SEARCH · Search PubMed

Results for “NEUTROPHILS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 559 records · Page 31Linked to original sources

PubMed2000

Opsonization of apoptotic neutrophils by anti-neutrophil cytoplasmic antibodies (ANCA) leads to enhanced uptake by macrophages and increased release of tumour necrosis factor-alpha (TNF-alpha).

Since proteinase 3 (PR3)-ANCA interact with PR3 on the surface of apoptotic polymorphonuclear neutrophils (PMN) and ingestion of apoptotic PMN is known to modulate macrophage inflammatory reactions, we raised the question whether PR3-ANCA-opsonized apoptotic PMN influence the uptake by macrophages and their state of activation. We therefore analysed the effects of PR3-ANCA-opsonized apoptotic PMN on the uptake process by enzymatic assay. We further investigated the production of TNF-alpha, IL-10, IL-12 and the secretion of lipid inflammatory mediators (TxB2, leukotriene B4 (LTB4) and prostaglandin E2 (PGE2)) by human monocyte-derived macrophages using FACS and ELISA methods. We show that PMN-opsonization by PR3-ANCA substantially enhances phagocytosis by macrophages and thereby triggers the production of TNF-alpha and TxB2. These in vitro findings indicate that PR3-ANCA opsonization of apoptotic PMN might be an important mechanism in the pathogenesis of Wegener's granulomatosis (WG), prompting macrophages to produce proinflammatory mediators. These mediators, mainly TNF-alpha, might prime further PMN leading to perpetuation of the known priming-dependent mechanisms of ANCA action.

Antibodies, Antineutrophil Cytoplasmic↗

PubMed2002

Supernatants of stored polymorphonuclear neutrophils exhibit growth-promoting activity in several cell lines: perforin expression in polymorphonuclear neutrophils and its role in down-regulation of growth-promoting activity.

BACKGROUND AND OBJECTIVES: Polymorphonuclear neutrophils (PMNs) play important roles in the host immune defence. This study was performed to identify roles of PMNs other than those already known. MATERIALS AND METHODS: PMNs were separated from the peripheral blood of healthy individuals and stored in vitro for 24 h in the presence or absence of an anti-human Fc receptor (FcR) gamma III antibody, namely, anti-CD16 monoclonal antibody (mAb). Stored supernatants were harvested and incubated with several leukaemia and transformed cell lines for 48 h. The increase in growth rate was assessed by the increase in the amount of 3H-thymidine incorporated into these cells. Expression of perforin on PMNs, which is thought to decrease cell viability, was elucidated by flow cytometry (FCM) analysis. The presence of perforin in the stored supernatants was determined using an enzyme-linked immunosorbent assay (ELISA). A serine protease inhibitor, which is known to block the effect of perforin, was added to the cultures of several leukaemia and transformed cell lines to confirm the effect of perforin in reducing cell viability. RESULTS: Growth promotion of some cell lines cultured with the stored supernatants of PMNs was observed both in the presence and absence of anti-CD16 mAb, which was used as a trigger molecule of PMNs. This was particularly notable in the case of Raji and Daudi (both Burkitt lymphoma) cell lines and Epstein-Barr virus (EBV)-transformed B-lymphoblastoid cell lines (B-LCLs) derived from healthy individuals. Perforin expression was observed in both freshly prepared and stored PMNs, regardless of the presence or absence of anti-CD16 mAb. ELISA also detected perforin in the stored supernatants in both the presence and absence of anti-CD16 mAb. The increase in growth rate was induced in the presence of not only a serine protease inhibitor but also an anti-perforin mAb. CONCLUSIONS: Stored supernatants of PMNs exhibit up-regulation of cell growth in several cell lines; this up-regulation is particularly prominent in B-lineage cell lines. Furthermore, perforin appeared to be expressed on PMNs constitutively and secreted into the extracellular fluid. Results of this study strongly suggest that the growth-promoting activity in supernatants of stored PMNs is partially inhibited by perforin, which is thought to be produced by PMNs themselves.

B-Lymphocytes↗

PubMed2001

Cytokine-modulated inhibition of neutrophil apoptosis at local site augments exudative neutrophil functions and reflects inflammatory response after surgery.

BACKGROUND: The fate of exudative polymorphonuclear neutrophils (PMNs) at the local site after surgery is not well understood. We evaluated the fate and functions of exudative PMNs at the local site in patients who were undergoing major surgery. We also investigated the relation between PMN apoptosis and cytokine levels at the local site during the postoperative period. METHODS: Exudative PMNs were isolated from 11 patients during the postoperative period. Apoptosis, reactive oxygen intermediates (ROI) production, CD16, and tumor necrosis factor receptor expression of the PMNs were determined by flow cytometry. Cytokine levels in the drainage fluid were measured. RESULTS: Exudative PMN apoptosis was markedly inhibited on postoperative day 1 and then increased in a time-dependent manner. IL-6 and granulocyte macrophage colony-stimulating factor were significant factors to inhibit exudative PMN apoptosis; tumor necrosis factor-alpha and IL-10 were the factors to increase apoptosis. ROI production and CD16 expression of exudative PMNs were augmented when PMN apoptosis was inhibited in the early postoperative period. CONCLUSIONS: Exudative PMN apoptosis was inhibited after surgery; PMN function was augmented after surgery. Cytokines at the local site may modulate exudative PMN apoptosis. Exudative PMN apoptosis reflected the inflammatory response after surgery. Understanding the mechanisms of PMN apoptosis and its pathophysiologic significance at local inflammatory sites in vivo may help in the design of more rational treatments.

Aged↗

PubMed1999

Prednisolone interferes with neutrophil adhesion and neutrophil mediated endothelial injury.

Adhesion of leukocytes to vascular endothelium is a crucial step in inflammation. This interaction may result in damage of the endothelial cells (EC). We evaluated the effects of prednisolone on adhesive interactions between human polymorphonuclear neutrophil granulocytes (PMN) and human umbilical vein endothelial cells (HUVEC) as well as PMN mediated cytotoxicity to HUVEC (as release of 51chromium), mediated by N-formyl-methionyl-leucyl-phenylalanine (fMLP), lipoxin A4 (LXA4), and the calcium ionophore A23187 in vitro. Prednisolone dose-dependently interfered with adhesion and cytotoxicity induced by fMLP. Prednisolone (at 10 microM) led to a 39% reduction of adhesion and an almost complete inhibition of cytotoxicity, mainly by effects on the PMN. Prednisolone also interfered with cytotoxicity induced by LXA4 by effects on PMN as well as on HUVEC. Adhesion and cytotoxicity induced by the calcium ionophore A23187 was not affected in any way by prednisolone. Thus, in these in vitro models of vasculitis, prednisolone interferes with adhesive and cytotoxic interactions induced by receptor-dependent agonists. These protective effects of prednisolone might explain some of the beneficial effects of glucocorticoids in the treatment of vasculitis.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed1990

Human neutrophil adherence to laminin in vitro. Evidence for a distinct neutrophil integrin receptor for laminin.

We used mAbs against polymorphonuclear leukocyte (PMN) surface proteins to investigate the mechanisms by which stimulated human neutrophils (PMNs) adhere in vitro to laminin, the major glycoprotein of mammalian basement membrane. mAb IB4, which is directed against the common beta 2 chain of the CD11/CD18, only partially inhibited the adherence of PMA-stimulated PMNs to both laminin and to subendothelial matrices. In contrast, IB4 completely inhibited PMA-stimulated PMN adherence to gelatin, fibronectin, collagen IV, and endothelial cell monolayers. PMA-stimulated PMNs from a patient with severe congenital CD11/CD18 deficiency also adhered to laminin, but not to gelatin or endothelial cell monolayers. Therefore, PMA-stimulated PMNs adhere to laminin by both CD11/CD18-dependent and CD11/CD18-independent mechanisms. Expression of CD11/CD18-independent adherence to laminin was agonist dependent, occurring after stimulation with the calcium ionophore A23187 and recombinant TNF-alpha, but not with the chemotactic factors FMLP, platelet activating factor, or recombinant human C5a. Expression of CD11/CD18-independent adherence was also divalent cation dependent, occurring in the presence of Mg2+ but not Ca2+ as the sole added divalent cation. The mAbs AIIB2 and 13, which are directed against the beta 1 subunit of the VLA integrins, significantly inhibited the CD11/CD18-independent adherence of normal PMNs to laminin, and completely abolished the adherence of CD11/CD18-deficient PMNs to laminin. Both anti-beta 1 mAbs bound to PMNs, as demonstrated by flow cytometry, and immunoprecipitated a membrane molecule of Mr 130,000 daltons from 125I-labeled, detergent-solubilized PMNs. These data suggest that human PMNs possess beta 1 and beta 2 classes of integrins, and that both mediate PMN adherence.

Animals↗

PubMed1995

A novel class of autoantigens of anti-neutrophil cytoplasmic antibodies in necrotizing and crescentic glomerulonephritis: the lysosomal membrane glycoprotein h-lamp-2 in neutrophil granulocytes and a related membrane protein in glomerular endothelial cells.

Necrotizing and crescentic glomerulonephritis (NCGN) is frequently associated with circulating antineutrophil cytoplasmic autoantibodies (ANCA). It is established that ANCA are specific for soluble enzymes of granules of polymorphonuclear neutrophil granulocytes (PMN), such as myeloperoxidase (MPO) or protease 3 (PR3). The purpose of this study was to identify membrane proteins of PMNs, and/or glomerular cells, as additional autoantigenic ANCA targets. When membrane protein fractions were prepared from PMNs and isolated human glomeruli, and immunoblotted with ANCA sera of NCGN patients, two bands with apparent molecular masses of 170 and 80-110 kD (gp170/80-110) were labeled in PMNs, and a 130-kD glycoprotein (gp130) in glomeruli. Gp130 was purified, and monoclonal and rabbit antibodies (Abs) were produced which showed the same double specificity as the patient's ANCA. Using these probes, evidence was provided that gp170/80-110 is identical with human lysosomal-associated membrane protein 2 (h-lamp-2), because both proteins were immunologically cross-reactive and screening of a cDNA expression library from human promyelocytic leukemia cells with anti-gp130 Ab yielded a clone derived from h-lamp-2. Gp170/80-110 was localized primarily in granule membranes of resting PMNs, and was translocated to the cell surfaces by activation with FMLP. By contrast, gp130 was localized in the surface membranes of endothelial cells of human glomerular and renal interstitial capillaries, rather than in lysosomes, as found for h-lamp-2. Potential clinical relevance of autoantibodies to gp170/80-110 and gp130 was assessed in a preliminary trial, in which ANCA sera of patients (n = 16) with NCGN were probed with purified or recombinant antigens. Specific reactivity was detected in approximately 90% of cases with active phases of NCGN, and frequently also in combination with autoantibodies specific for PR3 or MPO. Collectively, these data provide evidence that h-lamp-2 in PMNs and a different, structurally related 130-kD membrane protein on the cell surface of renal microvascular endothelial cells are autoantigenic targets for ANCA in patients with active NCGN.

Amino Acid Sequence↗

PubMed1996

Antineutrophil cytoplasmic autoantibodies interact with primary granule constituents on the surface of apoptotic neutrophils in the absence of neutrophil priming.

The pathogenic role of antineutrophil cytoplasmic autoantibodies (ANCA) remains controversial because of the difficulty in explaining how extracellular ANCA can interact with intracellular primary granule constituents. It has been postulated that cytokine priming of neutrophils (PMN), as may occur during a prodromal infection, is an important trigger for mobilization of granules to the cell surface, where they may interact with ANCA. We show by electron microscopy that apoptosis of unprimed PMN is also associated with the translocation of cytoplasmic granules to the cell surface and alignment just beneath an intact cell membrane. Immunofluorescent microscopy and FACS analysis demonstrate reactivity of ANCA-positive sera and antimyeloperoxidase antibodies with apoptotic PMN, but not with viable PMN. Moreover, we show that apoptotic PMN may be divided into two subsets, based on the presence or absence of granular translocation, and that surface immunogold labeling of myeloperoxidase occurs only in the subset of PMN showing translocation. These results provide a novel mechanism that is independent of priming, by which ANCA may gain access to PMN granule components during ANCA-associated vasculitis.

Antibodies, Antineutrophil Cytoplasmic↗

PubMed2005

Neutrophil migration across tight junctions is mediated by adhesive interactions between epithelial coxsackie and adenovirus receptor and a junctional adhesion molecule-like protein on neutrophils.

Neutrophil (polymorphonuclear leukocytes [PMN]) transepithelial migration during inflammatory episodes involves a complex series of adhesive interactions and signaling events. Previous studies have shown that key adhesive interactions between leukocyte CD11b/CD18 and basally expressed fucosylated glycoproteins followed by binding to desmosomal-associated JAM-C are key elements of the transmigration response. Here we provide the first evidence that PMN-expressed junctional adhesion molecule-like protein (JAML) regulates transmigration via binding interactions with epithelial coxsackie and adenovirus receptor (CAR). Experiments with a JAML fusion protein revealed specific binding of JAML to epithelial CAR expressed at tight junctions in T84 cell monolayers and normal human colonic mucosa. Furthermore, JAML-CAR binding is mediated via the membrane distal immunoglobulin (Ig) loop of CAR and the membrane proximal Ig loop of JAML. PMN bound to immobilized CAR but not JAML in a divalent cation-independent manner. Lastly, in assays of PMN transepithelial migration, JAML/CAR fusion proteins and their antibodies significantly inhibited transmigration in a specific manner. Taken together, these results indicate that JAML and CAR are a novel pair of adhesion molecules that play an important role in modulating PMN migration cross epithelial tight junctions. These findings add a new element to a multistep model of PMN transepithelial migration and may provide new targets for anti-inflammatory therapies.

Antibodies, Monoclonal↗

PubMed2004

Mobilization of neutrophil sialidase activity desialylates the pulmonary vascular endothelial surface and increases resting neutrophil adhesion to and migration across the endothelium.

The amount of sialic acid on the surface of the neutrophil (PMN) influences its ability to interact with other cells. PMN activation with various stimuli mobilizes intracellular sialidase to the plasma membrane, where it cleaves sialic acid from cell surfaces. Because enhanced PMN adherence, spreading, deformability, and motility each are associated with surface desialylation and are critical to PMN diapedesis, we studied the role of sialic acid on PMN adhesion to and migration across pulmonary vascular endothelial cell (EC) monolayers in vitro. Neuraminidase treatment of either PMN or EC increased adhesion and migration in a dose-dependent manner. Neuraminidase treatment of both PMNs and ECs increased PMN adhesion to EC more than treatment of either PMNs or ECs alone. Moreover, neuraminidase treatment of ECs did not change surface expression of adhesion molecules or release of IL-8 and IL-6. Inhibition of endogenous sialidase by either cross-protective antineuraminidase antibodies (45.5% inhibition) or competitive inhibition with pseudo-substrate (41.2% inhibition) decreased PMN adhesion to ECs; the inhibitable sialidase activity appeared to be associated with activated PMNs. Finally, EC monolayers preincubated with activated PMNs became hyperadhesive for subsequently added resting PMNs, and this hyperadhesive state was mediated through endogenous PMN sialidase activity. Blocking anti-E-selectin, anti-CD54 and anti-CD18 antibodies decreased PMN adhesion to tumor necrosis factor-activated ECs but not to PMN-treated ECs. These data implicate desialylation as a novel mechanism through which PMN-EC adhesion can be regulated independent of de novo protein synthesis or altered adhesion molecule expression. The ability of activated PMNs, through endogenous sialidase activity, to render the EC surface hyperadherent for unstimulated PMNs may provide for rapid amplification of the PMN-mediated host response.

Animals↗

PubMed2000

A new mechanism for IL-5-dependent helminth control: neutrophil accumulation and neutrophil-mediated worm encapsulation in murine filariasis are abolished in the absence of IL-5.

IL-5 production and eosinophilia are features of helminth infections, but results concerning the role of IL-5 and eosinophils (EP) in worm control are contradictory. We describe here a novel, IL-5-dependent mechanism of helminth control in vivo, using a fully permissive murine filariasis model, i.e. infection of BALB/c mice with Litomosoides sigmodontis. Worm control was exerted by the formation of inflammatory nodules around adult filariae which initially remained alive but were eventually killed within several weeks. The cell population essential for inflammatory nodule formation was found to be neutrophils (NP) but not EP. Neutralization of IL-5 led to a failure of both EP and NP accumulation at the site of infection (i.e. the thoracic cavity), resulting in cessation of inflammatory nodule formation around worms and in their survival. The role of NP in this process was confirmed by treatment of mice with anti-granulocyte colony stimulating factor (G-CSF) which also resulted in a lack of inflammatory nodule formation and worm killing albeit in the presence of EP. Since IL-5, due to the absence of IL-5 receptors on NP, does not act on these cells directly, it was investigated if anti-IL-5 altered the production of NP-chemotactic cytokines. In anti-IL-5-treated mice, cytokines known to promote NP accumulation like tumor necrosis factor-alpha, G-CSF and KC (IL-8) were found to be strongly reduced, while NP-deactivating cytokines like IL-10 were increased. In conclusion, IL-5 constitutes a cytokine essential for NP-mediated worm control in filarial infection.

Animals↗

PubMed1991

Prognostic markers in diarrhoea-associated haemolytic-uraemic syndrome: initial neutrophil count, human neutrophil elastase and von Willebrand factor antigen.

The observed increase in plasma von Willebrand factor antigen (vWF:Ag) in patients with the haemolytic-uraemic syndrome is presumed to be secondary to endothelial damage, which is a central event in these diseases. As the prognostic value of such changes has not been previously evaluated, vWF:Ag has been measured in plasma from children reported to a national survey of haemolytic-uraemic syndrome. Human neutrophil elastase was also measured, as an initial neutrophilia has been shown to have prognostic value in diarrhoea-associated haemolytic-uraemic syndrome. Despite a significant elevation of plasma vWF:Ag concentration in these patients at presentation, the values did not correlate with the period of thrombocytopenia, the need for dialysis, or outcome. However, children with a poor outcome had significantly greater plasma elastase concentrations compared to those who had a good outcome.

Antigens↗

PubMed1994

Differential activation of alveolar, pulmonary arterial, and systemic arterial neutrophils demonstrates the existence of distinct neutrophil subpopulations in experimental sepsis.

Neutrophils (PMNs) are considered key cellular mediators of sepsis induced acute lung injury. PMN activation is manifest by increased beta 2 integrin expression and enhanced superoxide radical (O2-) generation. What is unclear is at which anatomical sites PMNs are activated and at which sites they release O2- and mediate lung injury. In this study we compared alveolar (ALV), systemic arterial (SA), and pulmonary arterial (PA) PMNs CD18 receptor expression, measured by fluorescent immunophenotyping and, O2- generation, measured by reduction of ferricytochrome C, in septic swine. Swine were anesthetized and ventilated, and given a 1-h infusion of live Pseudomonas aeruginosa. PA, SA, and ALV PMNs were isolated at 0 and 5 h. ALV PMNs O2- was reduced compared to SA blood PMNs O2- at 5 h, (AIV 5 h 23.6 +/- 3 vs. SA 0 h 34.3 +/- 5, p < .05). SA PMNs O2- generation was also significantly reduced compared to PA PMNs at 5 h (PA 5 h 21 +/- 2.5 vs. SA 5 h 16.9 +/- 2.6, p < .05). Alv PMNs expressed significantly greater CD18 receptor levels than SA blood PMNs at 5 h (AIV PMNs 5 h, 76 +/- 6 vs. SA PMNs 5 h 51 +/- 3, p < .05), however, PA PMNs CD18 receptor levels were not significantly different from SA PMNs levels at 5 h. These data corroborate a dissociation between two PMN functions in sepsis. O2- generation was reduced across the lung and following migration. However, alveolar PMNs had significantly upregulated CD18 expression compared to PMNs in PA and SA.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1997

Intercellular adhesion molecule-1 (ICAM-1) is expressed on human neutrophils and is essential for neutrophil adherence and aggregation.

This study investigated the expression and regulation of intercellular adhesion molecule-1 (ICAM-1) on human polymorphonuclear neutrophils (PMNs), and its potential role in PMN-PMN adherence and aggregation as observed during systemic inflammatory response syndrome. Normal human PMNs were found to express ICAM-1 with 90% positive population, and this expression was augmented by endotoxin (lipopolysaccharide, LPS) and tumor necrosis factor-alpha (TNF-alpha) stimulation. The presence of ICAM-1 mRNA in human PMNs was further detected by reverse transcription-polymerase chain reaction before and after LPS and TNF-alpha treatment. Furthermore, incubation of PMNs with LPS and TNF-alpha resulted in significant increases in PMN-PMN adherence and aggregation, while addition of either anti ICAM-1 mAb or anti CD11b/CD18 mAb significantly inhibited LPS and TNF-alpha-mediated PMN-PMN adherence and aggregation. These novel findings demonstrate that ICAM-1 is expressed on human PMNs and responsible for PMN aggregation, and suggest that the interaction between ICAM-1 and CD11b/CD18 may be the molecular basis for PMN aggregation and clumping in the microcirculation during systemic inflammatory response syndrome.

Adult↗

PubMed1992

Infiltrating neutrophils differ from circulating neutrophils when stimulated with C5a, NAP-1/IL-8, LTB4 and FMLP.

In this study we report on functional characteristics of pustule as well as blood polymorphonuclear neutrophils (PMN) in a patient suffering from relapsing bullous staphyloderma. Large numbers of viable PMN from newly formed pustules as well as from the peripheral blood were investigated. During the course of disease chemotactic migration, enzyme degranulation, superoxide-anion generation and leukotriene B4 production were determined simultaneously. The results revealed C5a- and NAP-1/IL-8-specific dysfunction of pustule PMN as compared with blood PMN. In contrast, FMLP-elicited functional activities of pustule PMN were only slightly affected. Our findings provide evidence that in inflamed tissue invading PMN are regulated by in situ generated mediators. C5a produced by staph, aureus-induced activation of the alternative pathway of the complement cascade represents a predominant regulatory factor in situ. Furthermore, the results substantiate previous observations concerning different modulation of C5a and f-met-peptide receptors on human PMN.

Chemotaxis, Leukocyte↗

PubMed1999

Neutrophil inhibitory factor abrogates neutrophil adhesion by blockade of CD11a and CD11b beta(2) integrins.

We studied the basis of inhibition of polymorphonuclear leukocyte (PMN) adhesion induced by neutrophil inhibitory factor (NIF), a 41-kDa CD11/CD18 beta(2) integrin-binding protein isolated from the canine hookworm (Ancylostoma caninum). NIF blocked PMN adhesion in a concentration-dependent manner with complete blockade occurring at approximately 10 nM NIF. Because CD11a and CD11b beta(2) integrins are functionally active on stimulated PMNs, and yet NIF is postulated to inhibit only CD11b integrin by binding to its I domain, we evaluated the contributions of CD11a and CD11b beta(2) integrins in the mechanism of inhibition of PMN adhesion to endothelial cells. We observed an additive inhibitory effect (>90% inhibition) of PMN adhesion to endothelial cells when NIF was used in combination with anti-CD11b monoclonal antibodies, which alone at saturating concentrations reduced PMN adhesion by only 50%. NIF also prevented aggregation of phorbol ester-stimulated JY lymphoblastoid cells that expressed only the functionally active CD11a, suggesting that NIF also can inhibit CD11a-dependent response. We transduced the NIF cDNA into human dermal microvessel endothelial cells in which NIF synthesis and release prevented PMN adhesion to the transduced human dermal microvessel endothelial cells. These data indicated that the potent antiadhesive effect of NIF may be the result of inhibition of CD11a and CD11b beta(2) integrins on PMNs. Moreover, the strategy of NIF release from transduced endothelial cells suggests the feasibility of blocking the CD11a- and CD11b beta(2) integrin-dependent PMN adhesion and PMN migration responses specifically at sites of endothelial cell activation.

Animals↗

PubMed1991

Mechanisms of fungal pathogenicity: correlation of virulence in vivo, susceptibility to killing by polymorphonuclear neutrophils in vitro, and neutrophil superoxide anion induction among Blastomyces dermatitidis isolates.

Seven Blastomyces dermatitidis isolates varying in virulence for mice were compared for susceptibility to polymorphonuclear neutrophil (PMN) killing and the ability to induce superoxide anion (O2-) production by PMNs in vitro. In vitro killing of six B. dermatitidis isolates by murine peripheral blood PMNs or by PMNs elicited from the peritoneal cavity by a local immune reaction (B. dermatitidis-immune mice given killed B. dermatitidis intraperitoneally 24 h earlier) inversely correlated with in vivo virulence (most to least virulent) isolates: VV, V, V40, KL-1, A2, and GA-1). The capacity of isolates to induce O2- production by PMNs also inversely correlated with in vivo virulence. Isolate A, of intermediate in vivo virulence, was a good inducer of O2- production in vitro but was no more susceptible to in vitro killing by PMNs than isolate V, VV, or V40. Fungal intracellular superoxide dismutase or catalase content did not correlate with in vivo virulence or in vitro killing by PMNs. Isolate A, however, had two to four times the intracellular catalase activity as did other B. dermatitidis isolates, suggesting a possible mechanism for its enhanced resistance to in vitro killing by PMNs. Therefore, while in vitro killing by PMNs and the capacity to induce O2- production by PMNs inversely correlated with virulence for six B. dermatitidis isolates, isolate A was an exception: its resistance to killing by PMN-generated oxygen metabolites in vitro but its susceptibility to killing in vivo suggest that its in vivo killing occurs by other, perhaps nonoxidative, mechanisms.

Animals↗

PubMed2002

Cryptococcal glucuronoxylomannan inhibits adhesion of neutrophils to stimulated endothelium in vitro by affecting both neutrophils and endothelial cells.

Cryptococcal infections are often characterized by a paucity of leukocytes in the infected tissues. Previous research has shown that the capsular polysaccharide glucuronoxylomannan (GXM) inhibits leukocyte migration. In this study we investigated whether the capsular polysaccharide GXM affects the migration of neutrophils (polymorphonuclear leukocytes [PMN]) through the endothelium by interfering with adhesion in a static adhesion model. Pretreatment of PMN with GXM inhibited PMN adhesion to tumor necrosis factor alpha (TNF-alpha)-stimulated endothelium up to 44%. Treatment of TNF-alpha-stimulated endothelium with GXM led to a 27% decrease in PMN adhesion. GXM treatment of both PMN and endothelium did not have an additive inhibitory effect. We demonstrated that GXM-induced L-selectin shedding does not play an important role in the detected inhibition of adhesion. L-selectin was still present on PMN in sufficient amounts after GXM treatment, since it could be further inhibited by blocking antibodies. Furthermore, blocking of GXM-related L-selectin shedding did not abolish the GXM-related inhibition of adhesion. GXM most likely exerts its effect on PMN by interfering with E-selectin-mediated binding. The use of blocking monoclonal antibodies against E-selectin, which was shown to decrease adhesion in the absence of GXM, did not cause additive inhibition of PMN adhesion after GXM pretreatment. The use of blocking antibodies also demonstrated that the inhibiting effect found after GXM treatment of endothelium probably involves interference with both intercellular adhesion molecule-1 and E-selectin binding.

CD18 Antigens↗

PubMed1999

A(3) adenosine receptor activation attenuates neutrophil function and neutrophil-mediated reperfusion injury.

This study tested the hypothesis that A(3) adenosine receptors inhibit neutrophil (PMN) function and PMN-mediated reperfusion injury. 2-Chloro-N(6)-(3-iodobenzyl)adenosine-5'-N-methyluronamide (Cl-IB-MECA), an A(3) agonist, did not attenuate superoxide production or myeloperoxidase release from stimulated PMNs. However, Cl-IB-MECA reduced platelet-activating factor-stimulated PMN adherence to coronary endothelium at low concentrations: 52 +/- 27, 45 +/- 10, and 87 +/- 23 PMNs/mm(2) at 0.1, 1.0, and 10 nM vs. 422 +/- 64 PMNs/mm(2) with platelet-activating factor alone. This inhibition was not blocked by A(1) (5 microM KW-3902) or A(2a) (5 microM KF-21326) antagonists: 44 +/- 3 and 43 +/- 2 PMNs/mm(2), respectively. Endothelial pretreatment with 1 nM Cl-IB-MECA reduced PMN adherence, which was reversed by the A(3) antagonist MRS-1220 (100 nM). PMN-mediated reperfusion injury was initiated in isolated rabbit hearts by infusion of 28 x 10(6) PMNs/min for 10 min early in reperfusion. PMNs caused a significant decrease in recovery of left ventricular developed pressure and positive and negative time derivatives of pressure (23 +/- 3, 25 +/- 3, and 23 +/- 3% of baseline, respectively) vs. buffer-perfused hearts (43 +/- 7, 44 +/- 7, and 45 +/- 6%, respectively). Cl-IB-MECA (10 nM) given at reperfusion attenuated the PMN-mediated loss of contractile recovery (40 +/- 3, 46 +/- 5, and 42 +/- 4% of baseline). Cl-IB-MECA reduced myeloperoxidase release activity (5.3 +/- 0.6 absorbance units/min) and CD18-positive cells (54 +/- 9 cells/slide) compared with the untreated PMN group (17.9 +/- 1.7 absorbance units/min and 183 +/- 68 cells/slide). We conclude that Cl-IB-MECA attenuates reperfusion injury by decreasing PMN-endothelial cell interactions. These results suggest that the A(3) adenosine receptor may be a novel therapeutic target for treatment of myocardial ischemia and reperfusion.

Animals↗