Interaction Of Polymorphonuclear Leukocytes Research Articles

Human severe sepsis cytokine mixture increases β2-integrin-dependent polymorphonuclear leukocyte adhesion to cerebral microvascular endothelial cells in vitro.

IntroductionSepsis-associated encephalopathy (SAE) is a state of acute brain dysfunction in response to a systemic infection. We propose that systemic inflammation during sepsis causes increased adhesion of leukocytes to the brain microvasculature, resulting in blood-brain barrier dysfunction. Thus, our objectives were to measure inflammatory analytes in plasma of severe sepsis patients to create an experimental cytokine mixture (CM), and to use this CM to investigate the activation and interactions of polymorphonuclear leukocytes (PMN) and human cerebrovascular endothelial cells (hCMEC/D3) in vitro.MethodsThe concentrations of 41 inflammatory analytes were quantified in plasma obtained from 20 severe sepsis patients and 20 age- and sex-matched healthy controls employing an antibody microarray. Two CMs were prepared to mimic severe sepsis (SSCM) and control (CCM), and these CMs were then used for PMN and hCMEC/D3 stimulation in vitro. PMN adhesion to hCMEC/D3 was assessed under conditions of flow (shear stress 0.7 dyn/cm2).ResultsEight inflammatory analytes elevated in plasma obtained from severe sepsis patients were used to prepare SSCM and CCM. Stimulation of PMN with SSCM led to a marked increase in PMN adhesion to hCMEC/D3, as compared to CCM. PMN adhesion was abolished with neutralizing antibodies to either β2 (CD18), αL/β2 (CD11α/CD18; LFA-1) or αM/β2 (CD11β/CD18; Mac-1) integrins. In addition, immune-neutralization of the endothelial (hCMEC/D3) cell adhesion molecule, ICAM-1 (CD54) also suppressed PMN adhesion.ConclusionsHuman SSCM up-regulates PMN pro-adhesive phenotype and promotes PMN adhesion to cerebrovascular endothelial cells through a β2-integrin-ICAM-1-dependent mechanism. PMN adhesion to the brain microvasculature may contribute to SAE.

Induction of IgA Deposits and Glomerulonephritis by IgA Rheumatoid Factor

Induction of IgA Deposits and Glomerulonephritis by IgA Rheumatoid Factor

Moderate-intensity exercise suppresses platelet activation and polymorphonuclear leukocyte interaction with surface-adherent platelets under shear flow in men.

The reciprocal modulation of platelet and polymorphonuclear leukocyte (PMN) activities is important in the pathogenesis of thrombosis and inflammation. This study investigated how moderate exercise affects shear-induced platelet activation and subsequent PMNs interaction with platelet-related thrombi under shear flow. Sixteen sedentary healthy men engaged in moderate exercise (about 60% VO(2max)) on a bicycle ergometer. Platelet activation, PMNs interaction with surface-adherent platelets, and PMN-dependent inhibition of platelet activation under shear flow were measured both before and immediately after exercise. The results of this study can be summarized as follows: (1) moderate exercise was associated with lower extents of shear-induced platelet adhesion and aggregation, binding of von Willbrand factor (vWF) to platelets, and glyco-protein IIb/IIIa activation and P-selectin expression on platelet than at rest; (2) the velocity and percentage of rolling PMNs increased while the number of PMNs remaining bound to surface-adherent platelets decreased after moderate exercise; (3) although treating the PMNs with oxidized-low density lipoprotein (Ox-LDL) enhanced PMNs interaction with surface-adherent platelets, moderate exercise suppressed the enhancement of platelet-PMN interaction by Ox-LDL; (4) moderate exercise decreased platelet [Ca (2+)](i) elevation induced by ADP and platelet [Ca(2+)](i) levels mediated by PMN and Ox-LDL-treated PMN; and (5) plasma and PMN-derived nitric oxide metabolites and plasma vWF antigen and activity increased after moderate exercise, whereas plasma and platelet-derived soluble P-selectin levels remained unchanged in response to exercise. Therefore, we conclude that moderate-intensity exercise suppresses shear-induced platelet activation and subsequent PMNs adhesion to platelets deposited at sites of vascular injury under flow, thereby reducing the risks of vascular thrombosis and inflammation.

Polymorphonuclear leukocyte degranulation induced by leukotoxin from Actinobacillus actinomycetemcomitans.

The ability of leukotoxin from Actinobacillus actinomycetemcomitans to induce release of lysosomal constituents was studied with human polymorphonuclear leukocytes (PMNL). Leukotoxin purified from A. actinomycetemcomitans or bacterial cells of a leukotoxic strain were mixed with human PMNL and the suspension was incubated under anaerobic conditions. Samples were taken at certain time intervals to examine the cell morphology of PMNL by electron microscopy and the extracellular concentrations of the granule components lactoferrin and elastase by enzyme-linked immunosorbent assay (ELISA). Electron microscopy revealed that within 10 min of exposure to leukotoxin, the number of intracellular granules was markedly reduced and the remaining granules were translocated to the periphery in PMNL. At the same time, the extracellular concentrations of lactoferrin and elastase were elevated, while that of the cytosolic enzyme lactate dehydrogenase, an indicator of cell lysis, remained low. The lysosome molecules CD63 and CD66b were also exposed on the PMNL surface, indicating fusion of lysosomes with the plasma membrane. These effects were completely abolished by the addition of anti-leukotoxin serum. Pre-incubation of PMNL with monoclonal antibodies to CD11a and CD18 that recognize alpha- and beta-chains of the LFA-1 integrin, a leukotoxin receptor on PMNL, inhibited the cytolysis, but not the release of granule components. The present results demonstrate the ability of A. actinomycetemcomitans leukotoxin to trigger a rapid release of lysosomal compounds in human PMNL. The release is due to an active process stimulated by the interaction of PMNL with the toxin or toxin-carrying bacteria.

Rheumatoid pannus formation: synovial cell attachment to the surface of cartilage

As a part of the rheumatoid synovial tissue reaction, proliferating synovial cells penetrate the cartilage in the form of a pannus, and cartilage destruction takes place in the zone between the cells and cartilage. The cellular origin of rheumatoid pannus has been debated by many investigators, and it is accepted that fibroblast proliferation, endothelial cells proliferation and monocyte chemotaxis are probably involved. It has been observed that fibroblasts in the pannus share properties of the fibroblasts and chondrocytes. Mast cell activation is frequently associated with proinflammatory cytokine and metalloprotease expression, suggesting an important role for the mast cell in mediating matrix degradation. The mechanism of interaction of polymorphonuclear leukocytes with immune complexes trapped in rheumatoid cartilage resembles that associated with phenomenon of frustrated phagocytosis. Increased levels of IL-1 in the rheumatoid joint may play an important role in joint destruction by stimulation of pannus formation through induction of synovial cell attachment to the articular surface. Synovial cell attachment to cartilage may be the initial step in pannus formation. We have recently shown that the increased expression of VLA-5 and ICAM-1 at the cartilage-pannus junction may result from the interaction of synovial mononuclear cells with matrix proteins. Therefore, we have raised the possibility that VLA-5 may facilitate the growth of pannus by virtue of its ability to react with fibronectin with resulting proliferation of the synoviocytes of the pannus. Further study will be needed in order to understand the precise mechanism of cartilage erosion and pannus formation in the various arthritic disorders.

Rheumatoid pannus formation: synovial cell attachment to the surface of cartilage

As a part of the rheumatoid synovial tissue reaction, proliferating synovial cells penetrate the cartilage in the form of a pannus, and cartilage destruction takes place in the zone between the cells and cartilage. The cellular origin of rheumatoid pannus has been debated by many investigators, and it is accepted that fibroblast proliferation, endothelial cells proliferation and monocyte chemotaxis are probably involved. It has been observed that fibroblasts in the pannus share properties of the fibroblasts and chondrocytes. Mast cell activation is frequently associated with proinflammatory cytokine and metalloprotease expression, suggesting an important role for the mast cell in mediating matrix degradation. The mechanism of interaction of polymorphonuclear leukocytes with immune complexes trapped in rheumatoid cartilage resembles that associated with phenomenon of frustrated phagocytosis. Increased levels of IL-1 in the rheumatoid joint may play an important role in joint destruction by stimulation of pannus formation through induction of synovial cell attachment to the articular surface. Synovial cell attachment to cartilage may be the initial step in pannus formation. We have recently shown that the increased expression of VLA-5 and ICAM-1 at the cartilage-pannus junction may result from the interaction of synovial mononuclear cells with matrix proteins. Therefore, we have raised the possibility that VLA-5 may facilitate the growth of pannus by virtue of its ability to react with fibronectin with resulting proliferation of the synoviocytes of the pannus. Further study will be needed in order to understand the precise mechanism of cartilage erosion and pannus formation in the various arthritic disorders.

Reduced intracellular oxidative metabolism promotes firm adhesion of human polymorphonuclear leukocytes to vascular endothelium under flow conditions.

The interaction of polymorphonuclear leukocytes (PMN) with the vascular endothelium and their subsequent extravasation to the tissues is a key step during different physiological and pathological processes. In certain of these pathologies the oxygen tension becomes very low, leading to reduced cellular oxidative status. To evaluate the effect of lowering the intracellular redox status in the interaction of PMN with the endothelium, exposure to hypoxic conditions as well as treatment with different antioxidant agents was carried out. PMN exposure to hypoxia enhanced beta2 integrin-dependent adhesion to intercellular adhesion molecule-1-coated surfaces, concomitant with a decrease in the intracellular redox status of the cell. As occurs with hypoxia, treatment with antioxidants produced a decrease in the oxidation state of PMN. These agents enhanced adhesion of PMN to human umbilical vein endothelial cells stimulated with tumor necrosis factor-alpha (TNF-alpha), and this effect was also mediated by beta2 integrins LFA-1 and Mac-1. Adhesion studies under defined laminar flow conditions showed that the antioxidant treatment induced an enhanced adhesion mediated by beta2 integrins with a decrease in the fraction of PMN rolling on TNF-alpha-activated endothelial cells. The up-regulated PMN adhesion was correlated to an increase in the expression and activation of integrin Mac-1, without loss of L-selectin surface expression. Altogether, these results demonstrate that a reduction in the intracellular oxidative state produces an enhanced beta2 integrin-dependent adhesion of PMN to stimulated endothelial cells under conditions of flow.

Interactions of neutrophils and endothelial cells under low flow conditions in vitro.

The interactions of polymorphonuclear leukocytes (PMN) and endothelial cells are modulated by adhesion molecules, inflammatory cytokines, and shear stress. We investigated the changes in PMN-endothelial cell interactions induced by interleukin (IL)-1 beta under low flow conditions. PMN were isolated from the venous blood of healthy adults, and endothelial cells were obtained from human umbilical veins. The number of PMN that adhered to the endothelial cells monolayer that was treated with IL-1 increased significantly at shear stresses from .5 to 4.0 dyn/cm2 as compared with untreated endothelial cells. Anti-intercellular adhesion molecule (ICAM)-1 monoclonal antibody (mAb), anti-E-selectin mAb, and anti-CD18 mAb each significantly inhibited the increase in PMN adherence induced by IL-1 at a low shear stress (1.0 dyn/cm2). Anti-CD18 mAb significantly reduced the number of PMN that migrated through the endothelial monolayer by blocking the adherence of PMN to the luminal surface of the endothelial cells, as well as their transendothelial migration. In contrast, anti-ICAM-1 and anti-E-selectin mAb each reduced the number of PMN that migrated by reducing the number of PMN that adhered to the luminal surface without significantly influencing the percent of the adherent PMN that had migrated. Although anti-L-selectin mAb reduced the adherence and migration of PMN, these effects were not statistically significant. These results indicated that under low flow conditions, as well as in the nonflow state, PMN-endothelial cell interactions were elicited via CD11/CD18 and ICAM-1 without the involvement of selectins.

Endothelium-derived Nitric Oxide Decreases Polymorphonuclear Leukocyte Interaction with the Deeply Injured Arterial Wall under Intermediate and High Shear Conditions

Previous studies have shown that nitric oxide (NO) inhibits specific agonist-induced polymorphonuclear leukocyte (neutrophil) and platelet aggregation in vitro. However, the inhibitory effects of NO on neutrophil interaction with the deeply injured arterial wall under conditions of flow is unknown. Therefore, we investigated the influence of NO derived from the endothelium on neutrophil and platelet interactions with the downstream arterial media under controlled flow conditions. Porcine aortic media, simulating deep arterial wall injury, was exposed to flowing porcine non-anticoagulated arterial blood for 5 min at intermediate (1006 s(-1)) and high (3397 s(-1)) shear conditions, and deposition of radiolabeled neutrophils and platelets was quantified. Neutrophil deposition on the exposed arterial media was reduced, by more than 30%, by pretreatment of the endothelium with the physiological precursor of NO, L-arginine, from 84.1 +/- 13.7 to 57.4 +/- 7.2 x 10(3)/cm2 (p < 0.05) at 1006 s(-1), and from 99.3 +/- 9.8 to 65.5 +/- 8.7 x 10(3)/cm2 (p < 0.05) at 3397 s(-1) of shear rate, relative to control. Pretreatment of the endothelium with the inactive stereoisomer D-arginine had no effect on neutrophil deposition. These specific inhibitory effects of L-arginine were completely abolished by the inhibitor of NO synthesis, N(omega)-nitro-L-arginine methyl ester (L-NAME) at both shear rates. Endothelial pretreatment with D-arginine, or with L-arginine, in the absence or presence of L-NAME, did not significantly influence platelet interaction with the thrombogenic arterial media at intermediate and high shear rates. These results indicate that NO derived from the endothelium can modulate and has a greater influence on neutrophil, than on platelet, interaction with the injured arterial wall exposing the media under conditions of flow typical to moderately and severely stenosed arteries.

Interaction of polymorphonuclear leukocytes with Yersinia enterocolitica: role of the Yersinia virulence plasmid and modulation by the iron-chelator desferrioxamine B.

The impact of desferrioxamine B (DFOB) on intracellular calcium mobilization, chemoluminescence (CL) signaling, phagocytosis, and bacterial killing of Yersinia enterocolitica by polymorphonuclear leukocytes (PMNL) was investigated. DFOB did not alter calcium signaling in PMNL but transiently increased phagocytosis. Likewise, higher counts of viable bacteria in PMNL and increased CL signals after stimulation with Y. enterocolitica were observed in the presence of DFOB. However, DFOB reduced the CL signal elicited individually by zymosan, PMA, and FMLP. Comparison of plasmid-cured with plasmid-harboring Y. enterocolitica revealed that plasmid-encoded determinants modulate phagocytosis, CL signal, and bactericidal properties of PMNL. These data demonstrate that DFOB alters microbicidal properties of PMNL and modulates their interaction with Y. enterocolitica and provide further evidence for a putative dual role of DFOB in the pathogenesis of Yersinia infection, namely growth support of the pathogen and modulation of the antimicrobial host response.

Oxidant stress and potentiation of ischemia/reperfusion injury to the perfused rat liver by human polymorphonuclear leukocytes

The accumulation and activation of polymorphonuclear leukocytes in the liver may play an important role in liver damage following ischemia and reperfusion. To study the effects of polymorphonuclear leukocytes on hepatic function, human polymorphonuclear leukocytes were infused into perfused rat livers. Infusion of polymorphonuclear leukocytes into continuously oxygenated livers led to an increased consumption of oxygen by the perfused liver which paralleled the production of superoxide anion radicals by activated polymorphonuclear leukocytes. The increased use of oxygen was followed by a decrease in the sinusoidal efflux of glutathione and a marked increase in the biliary excretion of glutathione disulfide, indicating that polymorphonuclear leukocytes were activated within the liver, and created a potentially deleterious oxidant stress. When polymorphonuclear leukocytes were infused into rat livers that had been subjected to 45 min of warm ischemia followed by reperfusion, the release of lactate dehydrogenase upon reperfusion of ischemic liver was significantly higher from livers exposed to polymorphonuclear leukocytes than from livers subjected to the same period of ischemia without leukocytes. This indicates that polymorphonuclear leukocytes potentiate ischemia/reperfusion injury. The present in vitro system provides a model to study pharmacological interventions designed to modulate the potentially deleterious interactions of polymorphonuclear leukocytes with the liver.

Outer membranous vesicles and leukotoxic activity of Actinobacillus actinomycetemcomitans from subjects with different periodontal status

Strains of A. actinomycetemcomitans (A.a) from juvenile periodontitis patients (JP), adult periodontitis patients (AP), and 14-yr-old healthy children were tested for the correlation between leukotoxin activity and the number of outer membranous vesicles measured in electron micrographs. To determine the potential for connective tissue destruction following the interaction of polymorphonuclear leukocytes (PMN) with the bacteria, the lysosomal release of neutrophil elastase was assessed. The highest potential to kill leukocytes and to release lysosomal elastase from them was observed in the strains isolated from JP patients. No correlation existed between leukotoxic activity and the number of outer membranous vesicles per bacterium when the data from A.a. strains from all sources were combined. Furthermore, no significant differences were found between the numbers of outer membranous vesicles in the three groups tested. The only significant correlation between the number of vesicles and leukotoxicity was found in the A.a. strains derived from the mouths of healthy children.

Effects of fibronectin on the interaction of polymorphonuclear leukocytes with unopsonized and antibody-opsonized bacteria.

Fibronectin (Fn) affects the interaction of polymorphonuclear leukocytes (PMNLs) with certain bacteria. Fn alone enhanced the response, in a chemiluminescence (CL) assay, of PMNLs to Staphylococcus aureus (P less than .05) and Staphylococcus epidermidis (P less than .01) but had no effect on type III, group B streptococci (GBS) or Escherichia coli. When GBS or E. coli were first preopsonized in antibody, Fn significantly enhanced the CL response of PMNLs (P less than .05). The intracellular metabolic inhibitor NaN3 but not the extracellular scavengers superoxide dismutase or human serum albumin inhibited Fn-enhanced CL; this fact suggests that enhancement of the respiratory burst by Fn is an intracellular event. We used an acridine orange-crystal violet monolayer assay to examine the effects of Fn on ingestion and intracellular killing of bacteria by PMNLs. Fn alone promoted uptake and killing of S. aureus (P less than .01) and S. epidermidis (P less than .05) by PMNLs but did not enhance monolayer phagocytosis of GBS or E. coli, unless these bacteria were preopsonized in antibody (P less than .01).

Interaction of polymorphonuclear leukocytes with cartilage in vitro. Catabolic effects of serine proteases and oxygen radicals.

The ability of purified PMN serine proteases as well as oxygen-derived free radicals (ODFR) generated by activated phagocytes to damage cartilage matrix has been thoroughly investigated in vitro. The question in the present study was the extent to which enzymatic and ODFR-mediated mechanisms can contribute to the degradation of bovine cartilage slices by zymosan-stimulated PMN. Tissue destruction as assessed by mechanical parameters of stability as well as by liberation of uronic acids from matrix proteoglycans was not inhibitable by the radical scavengers superoxide dismutase (SOD) and catalase (CAT), while serine protease inhibitors led to a significant reduction of matrix degradation. Thus an enzymatic mechanism may play a major part in PMN-induced cartilage damage. Besides this predominant role of especially serine proteases a direct, non-zymosan-dependent stimulatory effect of cartilage matrix on PMN to release elastase into the incubation medium was detected. Hence an as-yet unknown mechanism of PMN activation is indicated, while unspecific effects by bacterial contamination, complement factors, or endotoxin could be excluded as an explanation for the observed phenomenon.

Human endothelial cell damage induced by interactions between polymorphonuclear leukocytes and immune complex-coated erythrocytes

We have examined, in vitro, the effects of autologous erythrocytes (RBC) coated with soluble immune complexes (RBC-IC) on the interactions of polymorphonuclear leukocytes (PMN) with human endothelial cell (EC) cultures. RBC-IC were prepared by incubating human RBC with soluble immune complexes, prepared with keyhole limpet hemocyanin (KLH) and rabbit anti-KLH in antigen excess, using normal human serum as a complement source. Several parameters believed to be related to EC-PMN interactions, including adherence of PMN to EC, detachment of EC after incubation with media harvested from RBC-IC-stimulated PMN, and the release of 2-deoxy- d-[ 3H]glucose from damaged EC, were investigated. The proportion of PMN adhering to EC increased in direct proportion to the number of RBC-IC used to stimulate PMN. Media harvested from PMN stimulated with RBC, RBC incubated with complement, RBC-IC, or opsonized zymosan caused variable degrees of detachment of cultured EC. The percentage of EC detached was directly related to the intensity of the PMN degranulation as measured by lysozyme release with a correlation coefficient of 0.935, comparing the natural log of the lysozyme released to the percentage EC detachment. Finally, RBC-IC added to PMN and EC induced PMN-mediated EC damage as measured by the release of 2-deoxy- d-[ 3H]glucose from the labeled EC. The release of 2-deoxy- d-[ 3H]glucose from the labeled EC was directly related to the number of RBC-IC used to stimulate the PMN. These data indicate that RBC-IC are able to stimulate the type of interactions between PMN and EC that are believed to cause EC damage and may play a role in the initiation or exacerbation of inflammatory vascular lesions.

Interaction of polymorphonuclear leukocytes with calcium pyrophosphate dihydrate crystals deposited in chondrocalcinosis cartilage.

Electron microscopy was used to investigate the characteristics of calcium pyrophosphate dihydrate (CPPD) crystals in chondrocalcinosis (pseudogout syndrome). Crystals in midzone cartilage were frequently seen adjacent to chondrocytes. Great variation in crystal size and shape was observed. Most of the pyrophosphate crystals that had been phagocytosed by polymorphonuclear leukocytes of synovial fluid from patients with acute pseudogout were small (less than or equal to 1 micron), indicating that small crystals can cause intense inflammation. Large numbers of polymorphonuclear leukocytes became attached to the eroded articular surface and phagocytosed microcrystals. Interaction of polymorphonuclear leukocytes with CPPD crystals in the superficial region of articular cartilage may stimulate the release of inflammatory mediators.

Polymorphonuclear Leukocytes, Complement, and Trichophyton rubrum

Trichophyton rubrum can activate complement. In order to assess the role of complement in host defense, fresh human serum was incubated with fungus. Factors were produced which were chemotactic for polymorphonuclear leukocytes (PMNL), but only if complement activation was allowed. This suggests that the chemotactic factor or factors were derived from complement. Incubation of T. rubrum with fresh serum did not prevent fungal growth on subsequent culture, but did inhibit incorporation of radiolabeled N-acetylglucosoamine. The interaction of PMNL and fungi was studied, and the role of complement as a mediator was assessed. PMNL adhered well to fungi provided that the fungal hyphae had been preincubated with fresh human serum to provide complement opsonins. Opsonized and unopsonized fungi both stimulated a respiratory burst in normal PMNL as measured by chemiluminescence, but the burst was generated much faster with opsonized hyphae. Although hyphae with adherent PMNL subsequently proliferated in culture, the incorporation of N-acetylglucosoamine was inhibited 96% when the hyphae were opsonized with fresh serum and then incubated with PMNL. Inhibition was also observed with unopsonized fungi, but to a lesser degree. Varying the ratio of PMNL to hyphae showed that inhibition by PMNL was far more efficient if hyphae were opsonized. In contrast to hyphae, opsonized fungal spores were killed by PMNL so that no growth was observed in subsequent cultures. This killing was not observed if PMNL were omitted or if spores were preincubated with heat-inactivated serum rather than fresh serum. Activation of complement apparently opsonizes the spores so that they can be ingested and killed by viable PMNL. Contents of disrupted PMNL failed to inhibit fungal growth. Complement and PMNL may aid the host in defending itself against infection by dermatophytes.

Role of anti-pilus antibodies in host defense against gonococcal infection studied with monoclonal anti-pilus antibodies

Several monoclonal antibodies directed against gonococcal pili have been used to investigate the potential contribution of anti-pilus antibodies to host defense against gonococcal infection. Included were two antibodies (SM1 and SM2) which reacted with conserved determinants present on pili from all strains tested and others which exhibited antigenic specificity. Immunoblotting experiments revealed that antibodies SM1 and SM2 recognize epitopes on two different peptides derived by CNBr cleavage of alpha-pili from Neisseria gonorrhoeae P9-2. All antibodies used were capable of activating complement, as shown by their ability to bind Clq, and one type-specific antibody was effective in complement-mediated bactericidal killing. Antibodies directed against at least some pilus epitopes may therefore contribute to bactericidal activity during the course of natural infection. The opsonic effect of type-specific antibodies was demonstrated by their ability to stimulate luminol-dependent chemiluminescence of human polymorphonuclear leukocytes and promote phagocytic killing of variant P9-2. Phagocytic killing in the presence of each monoclonal antibody paralleled the increase in chemiluminescence, suggesting that for this variant killing was an inevitable consequence of the interaction of polymorphonuclear leukocytes with gonococci opsonized with anti-pilus antibodies. Antibody-mediated chemiluminescence of polymorphonuclear leukocytes was enhanced in the presence of human complement, and a weak opsonic effect was detected with one of the cross-reacting antibodies (SM1) when this system was used. Although cross-reacting antibody SM1 and type-specific antibody SM13 showed considerable differences in biological properties, they were of the same isotype and bound to native pili on intact gonococci in similar numbers and with similar avidity.

Bactericidal effects of photoradiation therapy with hematoporphyrin derivative.

Hematoporphyrin derivative (Hpd) localizes selectively in malignant and rapidly metabolizing tissues and undergoes a cytotoxic reaction when exposed to light of a specific wavelength. Hpd has been studied extensively with regard to the diagnosis and treatment of tumors but not with regard to bactericidal activity. This investigation assessed the effect of light-activated Hpd on various microorganisms, on human polymorphonuclear leukocytes, and on the interactions of polymorphonuclear leukocytes and bacteria. Light-activated Hpd was 99.9% bactericidal against Staphylococcus aureus, Streptococcus faecalis, Bacteroides fragilis, Streptococcus M-G intermedius, Streptococcus mutans, Peptostreptococcus anaerobius, Peptococcus magnus, and Clostridium perfringens, but did not affect Escherichia coli, Pseudomonas aeruginosa, or Candida albicans. Photoactivation of Hpd rendered 98% of polymorphonuclear leukocytes inviable. Combinations of light-activated Hpd and polymorphonuclear leukocytes had a 4-log (99.99%) bactericidal effect on both intra- and extracellular S. aureus. The ability of Hpd to localize in inflammatory tissues may have therapeutic applications in the treatment of abscesses.

Interaction of polymorphonuclear leukocytes and viruses in humans: adherence of polymorphonuclear leukocytes to respiratory syncytial virus-infected cells.

The nature of neutrophil-respiratory syncytial virus (RSV) interaction was investigated by assessing factors that influence neutrophil adherence to RSV-infected tissue culture monolayers. The adherence of neutrophils to infected cells was directly proportional to the degree of RSV replication as evidenced by infectious virus production, cytopathological changes, or viral antigen appearance. Sixty-one percent of the neutrophils adhered to the RSV-infected cells as compared with 52.7% on noninfected monolayers (P less than 0.05). The addition of RSV-specific antibody markedly increased polymorphonuclear leukocyte adherence to 88.5% (P less than 0.001). Complement in the absence of antibody augmented polymorphonuclear leukocyte adherence, but to a lesser degree, 69.0% (P less than 0.025). Arachidonic acid metabolism appeared to play a critical role in the adherence process; thromboxane was the single most important arachidonic acid metabolite. Inhibition of thromboxane synthesis reduced antibody-dependent polymorphonuclear leukocyte adherence on RSV-infected cells to 52.3% (P less than 0.025). These observations suggest a role for neutrophils in RSV infection. It is proposed that neutrophils may participate in RSV infection at the site of viral replication through the attachment to infected cells and the subsequent release of mediators of inflammation.