Murine cytomegalovirus-induced macrophage dysfunction

Macrophages infected in vitro with murine cytomegalovirus (MCMV) manifest depressed phagocytic uptake of a variety of particles within hours after the initiation of infection. Analysis of kinetics of uptake of radiolabeled Staphylococcus aureus by MCMV-infected macrophages indicates that the diminished uptake results from a depression in the calculated maximum velocity of uptake (Vmax) with the apparent Michaelis constant (KM) remaining unaltered. This pattern of altered uptake is typical of that seen after manipulations that affect the surface interactions of macrophages with ingestible particles. Coincubation of macrophages and radiolabeled Staphylococcus with opsonizing antibody resulted in normalization of the phagocytic rates. The surface localization of the defective phagocytosis was further confirmed by light and scanning electron microscopy of the macrophages incubated with Staphylococcus or latex spherules. These data indicate that defective macrophage surface that interferes with the initial macrophage-particle interactions that initiate nonimmune phagocytosis.     

Deficient intracellular killing of bacteria by murine alveolar macrophages

Microbiologic methods were used to assess the in vitro phagocytosis and intracellular killing of various species of bacteria by freshly isolated murine peritoneal and alveolar macrophages. Peritoneal macrophages showed effective phagocytosis of opsonized Streptococcus pneumoniae, Streptococcus pyogenes, Pseudomonas aeruginosa, Staphylococcus epidermidis, and Listeria monocytogenes, and moderate ingestion of Staphylococcus aureus and Escherichia coli. Alveolar macrophages were poor in phagocytosing opsonized S. pyogenes, S. aureus, and E. coli; ingestion of S. pneumoniae, P. aeruginosa, and S. epidermidis was moderate. Peritoneal macrophages killed 40 to 80% of these bacteria intracellularly, but alveolar macrophages showed almost no intracellular killing of bacteria. To find out whether there is a correlation between the poor bactericidal activity of alveolar macrophages and the oxygen-dependent microbicidal mechanisms of these cells, we determined the uptake of oxygen and the release of superoxide anion and hydrogen peroxide by macrophages at rest and after stimulation with phorbol myristate acetate (PMA) or opsonized S. aureus. Upon exposure to these stimuli, peritoneal macrophages, but not alveolar macrophages, showed an increased uptake of oxygen and release of superoxide anion and hydrogen peroxide. Because alveolar macrophages contain surface active material (SAM), we investigated the phagocytosis and intracellular killing of bacteria and the release of hydrogen peroxide by peritoneal macrophages pretreated with SAM. The results showed reduced phagocytosis and impaired intracellular killing of S. epidermidis by these macrophages. The release of hydrogen peroxide by SAM-pretreated peritoneal macrophages upon stimulation with PMA or opsonized S. aureus was equal to that of the control peritoneal macrophages.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of physical activity stress on the phagocytic process of peritoneal macrophages from old guinea pigs.

The different stages of the phagocytic function in peritoneal macrophages from old guinea pigs (27 +/- 3-months-old) were studied before, immediately after and 24 h after being subjected to physical activity stress (swimming until exhaustion) which raised the blood levels of corticosterone. The phagocytosis of opsonized Candida albicans was stimulated immediately after physical activity. No modifications in adherence, chemotaxis, ingestion of inert particles, or microbicide capacity, measured by nitroblue tetrazolium (NBT) reduction, were found. At 24 h, when no stress could be shown by corticosterone analysis, the phagocytosis of opsonized C. albicans remained stimulated and chemotaxis was increased while ingestion of inert particles and microbicide capacity remained unchanged. The adherence, however, was at a smaller level. No correlations were found between the corticosterone levels and the status of the phagocytic process of peritoneal macrophages.     

Respiratory burst activity is impaired during phagocytosis of gelatinized fixed erythrocytes by inflammatory macrophages

The ability of immune and nonimmune opsonized gelatin-coated particles to stimulate respiratory burst activity by inflammatory macrophages was studied. The uptake and phagocytosis of⁵¹Cr-labeled gelatin-coated fixed erythrocytes, opsonized with either specific IgG or purified plasma fibronectin, was measured in monolayer cultures of rat inflammatory peritoneal macrophages. Respiratory burst activity was evaluated in monolayers of rat inflammatory peritoneal macrophages by measuring: (1) luminol-dependent chemiluminescence and (2) the production of¹⁴CO₂ from the oxidation of [1-¹⁴C] glucose. Uptake of opsonized gelatin-coated, fixed erythrocytes resulted in no stimulation of chemiluminescence and only a limited stimulation of [1-¹⁴C] glucose oxidation. Respiratory burst activity produced by phorbol myristate acetate was not inhibited during the uptake of opsonized gelatincoated particles. These data suggest that metabolic processes associated with macrophage respiratory burst activity may not be coupled to the ingestion of opsonized gelatin-coated fixed erythrocytes.     

Macrophage phagocytic recognition sites. Demonstration of selectivity by hetero- and alloantisera.

Separate and independent phagocytic recognition sites have been identified on mouse peritoneal macrophages through the use of xenogeneic antimacrophage serum (AMS) and allogeneic anti H-2 antisera. Anti H-2d and anti H-2b antisera inhibit the binding and ingestion of opsonized erythrocytes (EA) by macrophages bearing H-2 haplotypes d and b, respectively. AMS and its F(ab')2 and Fab fragments inhibit the binding and ingestion of EA, and the ingestion but not the binding of 125I-labelled Shigella by macrophages. Neither antiserum inhibited the binding or ingestion of latex particles by macrophages. The results suggest that particulate binding to macrophages can be inhibited by two different mechanisms: a non-specific one where antibody bound to certain cell-surface antigens can mediate either directly or indirectly, and a specific interaction with Fc receptors. The possible mechanisms of non-specific antibody mediated phagocytic inhibition are discussed.     

Ingestion of yeast forms of Sporothrix schenckii by mouse peritoneal macrophages.

The ingestion by thioglycolate-elicited mouse peritoneal macrophages of yeast forms of two strains of Sporothrix schenckii was studied. Yeast forms opsonized with concanavalin A (ConA) were extensively phagocytized, and the phagocytic indexes depended on the concentration of ConA and apparently on the number of lectin receptors at the yeast surface as well. Neuraminidase treatment of S. schenckii increased the ingestion of unopsonized yeasts 7.7-fold. The addition of monosaccharides and derivatives partially inhibited phagocytosis. Mannose, rhamnose, and galactose, which are major constituents of S. schenckii surface antigens, reduced the phagocytic indexes by 40 to 50%. Glucosamine, N-acetylglucosamine, and N-acetylneuraminic acid were equally effective as inhibitors of phagocytosis. A mixture of five neutral sugars and glucosamine inhibited phagocytosis by 73%. The inhibitory effect of simple sugars could be amplified by using neuraminidase-treated yeast cells. Pentoses and glucose were inactive or slightly inhibitory. A purified rhamnomannan inhibited phagocytosis of the homologous strain, whereas partially purified peptidopolysaccharides were toxic to peritoneal macrophages. A partially purified galactomannan from S. schenckii was inhibitory (62% inhibition), and a peptidopolysaccharide fraction in which the O-linked carbohydrate chains had been removed neither was toxic to macrophages nor inhibited phagocytosis. Pretreatment of macrophages with simple sugars under conditions inhibiting ingestion or binding of S. schenckii did not affect phagocytosis of latex particles or sensitized sheep erythrocytes. The presence of receptors at the peritoneal macrophages which bind S. schenckii cell surface components is suggested.     

Phagocytosis of Agarose Beads by Receptors for C3b (CR1) and iC3b (CR3) on Human Alveolar Macrophages Cultured on Fibronectin in Vitro

We studied the phagocytosis of agarose beads by human alveolar macrophages in terms of the morphology, the receptors involved, and the cellular substrates (plastic or fibronectin) used. Beads coated with C3b (58%) and iC3b (42%) by treatment with serum, were ingested during 45 min by CR1 and CR3 on the macrophages. This ingestion was inhibited 80-90% by the presence of polyclonal F(ab')2 anti-C3 fragments. Since the phagocytosis of both C3b- and iC3b-coated beads was about threefold stronger than for C3b-coated beads (trypsinized serum-treated beads), the results indicate that the CR3 is more phagocytic than the CR1. The phagocytosis of initially complement uncoated beads, which are slowly opsonized with macrophage-produced C3b and iC3b in vitro, was also strongly inhibited (70-80%) by the presence of anti-human C3 F(ab')2 fragments. There was an increased phagocytosis (10-17%) of complement precoated beads by macrophages cultured on the fibronectin substrate versus the plastic substrate. The morphology and rapid phagocytosis of the complement precoated beads was demonstrated by SEM. The general impression was that membranous protrusions stretched towards the beads, which became increasingly enclosed by plasma membrane.     

Peroxidase activity of alveolar macrophages.

Peroxidase activity was studied in alveolar macrophages and compared to the peroxidase activity in polymorphonuclear leukocytes using cytochemical techniques. A dense reaction product for peroxidase was observed in the primary lysosomes of polymorphonuclear leukocytes, but no significant peroxidase or peroxidative enzymes could be detected in rabbit alveolar macrophages. Furthermore, following vigorous phagocytosis of zymosan particles by alveolar macrophages in vitro, no peroxidase could be detected in association with the phagocytic vacuole. Exogenous horseradish peroxidase was ingested readily by alveolar macrophages so that abundant reaction product was demonstrated in pinocytotic vesicles and phagocytic vacuoles. The uptake of exogenous peroxidase by pinocytosis appeared to be more vigorous in alveolar macrophages than in polymorphonuclear leukocytes. These studies demonstrate that alveolar macrophages do not contain significant quantities of peroxidase and suggest that, it contrast to polymorphonuclear leukocytes, peroxidative metabolism does not contribute in a major way to microbial killing by alveolar macrophages.     

A rapid radiometric assay for measuring phagocytosis of Saccharomyces cerevisiae in macrophage cultures

A new assay was developed to measure yeast phagocytosis in cultures of murine resident peritoneal macrophages. Saccharomyces cerevisiae was radiolabeled during exponential growth in nutrient broth supplemented with [3H]glucose. Following ingestion of the radiolabeled heat-killed yeast particles for 15 min, phagocytic capacities were measured in harvested macrophage lysates by liquid scintillation spectrometry. The new procedure compares favorably with light microscopic techniques and appears to be a more sensitive method for quantitating phagocytic function. Dose-response studies indicate, that over a wide range of dexamethasone concentrations, the radiometric procedure consistently measures greater inhibitory effects for the steroid induced suppression of phagocytosis.     

High-affinity binding of fibronectin to cultured Kupffer cells

Hepatic Kupffer cells are a major component of the reticuloendothelial or macrophage system. They were the first phagocytic cell type whose phagocytosis was shown to be influenced by plasma fibronectin, a dimeric opsonic glycoprotein. In the current study, the binding of soluble radioiodinated fibronectin purified from rat serum to isolated rat hepatic Kupffer cells was investigated using a cultured Kupffer cell monolayer technique. Binding was specific, since unlabeled purified fibronectin competed in a dose-dependent manner with the 125I-fibronectin for binding to the Kupffer cells. Addition of gelatin enhanced the binding of 125I-fibronectin to Kupffer cells. The phagocytosis of gelatinized-coated red cells by Kupffer cells was increased either by preopsonizing the target particles with purified fibronectin or by the addition of purified fibronectin to the culture medium. In contrast, exposure of the Kupffer cells to medium containing purified fibronectin followed by wash-removal of the fibronectin did not increase the uptake of gelatin-coated red blood cells, even though fibronectin was detected on the surface of the Kupffer cells by immunofluorescence. Trypsinized monolayers expressed decreased capacity to bind 125I-fibronectin as well as fibronectin-coated sheep erythrocytes. The binding of 125I-fibronectin-gelatin complexes was inhibited by excess unlabeled fibronectin. We calculated that specific high-affinity (Kd = 7.46 x 10(-9) M) binding sites for fibronectin exist on Kupffer cells. There are approximately 2,800-3,500 binding sites or putative "fibronectin receptors" per Kupffer cell. These sites appear to mediate the enhanced phagocytosis of gelatin-coated particles opsonized by fibronectin.     

Receptor-mediated phagocytosis of rat macrophages is regulated differentially for opsonized particles and non-opsonized particles containing β-glucan

Experiments were conducted to test the hypothesis that opsonic and non-opsonic phagocytic capacities are differentially regulated by resting and wound-derived macrophages. Furthermore, the phagocytosis of non-opsonized zymosan and beta-glucan particles was quantified to determine whether cells differentially regulate non-opsonic lectinophagocytosis in accordance with the carbohydrate composition of the ligand. In that regard, wound macrophages exhibited profound differential regulation in lectinophagocytosis with a seven-fold increase in phagocytosis of beta-glucan particles following overnight culture but with a relatively modest increase in internalization of mannan-containing zymosan. Cultured peritoneal macrophages increased uptake of both particles similarly. Upon activation with interferon-gamma/lipopolysaccharide (IFN-gamma/LPS), wound macrophages selectively suppressed beta-glucan ingestion, while phagocytosis of zymosan particles was unaffected. Lectinophagocytosis was decreased in activated peritoneal macrophages regardless of particle composition and was due in part to a nitric oxide-dependent mechanism which was without a role in regulation of wound macrophage lectinophagocytosis. Overnight culture of wound macrophages suppressed their capacity for opsonic-dependent phagocytosis independently of activation, whereas suppression of phagocytosis by peritoneal macrophages was activation-dependent. Regulation of all three phagocytic pathways was achieved distinctly by peritoneal and wound-derived macrophages, with changes found in the percentage of resident peritoneal macrophages capable of phagocytosis, whereas the phagocytic capacity of wound macrophages was primarily affected by the number of particles ingested by individual cells. Taken together, these findings demonstrate that the differential regulation of phagocytic pathways encompasses the nature of the phagocytic particle, the site from which macrophages are obtained, their response to activating agents and the mechanism through which the cell population alters its phagocytic potential.     

A modified colorimetric method for the measurement of phagocytosis and antibody-dependent cell cytotoxicity using 2,7-diaminofluorene.

A sensitive and rapid colorimetric method for the in vitro determination of phagocytic activity and antibody-dependent cell-mediated cytotoxicity (ADCC) is described. The assay uses red blood cells (RBC) as target cells and relies on the specific oxidation of 2,7-diaminofluorene (DAF) by the pseudoperoxidase activity of hemoglobin (Hb). Generation of fluorene blue (FB), the chromophore formed upon oxidation of DAF, was a linear function of erythrocyte concentration. The oxidation of DAF by peritoneal macrophages (M phi) containing myeloperoxidase was negligible, confirming that the development of color was exclusively due to the pseudoperoxidase activity of Hb. A positive correlation was observed between FB formation and increased phagocytosis of opsonized erythrocytes. Phagocytosis increased as a function of time, reaching a maximum at 90 min of incubation. The phagocytosis of IgG-opsonized erythrocytes was greater than non-opsonized erythrocytes and was inhibited by high concentrations of non-specific human or mouse IgG, showing that phagocytosis was mediated by the Fc gamma receptor of macrophages. The interaction between opsonized RBC and macrophages also evoked an antibody-dependent extracellular lysis, however this process was slower than ingestion. The DAF phagocytosis assay has shown to be very sensitive, simple, rapid and safe.     

Acetylspiramycin and the immune system. I. Effects of acetylspiramycin on phagocytosis by mouse macrophages in vitro and in vivo

A study was made of the effect of acetylspiramycin (ASPM) on the phagocytic activity of mouse macrophages in vitro and in vivo, using opsonized, 51Cr-labelled sheep red blood cells (SRBC) as test particles. Resident mouse peritoneal macrophages cultured with ASPM (25-100 micrograms/ml for 18 h) showed a 62-92% reduction in phagocytosis. This was due to decreases in both attachment and ingestion of SRBC and was additional to the detachment of some macrophages from the surface of the culture chamber. Morphologically the macrophages were vacuolated, with some nuclear condensation. When the cells were cultured for a further 48 h after removal of ASPM there was almost complete functional and morphological recovery. When mice were treated with ASPM (50-100 mg/kg orally for 7 days) their peritoneal macrophages showed increases of 57-121% in phagocytic activity in vitro. In mice treated with ASPM (200 mg/kg orally for 7-21 days) the clearance of i.v. injected opsonized SRBC was significantly accelerated. Thus, although ASPM is reversibly toxic to macrophages in vitro, it is not toxic in vivo, but actually stimulates the mononuclear phagocyte system. It is possible that metabolites of ASPM, such as neospiramycin, produced in vivo but not in vitro, are responsible for the stimulation.     

Phagocytosis of staphylococci by human polymorphonuclear leukocytes is enhanced in the presence of endothelial cells.

The role of various surfaces in the phagocytosis of Staphylococcus aureus by human polymorphonuclear leukocytes (PMN) was studied. Uptake of both opsonized and unopsonized staphylococci on the surface of a monolayer of human venous endothelial cells was compared with uptake on an inert plastic surface, with an assay that uses radiolabeled bacteria. Uptake of unopsonized S. aureus was threefold higher on the endothelial cell surface than on the plastic surface and was followed by efficient killing of the phagocytosed staphylococci. Uptake of unopsonized S. aureus on endothelial cells was not inhibited by treatment of the PMN with pronase or 2-deoxy-D-glucose and was only partially inhibited by cytochalasin B treatment of the PMN. The supporting effect of endothelial cells on the phagocytosis of unopsonized S. aureus was not due to opsonization of the bacteria by immunoglobulin or complement from the endothelial cell surface, nor to coating with fibronectin.     

Human polymorphonuclear leucocyte receptors for staphylococcal opsonins

The presence of receptors on the plasma membrane of human polymorphonuclear (PMN) leucocytes for factors related to complement and for the Fc region of immunoglobulin has not been clearly defined for opsonized bacteria. To separate the activity of these two receptors, the uptake of [³H]thymidine labelled staphylococci opsonized with normal serum or heat-inactivated serum was measured. Phagocytosis was depressed when bacteria opsonized with normal serum were incubated with trypsin-treated leucocytes, suggesting that complement receptors of human PMN leucocytes are trypsin-sensitive. Phagocytosis of bacteria opsonized with heat-inactivated serum was not depressed by trypsin, but was blocked by incubating PMN leucocytes with heat-aggregated IgG and by incubating opsonized bacteria with protein A. In experiments performed to quantify the number of bacteria attached to but not ingested by PMN leucocytes, it was shown that both complement and Fc receptors participate in the ingestion phase of phagocytosis. Cell membranes of human PMN leucocytes possess two receptors for opsonized staphylococci; a complement receptor which is utilized when bacteria are opsonized in normal serum and an Fc receptor when bacteria are opsonized in heat-inactivated serum. Both receptors participate in the ingestion as well as the attachment phase of phagocytosis.     

Ultrastructural and immunological aspects of the phagocytosis of Trypanosoma brucei by mouse peritoneal macrophages.

Trypanosome-activated mouse peritoneal macrophages phagocytized and digested Trypanosoma brucei in vitro and in vivo, but in the absence of specific antiserum and complement the degree of phagocytosis was minimal. Ultrastructurally, the parasites attached to the macrophage by their flagella, and ingestion proceeded flagellum first. Once ingested, T. brucei was degraded, presumably due to fusion of the parasite-containing phagosome with lysosomes. Contrariwise, normal mouse peritoneal macrophages displayed negligible ability to ingest T. brucei, even in the presence of specific antiserum and complement. During trypanosomiasis in deer mice (Peromyscus maniculatus), the development of hypergammaglobulinemia correlated with enhanced phagocytosis of T. brucei by macrophages, but only at early post-inoculation days (PID 5 to 15). Complement lysis of trypanosomes was not identified in these experiments. Between PID 20 to 30, antiserum and complement either had no phagocytosis-promoting ability or depressed the phagocytosis of T. brucei by macrophages. These results indicate that both specific antibody and complement contribute to the ingestion of T. brucei by activated macrophages, but that parasite antigenic variation effectively abrogates the phagocytic defense mechanism.     

Effect of lentinan and mannan on phagocytosis of fluorescent latex microbeads by mouse peritoneal macrophages: a flow cytometric study

Lentinan, an immunopotentiating beta-1,3-glucan polysaccharide stimulated the in vitro phagocytosis of BSA-coated, C3b- or monoclonal immunoglobulin (IgG2b)-coated fluorescent microspheres by resident or thioglycollate-elicited mouse macrophages in a dose-dependent manner. Analysis of flow cytometric data has shown that microbead phagocytosis of resident macrophages, which exhibit a lower basic phagocytic activity than the thioglycollate elicited ones, has been augmented by up to 900% due to lentinan. The percent ratio of phagocytes among peritoneal exudate cells, however, remained unchanged after short-term lentinan stimulation. Preincubation of the cells with lentinan resulted in increased ingestion of the microbeads. Activation of phagocytosis by lentinan is therefore due in part to the direct stimulation of the cells, however, lentinan also serves as supplementary opsonin for C3b-coated beads. Mannan inhibited the ingestion of C3b-coated microspheres by 75%, which was abolished in part when lentinan was also added to the cells. Mannan did not influence the phagocytosis of BSA-coated or IgG-coated beads. Our data, based solely on in vitro studies, suggest a beta-glucan receptor mediated activation of phagocytes by lentinan. These receptors are different from the C3b, Fc or mannose receptors. It is very likely that stimulation of phagocytic activity of macrophages by lentinan may contribute to the antitumor action of this immunopotentiating polysaccharide.     

The role of alveolar macrophages in the pathogenesis of aspiration pneumonitis

RATIONALE: A robust TNFalpha response is seen following aspiration of food particles, while there is only a modest response to acid. OBJECTIVES: To examine the direct effects of acid and particulate components of gastric content on local and systemic macrophages. METHODS: Pathogen-free Long-Evans rats were injured with intratracheal instillation of normal saline (SHAM), low pH saline (ACID), small non-acidic particles (SNAP) or acidified particles (CASP). The alveolar (local) and the peritoneal (systemic) macrophages were harvested following the injury. MEASUREMENTS: We examined the phagocytic activity and TNFalpha release by the alveolar and peritoneal macrophages following in vivo and in vitro exposure to acid and/or food particles. TNFalpha release by macrophages was examined in response to E. coli lipopolysaccharide (LPS) stimulation. MAIN RESULTS: In rats injured with gastric particles, the number of the mononuclear cells was higher than those obtained from acid-injured animals. Both in vivo and in vitro exposure of the alveolar macrophages to SNAP resulted in increased production of TNFalpha within 8 hours. Transient exposure of the alveolar macrophages to a low pH environment suppressed LPS-induced production of this cytokine. Additionally, the phagocytic activity of the alveolar macrophages was inhibited by in vitro exposure of the macrophages to acid. CONCLUSIONS: We conclude that the two components of gastric aspiration have diverse effects on local and systemic macrophages. Although there is a synergy between acid and gastric particulate in producing an acute lung injury, the modulatory effects of these injuries on the alveolar macrophages are averse.     

Bactericidal mechanisms in rabbit alveolar macrophages: evidence against peroxidase and hydrogen peroxide bactericidal mechanisms.

The role of peroxidase-mediated bacterial killing by rabbit alveolar macrophages was examined. During 3 h of incubation in vitro, alveolar macrophages ingested and killed greater than 88% of the Streptococcus faecalis, Proteus mirabilis, or Streptococcus pneumoniae present in the incubation mixture. Preincubation of alveolar macrophages with inhibitors of catalase, 3-amino-1,2,4-triazole or sodium nitrite, did not alter their bactericidal potential. Iodination of ingested zymosan particles, a peroxidase-dependent and hydrogen peroxide-dependent reaction, was not observed, in spite of vigorous phagocytosis by alveolar macrophages. Furthermore, iodination by alveolar macrophages was not significantly increased when peroxidase-coated zymosan particles were ingested. The results suggest that hydrogen peroxide may not be available to the phagocytic vacuole for microbial killing. Since tetrazolium dye reduction reflects the activity of an oxidase responsible for stimulated oxygen consumption by polymorphonuclear leukocytes, this reaction was also measured. Rabbit alveolar macrophages incubated with latex particles did not exhibit an increased dye reduction compared with resting cells. The absence of significant stimulation of tetrazolium dye reduction indicates that the oxidase reaction does not occur in the proximity of the phagocytic vacuole of alveolar macrophages.     

Augmentation of glucose transport in macrophages after particle ingestion

Guinea pig and mouse peritoneal macrophages in culture transport glucose by a specific, saturable system with characteristics compatible with facilitated diffusion. Phagocytosis of killed staphylococci or polystyrene latex spheres results in a significant increase in uptake of 2-deoxy-d-glucose. Reciprocal plot analysis showed that the K(m) values were lowered as a consequence of phagocytosis by a factor of between 2 and 3 in both cell types; V(max) values were not significantly changed. The nature of the intracellular sugar pool was analyzed and found to consist of free and phosphorylated 2-deoxy-d-glucose at a relatively constant ratio of 1:2 after periods of uptake between 1 and 20 min. Phagocytosis resulted in increased levels of both free and phosphorylated sugars in the cytoplasm. Since the K(m) values were lowered, augmented glucose uptake could not be accounted for by altered hexokinase activity. It was concluded that phagocytosis induces changes in the glucose transport system per se. The data are compatible with the metabolic changes known to be associated with particle ingestion by phagocytic cells. The mechanism by which glucose transport is augmented after loss of significant amounts of cell surface during the phagocytic process is not yet known.