Viable Macrophages Research Articles

Recombinant Escherichia coli express a defined, cytoplasmic epitope that is efficiently processed in macrophage phagolysosomes for class II MHC presentation to T lymphocytes.

Although the processing of soluble Ag for presentation to T cells has been extensively studied in vitro, similar studies of phagocytic Ag processing have been limited. We have developed an in vitro model system to study the ability of macrophages to process recombinant Escherichia coli strain HB101 with cytoplasmic or surface expression of the well characterized T cell epitope of hen egg lysozyme (HEL) 52-61. This epitope was expressed within full length HEL or within a fusion protein containing the HEL epitope. Phagocytosis of E. coli with cytoplasmic expression of HEL or the HEL fusion protein resulted in strong presentation of HEL(52-61) to T cells. Surface-conjugated HEL was processed with even greater efficiency. Processing required viable macrophages, was inhibited by cytochalasin D, and was achieved within 20 min of bacterial contact with the macrophages. Within this time span, phagosomes containing bacteria fused with lysosomes, and the bacteria were extensively degraded. Uptake of as few as four bacteria per macrophage produced an Ag-specific T cell response. We conclude that bacterial compartmentalization of the antigenic epitope (cytoplasmic vs surface) had some effect on its processing, but that phagocytic Ag processing organelles contain extensive capacity to degrade internalized bacteria and liberate intracellular Ag epitopes for recycling and presentation, consistent with a central role for phagolysosomes. Thus, future recombinant bacterial vaccines may be effectively designed with T cell epitopes expressed either on the surface or within the bacterial cytoplasm.

Variations in CD4 expression by human monocytes and macrophages and their relationships to infection with the human immunodeficiency virus.

The expression of CD4 antigen on the surface of LeuM3-positive human blood monocytes was found to be variable with 65 to 90% of cells from 46 normal human volunteers being positive by dual staining flow cytometry. When monocytes adhered to plastic (but not when cultured on Teflon), a marked decrease in CD4 expression was observed between 1 and 24 h post-adherence. CD4 expression could not be detected in macrophages adhered to plastic for 5 days by using four anti-CD4 monoclonal antibodies in flow cytometry or direct immunofluorescence. Conversely an increasing proportion of adherent cells expressed LeuM3 and OKM5 surface antigens over the 5 days. CD4 mRNA levels were measured by slot-blot and Northern hybridization, and total cellular CD4 protein levels by immunoprecipitation. Both cellular mRNA and CD4 levels remained constant throughout the 5 day period but membrane CD4 protein levels were greatly reduced indicating that the down-regulation of CD4 was post-translational. Infection with two of six fresh human immunodeficiency virus (HIV) isolates showed different kinetic patterns when tested on purified monocytes recently adhered to plastic and macrophages adherent for 5 days. HIV antigen and reverse transcriptase levels in infected monocyte cultures remained high for 3 to 4 weeks before detachment and necrosis of the cells occurred. Infection of macrophages generated much lower levels of antigen and reverse transcriptase which declined to very low or undetectable levels over 2 weeks, leaving persisting viable macrophages. One week after infection HIV nucleic acid was detected in 69 +/- 7% of monocytes and 6 +/- 3% of macrophages by in situ hybridization. Blocking experiments with anti-Leu3a monoclonal antibody suggested that HIV infection of 5 day adherent macrophages occurred mainly by a mechanism other than binding to CD4.

Formalin-fixed macrophages bind tumor targets similarly to viable macrophages.

Macrophages (MPs) fixed with 1% formalin in PBS bound targets similarly to viable MPs. Like binding between viable MPs and tumor cells, the process was temperature and calcium dependent. Fixed MPs discriminated targets similarly to viable MPs. Targets not bound by viable MPs were not bound by fixed MPs. The lectin Bandeiraea simplicifolia (ASI-B4) was able to enhance MP binding to tumor cells regardless of whether MPs were fixed or viable. However, it did not appear that ASI-B4-like molecules were involved in the direct recognition of F5b tumor cells by MPs. Target cells could not be fixed in 1% formalin for binding to occur. These data suggest that the receptor on the MP for tumor cell binding is functional in the absence of active physiological processes. In contrast, tumor cell processes that are dependent upon target cell viability are required for binding.

Surface charge of macrophages and their interaction with charged particles.

The distribution and concentration of surface ionogenic groups on murine peritoneal macrophages and the responses of their plasmalemma to charged markers were investigated by electron microscopy. Quantitation of the distribution of cationized ferritin (CF) as a marker for anionic groups on fixed cells revealed surface anions on invaginated parts of the plasmalemma to be fewer than those on flat or projecting segments. Cationic groups on the surface membrane, however, could not be labeled with anionized ferritin (AF). Interaction of viable macrophages with cationic particles at 37 degrees C resulted in their "internalization" within vesicles and coated pits and a closer apposition between many segments of plasmalemma than with neutral or anionic substances. The process occurred unaltered at 4 degrees C and was unaffected by cytochalasin B and colchicine, suggesting that this close apposition between segments of plasmalemma resulted from neutralization of surface negative electrostatic charges by the cationic material and did not reflect endocytosis.

Arginine metabolism in wounds.

Arginine metabolism in wounds was investigated in the rat in 1) lambda-carrageenan-wounded skeletal muscle, 2) Schilling chambers, and 3) subcutaneous polyvinyl alcohol sponges. All showed decreased arginine and elevated ornithine contents and high arginase activity. Arginase could be brought to the wound by macrophages, which were found to contain arginase activity. However, arginase was expressed by macrophages only after cell lysis and no arginase was released by viable macrophages in vitro. Thus the extracellular arginase of wounds may derive from dead macrophages within the injured tissue. Wound and peritoneal macrophages exhibited arginase deiminase activity as demonstrated by the conversion of [guanido-14C]arginine to radiolabeled citrulline during culture, the inhibition of this reaction by formamidinium acetate, and the lack of prokaryotic contamination of the cultures. These findings and the known metabolic fates of the products of arginase and arginine deiminase in the cellular populations of the wound suggest the possibility of cooperativity among cells for the production of substrates for collagen synthesis.

The role of membrane gangliosides in murine alveolar macrophage-mediated suppression of the immune response

Generation of aldehydes on cell membranes of viable alveolar macrophages (AM) by mild oxidation with sodium periodate was previously shown to result in total abrogation of AM-mediated suppression of the plaque-forming cell (PFC) response of spleen cells previously primed with sheep erythrocytes (SRBC). These results suggested a possible role for macrophage sialoglycoconjugates, such as gangliosides and sialoglycoproteins, in suppression. In the present report, it is shown that a purified mixture of gangliosides suppressed the PFC response of SRBC-primed spleen cells in a dose-dependent manner. Addition of rabbit anti-mouse brain antiserum (RAMB), which reacts with the gangliosides, reversed both ganglioside- and AM-mediated suppression of the PFC response. Pretreatment of AM but not spleen cells with RAMB also resulted in the reversal of AM-mediated suppression. The expression of gangliosides on the membrane of AM was detected with RAMB in an enzyme-linked immunosorbent assay (ELISA). The results suggest that membrane gangliosides may play an important role in the AM-mediated suppression of the PFC response. Since paraformaldehyde-fixed AM were not suppressive, it is speculated that AM release the suppressive gangliosides into the culture medium and rabbit antimouse brain antibody either prevents their release and/or neutralizes the suppressive function of released gangliosides.

Effects of chlorphentermine and nitrogen dioxide on murine alveolar macrophages.

Male Swiss-Webster mice were treated daily for 14 days with either 120 mg/kg chlorphentermine (CP) to produce pulmonary lipidosis or an equal volume of water. Animals in each treatment group were then exposed by whole-body inhalation to either air or NO2 for 48 h. Immediately following exposure, alveolar macrophages (MPs) were collected from each animal by bronchoalveolar lavage. Assays performed on adherent viable MPs showed some changes in metabolic reduction, phagocytosis, and killing activity. 5'-Nucleotidase activity and yeast phagocytosis and killing assays suggested that CP elicited an increase in phagocytosis over control levels. Although the percentage metabolic reduction and microbicidal killing activities following CP were not increased when compared to controls, absolute reduction and killing (percentage values times total MPs) were significantly increased. These increased functions seemed to be highly dependent on the large increase in the total number of MPs induced by CP. It is possible that the large accumulation of MPs in the airways of the lipidotic lung may help protect the alveolar epithelium from NO2 by quenching free radicals produced during NO2-induced lipid peroxidation.

Some peculiarities of the pulmonary phagocytotic response: dust retention kinetics and silicosis development during long term exposure of rats to high quartz dust levels.

Rats were exposed to quartz dust (about 90 mg/m3) for five hours a day, five times a week either throughout the 48 weeks of the experiment or for a total of 40 weeks plus eight weeks of "rest." Cytological study of bronchoalveolar lavage showed that at a certain level of silicotic changes in the lungs, a pronounced breakdown in pulmonary dust clearance by macrophages could be observed. There was, however, a concomitant compensatory increase in the contribution to pulmonary phagocytosis by the neutrophil leukocytes (NL). As a result, pulmonary dust kinetics could be mathematically described using a constant clearance rate both throughout the 48 weeks of exposure and during the eight weeks after the end of the 40 week exposure. It is shown in a separate experiment that enhanced recruitment of NL into the airways may be due not only to an attractant effect of the products of macrophage breakdown (PMB) themselves but also to the release of an NL attractant factor by viable macrophages activated under influence of the PMB.

Treatment of alveolar macrophages with cytochalasin D inhibits uptake and subsequent growth of Legionella pneumophila.

Legionella pneumophila multiplied rapidly in guinea pig and rat alveolar macrophages but failed to grow when phagocytic activity was inhibited by pretreatment with 0.5 or 1.0 microgram of cytochalasin D per ml. Attachment was not inhibited by cytochalasin D. No extracellular multiplication occurred when L. pneumophila were in close proximity to viable functional macrophages or even when the bacteria were attached to plasma membranes of the macrophages. Nonopsonized L. pneumophila were avidly phagocytized by alveolar macrophages. When bacteria were centrifuged onto a cell pellet, more than 85% of the phagocytes contained one or more bacteria within 15 min. In contrast, under the same conditions only approximately 15% of the macrophages contained nonopsonized Escherichia coli or Staphylococcus aureus. Phagocytosis of L. pneumophila by untreated guinea pig macrophages occurred by extension of pseudopodia around the bacteria in a classical manner. The failure of the bacteria to actively penetrate the phagocyte suggests that their intracellular survival must not depend on avoidance of a phagosome but rather on an inhibition of or resistance to subsequent microbicidal functions of the macrophage.

Cytoplasmic motions, rheology, and structure probed by a novel magnetic particle method.

The motions of magnetic particles contained within organelles of living cells were followed by measuring magnetic fields generated by the particles. The alignment of particles was sensed magnetometrically and was manipulated by external fields, allowing non-invasive detection of particle motion as well as examination of cytoplasmic viscoelasticity. Motility and rheology data are presented for pulmonary macrophages isolated from lungs of hamsters 1 d after the animals had breathed airborne gamma-Fe2O3 particles. The magnetic directions of particles within phagosomes and secondary lysosomes were aligned, and the weak magnetic field produced by the particles was recorded. For dead cells, this remanent field was constant, but for viable macrophages, the remanent field decreased rapidly so that only 42% of its initial magnitude remained 5 min after alignment. A twisting field was applied perpendicular to the direction of alignment and the rate at which particles reoriented to this new direction was followed. The same twisting was repeated for particles suspended in a series of viscosity standards. Based on this approach, the low-shear apparent intracellular viscosity was estimated to be 1.2-2.7 X 10(3) Pa.s (1.2-2.7 X 10(4) poise). Time-lapse video microscopy confirmed the alignment of ingested particles upon magnetization and showed persistent cellular motility during randomization of alignment. Cytochalasin D and low temperature both reduced cytoplasmic activity and remanent-field decay, but affected rheology differently. Magnetic particles were observed in association with the microtubule organizing center by immunofluorescence microscopy; magnetization did not affect microtubule distribution. However, both vimentin intermediate filaments and f-actin reorganized after magnetization. These data demonstrate that magnetometry of isolated phagocytic cells can probe organelle movements, rheology, and physical properties of the cytoskeleton in living cells.

Carbohydrate-specific adhesion of alveolar macrophages to mannose-derivatized surfaces.

The ability of rabbit alveolar macrophages to specifically recognize and adhere to surfaces derivatized with carbohydrates was examined. Otherwise inert polyacrylamide gels were derivatized with aminohexylglycosides as previously described (Guarnaccia, S. P., and Schnaar, R. L. (1982) J. Biol. Chem. 257, 14288-14292). Intact viable rabbit alveolar macrophages, isolated by lung lavage, were placed in contact with surfaces derivatized with different glycosides. Only those surfaces derivatized with alpha-D-mannose residues were capable of supporting rabbit alveolar macrophage adhesion. Adhesion was rapid, obtaining maximal levels within 10 min, and occurred readily at either 0 or 37 degrees C. The carbohydrate specificity of the cell adhesion was investigated by the use of soluble carbohydrate inhibitors. The potency of various saccharides to block the adhesion correlated with that demonstrated for blocking the uptake or binding of radiolabeled soluble glycoproteins (Shepherd, V. L., Lee, Y. C., Schlesinger, P. H., and Stahl, P. D. (1981) Proc. Natl. Acad. Sci. U.S.A. 78, 1019-1022). Thus, the order of potency observed was: D-Man congruent to L-Fuc greater than D-GlcNAc congruent to D-Glc much greater than D-Gal congruent to D-GalNAc congruent to L-rhamnose. While soluble monosaccharides were capable of blocking adhesion when added in millimolar concentrations, polymannosylated neoglycoproteins were able to block adhesion in the nanomolar concentration range. Adhesion to the mannose-derivatized surfaces was a dynamic event even at 0 degrees C, since adhesion was less susceptible to monosaccharide inhibition at later incubation times. Surfaces derivatized with aminohexyl S-mannoside ligands were more effective in supporting adhesion than those derivatized with the corresponding O-mannosides. Soluble inhibitor studies suggest that this was due to a more favorable conformation of the S-glycoside for binding to the cell surface receptor. The results reported here demonstrate that the previously reported alveolar macrophage mannose/fucose receptor can mediate carbohydrate-specific cell adhesion.

A chemoattractant receptor on macrophages exists in two affinity states regulated by guanine nucleotides.

The binding characteristics of the oligopeptide chemoattractant receptor on guinea pig macrophages and macrophage membrane preparations were characterized using detailed binding studies and computer analysis. Viable macrophages bound the radiolabeled chemoattractant N-formyl-methionyl-leucyl-[3H]phenylalanine with single dissociation constant (KD) of 18.4 +/- 4.6 nM with 15,300 +/- 1,800 sites per cell. Binding data from membrane preparations indicated the presence of two classes of binding sites with KD of 1.5 +/- 0.4 nM and 25.5 +/- 11.0 nM. Approximately 23% of the receptors were in the high affinity state. In the presence of added guanine nucleotide di- or triphosphates, the high affinity receptors in the membrane preparations were converted to low affinity states with no change in the total receptor number. Nonhydrolyzable derivatives of GTP were most potent in converting the receptor from its high to low affinity state. These data suggest that the affinity state of the oligopeptide chemoattractant receptor in macrophages is regulated by guanine nucleotides and GTPase, implying that the transduction mechanisms of this receptor may be controlled by a guanine nucleotide regulatory unit.

In vitro response of murine alveolar and peritoneal macrophages to Mycobacterium intracellulare.

Normal resident and BCG-activated alveolar and peritoneal macrophages from female Swiss Webster mice were compared for their ability to ingest and subsequently control the multiplication of Mycobacterium intracellulare in vitro. Resident peritoneal macrophages failed from the moment of ingestion to control the multiplication of engulfed bacilli resulting in host cell lysis, whereas activated peritoneal macrophages and both resident and activated alveolar macrophages constrained bacterial division for at least 7 days before comparable bacterial multiplication led to phagocyte death. The number of bacilli needed to lyse a macrophage was impossible to determine precisely because viable macrophages commonly contained several hundred mycobacteria. Minimal intracellular bacterial generation times were 20 h for each macrophage type. Differences in the rates of bacterial phagocytosis between both macrophage types, either resident or activated, are intrinsic properties of the macrophages and were not induced by the mycobacteria, because the same patterns of particle ingestion were observed after exposure to latex microspheres.

Antigen presentation by human monocytes: evidence for stimulant processing and requirement for interleukin 1.

We studied the role of stimulant processing and presentation and of IL 1 in monocyte-mediated activation of human lymphoproliferative responses. The effects of two lysosomotropic agents, ammonium chloride and chloroquine, on the capacity of human monocytes to activate T lymphocyte responses to the soluble antigen streptolysin O (SLO) and to the polyclonal stimulant S. aureus protein A (SpA) were investigated. These agents inhibited the presentation of SLO and SpA by human monocytes in a dose-dependent manner. The inhibition occurred if monocytes were treated with ammonium chloride and chloroquine for 1.5 hr, starting only 30 min after exposure to the stimulants, whereas only minimal inhibition occurred when monocytes were treated with the two lysosomotropic compounds 2 hr after pulsing with SLO or SpA. In contrast, cell membrane alloantigen presentation by monocytes in the MLR was not affected by ammonium chloride or chloroquine treatment. Thus, these reversible inhibitors of monocyte phagosome-lysosome functions presumably interfere with intracellular processing of the stimulants but do not seem to interfere with alloantigen presentation at the cell surface. Furthermore, we investigated whether gently fixed monocytes were still capable of passively presenting stimulant or whether active metabolic processes as well as IL 1 were required. We observed that only monocytes treated with paraformaldehyde after SLO or SpA pulsing stimulated a proliferative response by T lymphocytes, provided 50 U/ml of partially purified human IL 1 were added back to cultures. In contrast, monocytes fixed before exposure to SLO or SpA were not able to stimulate T lymphocytes even if supplemented by IL 1. Taken together these data suggest that a finite incubation period is required for human monocytes to become able to present SLO or SpA to T lymphocytes. During this time the soluble stimulants presumably undergo some metabolic process in viable macrophages perhaps at the phagosome-lysosome level, to become recognizable by T lymphocytes.

Direct evidence for the presence of selective binding sites for ( 3H) prostaglandin E 2 on rat peritoneal macrophages

A method is presented which provides for a simple and rapid determination of PGE 2 receptors on viable peritoneal macrophages. Incubation of the harvested cells with ( 3H)PGE 2 revealed specific binding of ( 3H)PGE 2 by use of the Millipore filter assay system. Maximum binding was attained in the presence of 1 mM EDTA. Specific binding was saturable at 65 fmol/mg protein with an equilibrium dissociation constant (K d) of 3.2 × 10 −8M. Inhibition of ( 3H)PGE 2 binding with unlabelled prostaglandins revealed a potency series of PGE 2>PGE 2>PGI 2. The PGE 2 concentration which displaced 50% of the labelled ligand was 10 −7M. Comparable kinetic data were obtained for adenylate cyclase stimulation, since the concentration which showed a halfmaximal stimulation of cAMP production was 2 × 10 −7M of PGE 2. Since PGE 1 and PGI 2 compete with ( 3H)PGE 2 binding in a non-parallel manner compared to PGE 2 itself, it is proposed that macrophages possess different types of PG receptors.

Kinetics of tumor cell cytostasis by sea star factor-activated macrophages

Macrophages obtained from Wistar/Furth (W/Fu) and Fischer (F344) rats receiving intraperitoneal injection of 0.2 mg of sea star factor (SSF) exert a profound suppressive effect on proliferation of tumor cells in vitro. The cytostatic effect of these activated macrophages is not immunologically specific, and is demonstrably effective against syngeneic, allogeneic, or xenogeneic targets (the latter of murine origin, P815-X2 of DBA/2 strain). Evidence suggests that cytostasis can be resolved into three discrete temporally progressive steps: cytoadhesion, macrophage-dependent, and macrophage-independent states. Interference with the first stage by the use of high molecular weight dextran blocks development of macrophage-dependent cytostasis. Suppression of this second stage by selective macrophage toxicity using silica blocks the final event of irreversible macrophage-independent cytostasis. Taken together, these data suggest that suppression of tumor cell division by SSF-activated macrophages requires direct contact for a relatively prolonged period between viable effector macrophages and tumor target cells to achieve maximal cytostasis.

Characterization of a high-affinity receptor for phorbol esters in rat alveolar macrophages.

Macrophages display varied responses to the tumor promoter, TPA. In this study, a high-affinity receptor for phorbol ester is characterized in a viable alveolar macrophage population. The binding assay is performed using tritiated PDBu and specific binding is demonstrated to be temperature-sensitive. At 37 degrees C, the level of bound ligand reaches maximal binding within 2-5 min but rapidly decays to within 30% of the original specific binding. Equilibrium, however, can be established when the assay is carried out at 4 degrees C. The data indicate that at this temperature maximal binding is reached within 2 h and remains constant thereafter. Scatchard analysis shows that the receptor has an apparent Kd of 21 nM and each macrophage possesses 2 X 10(5) binding sites. Active phorbol derivatives such as TPA and PDBu compete with the labeled ligand for the receptor, whereas the inactive phorbol alcohol does not modulate the specific binding. Mezerein, a related diterpene which has been shown to share some of the properties of phorbol esters, also competes for the binding site. The high-affinity receptor is not affected by zymosan or EIgG phagocytosis. Inflammatory mediators such as prostaglandins E2 and F2 alpha and platelet-activating factor do not compete for the receptor.

Automated colorimetric assay for T cell cytotoxicity

A colorimetric method has been developed for detecting the lysis of target cells by cytotoxic T lymphocytes (Tc). The method entails incubating Tc cells with thioglycollate-induced macrophage targets and estimating macrophage survival at the end of the assay by staining viable macrophages with the dye neutral red. The method is substantially more sensitive than the 51Cr release assay and can be used to detect alloreactive Tc cells and H-2-restricted Tc cells against viruses, haptens and minor-H antigens. Furthermore, the assay is applicable to limit dilution analysis of Tc cell precursors. The method is cheap, avoids radioactive materials and by measuring optical densities with automated spectrophotometers developed for microELISA systems, results can be obtained 50–100 times faster than with the radioactive procedure.

Effect of nitrofurans on isolated and viable human blood granulocytes and guinea-pig alveolar macrophages

Effect of nitrofurans on isolated and viable human blood granulocytes and guinea-pig alveolar macrophages

Luminal lymphoid cells in the rabbit intestine

In normal rabbits, lymphocytes have been identified in large numbers on the luminal epithelial aspects of both Peyer's patches and the appendix by scanning and transmission electron microscopy. Luminal cells shared an intimate relationship with intestinal microorganisms. Irrigation of the appendiceal lumen has proved a useful technique for collecting 8.5 × 106 (mean) viable lymphocytes (73%) and macrophages (22%). Functional characteristics (mitogen responsiveness, T-cell numbers and cells with positive cytoplasmic immunoglobulin A fluorescence) were similar to isolated intestinal mucosal cell preparations. In vivo cytokinetic studies indicated that 50% of luminal appendiceal lymphocytes were recently divided (within 5 h). The passage of lymphoid cells into the appendix lumen was antigen responsive, as was the size of the appendiceal lymphoid mass. This evidence suggests that migration of lymphoid cells into the lumen of the intestine in healthy animals occurs normally probably from the gut-associated lymphoid tissue—a phenomenon similar to that observed in the bronchial tract. Both mucosal surfaces may, therefore, be important sites of lymphocyte and macrophage traffic.