Characterization of mannose receptor-dependent phagocytosis mediated by Mycobacterium tuberculosis lipoarabinomannan

The macrophage mannose receptor (MR) along with complement receptors mediates phagocytosis of the M. tuberculosis virulent strains Erdman and H37Rv. We have determined that the terminal mannosyl units of the M. tuberculosis surface lipoglycan, lipoarabinomannan (LAM), from the Erdman strain serve as ligands for the MR. The biology of the MR (receptor binding and trafficking) in response to phagocytic stimuli is not well characterized. This study analyzes the MR-dependent phagocytosis mediated by Erdman LAM presented on a 1-micron-diameter phagocytic particle. Erdman LAM microspheres exhibited a time- and dose-dependent rapid increase in attachment and internalization by human monocyte-derived macrophages (MDMs). In contrast, internalization of LAM microspheres by monocytes was minimal. Microsphere internalization by MDMs was visualized and quantitated by immunofluorescence and confocal and electron microscopy and resembled conventional phagocytosis. Phagocytosis of LAM microspheres by MDMs was energy, cytoskeleton, and calcium dependent and was mannan inhibitable. Trypsin treatment of MDMs at 37 degrees C, which depleted surface and recycling intracellular pools of the MR, reduced the subsequent attachment of LAM microspheres. Trypsin treatment at 4 degrees C allowed for subsequent recovery of LAM microsphere phagocytosis at 37 degrees C by recycled MRs. Pretreatment of MDMs with cycloheximide influenced LAM microsphere phagocytosis to only a small extent, indicating that MR-dependent phagocytosis of the microspheres was occurring primarily by preformed recycled receptors. This study characterizes the requirements for macrophage phagocytosis of a LAM-coated particle mediated by the MR. This model will be useful in further characterization of the intracellular pathway taken by phagocytic particles coated with different LAM types in macrophages following ingestion.     

Clathrin-coated pit-associated proteins are required for alveolar macrophage phagocytosis

During phagocytosis, phagocytic receptors and membrane material must be inserted in the pseudopod membrane as it extends over the phagocytic target. This may require a clathrin-mediated recycling mechanism similar to that postulated for leading edge formation during cell migration. To investigate this possibility, liposomes were used to deliver to intact rat alveolar macrophages (AMs): 1) Abs to clathrin, clathrin adaptor AP-2, and hsc70, and 2) amantadine. Phagocytosis was assayed by fluorometric and colorimetric techniques. Liposome-delivered Abs to clathrin and AP-2 inhibited AM phagocytosis of zymosan-coated, fluorescent liposomes from 16.3+/-0.3 to 5.8+/-0.3, and 10.1+/-0.9 to 4.8+/-0.2 liposomes/cell (p<0.01). Similarly, liposome-delivered Ab to clathrin also inhibited AM phagocytosis of IgG-opsonized RBCs from 11.7+/-1.7 to 3.8+/-0.7 RBCs/cell (p<0.01). Amantadine, which blocks the budding of clathrin-coated vesicles, inhibited phagocytosis from 13.8+/-0.8 to 5.7+/-0.6 (p<0.01). Ab blockade of hsc70, which catalyzes clathrin turnover, also inhibited phagocytosis from 9.1+/-0.5 to 4.3+/-0.2 (p<0.01). These findings suggest that clathrin-mediated receptor/membrane recycling is required for phagocytosis.     

Effect of phagocytosis on the reduced soluble sulfhydryl content of human granulocytes

The role of reduced glutathione in relation to hexose monophosphate shunt activity and peroxide detoxification has been well established in human erythrocytes. Less is known about the content of reduced glutathione in phagocytic leukocytes and the changes that occur during functional activity. We have measured the reduced sulfhydryl content of normal resting human granulocytes and of cells isolated from a patient with chronic granulomatous disease. Normal cells and those from the patient with chronic granulomatous disease contained similar concentrations of reduced sulfhydryls. Stimulation of a phagocytic response by incubation with opsonized zymosan particles resulted in prompt and nearly complete depletion of intracellular glutathione from normal granulocytes. This fall in reduced glutathione concentration was dependent on the phagocytic load. Exposure of chronic granulomatous disease granulocytes to a similar phagocytic load resulted in a slower and less complete fall in reduced glutathione. In normal cells, those from the chronic granulomatous disease patient, and those from an obligate carrier of the disease, the decrement in reduced glutathione during phagocytosis was correlated with oxidation of 14C-1-glucose and 14C-formate, nitroblue tetrazolium reduction, and the chemiluminescence phenomenon.     

The validity of a nursing assessment and monitoring of signs and symptoms scale in ICU and non-ICU patients

PURPOSE: This study examined the validity of medical-record-based nursing assessment and monitoring of signs and symptoms (nursing surveillance) in predicting patients who were admitted to ICUs and those admitted to non-ICUs. The association of this assessment and monitoring with differences in an intermediate patient outcome, instability at discharge, was also explored. Patients admitted to either setting with a diagnosis of acute myocardial infarction, cerebrovascular accident, congestive heart failure, or pneumonia, were included in the study. METHOD: A secondary analysis was carried out using a subset of data originally collected for a quality-of-care study. Data from the medical records of 11,246 patients (52% female, 48% male) with a mean age of 76.4 years were used in the present study. RESULTS: ICU patients (n = 3969) were found to have a longer length of stay and to be sicker on admission than non-ICU patients (n = 7277). Overall, patients in the ICU received significantly higher nursing assessment and monitoring of signs and symptoms scores than non-ICU patients. Nursing assessment and monitoring of signs and symptoms scores were lower for patients discharged with greater instability for three of the four diseases (cerebrovascular accidents, congestive heart failure, and pneumonia).     

A requirement for phosphatidylinositol 3-kinase in pseudopod extension

Phagocytosis requires actin assembly and pseudopod extension, two cellular events that coincide spatially and temporally. The signal transduction events underlying both processes may be distinct. We tested whether phagocytic signaling resembles that of growth factor receptors, which induce actin polymerization via activation of phosphatidylinositol 3-kinase (PI 3-kinase). Fcgamma receptor-mediated phagocytosis was accompanied by a rapid increase in the accumulation of phosphatidylinositol 3,4,5-trisphosphate in vivo, and addition of wortmannin (WM) or LY294002, two inhibitors of PI 3-kinase(s), inhibited phagocytosis but not Fcgamma receptor-directed actin polymerization. However, both compounds prevented maximal pseudopod extension, suggesting that PI 3-kinase inhibition produced a limitation in membrane required for pseudopod extension. Availability of plasma membrane was not limiting for phagocytosis, because blockade of ingestion in the presence of WM was not overcome by reducing the number of particles adhering to macrophages. However, decreasing bead size, and hence the magnitude of pseudopod extension required for particle engulfment, relieved the inhibition of phagocytosis in the presence of WM or LY294002 by up to 80%. The block in phagocytosis of large particles occurred before phagosomal closure, because both compounds inhibited spreading of macrophages on substrate-bound IgG. Macrophage spreading on IgG was accompanied by exocytic insertion of membrane from an intracellular source, as measured by the dye FM1-43. These results indicate that one or more isoforms of PI 3 kinase are required for maximal pseudopod extension but not phagocytosis per se. We suggest that PI 3-kinase is required for coordinating exocytic membrane insertion and pseudopod extension.     

Characterization of iron-dependent endogenous superoxide dismutase of Plasmodium falciparum

The characterization of a new mAb, named 2F4/11, specific for porcine myelomonocytic cells is described. This mAb immunoprecipitates a non-covalently linked heterodimer of 155,000/95,000, which is expressed by granulocytes, monocytes and tissue macrophages but not by lymphocytes, erythrocytes or platelets. Immunoblot analysis localizes the 2F4/11 epitope on the largest subunit of the heterodimer. Mab 2F4/11 is able to block phagocytosis of complement-opsonized zymosan particles by PMN granulocytes and alveolar macrophages, as well as adherence to plastic surfaces of PMA-activated PMN. Together, these results suggest that mAb 2F4/11 recognizes the CD11b or alpha chain of the porcine complement type 3 receptor (CR3).     

Prostaglandin E2 secretion, cell maturation, and CD14 expression by monocyte-derived macrophages from localized juvenile periodontitis patients

Free eicosapentaenoic acid (EPA) was found to inhibit dose dependently the chemiluminescence of human neutrophil granulocytes phagocytosing zymosan and their chemotaxis induced by C5a-containing zymosan-activated serum (ZAS) and platelet-activating factor. Rigidification of plasma membranes in the ZAS-treated cells could be observed by measuring the fluorescence anisotropy. The cells were labeled by 3-[p-(6-phenyl-1,3,5-hexatrienoil) phenyl] propionic acid, reporting plasma membrane for determination of membrane fluidity. In resting, nonstimulated neutrophils, EPA dose dependently increased the fluidity of plasma membrane. In zymosan-activated cells, however, after a short fluidization, the basic effect of EPA was a rigidification compared to very low fluorescence anisotropy values of activated control cells. This diminished fluidity, increased membrane stability of plasma membranes can be one of the reasons for the decreased functions (phagocytosis and chemotaxis) of human EPA-treated neutrophils.     

Coiling phagocytosis of trypanosomatids and fungal cells

Coiling phagocytosis has previously been studied only with the bacteria Legionella pneumophila and Borrelia burgdorferi, and the results were inconsistent. To learn more about this unconventional phagocytic mechanism, the uptake of various eukaryotic microorganisms by human monocytes, murine macrophages, and murine dendritic cells was investigated in vitro by video and electron microscopy. Unconventional phagocytosis of Leishmania spp. promastigotes, Trypanosoma cruzi trypomastigotes, Candida albicans hyphae, and zymosan particles from Saccharomyces cerevisiae differed in (i) morphology (rotating unilateral pseudopods with the trypanosomatids, overlapping bilateral pseudopods with the fungi), (ii) frequency (high with Leishmania; occasional with the fungi; rare with T. cruzi), (iii) duration (rapid with zymosan; moderate with the trypanosomatids; slow with C. albicans), (iv) localization along the promastigotes (flagellum of Leishmania major and L. aethiopica; flagellum or posterior pole of L. donovani), and (v) dependence on complement (strong with L. major and L. donovani; moderate with the fungi; none with L. aethiopica). All of these various types of unconventional phagocytosis gave rise to similar pseudopod stacks which eventually transformed to a regular phagosome. Further video microscopic studies with L. major provided evidence for a cytosolic localization, synchronized replication, and exocytic release of the parasites, extending traditional concepts about leishmanial infection of host cells. It is concluded that coiling phagocytosis comprises phenotypically similar consequences of various disturbances in conventional phagocytosis rather than representing a single separate mechanism.     

Phagocytosis of rod outer segments by retinal pigment epithelial cells requires alpha(v)beta5 integrin for binding but not for internalization

Phagocytosis of shed photoreceptor rod outer segments (ROS) by the retinal pigment epithelium (RPE) is essential for retinal function. Here, we demonstrate that this process requires alpha(v)beta5 integrin, rather than alpha(v)beta3 integrin utilized by systemic macrophages. Although adult rat RPE expressed both alpha(v)beta3 and alpha(v)beta5 integrins, only alpha(v)beta3 was expressed at birth, when the retina is immature and phagocytosis is absent. Expression of alpha(v)beta5 was first detected in RPE at PN7 and reached adult levels at PN11, just before onset of phagocytic activity. Interestingly, alpha(v)beta5 localized in vivo to the apical plasma membrane, facing the photoreceptors, and to intracellular vesicles, whereas alpha(v)beta3 was expressed basolaterally. Using quantitative fluorimaging to assess in vitro uptake of fluorescent particles by human (ARPE-19) and rat (RPE-J) cell lines, alpha(v)beta5 function-blocking antibodies were shown to reduce phagocytosis by drastically decreasing (85%) binding of ROS but not of latex beads. In agreement with a role for alpha(v)beta5 in phagocytosis, immunofluorescence experiments demonstrated codistribution of alpha(v)beta5 integrin with internalized ROS. Control experiments showed that blocking alpha(v)beta3 function with antibodies did not inhibit ROS phagocytosis and that alpha(v)beta3 did not colocalize with phagocytosed ROS. Taken together, our results indicate that the RPE requires the integrin receptor alpha(v)beta5 specifically for the binding of ROS and that phagocytosis involves internalization of a ROS-alpha(v)beta5 complex. Alpha(v)beta5 integrin does not participate in phagocytosis by other phagocytic cells and is the first of the RPE receptors involved in ROS phagocytosis that may be specific for this process.     

A controlled study of leukocyte activation in septic patients

OBJECTIVE: Qualitative and quantitative evaluation of leukocyte activation in septic patients in comparison to two control groups. DESIGN: A prospective clinical study in which the leukocyte oxidative output of whole blood was measured in three groups of patients. Two chemiluminescence markers (luminol or lucigenin), indicative of either total oxidant output or superoxide production, and three stimuli (opsonized zymosan, formyl-methionyl-leucyl-phenylalanine (fMLP), phorbol myristate acetate) (PMA), representing different pathways of leukocyte activation, were used. Tumor necrosis factor, interleukin-6 and C-reactive protein (TNF, IL-6, and CRP) were determined to evaluate the severity of the inflammatory process. SETTING: Intensive care and surgical units of a university hospital. PATIENTS: Seventy-four healthy patients, ten ICU patients without signs of sepsis or systemic inflammatory response syndrome and 19 septic patients were studied. MEASUREMENT AND MAIN RESULTS: With all three stimuli, whole blood total oxidative output and superoxide production were generally increased in septic patients. This was most likely due to the increased leukocyte numbers in these patients. When the chemiluminescence values were normalized per phagocyte (granulocytes and monocytes), the total oxidative output of septic phagocytes decreased with opsonin and fMLP but increased with PMA, while superoxide output decreased regardless of the stimuli used. TNF, IL-6 and CRP, although increased in septic patients as compared to ICU controls, correlated weakly with oxidant output. CONCLUSIONS: The oxidative output of whole blood was increased in septic patients compared to controls because of elevated leukocyte numbers. However, oxidant output normalized for phagocyte numbers generally decreases during sepsis for most stimuli. Cytokines and CRP do not appear to be associated with the extent of oxidant output during sepsis.     

Decreased CD11b expression, phagocytosis, and oxidative burst in urban particulate pollution-exposed human monocytes and alveolar macrophages

Elevated levels of air pollution particulates < or = 10 microm in diameter (PM10) have been associated with an increase in mortality and morbidity due to pulmonary complications, including pneumonia. Impairment of inflammatory and host defense functions of the alveolar macrophage (AM) may be a precipitating factor. The present study was undertaken to determine whether human AM and blood derived monocytes (MO) modulate the expression of receptors important for phagocytosis of opsonized microbes (CD11b, CD11c), gram-negative bacteria (CD14), extracellular matrix interaction (CD29), and immune responses (CD11a, CD54, HLA-DR) when exposed to particulates obtained from urban air (UAP). Furthermore, phagocytosis of and oxidant generation by opsonized yeast were investigated in particle-exposed cells. AM and MO exposed to UAP for 18 h expressed significantly lower levels of CD11b and CD29. CD14 expression was markedly decreased in MO but not in AM, and CD11c was reduced in AM but not in MO. CD11a, CD54, and HLA-DR were unaltered in both phagocyte populations. Decreased receptor expression was not dependent on particle load in the cells. Phagocytosis of Saccharomyces cerevisiae and the chemiluminescence response were also significantly inhibited by UAP. Time-course studies revealed that decreased oxidant generation was evident already at 3 h postexposure, while significant effects on phagocytosis and CD11b expression were found at 18 h. These data indicate that exposure to particulate pollution is likely to impair host defense functions of AM and MO, which are important in elimination of a variety of pathogens in the lung.     

Work place challenge: spirometric response in polyurethane (isocyanate) paint workers

As many as 159 patients with pneumonia (all men aged 18-39) were examined. Functional activity of monocytes was studied in an integral test with nitroblue tetrazolium as was nonspecific cellular antiviral resistance by the level of viral damage to the monocytes and lymphocytes. The progression of pneumonia was found to be accompanied by a decrease in the number of phagocytizing mononuclears and the activity of phagocytosis. Nonspecific cellular antiviral resistance is significantly impaired. The proportion of monocytes and lymphocytes containing viral inclusions increases several-fold. The treatment of patients is accompanied by positive dynamics of indicators of functional status of monocytes and nonspecific cellular antiviral resistance. By the time of discharge from hospital the impaired functions of immunocompetent cells fail to completely restore.     

Prospective randomized comparison of imipenem-cilastatin and piperacillin-tazobactam in nosocomial pneumonia or peritonitis

Nosocomial pneumonia and acute peritonitis may be caused by a wide array of pathogens, and combination therapy is often recommended. We have previously shown that imipenem-cilastatin monotherapy was as efficacious as the combination of imipenem-cilastatin plus netilmicin in these two settings. The efficacy of imipenem-cilastatin is now compared to that of piperacillin-tazobactam as monotherapy in patients with nosocomial pneumonia or acute peritonitis. Three hundred seventy one patients with nosocomial pneumonia or peritonitis were randomly assigned to receive either imipenem-cilastatin (0.5 g four times a day) or piperacillin-tazobactam (4.5 g three times a day). Three hundred thirteen were assessable (154 with nosocomial pneumonia and 159 with peritonitis). For nosocomial pneumonia, clinical-failure rates in the piperacillin-tazobactam group (13 of 75 [17%]) and in the imipenem-cilastatin group (23 of 79 [29%]) were similar (P = 0.09), as were the numbers of deaths due to infection (6 in the imipenem-cilastatin group [8%], 7 in the piperacillin-tazobactam group [9%]) (P = 0.78). For acute peritonitis, clinical success rates were comparable (piperacillin-tazobactam, 72 of 76 [95%]; imipenem-cilastatin, 77 of 83 [93%]). For infections due to Pseudomonas aeruginosa, 45 patients had nosocomial pneumonia (21 in the piperacillin-tazobactam group and 24 in the imipenem-cilastatin group) and 10 had peritonitis (5 in each group). In the patients with nosocomial pneumonia, clinical failure was less frequent in the piperacillin-tazobactam group (2 of 21 [10%]) than in the imipenem-cilastatin [corrected] group (12 of 24 [50%]) (P = 0.004). Bacterial resistance to allocated regimen was the main cause of clinical failure (1 in the piperacillin-tazobactam group and 12 in the imipenem-cilastatin group). For the patients with peritonitis, no difference in clinical outcome was observed (five of five cured in each group). The overall frequencies of adverse events related to treatment in the two groups were similar (24 in the piperacillin-tazobactam group, 22 in the imipenem-cilastatin group). Diarrhea was significantly more frequent in the piperacillin-tazobactam group (10 of 24) than in the imipenem-cilastatin group (2 of 22). This study suggests that piperacillin-tazobactam monotherapy is at least as effective and safe as imipenem-cilastatin monotherapy in the treatment of nosocomial pneumonia or peritonitis. In P. aeruginosa pneumonia, piperacillin-tazobactam achieved a better clinical efficacy than imipenem-cilastatin, due to reduced development of microbiological resistance. Tolerance was comparable, with the exception of diarrhea, which was more frequent with piperacillin-tazobactam.     

Characterisation of granulocyte stimulation by thionins from European mistletoe and from wheat

Thionins are small basic peptides found in different plant species, which are known to exert cytotoxic properties. In addition, previous data indicated an activation of human granulocytes by thionins from European mistletoe (viscotoxins, VT). To extend these latter findings, we investigated the influence of VT and from thionins from wheat flour (purothionin) on human granulocytes by flow cytometry and tried to characterise the involved molecular structures and mechanisms. Phagocytosis was determined by incorporation of FITC-labelled Escherichia coli and respiratory burst by oxidation of dihydrorhodamine 123 to rhodamine 123. VT and purothionin significantly enhanced E. coli-stimulated phagocytosis and respiratory burst at 25 and 250 microgram/ml. Phagocytosis of damaged lymphocytes by granulocytes was detected by electron microscopy in the VT-stimulated (100 microgram/ml) but not in the control cultures. The poly-cationic structure of the intact molecule seems to be crucial, as evidenced by comparison of the burst and phagocytosis-enhancing effects induced by other poly-cationic (protamine sulphate, histone, poly-l-arginine, poly-l-lysine) and poly-anionic (poly-l-glutamic acid) peptides, while pore forming due to amphipathic properties seems to be less important. Ca2+ and Mg2+ could not inhibit VT-enhanced phagocytosis and, thus, could not inhibit binding of VT to granulocytes. In addition, verapamil at low concentrations inhibited VT activity, suggesting the involvement of Ca2+ channels for granulocyte activation by the VT. Similarly, thionins and histones in contrast to protamine sulphate induced cell death of granulocytes at 250 microgram/ml as demonstrated by an enhanced release of reactive oxygen intermediates in unstimulated granulocytes. From these data one may suggest that activity of VT is induced by strong unspecific ionic binding, probably followed by specific receptor binding, and thionins exhibit stimulatory and cytotoxic effects on immune cells, which have to be further characterised.     

MHC class II gene silencing in trophoblast cells is caused by inhibition of CIITA expression

A. baumannii is a multiresistant bacteria which is recognised as responsible for nosocomial infections and hospital outbreaks. The control of these outbreaks depends on the strain's typing and on the fight's policy against nosocomial infections. An outbreak of A. baumannii is occurred to patients who were hospitalized in Centre Hospitalier de Versailles. To investigate this outbreak, we have determined the biotype (Bouvet's method), the succeptibility pattern (disk diffusion and agar dilution results were analysed with the hierarchical classification and main component analysis) and the total DNA macrorestriction pattern (Pulse Field Gel Electrophoresis using SmaI restriction enzyme). A risk factors for A. baumannii acquisition were delineated in case-control study. During 2 years, 38 patients have been infected or colonized to A. baumannii. Thirty two patients were hospitalized in ICU. We studied 38 non repetitive clinical isolates and 9 strains of the patient's rooms. Four biotypes were defined by the Bouvet's typing method. Fourteen groups were obtained when succeptibility results were analysed with the hierarchical classification and 6 with the main composant analysis. The molecular typing permit us to define 4 epidemic and 6 sporadic strains. All the epidemic strains were isolated on ICU hospitalized patients. Our study has shown wide contamination in patient's rooms (Water tap, dry surfaces, patient's mattresses...). Environmental objects have been a major risk factor for A. baumannii acquisition. The control of this outbreak has been possible by application of hygienic measures (hands washing, isolment, meticulous cleaning of the ICU and environmental controls). No new case is occurred in the last year. Typing methods and case-control study are necessary to investigate cross-infections and take efficient measures against these outbreaks.     

Functional activity of peripheral blood neutrophils of rats during combined effects of hypoxia, hypercapnia and cooling

Functional activity of neutrophilic leukocytes was studied in blood of rats immediately following single and repeated gradual increase in carbon dioxide and decrease in oxygen concentrations with the ambient temperature at 2 to 3 degrees C. Phagocytic activity was shown to alter as the number of phagocytic neutrophilic granulocytes, absorptivity or the phagocytic index, and the coefficient of phagocytosis completeness were elevated and levels of oxygen-dependent and oxygen-independent metabolism were reduced.     

Endothelial cells potentiate oxidant-mediated Kupffer cell phagocytic killing

Phagocytosis and killing of circulating organisms by Kupffer cells (KCs) are discrete, important components of host defense. However, the killing mechanism(s) are not fully understood, and the potential role of adjacent nonparenchymal cells such as hepatic endothelial cells has not been defined. Rat KCs -/+ an hepatic endothelial cell enriched cellular fraction (HECEF) were incubated with Candida parapsilosis and assayed for phagocytosis and phagocytic killing by validated fluorochromatic vital staining. The role of reactive oxygen metabolites in KC phagocytic functions was examined by inhibition with superoxide dismutase and/or catalase. Diphenyleneiodonium and allopurinol were used to examine the potential roles of NADPH oxidase and xanthine oxidase, respectively, in generating these toxic oxidants. Coculture with HECEF increased KC phagocytic activity (from 75% to 88%) and candidacidal activity (from 20% to 31%). Superoxide dismutase, catalase, diphenyleneiodonium, or allopurinol caused inhibition of candidacidal activity, but did not affect phagocytosis, and did not block the potentiation of phagocytosis or of killing caused by coculture with HECEF. Reactive oxygen intermediates generated by both NADPH oxidase and xanthine oxidase-dependent pathways are important in KC killing of Candida parapsilosis. In vitro, KC phagocytosis and killing are potentiated (via a non-oxidant-mediated mechanism) by coculture with a preparation of hepatic non-parenchymal cells composed primarily of endothelial cells.     

A role for scavenger receptors in phagocytosis of protein-coated particles in rainbow trout head kidney macrophages

In macrophages of higher vertebrates, Fc receptors and receptors for complement and other serum factors, are generally known to enhance the phagocytic process. In lower vertebrates like salmonid fishes, none of these or other phagocytic receptors have been thoroughly characterized. The purpose of this study was to elucidate to what extent these and other receptors are involved in the process of phagocytosis in rainbow trout (Oncorhynchus mykiss) head kidney macrophages. We used tosyl activated, paramagnetic dynabeads (2.8 microm in diameter), specifically coated with 125I labeled Atlantic salmon (Salmo salar) IgM or bovine serum albumin (BSA) as phagocytic probes. The effect of complement opsonization was also investigated by incubating the beads in serum. Our results indicate that neither the Fc- nor the complement-receptor(s) were important for phagocytosis of these beads. Our data support the idea that scavenger receptors are involved in phagocytosis in rainbow trout head kidney macrophages, as the use of a competitive scavenger receptor ligand extensively decreased degradation of the labeled protein coat on the beads.     

Phagocytosis-enhancing effect of lactoferrin on bovine peripheral blood monocytes in vitro and in vivo

The effect of lactoferrin (LF) on in vitro and in vivo phagocytic ability of bovine blood monocytes was studied. It was demonstrated that bovine LF enhanced in vitro phagocytosis of bacteria and ovine erythrocyte-antibody complexes and increased intracellular killing of Staphylococcus albus. Monocytes of colostrum deprived calves, which were intravenously injected with LF, also exhibited elevated phagocytic properties.     

Optimal therapy for stress gastritis

OBJECTIVE: The authors compared the results of sucralfate versus H2 blocker +/- antacid as prophylaxis for stress ulceration in an intensive care unit patient population. SUMMARY BACKGROUND DATA: Stress ulceration carries high morbidity and mortality for the patient who is critically ill. Gastric acid neutralization is an effective prophylaxis. The impact of increased gastric colonization with bacterial pathogens on nosocomial pneumonia after acid neutralization is unclear. The efficacy of sucralfate prophylaxis for stress ulceration and its the effect on the nosocomial pneumonia rate is controversial. The financial implications of sucralfate prophylaxis versus H2 blocker-based acid neutralization therapy has not been studied. METHODS: Ninety-eight injured patients who were critically ill and who required intubation and intensive care unit (ICU) support for at least 72 hours without gastric feeding were randomized and received either maximal H2 blocker infusion therapy (continuous infusion of ranitidine at 0.25 mg/kg/hr after a loading dose of 0.5 mg/kg) plus antacids (for persistent pH < 4) or sucralfate (1 g every 6 hours via nasogastric tube) for stress ulcer prophylaxis. Efficacy in preventing stress ulcer complications was determined. The impact of each therapeutic approach on development of nosocomial pneumonia was evaluated. The charges/cost for each approach was analyzed. RESULTS: Heme-positive gastric aspirates occurred in 99% of the patients, whereas 12 (7 in the H2 blocker group and 5 in the sucralfate group) were grossly positive for blood. However, only one from each group required transfusion, and one in the H2 blocker group required operation. Gastric colonization preceded tracheobronchial colonization in five patients in the H2 blocker group and one patient in the sucralfate group; simultaneous gastric/oropharyngeal colonization preceded positive tracheobronchial growth in six patients who received H2 blocker and one patient who received sucralfate. The overall pneumonia rate was 27.5% in the H2 blocker group and 20.8% in the sucralfate group (p = 0.48). Days on ventilator were 13.5 versus 9.1, (p = 0.06), ICU lengths of stay were 14.7 versus 10.2 (p = 0.06), and hospital lengths of stay were 27.8 versus 20.0 (p = 0.029) for the H2 blocker group and sucralfate group, respectively. Based on current charges and protocols for optimal H2 blocker and sucralfate prophylaxis, use of sucralfate rather than H2 blockers would decrease the annual cost by more than $30,000 per bed. CONCLUSIONS: Sucralfate is as efficacious as maximal H2 blocker therapy for stress ulceration prophylaxis, and may have a beneficial effect on the incidence of nosocomial pneumonia. Sucralfate has a major reduction on nursing requirements for stress ulcer prophylaxis and would save approximately $30,000 per ICU bed per year in patient charges.