutrophil cytoplasmic antibody negative as well as anti-neutrophil cytoplasmic antibody positive Wegener's granulomatosis.

Antibodies, Antineutrophil Cytoplasmic↗
PubMed1996

Evidence for two putative receptors mediating chemotactic activity of cytokine-induced neutrophil chemoattractants (CINCs) for rat neutrophils.

Recently we have found that only cytokine-induced neutrophil chemoattractant (CINC)-3 induces an increase in intracellular [Ca2+] in rat neutrophils stimulated first with CINC-1, CINC-2 alpha or CINC-2 beta, and hypothesized that rat neutrophils have another receptor specific for CINC-3 in addition to a common receptor for all CINCs [Shibata F., et al., Eur. J. Biochem., 231, 306 (1995)]. To evaluate this hypothesis, chemotactic activity of these CINCs in vitro was determined by using rat neutrophils together with each CINC. In the presence of CINC-1, migration of neutrophils toward CINC-1, CINC-2 alpha and CINC-2 beta was inhibited, but that toward CINC-3 was not. Similar results were obtained when CINC-2 alpha or CINC-2 beta was added to neutrophils. However, addition of CINC-3 to neutrophil suspension in the upper chamber resulted in the complete inhibition of the neutrophil migration toward each CINC. The results support our hypothesis and indicate both the putative receptors can mediate chemotaxis of rat neutrophils.

Animals↗
PubMed1988

Neutrophil chemotactic factor release and neutrophil alveolitis in asbestos-exposed individuals.

Alveolar neutrophil accumulation occurs in asbestosis. To evaluate a possible role for release of neutrophil chemotactic factor (NCF) in the pathogenesis of asbestosis, spontaneous NCF release from alveolar macrophages obtained by bronchoalveolar lavage (BAL) in eight individuals with asbestosis, 13 asbestos-exposed individuals without asbestosis, and five control subjects has been studied. Alveolar macrophages were incubated in medium (four hours; 37 degrees C), and neutrophil responses to the supernatants were assayed in a microchemotaxis chamber. Alveolar macrophages from subjects with asbestosis released more NCF (97 +/- 19 neutrophils per high-power field [N/HPF]) than controls (3 +/- 1 N/HPF; p less than 0.01). Alveolar macrophages from individuals with asbestos exposure and increased BAL neutrophil proportions (n = 7) released more NCF (93 +/- 24 N/HPF) than individuals with asbestos exposure and normal BAL neutrophil proportions (n = 6; 11 +/- 6 N/HPF; p less than 0.02). The results show that spontaneous NCF release occurs in asbestosis and that NCF release is associated with neutrophil alveolitis in asbestos-exposed individuals without asbestosis, suggesting a pathogenic role for NCF in mediating this neutrophil alveolitis. The results of the study also suggest that the presence of crackles is a better predictor of the presence of neutrophil alveolitis than is an abnormal chest x-ray film.

Asbestos↗
PubMed1991

Neutrophil chemotaxis and neutrophil elastase in the aortic wall in patients with abdominal aortic aneurysms.

To test the hypothesis that elastin-derived peptides (EDP) from human aortic tissue may be chemotactic for inflammatory cells, we studied the chemotaxis of neutrophils and monocytes to EDP derived from abdominal aortic aneurysm (AAA), aortic occlusive disease (AOD), and control aortas. In addition, we determined if neutrophils deliver neutrophil elastase to the aorta in vivo by staining for neutrophil elastase (NE) throughout the course of abdominal aortic aneurysms with the monoclonal antibody to human NE. EDP from AAA, AOD, and control tissue demonstrated significant chemotactic activity for both neutrophils and monocytes. All neutrophils had a greater attraction to EDP from AAA tissue compared to AOD and control aorta. Neutrophils from AAA patients were more attracted to EDP of AAA tissue than were neutrophils of AOD or control patients attracted to their respective aortic EDP. Neutrophil elastase stained positive in the adventitia and thrombus throughout the course of the aneurysm, but was not found in the intima, media, or plaque of the aorta.

Aorta, Abdominal↗
PubMed2005

Pyocyanin production by Pseudomonas aeruginosa induces neutrophil apoptosis and impairs neutrophil-mediated host defenses in vivo.

Clearance of neutrophils from inflamed sites is critical for resolution of inflammation, but pathogen-driven neutrophil apoptosis can impair host defenses. We previously showed that pyocyanin, a phenazine toxic metabolite produced by Pseudomonas aeruginosa, accelerates neutrophil apoptosis in vitro. We compared wild-type and pyocyanin-deficient strains of P. aeruginosa in a murine model of acute pneumonia. Intratracheal instillation of either strain of P. aeruginosa caused a rapid increase in bronchoalveolar lavage neutrophil counts up to 18 h after infection. In wild-type infection, neutrophil numbers then declined steadily, whereas neutrophil numbers increased up to 48 h in mice infected with pyocyanin-deficient P. aeruginosa. In keeping with these differences, pyocyanin production was associated with reduced bacterial clearance from the lungs. Neutrophil apoptosis was increased in mice infected with wild-type compared with the phenazine-deficient strain or two further strains that lack pyocyanin production, but produce other phenazines. Concentrations of potent neutrophil chemokines (MIP-2, KC) and cytokines (IL-6, IL-1beta) were significantly lower in wild-type compared with phenazine-deficient strain-infected mice at 18 h. We conclude that pyocyanin production by P. aeruginosa suppresses the acute inflammatory response by pathogen-driven acceleration of neutrophil apoptosis and by reducing local inflammation, and that this is advantageous for bacterial survival.

Animals↗
PubMed2005

[Neutrophilic dermatosis and neutrophil disorders. A study of 31 clinical cases].

Neutrophilic diseases are a group of disorders--mainly dermatoses--in which polymorphonuclear neutrophils accumulate in the absence of an identified pathogen. Such neutrophil infiltration can lead to a variety of clinical manifestations, including inflammatory disorders of the digestive tract, and hematological and rheumatological disorders; monoclonal or polyclonal circulating IgA levels are elevated, and the disorders are sensitive to drugs acting on neutrophils. Other disorders associated with neutrophil accumulation do not share these criteria. Non neutrophilic manifestations may also be present, and determine the prognosis. Neutrophilic dermatoses are often chronic and relapsing-remitting. Spontaneous regression occurs in some cases. It is unclear whether these pleomorphic disorders should be grouped together under a single heading In addition, the causes of the neutrophil accumulation are unknown. During the past five years, we have managed 31 patients with neutrophilic dermatoses. Here we describe our findings and review previous reports.

Adult↗
PubMed1986

Endogenous inhibitor of protein kinase C: association with human peripheral blood neutrophils but not with specific granule-deficient neutrophils or cytoplasts.

A Ca2+-activated and phospholipid-dependent protein kinase (PKC) has been described in several cell systems, including the human neutrophil. We found that less than 30 pmol 32P/10 min/10(6) cell equivalents of phorbol ester- or 1-oleoyl-2-acetylglycerol-stimulated PKC activity was obtained when neutrophil homogenates were used as an enzyme source. However, detergent-soluble and detergent-insoluble fractions prepared from the same homogenates, respectively, catalyzed 578 +/- 50 and 136 +/- 40 pmol 32P/10 min/10(6) cell equivalents. Recombining detergent-soluble and detergent-insoluble fractions resulted in the complete loss of activity. We therefore explored the possibility of an endogenous inhibitor of PKC in neutrophils. Homogenates from neutrophil cytoplasts, which lack the nuclei and intracellular granules of whole neutrophils, yielded 813 +/- 28 pmol 32P/10 min/10(6) cell equivalents. In addition, total neutrophil homogenates from a patient with a specific granule deficiency yielded high activities, namely 424 +/- 48 pmol 32P/10 min/10(6) cell equivalents. Specific granule-deficient neutrophils possessed translocated and activated PKC, and phosphoprotein patterns from these cells resembled those from activated normal neutrophils. Our results suggested the existence of an inhibitor of previously active PKC. That this inhibitor is primarily associated with neutrophil-specific granule membranes was suggested by our finding of high PKC activity associated with cell preparations or combinations of cell fractions that were free of specific granules, but not necessarily of other cellular organelles. Preliminary characterization of the endogenous inhibitor indicated that it was protease- and heat-sensitive, and did not exhibit either protease or phosphatase activity. We speculate that the inhibitor may play a physiologic role in regulating the activity of its target enzyme.

Cytoplasmic Granules↗
PubMed1981

Vascular responses during acute neutrophilic inflammation. Their relationship to in vivo neutrophil emigration.

Hyperemia, an increase in vascular permeability, and the emigration of leukocytes are the basic manifestations of the acute inflammatory reaction. Many previous studies have employed phagocytosable material to induce inflammation and neutrophil infiltration. In this study, we induced neutrophil infiltration into rabbit skin by injecting the soluble chemotactic stimuli, zymosan-activated plasma, C5adesArg, N-formyl-methionyl-leucyl-phenylalanine, and factors released by Escherichia coli. During the evolution of the response, 51Cr-labeled leukocytes were used to quantitate neutrophil influx, 125I-labeled albumin was used to quantitate permeability, and 86Rb was used to quantitate blood flow. Simultaneous measurements showed a close correlation in time between the degree and peak rate of neutrophil influx and the degree of hyperpermeability and hyperemia. Dose-response experiments performed with 2 to 90 per cent (v/v) zymosan-activated plasma showed a direct correlation between the rate of neutrophil influx and the degree of vascular permeability in blood flow. No vascular responses were induced after injection of these chemotactic stimuli with neutrophil infiltration were inhibited by indomethacin or aspirin. It is concluded that the vascular hyperpermeability and hypermia accompanying neutrophilic inflammatory reactions may be induced by neutrophils during their migration across the microvascular walls and that prostaglandins may in part mediate these responses. Furthermore, phagocytosis by the neutrophils is not required to induce these vascular changes.

Animals↗
PubMed1994

Effect of anti-neutrophil cytoplasm autoantibodies on the intracellular calcium concentration of human neutrophils.

BACKGROUND: The discovery of circulating autoantibodies to neutrophil cytoplasm antigens (ANCA) has implicated autoimmune mechanisms in the pathogenesis of systemic vasculitis although it is uncertain whether these play a primary role or arise secondary to neutrophil injury. EXPERIMENTAL DESIGN: We examined the pathophysiologic effect of ANCA on intracellular cytosolic-free calcium concentration (Ca2+)i in neutrophils by preincubating cells with ANCA-positive IgG or F(ab')2 preparations followed by stimulation with calcium ionophore (A23187). The mechanism by which ANCA may affect (Ca2+)i was studied by analyzing the production of platelet-activating factor (PAF), an intracellular messenger which is the mediator through which A23187 acts. RESULTS: ANCA-positive F(ab')2 induced a small but insignificant increase in (Ca2+)i. Preincubation of neutrophils with ANCA-positive IgG or F(ab')2 reduced the calcium mobilization induced by subsequent stimulation with A23187 compared with experiments performed with antibody preparations from ANCA-negative disease or healthy controls. The suppression of A23187-induced calcium mobilization was dose-dependent and correlated with the serum ANCA levels at clinical presentation. ANCA did not bind PAF but reduced the binding of PAF to neutrophils, suggesting that ANCA may prevent the expression of PAF receptor on activated neutrophils. The preincubation of neutrophils with increasing concentrations of F(ab')2 preparation resulted in reduced membrane and supernatant concentrations of PAF, an effect that was more prominent with ANCA-positive F(ab')2. CONCLUSIONS: Our data suggest ANCA may potentially mediate a pathophysiologic effect on neutrophils through interference with the signal transduction pathways utilized in neutrophils' activation. One of the possible mechanisms underlying the suppressive effect of ANCA on A23187-induced calcium mobilization may be mediated through the reduction of PAF synthesis.

Antibodies, Antineutrophil Cytoplasmic↗
PubMed1994

Characterization of the human neutrophil C1q receptor and functional effects of free ligand on activated neutrophils.

The partial characterization and expression of the C1q receptor (C1q-R) in relation to other complement receptors present on the surface of neutrophils has been examined, as well as the effects of free C1q on cell function. A polyclonal anti-C1q-R antibody recognizes a 68-kD neutrophil surface protein. C1q-R expression was not upregulated upon warming, priming, or exposure to FMLP, but decreased after exposure to phorbol myristate acetate (PMA), because of shedding of the receptor into the extracellular medium, as detected by enzyme-linked immunosorbent assay. CR3 and CR1 expression was upregulated from intracellular pools after cell stimulation by PMA. No evidence of intracellular pools of C1q-R was found, as assessed by immunoblotting of subcellular fractions. But C1q-R appeared to be expressed early in cell differentiation, was detected on undifferentiated HL-60 cells, and like CR3 expression, increased upon 5 days differentiation towards a neutrophil lineage. However, C1q-R expression decreased upon additional culture, whereas CR3 expression continued to increase. A large variation in the percentage of peripheral cells expressing C1q receptors in donors was observed, ranging from 13% to 100%, contrasting with CR3 receptors that exhibited less variability. Interactions between free monomeric C1q and neutrophils were also studied. Incubation of stimulated neutrophils with 10 to 100 micrograms/mL C1q resulted in a further increase in CR3 expression and adherence to albumin-coated surfaces. Staphylococci opsonized with low quantities of C1q (0.1 to 1 microgram/mL) mediated a moderate and sustained respiratory burst in neutrophils, whereas a burst of similar magnitude was generated only with free C1q at concentrations 10- to 100-fold higher. Stimulation was only partially inhibited if cells were first treated with anti-C1q-R antibody, suggesting other C1q binding proteins may be present on the cell surface. In summary, neutrophil C1q receptor is approximately 68-kD, exhibits varying expression on different subjects, and is not upregulated from intracellular stores on exposure to soluble stimuli. Stimulated, but not resting, neutrophils selectively respond to raised levels of free C1q, resulting in altered cell function and enhanced CR3 receptor expression. These studies thus suggest complex roles for C1q in neutrophil function.

Antibodies↗
PubMed2005

Timing of neutrophil activation and expression of proinflammatory markers do not support a role for neutrophils in cervical ripening in the mouse.

The mechanisms that facilitate remodeling of the cervix in preparation for and during parturition remain poorly understood. In the current study, we have evaluated the timing of inflammatory cell migration in cervix through comparisons between wild-type mice and steroid 5alpha-reductase type 1 null mice (Srd5a1-/-), which fail to undergo cervical ripening due to insufficient local progesterone metabolism. The timing of migration and distribution of macrophages, monocytes, and neutrophils were examined using cervices from wild-type and Srd5a1-/- mice before Day 15 (d15) and during cervical ripening (late d18), and postpartum (d19). Neutrophil numbers were quantitated by cell counts and activity was estimated by measurement of myeloperoxidase activity. The mRNA and/or protein expression of neutrophil chemoattractants, CXCL2 and CXCL1, and other proinflammatory and adhesion molecules, including IL1A, IL1B, TNF, CCL11, CCL5, CCL3, ITGAM, and ICAM1, were measured in cervices collected before, during, and after birth. The effect of neutrophil depletion on parturition was tested. Tissue macrophages, myeloperoxidase activity, and expression of proinflammatory molecules are not increased within the cervix until after birth. Neutrophil numbers do not change after birth and neutrophil depletion before term has no effect on timing or success of parturition. These results suggest that cervical ripening does not require neutrophils. Moreover, neutrophil activation and a general inflammatory response are not initiated within the cervix until shortly after parturition. The timing of inflammatory cell migration and activation in pregnant cervix suggest a role for these cells in postpartum remodeling of the cervix rather than in the initiation of cervical ripening at parturition.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed2005

Neutrophil differentiated HL-60 cells model Mac-1 (CD11b/CD18)-independent neutrophil transepithelial migration.

During active intestinal inflammation granulocytes accumulate in the lumen of the gut where they damage the epithelium through the release of various products such as reactive oxygen species and proteolytic enzymes. Previously, using function blocking monoclonal antibodies, we showed that neutrophil migration across intestinal epithelial monolayers in response to various chemoattractants was partially beta(2) integrin Mac-1 (CD11b/CD18)-independent. Here, we show that treating neutrophils with intact monoclonal antibody (mAb) to CD18 activates the cells to express more CD11b. Thus our goal now was to determine whether neutrophil Mac-1-independent transepithelial migration proceeds independently of prior cell activation through Mac-1. We took two approaches, one using blocking Fab' fragments of mAb to CD18 and the second was to develop a neutrophil differentiated HL-60 cell line which is Mac-1 deficient to further study neutrophil/epithelial cell interaction. Anti-CD18 Fab' minimally activated neutrophils but inhibited approximately 75% of transepithelial migration to fMLP while having a minimal effect (</=25% inhibition) on the migration to C5a. Upon incubation with dimethylsulphoxide, HL-60 cells differentiated and up-regulated CD11b expression and migrated to C5a and n-formyl methionyl leucyl phenylalanine in a similar manner to peripheral blood neutrophils. In contrast, CD11b expression was minimal on HL-60 cells differentiated with dibutytyl cAMP to a neutrophil-like phenotype. These cells, however, readily migrated across both intestinal and lung epithelial monolayers in response to C5a. We conclude that Mac-1-independent transepithelial migration does not require prior activation of cells via Mac-1 ligation because HL-60 cells lacking Mac-1 (CD11b/CD18) expression migrate effectively. HL-60 cells differentiated with dbcAMP should greatly assist in the search for the Mac-1-independent ligands for neutrophil migration across epithelium.

Antibodies, Monoclonal↗
PubMed2000

The role of cytokine-induced neutrophil chemoattractant-1 in neutrophil-mediated remote lung injury after intestinal ischaemia/reperfusion in rats.

OBJECTIVE: Remote lung injury is induced by ischaemia/reperfusion (I/R) of the gastrointestinal tract and the liver following hypovolaemic shock. In the present study, the role of cytokine-induced neutrophil chemoattractant (CINC), a member of the interleukin (IL)-8 family, in neutrophil-mediated remote lung injury following intestinal I/R was investigated in anaesthetized rats. METHODOLOGY: The I/R group was subjected to 60 min of occlusion of the superior mesenteric artery with laparotomy, followed by 240 min of intestinal reperfusion. The sham-operated (sham) group was subjected to the same procedures with the exception of intestinal I/R. RESULTS: In the I/R group, the permeability index of the lung, the neutrophil count in pulmonary vascular lavage fluid and bronchoalveolar lavage fluid (BALF), lung myeloperoxidase activity and neutrophil oxidative production were all significantly greater than those in the sham group. Cytokine-induced neutrophil chemoattractant-1 levels in blood and BALF were significantly increased at 240 min after intestinal reperfusion. There was a significant relationship between neutrophils in BALF and CINC-1 level in BALE CONCLUSION: These findings suggest that intestinal reperfusion was associated with activation and accumulation of neutrophils in the lung and resulted in remote lung injury with increased microvascular permeability. Thus, CINC-1 in BALF may induce neutrophil migration from the pulmonary vessels to the interstitium and alveolar spaces in remote lung injury after intestinal I/R.

Animals↗
PubMed2003

The neutrophil-activating protein of Helicobacter pylori (HP-NAP) activates the MAPK pathway in human neutrophils.

Infection by Helicobacter pylori causes an acute inflammatory response followed by a chronic infection of the human gastric mucosa characterized by the infiltration of neutrophils andmononuclear inflammatory cells. The neutrophil-activating protein of Helicobacter pylori (HP-NAP) is a virulence factor that activates neutrophils, monocytes, and mast cells. However, the mechanism by which HP-NAP activates these cells is not fully understood. Here, we show that HP-NAP induces extracellular regulated kinase (ERK) and p38-mitogen-activated protein kinase (MAPK) activation in human neutrophils; c-Jun N-terminal kinase is not activated by HP-NAP. A MAPK/ERK kinase inhibitor and a p38-MAPK inhibitor suppress HP-NAP-mediated neutrophil oxidative burst, adhesion, andchemotaxis, but not actin polymerization. Pertussis toxin (PTX) inhibits all these neutrophil functions and the MAPK activation caused by HP-NAP. These results demonstrate that HP-NAP activates neutrophils through a PTX-sensitive pathway and that ERK and p38-MAPK are involved in many neutrophil functions stimulated by HP-NAP.

Actins↗
PubMed1993

Docosahexanoic acid (22:6, n-3) but not eicosapentaenoic acid (20:5, n-3) can induce neutrophil-mediated injury of cultured endothelial cells: involvement of neutrophil elastase.

Previously published work has indicated that polyunsaturated fatty acids (PUFA) may enhance neutrophil-mediated damage to host tissues. We have found that endothelial detachment was significantly increased by neutrophils pretreated with docosahexaenoic (22:6, n-3) and arachidonic (20:4, n-6) acids at 10-40 microM but not by eicosapentaenoic acid (20:5, n-3). Endothelial cell lysis as measured by 51Cr release was unaffected. The extent of detachment was dependent on both fatty acid and neutrophil pretreatment concentrations. A specific leukocyte elastase inhibitor abrogated the increased detachment but catalase had no effect. Measurement of prostaglandin I2 synthesis as an alternative nonlytic assay of endothelial function indicated that 20:4 but not 20:5 was able to stimulate neutrophil-induced endothelial PGI2 synthesis. Although all three PUFA (3-33 microM) were found to stimulate release from neutrophil-specific granules, only 22:6 and 20:4 could stimulate release of the azurophilic granules containing elastase to any significant extent. Saturated fatty acids (20:0 and 22:0) and the methyl ester of 22:6 did not cause either neutrophil-mediated endothelial detachment or degranulation. We conclude that neutrophils pretreated with 22:6 or 20:4 but not 20:5 can decrease endothelial integrity through detachment involving neutrophil elastase. These findings may have important implications for the dietary use of fish oils rich in n-3 fatty acids.

Amino Acid Chloromethyl Ketones↗
PubMed1985

Role of stimulated neutrophils from patients with systemic lupus erythematosus in tissue injury, with special reference to serum factors and increased active oxygen species generated by neutrophils.

To examine the possible correlation between tissue injury and neutrophil-produced active oxygen (AO) species in patients with systemic lupus erythematosus (SLE), we studied the capacity of the serum from six patients with untreated, active SLE to generate AO and release lysosomal enzymes by normal neutrophils. Cultured endothelial cells from human umbilical cord vein were incubated with serum-stimulated neutrophils to assess AO-induced tissue injury. Serum from patients with bacterial infections and healthy individuals served as controls. AO production was highest in the neutrophils stimulated with SLE patient-derived serum, while lysosomal enzyme release was only slightly increased. SLE neutrophils with or without stimulation and SLE serum-stimulated normal neutrophils produced significantly high levels of cytotoxicity upon coincubation with 51Cr-labeled human endothelial cells. These excessive cytotoxicities were reversed by the presence of superoxide dismutase and catalase, indicating the specificity of the AO effect on endothelial cell damage. These findings suggest that tissue damage in SLE may be partially due to excessive production of AO and that both neutrophils themselves and a serum factor which activates neutrophils are involved in the mechanism for vascular injury.

Adolescent↗
PubMed1997

Human neutrophil lipocalin (HNL) is a specific granule constituent of the neutrophil granulocyte. Studies in bronchial and lung parenchymal tissue and peripheral blood cells.

The neutrophilic granulocyte is a cytotoxic and potentially tissue-injuring cell participating in the destructive processes and symptoms seen in a variety of inflammatory diseases. Sensitive immunoassays have been introduced to measure the levels of specific secretory proteins of various inflammatory cells in blood and other body fluids. The aim has been to develop highly specific markers for each cell type. The results obtained by immunoassay have indicated that human neutrophil lipocalin (HNL) is a protein unique to the neutrophil. The present study investigated the specificity of HNL as a neutrophil marker in peripheral blood and lung tissue by using flow cytometry and immunocytochemistry. Flow cytometry and immunocytochemistry on peripheral blood showed that monoclonal antibodies to HNL only react with neutrophils and not with other types of leukocytes. Immunocytochemistry on plastic-embedded sections and on frozen sections of lung tissue showed that a cocktail of six monoclonal antibodies to HNL specifically reacts with neutrophils and not with epithelial cells or macrophages. By immunoelectron microscopical studies performed on healthy human neutrophils after low temperature embedding in Lowicryl K4M following aldehyde fixation and partial dehydration, it could be shown that HNL colocalized with lactoferrin (a known marker for secondary or specific granules) and that myeloperoxidase was localized in the primary or azurophil granules. The results confirm that HNL is a unique component of the secondary granules of the neutrophil granulocyte.

Acute-Phase Proteins↗