Sevoflurane Promotes Bactericidal Properties of Macrophages through Enhanced Inducible Nitric Oxide Synthase Expression in Male Mice

BACKGROUND

Sevoflurane with its antiinflammatory properties has shown to decrease mortality in animal models of sepsis. However, the underlying mechanism of its beneficial effect in this inflammatory scenario remains poorly understood. Macrophages play an important role in the early stage of sepsis as they are tasked with eliminating invading microbes and also attracting other immune cells by the release of proinflammatory cytokines such as interleukin-1β, interleukin-6, and tumor necrosis factor-α. Thus, the authors hypothesized that sevoflurane mitigates the proinflammatory response of macrophages, while maintaining their bactericidal properties.

METHODS

Murine bone marrow-derived macrophages were stimulated in vitro with lipopolysaccharide in the presence and absence of 2% sevoflurane. Expression of cytokines and inducible NO synthase as well as uptake of fluorescently labeled Escherichia coli (E. coli) were measured. The in vivo endotoxemia model consisted of an intraperitoneal lipopolysaccharide injection after anesthesia with either ketamine and xylazine or 4% sevoflurane. Male mice (n = 6 per group) were observed for a total of 20 h. During the last 30 min fluorescently labeled E. coli were intraperitoneally injected. Peritoneal cells were extracted by peritoneal lavage and inducible NO synthase expression as well as E. coli uptake by peritoneal macrophages was determined using flow cytometry.

RESULTS

In vitro, sevoflurane enhanced lipopolysaccharide-induced inducible NO synthase expression after 8 h by 466% and increased macrophage uptake of fluorescently labeled E. coli by 70% compared with vehicle-treated controls. Inhibiting inducible NO synthase expression pharmacologically abolished this increase in bacteria uptake. In vivo, inducible NO synthase expression was increased by 669% and phagocytosis of E. coli by 49% compared with the control group.

CONCLUSIONS

Sevoflurane enhances phagocytosis of bacteria by lipopolysaccharide-challenged macrophages in vitro and in vivo via an inducible NO synthase-dependent mechanism. Thus, sevoflurane potentiates bactericidal and antiinflammatory host-defense mechanisms in endotoxemia.

Exposure of Avian Embryos to Cycling Incubation Temperatures Reduces Adult Bactericidal Ability

In birds, the temperature at which eggs are incubated shapes many aspects of hatchling phenotype, but long-term effects are less studied. We studied the effect of incubation temperature and pattern on the subsequent development of innate immune function in Japanese quail (Coturnix japonica). We incubated quail eggs in one of three replicated treatments: control (37.5°C), low (36.0°C), and cyclical incubation. The cyclical treatment had the same average temperature as the low-temperature treatment (36.0°C) and an upper temperature that was the same as the control. When individuals were 5, 20, and 55 d of age (i.e., adults), we measured the ability of blood plasma to kill Escherichia coli. Throughout development there was a nonsignificant trend for immune function to be lower in the cycling treatment. In adulthood, however, individuals incubated at cycling temperatures had significantly lower immune function than control birds but did not differ from individuals incubated at constant low temperatures. Males and females responded similarly to the incubation treatment, but females developed a greater plasma bactericidal ability than males. We conclude that variation in innate immune function of adult birds is shaped by temperature fluctuations experienced during incubation.

Swarming growth and resistance of Proteus penneri and Proteus vulgaris strains to normal human serum

BACKGROUND

Proteus sp. strains isolated from patients with urinary tract infection (UTI) are often insensitive to the bactericidal action of normal human serum (NHS) which poses a clinical problem. The swarming phenomenon is an especially important factor in cases of UTIs gained through the ascending route. Both these virulence factors are connected with the cell surface components of bacteria, including lipopolysaccharide (LPS).

OBJECTIVES

The resistance of Proteus bacilli to the bactericidal activity of NHS and the swarming phenomenon were investigated as well as the possible relationships between these virulence factors and the chemical structure of LPS.

MATERIAL AND METHODS

The research was carried out on P. penneri and P. vulgaris species. Two preparations of sera were tested with respect to the bactericidal action of NHS. The ability of bacteria to swarm was checked on broth agar plates. The length of the O-specific part of LPS was estimated after poliacrylamide gel electrophoresis (PAGE) and staining with silver nitrate.

RESULTS

Among the 62 tested Proteus strains, over 62% of Proteus vulgaris and 50% of Proteus penneri strains were sensitive to the bactericidal action of NHS. However, the number of resistant strains grew dramatically when serum with blocked complement activation via the alternative pathway was used. From 102 of the Proteus sp. Strains, only few were unable to swarm over the solid surface of the media. The remaining showed diverse ability to translocate.

CONCLUSIONS

There was no definite correlation between the chemical structure of the O-specific chains of lipopolysaccharides and sensitivity or resistance of the Proteus sp. strains to NHS. Also, no significant relationships were found between the length or the chemical structure of the O-specific chains of the bacterial LPSs and the swarming phenomenon.

Corticosterone-immune interactions during captive stress in invading Australian cane toads (Rhinella marina)

Vertebrates cope with physiological challenges using two major mechanisms: the immune system and the hypothalamic pituitary-adrenal axis (e.g., the glucocorticoid stress response). Because the two systems are tightly integrated, we need simultaneous studies of both systems, in a range of species, to understand how vertebrates respond to novel challenges. To clarify how glucocorticoids modulate the amphibian immune system, we measured three immune parameters and plasma corticosterone (CORT), before and after inflicting a stressor (capture and captive confinement) on introduced cane toads (Rhinella marina) near their invasion front in Australia. Stress increased CORT levels, decreased complement lysis capacity, increased leukocyte oxidative burst, and did not change heterologous erythrocyte agglutination. The strength of the CORT response was positively correlated with leukocyte oxidative burst, and morphological features associated with invasiveness in cane toads (relative leg length) were correlated with stress responsiveness. No immune parameter that we measured was affected by a toad's infection by a parasitic nematode (Rhabdias pseudosphaerocephala), but the CORT response was muted in infected versus uninfected toads. These results illustrate the complex immune-stress interactions in wild populations of a non-traditional model vertebrate species, and describe immune adaptations of an important invasive species.

Human disturbance alters endocrine and immune responses in the Galapagos marine iguana (Amblyrhynchus cristatus)

Anthropogenic disturbance is a relevant and widespread facilitator of environmental change and there is clear evidence that it impacts natural populations. While population-level responses to major anthropogenic changes have been well studied, individual physiological responses to mild disturbance can be equally critical to the long-term survival of a species, yet they remain largely unexamined. The current study investigated the impact of seemingly low-level anthropogenic disturbance (ecotourism) on stress responsiveness and specific fitness-related immune measures in different breeding stages of the marine iguana (Amblyrhynchus cristatus). Specifically, we found stress-induced elevations in plasma corticosterone among tourist-exposed populations relative to undisturbed populations. We also found changes in multiple immunological responses associated with stress-related effects of human disturbance, including bacterial killing ability, cutaneous wound healing, and hemolytic complement activity, and the responses varied according to reproductive state. By identifying health-related consequences of human disturbance, this study provides critical insight into the conservation of a well-known species that has a very distinct ecology. The study also broadens the foundation of knowledge needed to understand the global significance of various levels of human disturbance.

The role of complement activity in the sensitivity of Salmonella O48 strains with sialic acid-containing lipopolysaccharides to the bactericidal action of normal bovine serum

Sialic acids are important constituents of animal tissue glycoconjugates and are also present in the antigens of some bacterial strains. Capsular polysaccharides with sialic acid (NeuAc) have been extensively studied with regard to sensitivity to the bactericidal action of serum, whereas little is known in this regard about lipopolysaccharides (LPS) which contain NeuAc. Strains of Salmonella O48, able to infect animals and containing the same structures of LPS with NeuAc, were examined for their susceptibility to the bactericidal action of normal bovine serum (NBS). The strains showed varied sensitivity to the bactericidal action of NBS, which indicates that the expression of LPS containing NeuAc residues is not critical for the strains' resistance to the serum's activity. In this study the mechanisms of complement activation responsible for killing serum-sensitive Salmonella O48 rods by NBS were also established. Three such mechanisms were distinguished: activation of the classical/lectin pathways, important (decisive) in the bactericidal mechanism of complement activation, parallel activation of the classical/lectin and alternative pathways, and independent activation of the classical and lectin or the alternative pathway.

Defensins: endogenous antibiotic peptides from human leukocytes

A variety of endogenous antimicrobial peptides equip mammals, amphibians, insects and plants to defend themselves against microbial pathogens. Defensins are small peptides of mammalian cells that contain 29-35 amino acid residues, including six invariant cysteines that form three intramolecular disulphide bonds. They are produced by the sequential proteolysis of precursors that contain approximately 95 amino acids and are synthesized by several types of cells, especially the bone marrow precursors of blood neutrophils. Defensins constitute 5-7% of the total protein in human neutrophils and are present in high concentration in the azurophil granules and phagocytic vacuoles. The production of defensins by human neutrophils amounts to approximately 10 mg/kg body weight per day. In certain mammalian species lung macrophages and specialized epithelial (Paneth) cells in the small intestine also produce defensins. Defensins are complexly folded, amphipathic, rich in antiparallel beta-sheet but devoid of alpha-helical domains. Their unusually broad antimicrobial spectrum encompasses Gram-positive and Gram-negative bacteria, many fungi, mycobacteria, spirochetes and several enveloped viruses. The antimicrobial properties of defensins result from their insertion into target cell membranes and the formation of voltage-sensitive channels. Given their abundance and broad spectrum of antimicrobial activity, defensins may contribute substantially to innate resistance to infection.

On-line determination of serum bactericidal activity using recombinant luminescent bacteria

Intensity of luminescence quenching in recombinant strains of Escherichia coli with cloned lux-operones by human blood serum is directly proportional to the degree of bactericidal effect assessed by nephelometric and bacteriological methods. This correlation was most characteristic of E. coli with luminescence genes from Photobacterium leiognathi, which substantiates its use in the development of the kinetic bioluminescent method to determine of serum bactericidal activity. The possibility of using this method for evaluation of activity of classic and alternative pathways of compliment activation was demonstrated by using zymosan or EGTA-Mg(2+)-treated sera and C1-C5-deficient sera.

Measurement of respiratory burst products generated by professional phagocytes

Activation of professional phagocytes, potent microbial killers of our innate immune system, is associated with an increase in cellular consumption of molecular oxygen (O2). The burst of 02 consumption is utilized by an NADPH-oxidase to generate highly-reactive oxygen species (ROS) starting with one and two electron reductions to generate superoxide anion (O2-) and hydrogen peroxide (H2O2), respectively. ROS are strongly bactericidal but may also cause tissue destruction and induce apoptosis in other immune competent cells of both the innate and the adaptive immune systems. Thus, the development of basic techniques to measure/quantify ROS generation/release by phagocytes during activation of the respiratory burst is of great importance, and a large number of techniques have been used for this purpose. Three of these techniques, chemiluminescence amplified by luminol/ isoluminol, the absorbance change following reduction of cytochrome c, and the fluorescence increase upon oxidation of p-hydroxyphenylacetate, are described in detail in this chapter. These techniques can be valuable tools in research spanning from basic phagocyte biology to more clinically-oriented research on innate immune mechanisms and inflammation.

Modeling the reactions of superoxide and myeloperoxidase in the neutrophil phagosome: implications for microbial killing

Neutrophils kill bacteria by ingesting them into phagosomes where superoxide and cytoplasmic granule constituents, including myeloperoxidase, are released. Myeloperoxidase converts chloride and hydrogen peroxide to hypochlorous acid (HOCl), which is strongly microbicidal. However, the role of oxidants in killing and the species responsible are poorly understood and the subject of current debate. To assess what oxidative mechanisms are likely to operate in the narrow confines of the phagosome, we have used a kinetic model to examine the fate of superoxide and its interactions with myeloperoxidase. Known rate constants for reactions of myeloperoxidase have been used and substrate concentrations estimated from neutrophil morphology. In the model, superoxide is generated at several mm/s. Most react with myeloperoxidase, which is present at millimolar concentrations, and rapidly convert the enzyme to compound III. Compound III turnover by superoxide is essential to maintain enzyme activity. Superoxide stabilizes at approximately 25 microM and hydrogen peroxide in the low micromolar range. HOCl production is efficient if there is adequate chloride supply, but further knowledge on chloride concentrations and transport mechanisms is needed to assess whether this is the case. Low myeloperoxidase concentrations also limit HOCl production by allowing more hydrogen peroxide to escape from the phagosome. In the absence of myeloperoxidase, superoxide increases to >100 microM but hydrogen peroxide to only approximately 30 microM. Most of the HOCl reacts with released granule proteins before reaching the bacterium, and chloramine products may be effectors of its antimicrobial activity. Hydroxyl radicals should form only after all susceptible protein targets are consumed.

The activity of several components of the innate immune system in diploid and triploid turbot

The use of triploid fish may be of interest in research, e.g. study of how this condition affects the size and activity of cells. In addition, triploid fish are sterile and production of triploids in fish species that are marketed after reaching sexual maturity may be of economic interest. In the present study, the effects of triploidy on the activity of several components of the innate immune system of turbot (Psetta maxima L) were determined. Triploid turbot had bigger cells (erythrocytes and neutrophils) but the number of blood erythrocytes, leucocytes and thrombocytes was lower than in diploid fish. The differential cell count was similar in both types of fish. The respiratory burst and the phagocytic activities were higher in neutrophils of triploid turbot. However, because the number of neutrophils was higher in diploids, the total respiratory burst activity and the phagocytosis per microliter of blood was similar in both types of fish. No differences were found in serum complement, lysozyme or bactericidal activities. The results indicate that the activities of the humoral components of the innate immune system tested are similar in diploid and triploid fish and that the lower leucocyte number found in triploids is compensated for by higher cell activity.

Capture stress and the bactericidal competence of blood and plasma in five species of tropical birds

In wild birds, relatively little is known about intra- or interspecific variation in immunological capabilities, and even less is known about the effects of stress on immune function. Immunological assays adaptable to field settings and suitable for a wide variety of taxa will prove most useful for addressing these issues. We describe a novel application of an in vitro technique that measures the intrinsic bacteria-killing abilities of blood. We assessed the capacities of whole blood and plasma from free-living individuals of five tropical bird species to kill a nonpathogenic strain of E. coli before and after the birds experienced an acute stress. Killing invasive bacteria is a fundamental immune function, and the bacteria-killing assay measures constitutive, innate immunity integrated across circulating cell and protein components. Killing ability varied significantly across species, with common ground doves exhibiting the lowest levels and blue-crowned motmots exhibiting the highest levels. Across species, plasma killed bacteria as effectively as whole blood, and higher concentrations of plasma killed significantly better. One hour of acute stress reduced killing ability by up to 40%. This assay is expected to be useful in evolutionary and ecological studies dealing with physiological and immunological differences in birds.

Identification of alternative pathway serum complement activity in the blood of the American alligator (Alligator mississippiensis)

Incubation of different dilutions of alligator serum with sheep red blood cells (SRBCs) that had not been sensitized with antibodies resulted in concentration-dependent hemolytic activity. This hemolytic activity was not affected by the presence of ammonium hydroxide and methylamine, known inactivators of the classical complement cascade. However, the hemolytic activities were inhibited by EDTA and salicylaldoxime, indicating that the alternate pathway is primarily responsible for these activities. Immunofixation of electrophoretically-resolved alligator serum proteins with antihuman C3 polyclonal antibodies resulted in detection of a protein antigenically similar to human C3 in alligator serum. SDS-PAGE, followed by Western blot analysis, revealed the presence of two alligator serum proteins with nearly identical molecular weights as human C3alpha and C3beta. SRBC hemolysis and antibacterial activity by alligator serum was significantly reduced in the presence of antihuman C3 antibodies. The hemolytic effect of alligator serum was shown to occur rapidly, with significant activity within 5 min and maximal activity occurring at 15 min. SRBC hemolysis was also temperature-dependent, with reduced activity below 15 degrees C and above 30 degrees C. These data suggest that the antibiotic properties of alligator serum are partially due to the presence of a complement-facilitated humoral immune response analogous to that described in mammalian systems.

Normal human sera contain bactericidal IgG that binds to the oligosaccharide epitope expressed within lipooligosaccharides of Neisseria gonorrhoeae

Although more than several investigators reported the presence of antibodies in normal human sera (NHS) that bind to lipooligosaccharide (LOS) of Neisseria gonorrhoeae, the specificities of those antibodies were not fully characterized. To identify anti-LOS antibodies in NHS, we used LOS from a serum-sensitive strain, JW31R, as an affinity ligand and purified IgG from NHS that bound to JW31R LOS. The affinity purified IgG (AP-IgG) binds to the oligosaccharide (OS) moiety of both the ligand LOS and its truncated form, 15253 LOS. Lipid A could be essential for maximum expression of the carbohydrate epitope that resides on 15253 OS. We also found that AP-IgG is capable of killing a serum-sensitive strain JW31R. The present work provided direct evidence that NHS contain bactericidal antibodies specific for a site close to the inner core OS expressed on gonococcal LOS. The present results not only show that anti-LOS antibodies specific for the inner core OS could play a major role in our defense against gram-negative bacteria. But also they demonstrated that such core OS or a nearby site could be utilized as possible targets for vaccine development against microbial infections.

Green fluorescent protein-expressing Escherichia coli as a selective probe for HOCl generation within neutrophils

Escherichia coli were transformed by electroporation to introduce a plasmid harboring a GFP gene-containing vector. The fluorescence of the purified GFP isolated from the transformant was quenched by myeloperoxidase (MPO)-generated HOCl, by peroxynitrous acid (ONOOH) and by enzymatically or radiolytically generated NO(2)(.) but not by other putative neutrophil-generated oxidants. Fluorescence from the bacterium was effectively quenched by HOCl but not peroxynitrite, oxidizing radicals derived from its O-O bond homolysis, or the other oxidants under study. Exposure of serum-opsonized bacteria to human neutrophils resulted in extensive loss of GFP fluorescence; fluorescence microscopy revealed that phagocytosed bacteria were completely quenched but that bacteria remaining in the external media were unquenched. Addition of sodium azide to the medium to inhibit MPO prevented neutrophil-mediated fluorescence quenching. Because the amount of HOCl required to inhibit bacterial fluorescence was an order of magnitude greater than required to inhibit colonial growth, these results imply that sufficient HOCl was formed within the neutrophil phagosome to kill the microbe.

[Conditions that influence bacterial luminescence in the presence of blood serum]

Conditions that influence the luminescence of natural and recombinant luminescent bacteria in the presence of blood serum were studied. In general, blood serum quenched the luminescence of the marine Photobacterium phosphoreum and the recombinant Escherichia coli strains harboring the luminescent system genes of Photobacterium leiognathi, but enhanced the luminescence of the soil bacterium Photorhabdus luminescens Zm1 and the recombinant E. coli strain harboring the lux operon of P. luminescens Zm1. The quenching effect of blood serum increased with its concentration and the time and temperature of incubation. The components of blood serum that determine the degree and specificity of its action on bacterial luminescence were identified.

Effects of granulocyte colony-stimulating factor on neutrophils and inflammatory cytokines in the early stage of severe acute pancreatitis in rats

BACKGROUND

The high mortality rate of severe acute pancreatitis (SAP) is closely associated with secondary infections of pancreatic and peripancreatic tissues. It was reported that granulocyte colony-stimulating factor (G-CSF) increased the number of leukocytes and enhanced their functions. However, an inflammatory response may be enhanced by an increased number of leukocytes. Our purpose was to study the roles of G-CSF in peritoneal-exudate neutrophils and inflammatory cytokines in the early stage of experimental SAP.

METHODS

SAP was induced by injecting 0.2 ml of 3% taurocholate acid into the biliopancreatic duct in male Wistar rats. G-CSF (90 microg/kg body weight) or saline was administered 1 h before the SAP induction. The number of neutrophils and their phagocytic and bactericidal activities were evaluated, and the concentrations of tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, and IL-1beta in plasma and ascitic fluid were measured 1 h and 3 h after the SAP induction.

RESULTS

The number of peritoneal-exudate neutrophils (PENs) at 3 h was increased by G-CSF administration (81 +/- 50 x 10(5) cells/total exudate), as compared with that shown with saline administration (28 +/- 13 x 10(5) cells/total exudate; P < 0.05). The numbers of phagocytic and bactericidal neutrophils were also elevated by G-CSF administration. G-CSF administration did not increase the concentrations of TNF-alpha, IL-6, and IL-1beta in the plasma and ascitic fluid.

CONCLUSIONS

G-CSF increases the numbers of neutrophils and enhances their functions against bacteria, but it does not enhance intraabdominal and systemic inflammatory responses in the early stage of SAP.

Phagocytic and bactericidal activity and morphological parameters of blood platelets in patients with Trichinella spiralis infection

PURPOSE

The production of IgE increases in parasitic invasions, triggering local or systemic inflammatory response with the involvement of blood platelets. The aim of the study was to assess the number and morphological parameters of blood platelets as well as their phagocytic and bactericidal activity in patients with Trichinella spiralis infection. It is interesting to investigate the blood platelet response following Trichinella spiralis in order to elucidate possible effects on non-specific immunity.

MATERIAL AND METHODS

Twenty-six patients with Trichinella spiralis (before and after antiparasitic therapy) and forty healthy subjects were examined. The platelet count and morphological parameters were determined using a hematologic analyzer Technicon H-1 System. The platelet phagocytic activity was determined by measuring the percentage of phagocytizing cells and the phagocytic index. The bactericidal activity was assessed measuring the percentage of the bacteria killed by platelets and plasma. The strain Staphylococcus aureus ATCC 6538P was used for this purpose.

RESULTS

In patients infected with T. spiralis morphological parameters do not change, except for the percentage of large platelets. In the course of trichinellosis the phagocytic index of platelets is statistically significantly decreased and platelet bactericidal activity is impaired, while the bactericidal activity of the plasma is statistically significantly increased, compared to healthy subjects.

CONCLUSIONS

The present study has revealed that due to T. spiralis infection, the percentage of large, young blood platelets is decreased. The parasitic infection causes impairment of non-specific immunity through decreased bactericidal activity of blood platelets.

Effect of temperature on phagocytic activity of neutrophils

The effect of temperature on phagocytic activity of neutrophils has been evaluated. Freshly collected heparinised blood samples from young healthy volunteers were incubated with heat killed Staphylococcus aureus at 37 degrees C, 38 degrees C, 39 degrees C and 40 degrees C for 20 minutes. Some of the neutrophils engulfed some heat killed bacteria. Then the blood smears were prepared and stained by Leishman's stain. Engulfed bacteria within the neutrophils stained intensely were observed and counted to find out the phagocytic index and avidity index of the neutrophils. It was found that phagocytic index increased significantly at 38 degrees C and 39 degrees C in comparison to that of at 37 degrees C but did not show significant increase when incubated at 40 degrees C. It seems that contractile elements responsible for the movement of the neutrophils through the formation of pseudopod is more activated at higher temperature (38 degrees C and 39 degrees C) in comparison to that of at normal body temperature (37 degrees C). Temperature higher than 39 degrees C may cause impairment in enzyme function responsible for assembly and disassembly of actin and myosin filaments in the cell causing decreased movement and decreased rate of formation of psudopod resulting in decreased phagocytic activity.

Effect of heparin binding on Helicobacter pylori resistance to serum

The objective of this study was to evaluate the effect of heparin binding to Helicobacter pylori cells on their survival in the presence of fresh rabbit serum with or without active complement components. Three H. pylori strains were compared and the amounts of heparin added reflected the physiological concentrations that can be found in animal tissues. No growth of H. pylori was noted in the presence of serum. Serum with or without active complement produced a reduction in c.f.u. for strains SPM 326, CCUG 17874(T) and SS1. However, addition of heparin resulted in increased survival of bacterial cells in serum with or without active complement. It appears that heparin binding to H. pylori can prevent bacterial cell death due to the alternative complement system. Heparin binding could also protect from heated serum (complement-inactivated), indicating protection from other serum components besides complement. In vivo, the process of heparin binding could possibly result in facilitated colonization due to a higher survival rate.

Antibacterial properties of serum from the American alligator (Alligator mississippiensis)

Treatment of alligator (Alligator mississippiensis) and human serum samples with Escherichia coli resulted in a time- and concentration-dependent inhibition of bacterial proliferation. When inoculated with E. coli, alligator serum exhibited 10-fold lower bacterial survival rates after 1 h than human serum. In addition, the antibacterial spectrum of alligator serum was shown to be much broader than that of human serum, with growth inhibition occurring in 100% of bacterial strains tested (compared to only 35% for human serum). Additional results showed that the antimicrobial activities of alligator serum could be completely inhibited by preincubation with proteases, indicating the proteinaceous nature of the antimicrobial activities. Furthermore, incubation of alligator serum at 56 degrees C for 30 min (classical human serum complement inactivation conditions) obliterated all antimicrobial properties of the alligator serum. The antibacterial activities occurred relatively quickly in vitro, with significant activity occurring within 5 min of inoculation with E. coli and maximal activity at 20 min. Also, the antimicrobial activity exhibited temperature dependence, with a substantial decrease in activity below 15 degrees C. These data suggest that the antimicrobial properties of alligator serum may be due to an active serum complement system.

Bactericidal activity response of blood neutrophils from critically ill patients to in vitro granulocyte colony-stimulating factor stimulation

OBJECTIVE

Neutrophil function impairment is common in nonneutropenic critically ill patients. Whether granulocyte colony-stimulating factor (G-CSF) may be useful for preventing nosocomial infection in these patients is debated. The response of blood neutrophils from critically ill patients to G-CSF was investigated in vitro.

DESIGN AND SETTING

Prospective study, laboratory investigation in two intensive care units.

PATIENTS

52 critically ill patients without immunosuppression.

MEASUREMENTS

Neutrophils obtained from 52 patients on the 5th day of their intensive care unit stay were incubated with and without G-CSF (1, 10, 100 ng/ml). Reactive oxygen species (ROS) release and bactericidal activity against Staphylococcus aureus and Pseudomonas aeruginosa were evaluated. Plasma cytokines (interleukin 10, tumor necrosis factor alpha, and G-CSF) were measured.

RESULTS

Median values (25th-75th percentiles) indicated no stimulatory effect of G-CSF on neutrophil bactericidal activity against either organism: S. aureus, 100% (95-109) of the unstimulated condition with 1 ng/ml G-CSF, and P. aeruginosa, 102% (98-109) with 1 ng/ml G-CSF. However, wide interindividual variability was found, ranging from marked inhibition to marked stimulation. Similar variability was found for ROS release. No correlations were found between ROS release and bactericidal activities against either bacterial strain. Inhibition of neutrophil bactericidal activity by G-CSF was associated with significantly higher plasma interleukin 10 concentrations. Plasma G-CSF levels were significantly higher in patients whose neutrophil bactericidal activity was unresponsive to G-CSF, suggesting G-CSF receptor downregulation.

CONCLUSIONS

The effect of G-CSF on in vitro neutrophil bactericidal activity varied widely, depending on endogenous levels of G-CSF and was not predictable based on severity scores.

[The mechanism of bactericidal activity in phagosomes of neutrophils]

Myeloperoxidase plays the key role in antimicrobial of phagocytes. This enzyme uses hydrogen peroxide and chloride to catalyze hypochlorous acid formation. HOCl is the most probable agent in the oxygen-dependent bactericidal activity in the phagocyte phagosome. Chlorination markers indicate HOCl generation in the quantities lethal for bacteria. Enzymatic assay for myeloperoxidase indicates proceeding of other reactions involved in bactericidal activity. Superoxide integrates many activities of this kind and is important for physiological function of myeloperoxidase. Elucidation of phagosomes biochemistry can help us to understand why certain pathogens survive in such unfavorable environment.

Bactericidal capability of blood platelets in eutrophic newborns

Bactericidal activity of the blood platelets from cord blood of 69 eutrophic newborns differed in relation to sex. In female newborns we noted 8.13% killed Staphylococcus aureus ATCC 6538 P, whereas in male newborns only 2.92%. These data point to the role of platelets in unspecific defense against infections.

A critical concentration of neutrophils is required for effective bacterial killing in suspension

We have examined the effect of neutrophil concentration on killing of a clinical isolate of Staphylococcus epidermidis. Human neutrophils at concentrations varying from 10(5) to 10(7) per ml were mixed in suspension with S. epidermidis at concentrations varying from 10(3) to 10(8) colony-forming units/ml, and the concentration of viable bacteria was assayed after various times at 37 degrees C. The rate of bacterial killing depended on the concentration of neutrophils and not on the ratio of neutrophils to bacteria. Below a critical concentration of neutrophils, bacteria growth was greater than neutrophil killing of bacteria even when the ratio of neutrophils to bacteria was 100:1. We fitted the time course of bacterial concentration and its dependence on neutrophil concentration with an exponential function, the exponent of which is (-kp + g)t, where k is the second-order rate constant for bacterial killing, p is the neutrophil concentration, g is the first-order rate constant for bacterial growth, and t is time. We found that k approximately 2 x 10(-8) ml per neutrophil per min, and g approximately 8 x 10(-3)/min. Only when p is greater than g/k, which we call the critical neutrophil concentration, does the bacterial concentration fall. Under optimal assay conditions, the critical neutrophil concentration was 3-4 x 10(5) per ml, a value very close to that (< or =5 x 10(5) per ml) known to predispose humans to bacterial and fungal infections.

Influence of secondary colonizers and human plasma on the adherence of Porphyromonas gingivalis in vitro

The influence of secondary colonizers (Fusobacterium nucleatum and Actinomyces naeslundii) and the effect of human plasma on the adherence of Porphyromonas gingivalis were investigated. Hydroxyapatite (HAP) discs coated with Streptococcus sanguis were immersed in a 3H-labeled bacterial cell suspension of F. nucleatum or A. naeslundii and then in a 14C-labeled P. gingivalis cell suspension. Bacterial cells on the discs were pyrolysed to quantify the radioisotopes released. The cell numbers of secondary colonizers on the discs increased with immersion time and this, in turn, resulted in significantly elevated adherence of P. gingivalis. These two secondary colonizers had very similar positive effects on the adherence of P. gingivalis. Human plasma significantly inhibited the adherence of P. gingivalis and secondary colonizers to S. sanguis-coated HAP discs. Adherence of P. gingivalis and A. naeslundii was strongly inhibited by plasma, while that of F. nucleatum was affected the least. Treatment with plasma, after immersion of streptococcal-coated discs in individual cell suspension of secondary colonizers, also reduced subsequent adherence of P. gingivalis. The rate of decrease was much smaller in F. nucleatum. These results indicate that both F. nucleatum and A. naeslundii enhance the adherence of P. gingivalis, and that the former may play a more important role in the establishment of P. gingivalis in dental plaque where plasma-derived components are present.

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

OBJECTIVE

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

DESIGN

Open.

SETTING

University hospital.

SUBJECTS

Ten healthy subjects.

INTERVENTION

Analysis of blood samples before and after omeprazole administration.

MEASUREMENTS AND MAIN RESULTS

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

CONCLUSIONS

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

6-formylpterin intracellularly generates hydrogen peroxide and restores the impaired bactericidal activity of human neutrophils

The effects of 6-formylpterin on the impaired bactericidal activity of human neutrophils were examined ex vivo. When neutrophils isolated from fresh blood were incubated with 6-formylpterin, the intracellular production of hydrogen peroxide (H(2)O(2)) occurred. The H(2)O(2) generation by 6-formylpterin in neutrophils occurred in the presence of diphenyleneiodonium (DPI), an inhibitor of NADPH-oxidase. When neutrophils were incubated with DPI, the killing rate of catalase-positive bacteria, Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), significantly decreased. This impaired bactericidal activity of the DPI-treated neutrophils was a mimic for chronic granulomatous disease (CGD). However, the killing rate of the DPI-treated neutrophils against E. coli and S. aureus significantly increased when 6-formylpterin was administered. Since 6-formylpterin intracellularly generates H(2)O(2) independent from the NADPH-oxidase, it was considered to improve the impaired bactericidal activity of the DPI-treated neutrophils. The use of 6-formylpterin may serve as an option of therapy for CGD.

Intraoperative prostaglandin E1 improves antimicrobial and inflammatory responses in alveolar immune cells

OBJECTIVE

Anesthesia and surgery decrease antimicrobial and increase proinflammatory functions of alveolar immune cells. Thus, anti-inflammatory agents that do not further suppress antimicrobial functions are required. We tested the hypothesis that intraoperative prostaglandin E1 (PGE1) suppresses proinflammatory responses and prevents the reduction in antimicrobial responses of alveolar immune cells.

DESIGN

Prospective, randomized, controlled, double-blind study.

SETTING

University hospital.

PATIENTS

A total of 40 patients undergoing elective orthopedic surgery under propofol/fentanyl anesthesia.

INTERVENTION

In double-blind fashion, the patients received PGE1 from the beginning to the end of surgery (PGE1 group, n = 20) or nothing (control group, n = 20).

METHODS AND MAIN RESULTS

Alveolar immune cells were harvested by bronchoalveolar lavage immediately after induction of anesthesia; 2, 4, and 6 hrs after induction of anesthesia; and at the end of surgery. We measured opsonized and nonopsonized phagocytosis. Microbicidal activity was evaluated to directly kill Listeria monocytogenes in alveolar macrophages. Finally, we determined the expression of proinflammatory cytokines including interleukin (IL)-1beta, IL-8, interferon-gamma, and tumor necrosis factor-alpha, and that of anti-inflammatory cytokines (IL-4 and IL-10) by semiquantitative polymerase chain reaction. Nonopsonized and opsonized phagocytosis and microbicidal activity of alveolar macrophages decreased and the expression of genes for all pro- and anti-inflammatory cytokines increased significantly over time in both groups. Starting 2-4 hrs after induction of anesthesia, the increases in gene expression of proinflammatory cytokines were 1.5-3 times smaller in the PGE1 than in the control group. Starting 6 hrs after anesthesia, the increase in gene expression of IL-10 was 1.5-3 times greater in the PGE1 than in the control group. Intraoperative decreases in phagocytic and microbial activities were the same in the two groups.

CONCLUSION

Intraoperative PGE1 not only suppressed proinflammatory responses, but also protected antimicrobial functions of alveolar macrophages, possibly because PGE1 is mostly inactivated in the pulmonary intravascular space. Our results suggest that intraoperative PGE1 protects the pulmonary immune defense in alveolar immune cells.

Recovery of intraoperative microbicidal and inflammatory functions of alveolar immune cells after a tobacco smoke-free period

BACKGROUND

Tobacco smoking inhibits alveolar macrophage function, but cessation of smoking markedly reduces the risk of postoperative pulmonary complications. The authors therefore evaluated the effect of nonsmoking duration on both antimicrobial and inflammatory functions of alveolar macrophages during anesthesia and surgery.

METHODS

The authors studied 15 patients who had never smoked, 15 current smokers, and 41 former smokers, all of whom underwent general anesthesia. Former smokers were further allocated to one of three groups depending on their smoke-free periods: 2 months (n = 13), 3-5 months (n = 13), and 6-12 months (n = 15). Alveolar immune cells were collected by bronchoalveolar lavage immediately after induction of anesthesia, at 2 and 4 h after induction of anesthesia, and at the end of surgery. Opsonized and nonopsonized phagocytosis were measured. Microbicidal activity was determined as the ability of the macrophages to kill Listeria monocytogenes directly. Finally, we determined the expression of proinflammatory cytokines, including interleukin 1beta, interleukin 8, interferon gamma, and tumor necrosis factor alpha, and of antiinflammatory cytokines (interleukin 4 and 10) by semiquantitative polymerase chain reaction.

RESULTS

Nonopsonized and opsonized phagocytosis and microbicidal activity of alveolar macrophages (antimicrobial functions) decreased 20-50%, and the expression of genes for all proinflammatory and antiinflammatory cytokines increased 3-30-fold over time in all groups. Starting 4 h after induction of anesthesia, the decreases in antimicrobial functions were 1.5-3 times greater in current and former smokers (2 months' abstinence) than in patients who had never smoked. Starting 4 h after anesthesia, the increase in expression of all cytokines, except interleukin 8, was twofold to fivefold less in current and former smokers (2-6 months' abstinence) than in patients who had never smoked.

CONCLUSION

Our data suggest that former smokers may have a limited ability to mount effective pulmonary immune defenses for long as 6 months after stopping cigarette use.

A comparative study of mammalian and reptilian alternative pathway of complement-mediated killing of the Lyme disease spirochete (Borrelia burgdorferi)

The potential bactericidal activity of the alternative complement pathway of mammalian and reptilian sera to Borrelia burgdorferi sensu stricto (s.s.) was evaluated in vitro. Complement-mediated killing was observed when cultured spirochetes were inoculated into sera from the western fence lizard (Sceloporus occidentalis) and from the southern alligator lizard (Elgaria multicarinata), but not when they were inoculated into serum from either the deer mouse (Peromyscus maniculatus) or from humans. Spirochetes were still alive after 4 hr in lizard serum that had been preheated at 56 C for 30 min to inactivate complement. Furthermore, when lizard serum was chelated with 10 mM ethylenediaminetetraacetic acid to block all complement activation, borreliacidal activity was arrested. When lizard serum was chelated with 10 mM ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid plus 4 mM MgCl2 to block only classical complement pathway activation, >85% of spirochetes were immobilized within 1 hr. Differences in B. burgdorferi s.s. mortality were not observed when chelators with or without MgCl2 were added to serum from either deer mice or humans. Proteins comprising the alternative complement pathway are responsible for the borreliacidal activity observed in the blood of S. occidentalis and E. multicarinata.

Antioxidative properties of serotonin and the bactericidal function of polymorphonuclear phagocytes

We investigated the antioxidative properties of platelet-released serotonin on the bactericidal function of polymorphonuclear neutrophils (PMN) since there is a surprising co-incidence of low blood serotonin and an increased rate of infections. The antioxidative properties of serotonin were demonstrated by its suppressive effects on phagocytosis-associated, luminol-enhanced chemiluminescence (CL). The bactericidal activity of PMN was determined by a microbiological assay using opsonized Staphylococcus aureus. Serotonin suppresses luminol-enhanced chemiluminescence in a dose-dependent manner indicating an interaction with reactive oxygen species, which are responsible for effective bacterial killing during the phagocytosis-associated "respiratory burst". The modulation of the bactericidal function of PMN by serotonin is complex and depends upon the amount of serotonin: at concentrations normally present at sites of tissue injury and consecutive thrombus formation (10(-6) to 10(-5) M) bacterial killing increases by about 50%. In contrast, at pharmacological concentrations (10(-3) to 10(-2) M) an adverse effect can be observed: the elimination of opsonized S. aureus is reduced by 30 to 90%. Exogenous serotonin is capable of modulating important biological functions of human PMN in vitro. At appropriate concentrations, the antibacterial defence improves significantly probably due to reduced autooxidation, whereas higher concentrations counteract an efficient bacterial killing.

Complement defects in aged mice compromise phagocytosis of Pseudomonas aeruginosa

PURPOSE

The role of complement in phagocytosis and killing of P. aeruginosa was examined using serum from aged vs young donor mice.

METHODS

Phagocytosis, complement hemolytic and microbicidal assays were used.

RESULTS

Serum from young donor mice contained a heat-labile factor which significantly enhanced phagocytic activity of cells from young mice compared with similarly treated aged donor serum. Use of cobra venom factor (CVF) to destroy C3 and the terminal complement components in serum from young or aged donor mice also significantly decreased the phagocytic activity of young cells. EGTA treatment of young or aged donor serum, to activate the alternative pathway and selectively inhibit activation of the classical pathway, resulted in a significant decrease in phagocytosis by young cells in the presence of donor serum from either group. Alternative pathway mediated hemolysis also was measured and was significantly reduced in aged vs young donor serum. PMN microbicidal activity was tested using cells from young mice in the presence of aged vs young donor serum, but no significant differences were noted.

CONCLUSION

These data provide evidence that defects in the alternative pathway of complement in the serum of aged animals lead to decreased phagocytic activity of cells from young mice, but not impaired bacterial killing.

Membrane permeabilization by thrombin-induced platelet microbicidal protein 1 is modulated by transmembrane voltage polarity and magnitude

Thrombin-induced platelet microbicidal protein 1 (tPMP-1) is a small, cationic peptide generated from rabbit platelets when they are exposed to thrombin in vitro. It has potent microbicidal activity against a broad spectrum of bacterial and fungal pathogens, including Staphylococcus aureus. Previous in vitro studies involving whole staphylococcal cells and planar lipid bilayers (as artificial bacterial membrane models) suggested that membrane permeabilization by tPMP-1 is voltage dependent (S.-P. Koo, M. R. Yeaman, and A. S. Bayer, Infect. Immun. 64:3758-3764, 1996; M. R. Yeaman, A. S. Bayer, S. P. Koo, W. Foss, and P. M. Sullam, J. Clin. Investig. 101:178-187, 1998). Thus, the aims of the present study were to specifically characterize the electrophysiological events associated with membrane permeabilization by tPMP-1 by using artificial planar lipid bilayer membranes. We assessed the influence of transmembrane voltage polarity and magnitude on the initiation and modulation of tPMP-1 membrane permeabilization at various concentrations of tPMP-1 (range, 1 to 100 ng/ml) added to the cis side of the membranes. The incidence of membrane permeabilization induced by tPMP-1 at all of the concentrations tested was more frequent at -90 mV than at +90 mV. It is noteworthy that membrane permeabilization due to 1-ng/ml tPMP-1 was successfully initiated at -90 mV but not at +90 mV. Further, the mean onset times of induction of tPMP-1 activity were comparable under the various conditions. Modulation of ongoing membrane permeabilization was dependent on voltage and tPMP-1 concentration. Membrane permeabilization at a low tPMP-1 concentration (1 ng/ml) was directly correlated with trans-negative voltages, while a higher tPMP-1 concentration (100 ng/ml) induced conductance which was more dependent on trans-positive voltages. Collectively, these data indicate that the mechanism of tPMP-1 microbicidal activity at the bacterial cytoplasmic membrane may involve distinct induction and propagation stages of membrane permeabilization which, in turn, are modulated by transmembrane potential, as well as peptide concentration.

Growth inhibitory and bactericidal efficacy of sera from Lyme borreliosis patients on B. burgdorferi strains

Two B. afzelii strains EB1 and FEM1, classified in normal human sera (NHS) as serum-resistant, and an intermediate serum-sensitive B. burgdorferi s.s. strain 297, were tested in regard of their serum sensitivity in immune sera (IS) of patients at all stages of Lyme borreliosis by a growth inhibition assay (GIA). Fifty-four per cent (13/24) of the tested IS were GIA positive, while the sera of patients in stage III disease inhibited the growth more frequently than did the patients with sera of stage II or stage I disease. Growth inhibition was predominantly directed against strain FEM1 (12/24), less against strain EB1 (4/24) and strain 297 (2/24). A growth inhibiting effect on two strains was only detectable for two IS and merely one stage III serum inhibited all three strains. Positive results in the GIA required fresh serum and resulted in the killing of the borreliae. The detection of the deposited complement components C3 and C9 on the surfaces of the inhibited strains by means of immunofluorescence assays confirmed the role of complement. In Westernblot analyses of strain FEM1, it was striking that GIA-positive IS reacted 3- to 5-fold more often with proteins of molecular masses of 48.9-, 38.6-, 27.5-, 25-, 23.1- (OspC), 21.7-, and 16-kDa, than did GIA-negative IS. Furthermore, two proteins of approximately 20- and 31.2-kDa reacted exclusively with GIA-positive IS. Antibodies reacting with these proteins could play a role in the growth inhibition of NHS-resistant borrelial strains, OspC.

Effects of maximal exercise on natural killer (NK) cell cytotoxicity and responsiveness to interferon-alpha in the young and old

We investigated the effects of a graded maximal exercise treadmill test on natural killer (NK) cell number, activity, and responsiveness to interferon-alpha (IFN-alpha) in young (22+/-0.7 yrs) and elderly (65+/-0.8 yrs) sedentary subjects. NK cell cytotoxicity (NKCC) was determined using Ficoll purified peripheral blood mononuclear cells (PBMCs) by a 51Cr release assay against NK-sensitive (K562) and NK-insensitive (Daudi) target cells at various effector:target (E:T) ratios before and immediately after exercise. PBMCs were incubated with rhu IFN-alpha (125 and 250u/10(6) PBMCs) or without for 2 hrs before addition to the 51Cr release assay. There were no differences in unstimulated NKCC against K562 or Daudi targets between the old and the young despite significantly (p=.01) higher percentages of CD56+ NK cells (21.1+/-2.3% in old vs 12.5+/-2.5% in young, pre-exercise). IFN-alpha increased NKCC versus both targets, and NK cells from old subjects were hyporesponsive to IFN-alpha stimulation; this was especially evident at low E:T ratios versus Daudi cells. Maximal exercise significantly increased (50-200%) unstimulated NKCC versus K562 and Daudi targets similarly in both young and old and increased the percentage of CD56+ cells in the PBMC fraction to 33.3+/-3.7% and 23.3+/-3.6% in old and young, respectively. We found a significant correlation between %CD56+ and basal NKCC versus K562s and Daudi cells in the young (i.e., r=.55; p=.02 vs K562s), but not the old (i.e., r=.20; p=.29 vs K562s) subjects. This indicates that, in the young, part of the exercise-induced increase in NKCC is due to an increase in NK cell number. Maximal exercise did not affect unstimulated per cell killing of K562s, but tended to increase per cell killing of Daudis. These results indicate that CD56+ cells from old subjects have an intrinsic defect in their ability to perform cytolysis and respond to IFN-alpha. Furthermore, a single bout of maximal exercise increases NKCC and CD56+ cell number similarly in both young and old subjects regardless of the target cell used.

Identification of human beta-defensin-2 in respiratory tract and plasma and its increase in bacterial pneumonia

Human beta-defensin-2 (hBD-2), a novel antimicrobial peptide, was originally isolated from human skin. We found that synthetic hBD-2 has high bactericidal activity against Escherichia coli under conditions nearly the same as in human bronchial airway surface liquid. We prepared an antiserum against hBD-2 and established a highly sensitive radioimmunoassay (RIA). Reverse-phase high-performance liquid chromatography coupled with the RIA showed that hBD-2 in patients with human lung, bronchoalveolar lavage flid, and plasma. The plasma concentration of hBD-2 in patients with bacterial pneumonia was 32.1 +/- 3.7 fmol/ml (mean +/- SE), 3.9-fold that of normal individuals. By reverse transcription-polymerase chain reaction, the hBD-2 gene transcript was detected in the respiratory epithelial surface of human lung. Human beta-defensin-2 seems to function in airway mucosal defense. Our findings provide a clue to elucidate its pathophysiological significance in respiratory infection.

Cefonicid 'restores' the depressed activities of polymorphonuclear cells from chronic haemodialysis patients and renal transplant recipients in vitro

BACKGROUND

Chronic haemodialysis patients and renal transplant recipients are highly susceptible to infection characterized by high morbidity and mortality and related to an impairment of the phagocytic response.

SUBJECTS AND METHODS

In order to elucidate how cefonicid, a cephalosporin with a broad spectrum of activity and once-daily dosage, influences this phagocytic response, the effects of the drug upon the functions of human PMNs from both healthy individuals and immunocompromised patients were investigated.

RESULTS

In vitro, PMNs from haemodialysed patients and renal transplant recipients showed a diminished phagocytic efficiency with reduced phagocytosis and bactericidal activity towards intracellular Klebsiella pneumoniae when compared with that seen in PMNs from healthy subjects. Cefonicid significantly affected the activity of PMNs from healthy volunteers, resulting in either an increased percentage of ingested klebsiellae or a reduced intracellular bacterial load when compared with the control, drug-free system. When cefonicid was added to PMNs from uraemic patients a pattern similar to that observed with phagocytes from healthy subjects was detected: the antibiotic was able to 'restore' the depressed primary functions of PMNs, resulting in a significant increase in both phagocytosis and killing activity.

CONCLUSIONS

Cefonicid, with its several immunoproperties observed in this study, possesses interesting beneficial properties which make it suitable for the treatment of infections in patients with impaired components of the immune system.

Neonatal neutrophil inflammatory responses: parallel studies of light scattering, cell polarization, chemotaxis, superoxide release, and bactericidal activity

Neutrophil dysfunction among newborn infants, especially those born prematurely, is well recognized, but the mechanism responsible for this phenomenon is yet to be clarified. In this study, we evaluated the stimulus response coupling in neutrophils from 90 healthy newborns and 96 healthy adults in an effort to establish whether defective neonatal neutrophil function is a result of impaired signal perception or immature responsiveness. Measurement of rapid- and slow-light scattering responses (LSR) to 1 microM FMLP stimulation revealed that neonatal neutrophils have about one-half the corresponding responsiveness of adult cells (rapid-LSR: 6.1 +/- 3.1 arbitrary light intensity units vs. 12.0 +/- 2.8, P < .001; and slow-LSR: 5.0 +/- 2.5 vs. 9.1 +/- 2.0; P < .001). The same markedly reduced activity was observed in newborn neutrophil chemotaxis and bactericidal activity in comparison with adult cells. Nevertheless, low FMLP concentrations (less than 1 nM) induced no difference in cell polarization between newborn and adult neutrophils, yet at higher FMLP concentrations, the newborn revealed significantly reduced cell polarization. Our data suggest that newborn infants bear a fully functional FMLP signal perception but lack the full capacity of inflammatory responsiveness.

Evaluation of the patient with recurrent bacterial infections

Recurrent bacterial infection is a complaint encountered regularly in the course of both adult and pediatric care. Defects of neutrophils and monocytes are most commonly associated with recurrent infection, but abnormalities of immunoglobulins and complement must be considered. Defensins, small antibacterial peptides, have been implicated recently in some of the infectious diathesis of cystic fibrosis. A thorough history and physical examination focused on severity, sequelae, and microbiology of infections can usually determine whether a patient needs further evaluation. The diseases and syndromes most frequently associated with recurrent infection are presented, along with discriminating clinical, pathologic, and microbiologic features.

Influence of blood transfusion on bactericidal activity of human leukocytes and sera against Yersinia enterocolitica and Salmonella typhimurium

Patients undergoing joint surgery and blood transfusion were studied. Serum and leukocyte bactericidal tests in vitro against Salmonella typhimurium and Yersinia enterocolitica were carried out preoperatively as well as on the 1st, 3rd and 7th days after the operation. The serum complement (C3 and C4) concentrations were determined at the same intervals. It was found that after blood transfusion the bactericidic activity of sera and the serum C3 complement concentrations were increased. In contrast the killing ability of leukocytes was suppressed.

Antimicrobial protection of the mouse testis: synthesis of defensins of the cryptdin family

We report the synthesis by mouse testicular cells of antibiotic peptides related to the defensins secreted by the Paneth cells of the intestinal epithelium. A Sertoli cell-derived line (15P-1), Sertoli cells in primary cultures, and explanted testicular tissue in culture medium were observed to release protease-sensitive material with a broad-spectrum antibacterial activity. The activity of 15P-1 culture medium was increased 10- to 50-fold in the presence of fractions enriched in round spermatids and of nerve growth factor. Two series of results suggest that this activity may correspond to the release by testicular cells of defensin peptides, and specifically, of peptides of the cryptdin family first identified in the Paneth cells of intestinal crypts. First, a characteristic nucleotide sequence corresponding to the conserved first exon of the mouse cryptdin and cryptdin-related (CRS) genes was evidenced in the RNA of 15P-1 cells and of the testis. Second, immunohistochemical analysis demonstrated the presence of cryptdins of the cryp-1, -2, -3, -6 group in 15P-1 cells, and identified two distinct localizations in the testis. Inside the seminiferous tubule, these cryptdins were found accumulated in Sertoli cells at stages corresponding to the maturation of spermatids. In the interstitial space, Leydig cells also contained immunoreactive cryptdins.

Studies on polymorphonuclear leukocyte bactericidal function III: the role of extracellular matrix proteins

We investigated the effect of the extracellular matrix proteins fibronectin (Fn) and laminin (Ln) on polymorphonuclear leukocytes (PMN) bactericidal activity. Adherence of PMN to increasing concentrations of Ln significantly increased the killing of Escherichia coli after 240 min of adherence, while fibronectin significantly increased PMN staphlacidal activity after 240 min of adherence. The addition of IL-1beta and IL-8 but not TNF-alpha increased PMN bactericidal activity against E. coli when PMN were adhered to Ln, while TNF-alpha and IL-8 increased PMN bactericidal activity against Staphylococcus aureus when PMN were adhered to Ln. TNF-alpha increased PMN killing of E. coli when PMN were adhered to Fn, while only IL-1beta increased the killing of S. aureus when PMN were adhered to FN. Anti-VLA-3 (alpha3/beta1) monoclonal antibodies (mAbs) inhibited the effect of Ln on PMN bactericidal activity, while anti-VLA-5 (alpha5/beta1) mAbs inhibited the effect of Fn on PMN bactericidal activity. Progressive cross-linkage of these two receptors led to a dose-dependent reduction in PMN bactericidal activity for both pathogens when PMN were adhered to Ln or Fn, respectively. These results demonstrate that extracellular matrix proteins +/- exogenously added cytokines have the capacity to regulate PMN bactericidal activity. The signals sent by these matrix proteins to increase PMN bactericidal activity are transduced primarily via separate alpha subunits of the beta1 integrin complex. Stimulation of these receptors might lead to potential upregulation of PMN bactericidal activity which would be potentially advantageous in vivo at sites of infection.

Wound hypoxia and acidosis limit neutrophil bacterial killing mechanisms

BACKGROUND

"Respiratory burst" activity, ie, O2- production, is dependent on PO2, temperature, pH, and glucose concentrations within the physiologic range.

OBJECTIVES

To determine whether environmental conditions characteristic of wounds may limit human neutrophil respiratory burst metabolism and to clarify the degree to which bactericidal oxidant production depends on local PO2.

METHODS

Human blood and wound neutrophils were stimulated with phorbol myristate acetate. Oxygen consumption and superoxide production were measured over a range of 30 to 300 mm Hg PO2, 0 to 40 mmol/L glucose, pH 6.0 to 8.0, and 30 degrees C to 37 degrees C. The apparent Michaelis Menten constant for oxidant production with respect to PO2 was calculated.

RESULTS

Oxygen consumption and O2- production were dependent on PO2 throughout the range tested. Half-maximal oxidant production occurred in the range of 45 to 80 mm Hg PO2 and maximal at PO2 higher than 300 mm Hg. These data agree with the highest previous estimates. Oxidant generation was also dependent on pH, temperature, and glucose concentration, but to a lesser extent.

CONCLUSIONS

Leukocyte bacterial killing capacity as measured by oxygen consumption and superoxide production are substantially impaired at the low oxygen tensions often found in wounds. Changes in pH, temperature, and glucose concentration have lesser but nonetheless significant consequences. The data provide a plausible mechanism for the vulnerability of some wounds to infection and for the previous finding that increasing oxygen tension at wound sites enhances bactericidal function. Thus, the data serve as a basis for future studies on prevention of wound infection.

Studies on polymorphonuclear leukocyte bactericidal function: II. The role of oxidative stress

We have previously detailed the effects of exogenous cytokines (IL-1 beta, TNF-alpha, and IL-8) on polymorphonuclear leukocyte (PMN) bactericidal function during normoxia. In these studies, we have investigated the effects of hypoxia +/- reoxygenation independently and with IL-1 beta, TNF-alpha, and IL-8 on PMN bactericidal activity. Hypoxia in and of itself did not significantly alter PMN bactericidal activity against Escherichia coli or Staphylcoccus aureus; however, after 2 h of reoxygenation (H/R), PMN bactericidal activity against E. coli was significantly reduced compared with levels seen after 2 h of hypoxia. Similar to what was observed during normoxia, TNF-alpha, IL-1 beta, and IL-8 increased PMN bactericidal activity during hypoxia compared with buffer control PMN for S. aureus but not E. coli after 4 h of hypoxia. Following H/R, neither TNF-alpha, IL-1 beta, nor IL-8 reversed the decline in bactericidal activity induced by reoxygenation alone. Monoclonal antibodies that blocked the functional epitope of particular cytokine receptors demonstrated that during both hypoxia and H/R IL-1 beta R type I, IL-8R type A, and TNF-alpha R p60 were the predominant receptors responsible for mediating the bactericidal effect of the cytokines. During hypoxia and H/R, the addition of exogenous cytokines did prevent the fall in bactericidal activity seen as PMN: target ratios decreased. The decline in bactericidal activity following H/R was mediated in part by reduced phagocytosis of serum-opsonized bacteria following H/R. These results demonstrated that oxidative stress in the form of hypoxia +/- reoxygenation independently modulate the effect of exogenously added cytokines on PMN bactericidal capability.

Studies on polymorphonuclear leukocyte bactericidal function: the role of exogenous cytokines

We investigated the effects of exogenous cytokines (interleukin (IL)-8, tumor necrosis factor (TNF)-alpha, and IL-1 beta) on polymorphonuclear neutrophil (PMN) bactericidal activity against both Staphylococcus aureus and Escherichia coli. Both baseline and IL-8-stimulated PMN bactericidal activity against E. coli, but not against S. aureus, declined significantly from 0 to 240 min. The decline in bactericidal activity was prevented by TNF-alpha, but not IL-1 beta. Bactericidal activity against both E. coli and S. aureus declined as PMN:target ratios went from 20:1 to 5:1. TNF-alpha and IL-1 beta preserved bactericidal activity even at a 5:1 PMN:target ratio against E. coli, whereas all three cytokines preserved bactericidal activity at a 5:1 PMN:target ratio against S. aureus. Dose-response curves demonstrated significant increases in bactericidal activity with physiologically relevant concentrations of cytokines (IL-8: .1-10 ng/mL; TNF-alpha: 1-10(2) U/mL; and IL-1 beta: 0-10 ng/mL). Binding of cytokine receptors with monoclonal antibodies directed against IL-8R Type A, TNF-alpha R (p60) or (p80), and IL-1 beta R Type I significantly reduced the effect of individual cytokines on PMN bactericidal activity. Inhibition of terminal, but not proximal, products of the PMN oxidative burst significantly reduced the effect of exogenous cytokines on PMN bactericidal activity. These results demonstrate that individual cytokines at relatively low concentrations enhance PMN bactericidal activity via oxidant-dependent mechanisms and that inhibiting cytokine functions may not be advantageous at infectious foci in vivo.

Impaired bacterial clearance after activation of the complement and coagulation systems

The aim of this study was to investigate the influence of the activation of the complement and coagulation systems on bacterial clearance and killing capacity of the reticuloendothelial system in rabbits. To enable quantification of the clearance process, defined numbers of exogenous Escherichia coli (1.3 x 10(8) colony-forming units) were injected intravenously, after complement activation with inulin-activated rabbit serum (n = 6), after complete defibrination with the snake toxin ancrod (n = 6), and in sham-operated animals (controls, n = 6). During the following 180 min observation period, parameters monitored were arterial pressure, fibrinogen, blood gases, and bacterial counts in blood and tissue samples of liver, kidney, spleen, and lung. Defibrination produced a significant delay in blood clearance (p < .05) compared with controls, coupled with up to four times higher bacterial counts in organ homogenates. Complement activation did not affect bacterial elimination kinetics, but was associated with accumulation of E. coli in lung and kidney (up to 100-fold of control values, p < .001). The impaired bacterial clearance associated with increased organ colonization after activation of the complement and coagulation systems reflect reticuloendothelial system dysfunction, thus pointing toward a weaker resistance against bacterial infection.