Phagocytic Stimulation Research Articles

Activation of human monocyte--derived macrophages with lipopolysaccharide decreases human immunodeficiency virus replication in vitro at the level of gene expression.

Activation of T lymphocytes infected with the human immunodeficiency virus-1 (HIV-1) results in enhancement of viral replication mediated in part by activation of cellular NF kappa B capable of binding directly to sequences in the viral long terminal repeat, or LTR. Together with CD4+ T cells, macrophages constitute a major target for infection by HIV-1. Unlike lymphocytes, however, stimulation of mononuclear phagocytes is not associated with cell division and proliferation. Human monocyte-derived macrophages transfected with HIV-LTR-CAT constructs demonstrated down-regulation of CAT activity after stimulation with bacterial lipopolysaccharide (LPS) that mapped to a region distinct from NF kappa B binding sites. In contrast, fresh monocytes and the promonocytic U937 cell line both demonstrated up-regulation of HIV-LTR-CAT expression by LPS. Differentiation of U937 by PMA to establish a nondividing phenotype resulted in down-regulation of transfected HIV-LTR-CAT activity by LPS similar to that in mature macrophages. Human monocyte-derived macrophages infected with HIV-1 in vitro demonstrated a decrease in viral p24 release after incubation in LPS that was comparable to the negative regulation that occurred in the transient transfection assays. Factors controlling HIV replication may differ in dividing and nondividing hematopoietic cells and may contribute to restricted viral expression in nondividing cells.

Metabolic response of isolated liver cells to in Vivo phagocytic challenge

This study elucidates the in vivo metabolic response of different liver cells after a single phagocytic challenge. In vivo glucose uptake of different tissues and isolated liver cells was determined by a sequential double labeling version of the 2-deoxyglucose technique. After latex administration, glucose uptake more than doubled in the liver, increased by about 50% in the spleen and lung and was not changed in muscle and testis. Within 10 min after intravenous injection of latex beads, neutropenia developed, with no change in the number of lymphocytes. This was accompanied by a marked influx of polymorphonuclear leukocytes into the liver. Latex was found in 52%, 35%, and 14% of the isolated Kupffer cells, polymorphonuclear leukocytes and endothelial cells, respectively. In vivo glucose uptake increased by 111%, 142%, and 43% in these cells. Glucose uptake by the latex-free hepatocytes was also elevated, presumably by way of intercellular signals between parenchymal and non-parenchymal liver cells. Indomethacin pretreatment resulted in the delay of neutrophil immigration into tissues without any change in the glucose response of different liver cells. Thus phagocytic stimulation in vivo results in marked neutropenia, migration of neutrophils into the liver, increased glucose uptake by phagocytic cells of the liver and enhanced glucose metabolism by the non-phagocytic parenchymal cells.

Metabolic response of isolated liver cells to in vivo phagocytic challenge

This study elucidates the in vivo metabolic response of different liver cells after a single phagocytic challenge. In vivo glucose uptake of different tissues and isolated liver cells was determined by a sequential double labeling version of the 2-deoxyglucose technique. After latex administration, glucose uptake more than doubled in the liver, increased by about 50% in the spleen and lung and was not changed in muscle and testis. Within 10 min after intravenous injection of latex beads, neutropenia developed, with no change in the number of lymphocytes. This was accompanied by a marked influx of polymorphonuclear leukocytes into the liver. Latex was found in 52%, 35%, and 14% of the isolated Kupffer cells, polymorphonuclear leukocytes and endothelial cells, respectively. In vivo glucose uptake increased by 111%, 142%, and 43% in these cells. Glucose uptake by the latex-free hepatocytes was also elevated, presumably by way of intercellular signals between parenchymal and non-parenchymal liver cells. Indomethacin pretreatment resulted in the delay of neutrophil immigration into tissues without any change in the glucose response of different liver cells. Thus phagocytic stimulation in vivo results in marked neutropenia, migration of neutrophils into the liver, increased glucose uptake by phagocytic cells of the liver and enhanced glucose metabolism by the non-phagocytic parenchymal cells.

Activation of human monocytes by interleukin 2: Role of T lymphocytes

The effect of interleukin 2 (IL2) on the capability of human monocytes to secrete reactive oxygen species triggered via Fc-gamma receptor (Fc-gamma R) function had been investigated by measurement of chemiluminescence (CL). IL 2 did not activate highly purified (hp) monocytes to respond to Fc-gamma R mediated phagocytic stimulation with an enhanced respiratory burst activity unless low numbers of T cells had been co-cultured with hp monocytes. Supernatants from IL 2 treated PBMC contained interferon-gamma (IFN-gamma) and monocyte activating factor (MAF) activity. The secretion of both cytokine activities was strongly enhanced by cooperative function of monocytes. The correlation of IL 2 induced secretion of IFN-gamma and MAF activity was striking, however, monoclonal antibody (mAb) anti-human IFN-gamma failed to abrogate IL 2 stimulated and lymphocyte dependent monocyte activation. Although IL 2 had no direct monocyte activating effect, pretreatment of hp monocytes with IL 2 led to monocyte priming: subsequent co-culture with autologous control T cells enhanced the monocyte Fc-gamma R mediated CL response. The priming of monocytes by IL 2 was dependent on the interaction of IL 2 with the monocytic IL 2 receptor as shown by inhibition experiments with anti IL 2 R monoclonal antibody. Thus the IL 2 driven monocyte/T-cell interaction leads to an increased Fc-gamma R mediated monocytic respiratory burst activity and to the secretion of a soluble MAF activity, but there were no detectable amounts of IFN-gamma.

On the Biocompatibility of IBM 2997 Continuous Flow Plateletapheresis

During the procedure of centrifugation cytapheresis donors occasionally experience adverse clinical reactions. We evaluated the possibility of whether activation of granulocytes and their subsequent release reactions, which may have been triggered by this extracorporeal circuit, were responsible for these adverse effects. Six blood samples were obtained during various set intervals during plateletapheresis. Of these, four samples were taken directly from each donor. The remaining two were drawn from the efferent lines, i.e. those which return blood from the cytapheresis machine back to the donor. Reactive oxygen species produced by granulocytes were monitored by chemiluminescence using microamounts of whole blood or isolated granulocytes. Furthermore, secreted granulocyte products such as neutral proteinase elastase, present in plasma in a complex with alpha 1-proteinase inhibitor (complexed elastase), and lysosomal beta-glucuronidase were examined. A complete blood cell count, as well as values of haemoglobin, haematocrit, lactate dehydrogenase, protein, albumin and proteinase inhibitors such as alpha 2-macroglobulin and alpha 1-proteinase inhibitor were also determined. Complexed elastase increased from a preapheresis value of about 140 micrograms/l to about 180 micrograms/l at the end of the cytapheresis. All other clinical chemical and cytological values were 8 to 12 percent lower than preapheresis values, which can be attributed to inherent plasma volume expansion. Reduced chemiluminescence was observed upon stimulation of phagocytes in the whole blood assay (about 700 counts/min x 10(3) x 50,000 cells vs. about 600 counts/min x 10(3) x 50,000 cells). This decrease was also seen with stimulated granulocytes (about 5800 counts/min x 10(3) x 50,000 cells vs. about 4500 counts/min x 10(3) x 50,000 cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Uptake and utilization of human polymorphonuclear leukocyte granule myeloperoxidase by mouse peritoneal macrophages

Functional myeloperoxidase contained in granules of polymorphonuclear neutrophil leukocytes or in fixed whole cells can be endocytosed by mouse peritoneal macrophages. Acquired myeloperoxidase was distributed in what we considered to be the secondary lysosomal system and, following a phagocytic stimulation, was delivered to newly formed phagosomes containing the targets.

Evaluation of granulocyte-releasing products and chemiluminescence during cytapheresis.

During the procedures of centrifugation leukapheresis and plateletpheresis, donors occasionally experience adverse clinical reactions. The possibility of whether the activation of granulocytes and the subsequent release reactions, which may have been triggered by this extracorporeal circuit, were responsible for these adverse effects was evaluated. Six blood samples were obtained at set intervals during cytapheresis. Of these samples, four were taken directly from the donor. The remaining two were drawn from the efferent lines, i.e., those which return blood from the cytapheresis machine to the donor. Reactive oxygen species produced by granulocytes were measured by chemiluminescence (CL) using microamounts of whole blood or isolated granulocytes. Furthermore, secreted granulocyte products such as neutral proteinase elastase, which is present in plasma in a complex with alpha-1-proteinase inhibitor (E-alpha-1-PI), and lysosomal beta-glucuronidase were examined. A complete blood cell count and the values of hemoglobin, hematocrit, lactate dehydrogenase, protein, albumin, and proteinase inhibitors such as alpha-2-macroglobulin and alpha-1-proteinase inhibitor were also determined. Clinical chemical and cytologic values, with the exception of those for E-alpha-1-PI, were 10 to 17 percent lower than values before apheresis. These results can be attributed to inherent plasma volume expansion. Reduced CL was observed on the stimulation of phagocytes in the whole blood assay, as well as with stimulated granulocytes. Unstimulated granulocytes, on the other hand, showed an increased native CL. These data do not indicate a cytapheresis-mediated activation of the oxidative metabolism of granulocytes, and the concomitant discharge of proteolytic enzymes remains, therefore, of no clinical importance.

The Effect of Interleukin 2 on Fc-γ Receptor Function of Human Monocytes Requires Specific Intercellular Interaction

We examined the effect of interleukin 2 (IL 2) on the capacity of human monocytes tosecrete reactive oxygen species triggered via Fc-γ receptor (FcγR) function as measured by chemiluminescence (CL). IL 2 did not activate highly purified (hp) monocytes to respond to FcγR-mediated phagocytic stimulation with an enhanced respiratory burst activity, unless low numbers of T lymphocytes had been cocultured with hp monocytes. The degree of monocyte activation in peripheral blood mononuclear cells (PBMC) by IL 2 was dependent on T lymphocytes to monocytes ratios as well as on IL 2 concentrations. Optimal FcγR function was detected with IL 2 concentrations of 60 to 600 U/ml and one to two T lymphocytes per monocyte, whereas higher cellular ratios were suppressive. Supernatants from IL 2-treated PBMC contained interferon-γ), (IFN-γ) and monocyte activating factor (MAF) activity (= enhanced monocytic FcγR mediated CL). The secretion of both cytokine activities was strongly enhanced by a cooperative function of monocytes. The correlation of IL 2-induced secretion of IFN-γ and MAF activity was striking; however, monoclonal anti-IFN-γ antibodies failed to abrogate IL 2-stimulated and lymphocyte-dependent monocyte activation. Although IL 2 had no direct monocyte activating effect, pretreatment of hp monocytes withIL 2 led to a monocyte priming: subsequent coculture with autologous control T lymphocytes enhanced the monocyte FcγR-mediated CL response. The priming of monocytes by IL 2 was dependent on the interaction of IL 2 with the monocytic IL 2 receptor, as shown by inhibition experiments with anti-IL 2 receptor monoclonal antibodies. Thus, we observed an IL 2-driven monocyte/T lymphocyte interaction leading to an increased FcγR-mediated monocytic respiratory burst activity and to the secretion of a soluble MAF activity, but there were no detectable amounts of IFN-γ.

Phagocytic system stimulation in experimental atherosclerosis of chicks

The effects of activation of the phagocytic system by BCG on the development of diet-induced atherosclerosis was studied in chicken. Injections of BCG had a marked effect on atherogenesis, which was either inhibitory or stimulatory, depending on the route of BCG administration and on the timing. A slight, but significant inhibition was obtained by intraperitoneal injection of BCG administered during the dietary treatment. A more pronounced and significant inhibition was observed in chicks given BCG subcutaneously 8 weeks before the start of the dietary regimen. The findings are consistent with a previously proposed notion that immunization at an early age may affect the course of later life atherosclerosis.

Chemiluminescence microscopy reveals functional heterogeneity in single neutrophils undergoing oxygen burst.

Activated polymorphonuclear leukocytes (PMN) respond to various triggers with an oxygen burst, during which the release of reactive oxygen species (ROS) plays a key role in microbial killing. The biological function of the ROS-associated light emissions is not known. However, this particularly weak cell-derived chemiluminescence (CL) may serve as a parameter for the identification of PMN activation. In this study we describe a novel technique which we termed CL microscopy. A microscope-based low-light image-processing system was applied which was sensitive enough to detect single photons, capable of two-dimensional signal accumulation, and digital image analysis. This technique permitted, for the first time, the visualization of the oxygen burst in single cells. Furthermore, quantitative evaluation of cell-derived luminol-enhanced CL revealed functional heterogeneity. Single-cell investigations of activated living PMN of normal human donors showed clear differences in kinetics and intensity of the oxygen burst related to different stimuli. The chemical agent (phorbol 12-myristate 13-acetate) induced CL in 83% of PMN. In contrast, the complement-mediated phagocytic stimulation by opsonized zymosan gave much higher light intensities of individual cells, but only in part of the PMN population (30%). CL microscopy presents a new and highly sensitive technique with considerable potential for single-cell analysis in immunological research.

Enhanced chemiluminescence production by phagocytosing neutrophils in psoriasis.

Using serum-coated zymosan, the generation of reactive oxidants by measurement of chemiluminescence was shown to be significantly enhanced in isolated peripheral psoriatic neutrophils compared to normal controls. This response was observed irrespective of whether zymosan was opsonized with fresh autologous or normal AB serum. However, this increased activity was reduced with zymosan was opsonized with serum that was preheated at 56 degrees C for 30 min. There was no statistical correlation of chemiluminescence activity with degranulation of beta-glucuronidase in either normal or psoriatic subjects. In addition, chemiluminescence produced by normal cells was significantly increased when zymosan was opsonized with psoriatic serum. The plasma membrane-bound enzyme, NAD(P)H oxidase, which produces superoxide in response to phagocytic stimulation, was significantly increased in psoriatic neutrophils compared to normal controls. These data add further evidence for activated neutrophils in psoriasis.

Time dependence of transmembrane potential changes and intracellular calcium flux in stimulated human monocytes

An important characteristic of the functional differentiation of the blood monocyte is the development of its capacity to recognize and respond to stimuli. This ability is mediated to a large extent by specific receptor glycoproteins located on the cell surface. Stimulation of mononuclear phagocytes via these receptors results in a rapid rise in intracellular Ca++ concentration, accompanied or followed by a change in membrane potential, generation of oxidative products, degranulation, and effector functions such as phagocytosis, aggregation, or locomotion. While the development of these characteristics is difficult to characterize in vivo, several investigators have demonstrated in vitro changes in these cells that correlate with the development of effector function. To examine the mechanisms of specific membrane-stimulus interactions of monocytes as they differentiate into macrophage-like cells, we studied the responses of human monocytes and of monocytes incubated in serum-containing medium for up to 96 hr to the chemotactic peptide formyl-methionyl-leucyl-phenylalanine (fMLP). Freshly isolated monocytes exhibited little change in transmembrane potential following stimulation with an optimal concentration of peptide and underwent a significant increase only after 48 hr in culture. While constant resting intracellular Ca++ concentrations were maintained during the culture period, intracellular Ca++ levels following fMLP stimulation increased with with incubation in serum, for up to 96 hr. In contrast, fMLP-induced respiratory burst activity increased from 0 to 24 hr in culture; it remained elevated at 48 hr but declined again by 96 hr. Incubation of the cells for 24 hr increased their random (unstimulated) motility in modified Boyden chambers but did not alter the cells' directed (chemotactic) response to fMLP in comparison to the response of freshly isolated monocytes. Peptide binding to the cells did not increase during the incubation period, indicating that an increase in receptor number or in affinity for fMLP was not responsible for the enhanced responsiveness to fMLP as incubation time increased. These studies indicate that incubation of monocytes in serum-containing medium leads to a complex, altered series of responses to fMLP that correlate with the differentiation of the original monocytes in vitro and may relate to the in vivo differentiation of monocytes to macrophages.

Regulation of IgE-dependent antiparasite functions of rat macrophages and platelets by nedocromil sodium.

The IgE-dependent stimulation of mononuclear phagocytes and blood platelets can be measured by antiparasite cytotoxicity, oxygen-mediated chemiluminescence and, in macrophages, lysosomal enzyme activity. Using these parameters, the present study demonstrated an inhibition by nedocromil sodium of the IgE-mediated triggering of the nonmast cell inflammatory populations in the rat. These observations suggest that nedocromil sodium may be of value in the modulation of IgE-dependent cell activation inducing the release of inflammatory mediators.

Activation of hepatic glycogenolysis by phagocytic stimulation

Infusion of latex beads into isolated perfused rat livers transiently increased glucose output, perfusate lactate/pyruvate ratio and portal vein pressure, mimicking hepatic effects of heat-aggregated IgG (HAG). Indomethacin attenuated hepatic responses to latex beads, and extracellular calcium was required for full expression of hepatic responses. Prior infusion of HAG inhibited the glycogenolytic response to latex beads, supporting a common mechanism of action for the two agents.

Hemocytes of the pond snail Lymnaea stagnalis generate reactive forms of oxygen

Macrophagelike hemocytes of the pond snail Lymnaea stagnalis were stimulated in vitro with various particulate agents (latex, Escherichia coli, Staphylococcus saprophyticus, zymosan) and with phorbol myristate acetate in order to determine whether these blood cells show biochemical reactions reminiscent of a respiratory burst. Phagocytic stimulation of the hemocytes resulted in a superoxide dismutase-sensitive reduction of nitroblue tetrazolium, which is indicative of the generation of superoxide anions. Moreover, the hemocytes also produced hydrogen peroxide, and they showed a sodium azide-sensitive diaminobenzidine reaction. The hemocytes displayed a luminol-dependent chemiluminescence that differed for each stimulus used. Zymosan elicited a relatively high dose-dependent response. The chemiluminescence was (partly) inhibited by superoxide dismutase, azide, and cyanide. These data indicate the possible involvement of toxic oxygen intermediates in phagocytic defense reactions of L. stagnalis hemocytes.

POLYKARYON FORMATION BYMERCENARIA MERCENARIAHEMOCYTES

Examination of Mercenaria mercenaria hemocyte preparations on glass coverslips showed that adherent, macrophage-like cells tended to form multinucleated giant cells morphologically similar to classical Langhans cells and foreign body inflammatory giant cells, as seen in vertebrates. The frequency of giant cell formation varied from clam to clam, possibly reflecting each animal's physiological state, as influenced by pollutant exposure, other environmental stressors and disease. Treatment of the hemocytes with concanavalin A promoted hemocyte aggregation and increased the rate of giant cell formation. Attempts to increase polykaryon formation by in vivo or in vitro phagocytic stimulation of the hemocytes were generally unsuccessful.

Endotoxins and disease mechanisms.

In this chapter, current concepts about the mechanisms of action of endotoxin are reviewed. Particular attention is focused upon endotoxin-induced production of soluble mediators from macrophages and mononuclear cells and on the potential contribution of these mediators to endotoxin shock. In many cases, the interrelationships between these mediators as primary and/or secondary consequences of endotoxin stimulation of mononuclear phagocytes are discussed. Final comments address the relevance of these mediators to the therapy of endotoxin shock.

Effects of stallion seminal plasma on hydrogen peroxide release by leukocytes exposed to spermatozoa and bacteria

The ability of stallion seminal plasma to modify phagocytosis of spermatozoa and Streptococcus zooepidemicus was examined. Phagocytosis was monitored indirectly as the H 2O 2 produced by peripheral blood leukocytes after addition of spermatozoa or bacteria. Hydrogen peroxide production after addition of ejaculated spermatozoa was greater ( P < 0.01) than after addition of epididymal sperm. Furthermore, pre-incubation of epididymal sperm with 6.25–50% seminal plasma caused a dose-dependent increase in subsequent H 2O 2 production by leukocytes ( P < 0.05). In addition, equine serum was capable of opsonizing epididymal and ejaculated sperm. Seminal plasma also directly stimulated phagocyte function because leukocytes preincubated with 12.5% or 25% seminal plasma released more H 2O 2 after addition of S. zooepidemicus than control leukocytes ( P < 0.05). It is suggested that the opsonization of spermatozoa and the direct stimulation of phagocytes by seminal plasma may represent mechanisms for clearing spermatozoa and bacteria from the reproductive tract.

Leukotriene B4 stimulation of phagocytes results in the formation of inositol 1,4,5-trisphosphate. A second messenger for Ca2+ mobilization.

Inositol trisphosphate (InsP3) production and cytosolic free Ca2+ ([Ca2+]i) elevations induced by leukotriene B4 (LTB4)-receptor activation were studied in the human promyelocytic-leukaemia cell line HL60, induced to differentiate by retinoic acid. The myeloid-differentiated HL60 cells respond to LTB4 by raising their [Ca2+]i with a dose-response relationship similar to that shown by normal human neutrophils. The observations of the LTB4 transduction mechanism were compared with those of the transduction mechanism of the chemotactic peptide fMet-Leu-Phe in HL60 cells differentiated with dimethyl sulphoxide. Both LTB4 and fMet-Leu-Phe triggered a rapid (less than 5 s) elevation of [Ca2+]i, which occurred in parallel with the InsP3 production from myo-[3H]inositol-labelled cells. The threshold concentrations of the agonists, for InsP3 production, were found at 10(-9) M, a slightly higher concentration than that required to detect [Ca2+]i elevations. No significant changes were noted in the phosphoinositide levels upon stimulation with LTB4. Exposure to Bordetella pertussis toxin before LTB4 stimulation abolished both the increased formation of InsP3 and the rise of [Ca2+]i. LTB4 and fMet-Leu-Phe elicited elevations of inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] with no detectable lag time, followed by slower and more sustained inositol 1,3,4-trisphosphate elevations. Stimulation with various leukotriene analogues revealed a good correlation between both total InsP3 as well as Ins(1,4,5)P3 formation and elevations of [Ca2+]1. Thus LTB4 receptor activation results in an increased production of Ins(1,4,5)P3 via a transduction mechanism also involving a nucleotide regulatory protein, as previously described for the fMet-Leu-Phe transduction mechanism.

Role of guanine nucleotide regulatory protein in polyphosphoinositide degradation and activation of phagocytic leukocytes by chemoattractants.

Leukocyte activation by chemoattractants provides an important model to study the biochemical mechanisms of stimulus-response coupling in these cells. Well-defined chemotactic factors induce readily quantifiable responses in phagocytic leukocytes. These include directed migration and the production and release of toxic substances including oxygen radicals and lysosomal enzymes. The development of radiolabeled synthetic oligopeptides with potent chemotactic activity allowed the demonstration of chemoattractant receptors on polymorphonuclear leukocytes (PMNs) as well as macrophages. In membrane preparations from these cells, these receptors exist in high- and low-affinity states which are regulated by guanosine di- and triphosphates. This suggested that chemoattractant receptors interact with guanine nucleotide regulatory proteins (N or G proteins). Although chemoattractants elicit a rapid but transient increase in intracellular cAMP levels, they neither stimulate nor inhibit membrane-bound adenylate cyclase, suggesting a novel role for N proteins in certain receptor-transduction mechanisms. Stimulation of phagocytes by chemoattractants is also associated with a rapid increase in cytosolic Ca2+ concentrations ([ Ca2+]i) which appears to result from the production of inositol 1,4,5-triphosphate (IP3) as a consequence of the diesteric cleavage of phosphatidylinositol 4,5-bisphosphate (PIP2). Treatment of phagocytes with pertussis toxin (PT), which ADP-ribosylates and thereby inactivates certain N proteins, abolishes the cells' responsiveness to chemoattractants. More direct evidence for a role of a PT-sensitive N protein in leukocyte activation was provided by the demonstration that chemoattractants stimulate the hydrolysis of PIP2 in PMN membranes only in the presence of GTP. This receptor-mediated hydrolysis of PIP2 is not observed in plasma membranes prepared from PT-treated PMNs. Therefore, these studies suggest that occupancy of chemoattractant receptors activates a PT-sensitive N protein. The activated N protein shifts the Ca2+ requirement for phospholipase C activity from supraphysiological levels to ambient cytosolic Ca2+ concentrations. Cleavage of PIP2 results in the formation of the second messenger molecules, IP3 and 1,2-diacylglycerol, which can initiate cellular activation. These messengers also seem to activate responses which feed back to attenuate receptor stimulation of phospholipase.