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At least 19 recordsLinked to original sources
PubMed1985

Inhibition of macrophage phagocytosis by methylation inhibitors. Lack of correlation of protein carboxymethylation and phospholipid methylation with phagocytosis.

Adenosine (Ado), deoxyadenosine (dAdo), and adenine arabinoside (AraA) inhibit the phagocytosis of IgG-coated erythrocytes and zymosan by resident and thioglycollate-elicited macrophages (thio-macrophages) in a dose-dependent and reversible manner. 3-Deazaadenosine (3cAdo) and adenine (Ade) also inhibit the phagocytosis by resident macrophages. Homocysteine thiolactonate (Hcy) potentiates the inhibition by Ado and 3cAdo while erythro-9-(2-hydroxy-3-nonyl)adenine (EHNA) potentiates the inhibition by Ado, dAdo and AraA. This inhibition has a very rapid onset and the drugs do not interfere with the binding of IgG-coated erythrocytes to macrophages. The combination of Ado, Hcy and EHNA does not appreciably affect the intracellular level of ATP and S-adenosyl-L-methionine (AdoMet) in thio-macrophages but causes accumulations of Ado and S-adenosyl-L-homocysteine (AdoHcy) up to 135 and 145 nmol/mg of protein, respectively. During phagocytosis reversal, Ado is metabolized within 15 min while AdoHcy decreases log-arithmically with a half-life of 50 min. Carboxymethylation and phospholipid methylation, however, resume about 60-90 min after phagocytosis has recovered, and thus cannot function as transmembrane signals for phagocytosis. Other evidence showing the lack of correlation between phagocytosis and carboxymethylation inhibition include 1) Ado + Hcy inhibit carboxymethylation much better than Ado + EHNA (91 versus 75%) in thio-macrophage, but the two combinations show comparable phagocytosis inhibition potency; 2) Ado + Hcy inhibit carboxymethylation almost as well as Ado + Hcy + EHNA, but the latter is a much more effective drug combination for phagocytosis inhibition; 3) Ade and 3cAdo, although inhibiting resident macrophage phagocytosis as well as Ado + EHNA + Hcy, are much weaker carboxymethylation inhibitors; 4) dAdo and AraA potently inhibit phagocytosis but not carboxymethylation. The difference in the apparent methylation levels is not due to changes in the specific activities of AdoMet, which decrease with a half-life of 88 min. Interestingly, after the initial lag phase of about 90 min after the initiation of inhibition reversal, carboxymethylation and phagocytosis increase in parallel. In a log-log plot of carboxymethylation, phospholipid methylation, or phagocytosis versus the intracellular AdoHcy accumulation, a linear relationship is obtained. It is possible that AdoHcy accumulation is responsible for phagocytosis inhibition but inhibits by a mechanism other than interfering with protein and lipid methylations.

Adenine↗
PubMed2002

Complement receptor 3 (CD11b/CD18) mediates type I and type II phagocytosis during nonopsonic and opsonic phagocytosis, respectively.

Two types of opsonic phagocytosis have been defined depending on the receptor engaged: FcgammaRs mediate type I phagocytosis of IgG-coated particles; complement receptor 3 (CR3) mediates type II phagocytosis of complement-coated particles. In addition to opsonic phagocytosis, CR3 also mediates nonopsonic phagocytosis of zymosan (Z) and Mycobacterium kansasii through engagement of distinct sites. Using Chinese hamster ovary cells stably expressing human CR3, we studied CR3-mediated ingestion of nonopsonized particles, Z or M. kansasii, compared with opsonized zymosan (OZ). We show that 1) while OZ sinks into cells, Z is engulfed by pseudopodia as visualized by electron microscopy; 2) in contrast to OZ, nonopsonic phagocytosis of Z and M. kansasii depends on Rac and Cdc42 but not on Rho activity; and 3) CR3-mediated phagocytosis of Z depends on the kinase activity of the Src family tyrosine kinase Hck, while OZ internalization does not. Therefore, CR3 mediates type I phagocytosis under nonopsonic conditions and type II under opsonic conditions. This is the first evidence that a single receptor can mediate both types of phagocytosis depending on the ligand used.

Animals↗
PubMedDate not supplied

Phospholipases and phagocytosis: the role of phospholipid-derived second messengers in phagocytosis.

Phagocytosis, the process by which leukocytes recognize and destroy invading pathogens, is essential for host defense. The binding of foreign organisms to phagocytic leukocytes initiates a complex signaling cascade which ultimately results in the entrapment and destruction of the pathogen. The signal transduction pathway mediating phagocytosis is the subject of intense investigation and is known to include protein tyrosine kinases, GTP-binding proteins, protein kinase C (PKC), actin polymerization and membrane movement. A rapidly expanding body of evidence suggests that phospholipases play an integral role in phagocytosis by generating essential second messengers. Here we review the data linking activation of phospholipase A2 (PLA2), phospholipase C (PLC) phospholipase D (PLD), and phosphoinositide 3-OH kinase (PI(3)K) to antibody (IgG)-mediated phagocytosis. Evidence is presented that (1) PLA2-derived arachidonic acid (AA) stimulates NADPH oxidase and membrane redistribution during phagocytosis, (2) the inositol-3,4,5-triphosphate (IP3) and diacylglycerol (DAG) products of PLC activate NADPH oxidase and PKC, and (3) sequential activation of PLD and phosphatidic acid phosphohydrolase may provide an alternative pathway for generation of DAG. Additionally, considerable evidence exists that wortmannin, a PI(3)K inhibitor, depresses phagocytosis. This finding is discussed in the context of the extensive effects PI(3)K products have on endocytosis and exocytosis and the potential role of membrane redistribution in phagocytosis. Finally, a model is presented which integrates data obtained from a variety of phagocytic systems and illustrates potential interactions that may exist between phospholipase-derived second messengers and signaling events required for phagocytosis.

3-Phosphoinositide-Dependent Protein Kinases↗
PubMed1988

Strain variation in phagocytosis of Cryptococcus neoformans: dissociation of susceptibility to phagocytosis from activation and binding of opsonic fragments of C3.

Phagocytosis of Cryptococcus neoformans is markedly influenced by the presence of a polysaccharide capsule. We examined activation and binding of C3 fragments to eight isolates of C. neoformans. All isolates were shown to have capsules by light and electron microscopy. These strains differed in susceptibility to phagocytosis by neutrophils. Yeast cells were opsonized by incubation in normal human serum. Five strains were resistant to ingestion, two strains showed intermediate levels of resistance to ingestion, and one strain was quite sensitive to phagocytosis. Yeast cells opsonized with heat-inactivated serum (56 degrees C for 30 min) neither attached nor were ingested by neutrophils. A quantitative estimate of the amount of C3 bound to the yeast cells was determined by use of normal human serum containing 125I-labeled C3. The results showed approximately 5 X 10(6) to 10 X 10(6) C3 molecules per yeast cell regardless of whether the yeast cells were sensitive or resistant to phagocytosis. Bound C3 was eluted from the yeast cells by treatment with 0.1 M NH2OH (pH 10), and the eluted fragments were examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing conditions. Results of this analysis showed that little of the C3 was in the form of C3b, and there was substantial decay to iC3b, the inactive decay product of C3b. This pattern of decay was similar with all strains. Immunoelectron microscopy was used to assess the ultrastructural location of the C3 fragments bound to the yeast cells. C3 fragments were bound to the perimeter of the capsule regardless of whether the isolate was sensitive or resistant to phagocytosis. Thus, phagocytosis-sensitive and phagocytosis-resistant isolates were similar with regard to the amount, molecular form, and ultrastructural location of C3 fragments bound to the cryptococcal capsule. These results further indicate that activation of the complement cascade is necessary but not sufficient for phagocytosis of the yeast cell.

Complement Activation↗
PubMed1972

Quantitative studies of phagocytosis by polymorphonuclear leukocytes: use of emulsions to measure the initial rate of phagocytosis.

Polymorphonuclear leukocytes suspended in Krebs-Ringer phosphate medium ingest paraffin oil containing Oil Red O emulsified with a variety of substances. Spectrophotometric determination of Oil Red O in the cells after uningested particles have been removed by differential centrifugation provides a quantitative measure of phagocytosis. This system has been used to investigate the effects of several drugs and hormones on the initial rate of phagocytosis and to approach the question of how the surface of a particle influences its acceptability as a substrate for phagocytosis. The rate of uptake of paraffin oil emulsified with bovine albumin was constant for 6 min and was proportional to cell concentration when saturating concentrations of paraffin oil emulsion were used. At lower concentrations of substrate, the initial rate of phagocytosis was directly proportional to paraffin oil concentration. The increment in glucose oxidation associated with phagocytosis varied directly with the initial rate of particle uptake. The rate of ingestion of the albumin emulsion was not altered by serum (2-20%, v/v), glucose (5-20 mM), or omission of potassium from the medium. The rate of phagocytosis was decreased 65% if magnesium was omitted, and was essentially zero in the absence of divalent cations. The initial rate of uptake was inhibited by inhibitors of glycolysis, by N-ethylmaleimide (0.05-1 mM), colchicine (0.001-0.1 mM), theophylline (1 and 2 mM), dibutyryl cyclic AMP (1 mM), hydrocortisone (2.1 mM), and ethanol (85 mM). Inhibitors of oxidative phosphorylation and dexamethasone (0.01 mM) were without effect, while insulin (2 mU/ml) slightly stimulated the phagocytic rate. Paraffin oil emulsified with different agents was used to approach the question of how the surface of a particle influences its acceptability as a substrate for phagocytosis. Emulsions prepared with nonionic detergents, methylated proteins, and proteins with a weak net charge at pH 7.4 were poorly ingested. On the other hand emulsions prepared with agents of strong net positive or negative charge were rapidly taken up. The effect of divalent cations on the rate of phagocytosis varied with the nature of the emulsifier, but was not related in any simple, direct fashion to the net surface charge of the particles. However, it has not been conclusively established that charge was the only variable of the emulsion particles employed.

Animals↗
PubMed1985

Effect of antibodies directed against complement receptors on phagocytosis by polymorphonuclear leukocytes: use of iodination as a convenient measure of phagocytosis.

Two monoclonal antibodies (Mab), designated 60.3 and 60.1, markedly inhibited the phagocytosis of serum-opsonized zymosan by human polymorphonuclear leukocytes (PMN) as measured by the iodination reaction and by microscopic visualization. These antibodies also inhibited rosette formation with EC3bi without decreasing EC3b rosetting, suggesting that Mab 60.3 and 60.1 inhibit the phagocytosis of opsonized zymosan through reaction with the C3bi receptor (CR3) on the leukocyte surface. In support of this concept is the finding that the PMN of two patients with recurrent infections do not ingest opsonized zymosan, lack C3bi receptor function, and react weakly or not at all with Mab 60.3 and 60.1. At concentrations which completely inhibited ingestion of opsonized zymosan, both Mab partially inhibited iodination with Staphylococcus aureus 502A as the particle, and did not affect iodination when Staphylococcus epidermidis was used. This presumably reflects a variable need among the opsonized particles for CR3 for ingestion. Mab 60.3 also inhibited the phagocytosis of certain unopsonized particles as measured by iodination, indicating that the antigens recognized by the Mab do not influence phagocytosis solely by functioning as a C3bi receptor. Mab 60.3 increased the phagocytosis of unopsonized, heat-killed S. aureus by reaction with the PMN via its antibody-combining site, and with the staphylococcal protein A via its Fc region (reverse opsonization). This process required protein A-containing organisms (S. aureus 502A or Cowan 1 but not S. aureus Wood 46 or S. epidermidis), was inhibited by purified protein A, and was not seen either when the F(ab')2 or Fab fragments of the antibody, or when PMN which lack or have low levels of the antigen were employed. Thus, these studies, using iodination as a convenient method for the measurement of phagocytosis, demonstrated two effects of antibodies directed against PMN cell surface components: inhibition of phagocytosis by reaction with the C3bi receptor, and stimulation of phagocytosis by reverse opsonization.

Animals↗
PubMed1996

Macrophage phagocytosis of myelin in vitro determined by flow cytometry: phagocytosis is mediated by CR3 and induces production of tumor necrosis factor-alpha and nitric oxide.

Demyelination of axons in the central nervous system (CNS) during multiple sclerosis (MS) and its animal model experimental allergic encephalomyelitis (EAE) is a result of phagocytosis and digestion by macrophages (M phi) and the local release of inflammatory mediators like tumor necrosis factor-alpha (TNF-alpha) and nitric oxide (NO). We have investigated the process of myelin phagocytosis by M phi in vitro using flow cytometric analysis. The binding and uptake of CNS-derived myelin was dose dependent, was abolished in the presence of EDTA and was enhanced after opsonization with complement. The phagocytosis of opsonized myelin could be inhibited by antibodies directed against complement receptor type 3 (CR3). Furthermore, CR3 also contributes to phagocytosis of non-opsonized myelin, e.g. under serum-free conditions. The phagocytosis of CNS-derived myelin induced the production of substantial amounts of TNF-alpha and NO by the M phi. Our results indicate an important role for CR3 in myelin phagocytosis. The induction of TNF-alpha and NO which accompanies this phagocytosis may further contribute to the overall process of demyelination during MS or EAE.

Animals↗
PubMed1991

A phagocytosis capacity assay: parallel measurement of the phagocytosis and the intracellular killing in granulocytes and the influence of some substances on these processes.

A radiometric technique is described for the assessment of phagocytosis and killing of viable yeast cells by granulocytes. This technique does not require separation of extra- and intracellular microorganisms. In this method the phagocytes which contain viable yeast cells (Saccharomyces cerevisiae and Candida albicans) were disrupted by Triton X-100, and only the remaining yeast cells were isotope-labelled. The uptake of [75 Se]L-selenomethionine was used to measure the killing ability of phagocytes. This method is recommended to measure the influence of biological and pharmacological agents to ingest and kill leucocytes in vitro. The following substances affected phagocytosis and killing: Granatomycin C (decreased phagocytosis), cis-DDP (no influence), bestatin (stimulation of phagocytosis) and Z 190/69-HCl (oxazole) (stimulation of phagocytosis and killing).

Candida albicans↗
PubMed1981

Generation of a phagocytosis-stimulating factor by polymorphonuclear neutrophils during phagocytosis.

Polymorphonuclear neutrophils (PMNs) generated a phagocytosis-stimulating factor (PSF) intracellularly during phagocytosis of opsonized zymosan or latex particles. The generation of PSF by PMNs reached the maximum at 60 min after the start of phagocytosis. When PSF was washed out after preincubation with PMNs or opsonized zymosan particles, no enhancement of phagocytosis by PMNs was observed, suggesting that the continuous existence of PSF in the incubation medium is required for stimulation of phagocytosis.

Animals↗
PubMed1995

Cytokines modulate phagocytosis and intracellular digestion of collagen fibrils by fibroblasts in rabbit periosteal explants. Inverse effects on procollagenase production and collagen phagocytosis.

Degradation of fibrillar collagen may occur in the extracellular space by enzymes, such as the metalloproteinase collagenase, or in the lysosomal apparatus of fibroblasts following phagocytosis. As the mechanisms involved in the regulation of the latter process are unknown, we investigated possible modulating effects of the cytokines epidermal growth factor (EGF), platelet-derived growth factor (PDGF), interleukin-1 alpha (IL-1 alpha) and transforming growth factor-beta (TGF-beta) on both collagen phagocytosis and the release of collagenase in an in vitro model employing periosteal tissue explants. The data demonstrated that the level of intracellular collagen digestion could be influenced by cytokines: IL-1 alpha inhibited and TGF-beta enhanced phagocytosis of fibrillar collagen by periosteal fibroblasts, whereas the cytokines had an opposite effect on the release of procollagenase. In combination, IL-1 alpha and TGF-beta proved to have an antagonizing effect on either parameter. PDGF and EGF had no effect on phagocytosis or collagenase release. The level of phagocytosed collagen correlated positively with the actual breakdown of collagen as assessed by the release of hydroxyproline but negatively with the level of released procollagenase. Our findings demonstrated that cytokines are able to modulate both the phagocytosis of collagen fibrils by fibroblasts and their subsequent intracellular breakdown, as well as the release of procollagenase, an enzyme considered crucial for extracellular collagenolysis. Moreover, our data show a negative correlation between these two parameters. It is concluded that IL-1 alpha, EGF and TGF-beta may be important in modulating the contribution of the intracellular and extracellular route of collagen breakdown.

Animals↗
PubMed1956

Phagocytosis of bacteria in the absence of antibody and the effect of physical surface; a reinvestigation of surface phagocytosis.

The present experiments have shown that phagocytosis occurs in the absence of specific antibody and in the absence of a "suitable physical surface", as further that the presence of a rough surface does not increase the in vitro phagocytosis of pneumococci by polymorphonuclear leukocytes. This held true during repetition of Wood's experiments, as well as when more controlled quantitative techniques were employed, when conditions were made optimal for phagocytosis by increasing bacterial concentrations, and when blood leukocytes were substituted for exudate leukocytes. Evidence has been presented previously that the stimulation of phagocytosis of E. coli, B. abortus, and Type IV Pneumococcus, after contact with filter paper or an active compound present in filter paper, is a chemical effect rather than a physical effect. This type of stimulation did not occur with the Type I A5 Pneumococcus. The leukocyte of the circulating blood was found to be definitely superior to the exudate leukocyte in phagocytic capacity, under all the experimental conditions tested.

Antibodies↗
PubMed1990

Phagocytosis in Acanthamoeba: I. A mannose receptor is responsible for the binding and phagocytosis of yeast.

We have examined the initial events in phagocytosis by Acanthamoeba castellanii in order to understand this process at the molecular level and have determined that phagocytosis in this organism is mediated by a receptor which recognizes mannose-rich elements in the particle to be phagocytosed. We demonstrate that the binding and internalization of yeast particles can be inhibited by the sugars (D(+)-mannose and D(-)-fructose in a stereospecific, concentration-dependent manner. This inhibition is specific; these sugars did not inhibit the uptake of latex beads by this organism. Using mannosylated neoglycoproteins, which are much more potent inhibitors of particle binding as compared with the free sugar, we demonstrate the presence of a receptor on the amoeba cell surface which is necessary for the binding of yeast as the initial event of phagocytosis. The Acanthamoeba mannose receptor also appears to be able to mediate the delivery of soluble mannose-rich molecules to a degradative compartment such as the lysosome. Knowledge of this receptor will allow a better understanding of the molecular events of phagocytosis.

Acanthamoeba↗
PubMed1992

Membrane sorting during phagocytosis: selective exclusion of major histocompatibility complex molecules but not complement receptor CR3 during conventional and coiling phagocytosis.

We have used immunocytochemical techniques and enzyme cytochemistry to examine the distribution of plasma membrane proteins during coiling phagocytosis of Legionella pneumophila and conventional phagocytosis of Escherichia coli. Whereas class I and class II major histocompatibility complex (MHC) molecules are relatively excluded from nascent phagosomes during conventional and coiling phagocytosis, the CR3 complement receptor persists in nascent phagosomes. The staining pattern for alkaline phosphatase activity resembles that of MHC molecules, with a marked exclusion of phosphatase activity from L. pneumophila coils and nascent phagosomes. The staining pattern for 5'-nucleotidase activity, on the other hand, resembles that of CR3 with intense staining in the inner layers of L. pneumophila coils. These results demonstrate that the cell has the ability to exclude selectively certain membrane proteins from the nascent phagosome during phagocytosis, thereby producing a phagosomal membrane markedly different from the plasma membrane from which it is derived.

5'-Nucleotidase↗
PubMed1992

Cytokine enhancement of complement-dependent phagocytosis by macrophages: synergy of tumor necrosis factor-alpha and granulocyte-macrophage colony-stimulating factor for phagocytosis of Cryptococcus neoformans.

We have examined the regulation of complement dependent phagocytosis by macrophage-activating cytokines. Tumor necrosis factor (TNF)-alpha and granulocyte-macrophage colony-stimulating factor (GM-CSF), but not interferon-gamma, interleukin-4 or macrophage-CSF, stimulated ingestion of the encapsulated fungal pathogen Cryptococcus neoformans by resident peritoneal macrophages in vitro. This was dependent upon opsonization of the yeasts with complement, 72 h of incubation with the cytokines for maximum effect, and the obligate involvement of the macrophage CR3 receptor. TNF-alpha and GM-CSF synergized at low concentrations, resulting in dramatic up-regulation of phagocytosis when compared to either cytokine alone. Supernatants from C. neoformans-specific T cells also increased macrophage phagocytic efficiency. Finally, the administration of neutralizing mAb specific for TNF-alpha and GM-CSF increased mortality in C. neoformans-infected mice, and induced the rapid progression of disease with involvement of the brain and meninges. We conclude that TNF-alpha and GM-CSF are potent regulators of complement-dependent phagocytosis by murine macrophages. Macrophage activation with these two cytokines can completely overcome the anti-phagocytic properties of the virulent yeasts. Our results, therefore, implicate TNF-alpha and GM-CSF as important mediators of resistance to encapsulated pathogens such as C. neoformans where ingestion of the organism is a critical process in host resistance.

Animals↗
PubMed1980

Mechanism of phagocytosis in Dictyostelium discoideum: phagocytosis is mediated by different recognition sites as disclosed by mutants with altered phagocytotic properties.

The recognition step in the phagocytotic process of the unicellular amoeba dictyostelium discoideum was examined by analysis of mutants defective in phagocytosis, Reliable and simple assays were developed to measure endocytotic uptake. For pinocytosis, FITC-dextran was found to be a suitable fluid-phase marker; FITC-bacteria, latex beads, and erythrocytes were used as phagocytotic substrates. Ingested material was isolated in one step by centrifuging through highly viscous poly(ethyleneglycol) solutions and was analyzed optically. A selection procedure for isolating mutants defective in phagocytosis was devised using tungsten beads as particulate prey. Nonphagocytosing cells were isolated on the basis of their lower density. Three mutant strains were found exhibiting a clear-cut phenotype directly related to the phagocytotic event. In contrast to the situation in wild-type cells, uptake of E. coli B/r by mutant cells is specifically and competitively inhibited by glucose. Mutant amoeba phagocytose latex beads normally but not protein-coated latex, nonglucosylated bacteria, or erythrocytes. Cohesive properties of mutant cells are altered: they do not form EDTA-sensitive aggregates, and adhesiveness to glass or plastic surfaces is greatly reduced. Based upon these findings, a model for recognition in phagocytosis is proposed: (a) A lectin-type receptor specifically mediates binding of particles containing terminal glucose (E. coli B/r). (b) A second class of "nonspecific" receptors mediate binding of a variety of particles by hydrophobic interaction. Nonspecific binding is affected by mutation in such a way that only strongly hydrophobic (latex) but not more hydrophilic particles (e.g., protein-coated latex, bacteria, erythrocytes) can be phagocytosed by mutant amoebae.

Binding Sites↗
PubMed1975

Phagocytosis as a surface phenomenon. V. Contact angles and phagocytosis of rough and smooth strains of Salmonella typhimurium, and the influence of specific antiserum.

The angle made by a drop of saline in contact with a monolayer of Salmonella typhimurium or phagocytic cells, the contact angle, is a measure of their relative interfacial tension, and is predictive of a successful phagocytosis. Smooth strains of S. typhimurium possess a contact angle lower than the phagocytic cells and resist phagocytosis. Rough strains have an angle higher than the phagocytes and are readily engulfed. The lower contact angle of smooth strains can be increased by treatment with specific antibody resulting in more efficient phagocytosis.

Animals↗
PubMed1991

Phagocytosis of Mycobacterium leprae by human monocyte-derived macrophages is mediated by complement receptors CR1 (CD35), CR3 (CD11b/CD18), and CR4 (CD11c/CD18) and IFN-gamma activation inhibits complement receptor function and phagocytosis of this bacterium.

We have examined phagocytosis of Mycobacterium leprae by human monocyte-derived macrophages (MDM). Compared with monocytes, MDM exhibit greatly enhanced adherence of M. leprae (6.5 +/- 2-fold increase). MDM adherence of M. leprae is serum dependent and requires heat-labile serum components because heat inactivation of serum reduces adherence by 70 +/- 3%. mAb against C receptors CR1 (CD35), CR3 (CD11b/CD18), and CR4 (CD11c/CD18) inhibit phagocytosis of M. leprae in fresh nonimmune serum. Single mAb against each receptor inhibit M. leprae adherence by 25 +/- 4% - 33 +/- 6%. Single mAb used in combination against all three receptors inhibit M. leprae adherence by 51 +/- 6%. Most significantly, pairs of mAb used in combination against all three receptors inhibit by 80 +/- 4%. By electron microscopy, MDM ingest all M. leprae that adhere in fresh nonimmune serum. In the presence of mAb against CR1, CR3, and CR4, the percentage of MDM cross-sections that contain intracellular bacteria is reduced 66 +/- 3% and the mean number of bacteria per cross-section is reduced 78 +/- 10%. MDM activated by IFN-gamma exhibit markedly reduced adherence (by light microscopy) and ingestion (by electron microscopy) of M. leprae. MDM in culture for 5 days inhibit M. leprae adherence by 83 +/- 2% and ingestion by 88% when activated for 5 days. Paralleling this, IFN-gamma-activated MDM exhibit markedly reduced C receptor function, reflected by markedly decreased adherence and ingestion of C3b- and C3bi-coated E. Decreased C receptor function by IFN-gamma-activated MDM correlates with decreased surface expression of CR1 but not CR3 or CR4. CR1 expression on MDM in culture for 5 days is reduced by 32 +/- 9% and 75 +/- 3% after IFN-gamma activation for 5 and 2 days, respectively. This study demonstrates that MDM have an enhanced capacity to phagocytize M. leprae, and that in addition to CR1 and CR3, phagocytosis involves CR4, whose expression on MDM is highly maturation-dependent. This study also demonstrates that IFN-gamma activation markedly reduces the capacity of MDM to phagocytize M. leprae, and it provides a molecular mechanism for this phenomenon-decreased C receptor function.

Antibodies, Monoclonal↗
PubMed1977

Quantitative phagocytosis by human polymorphonuclear leucocytes. Use of radiolabelled emulsions to measure thae rate of phagocytosis.

A new micro-method for the quantitative measurement of phagocytosis by neutrophils is described. The material used for phagocytosis consists of a radioactive oil emulsion coated with E. coli lipopolysaccharide. Uptake of radioactive material is a function of cell number, duration of incubation, dilution of serum used for opsonization, content of lipopolysaccharide and concentration of emulsion. This method can be used to quantify rapidly and precisely phagocytosis rates of as few as 5 x 10(4)-10(6) polymorphonuclear leucocytes and the opsonic activity of 10 microliter serum.

Albumins↗