The effect of bilirubin on the fc receptor expression and phagocytic activity of mouse peritoneal macrophages

The effect of bilirubin on the phagocytic activity of mouse peritoneal macrophages and on the expression of Fc receptors and receptors for SRBC was studied. Intraperitoneally administered bilirubin influenced the expression of Fc receptors for IgM, IgG2B, IgA and IgE, whereas the expression of other receptors as well as the phagocytic activity of peritoneal macrophages remained unchanged. The possible mechanism of the effect of bilirubin on Fc receptors is discussed.     

Comparative study of the effect of thiabendazole and fungizone on Histoplasma capsulatum in macrophages.

The antifungal properties of Fungizone (amphotericin B intravenous solution) and thiabendazole on Histoplasma capsulatum within guinea pig macrophages were compared using the staining method and a newly developed plating method to determine the viability of intracellular H. capsulatum. The two methods were compared to determine the effectiveness of Fungizone and thiabendazole on H. capsulatum within macrophages. Fungizone was fungicidal for intracellular H. capsulatum, killing 99.9% of the yeasts at a concentration of 0.5 microgram/ml. There was some indication that non-viable intracellular yeasts were stained which could result in misinterpretation of the effectiveness of Fungizone using the staining method unless the yeasts are very closely examined for staining abnormalities. There was a good correlation between the two methods to demonstrate suppression of the multiplication of intracellular H. capsulatum in macrophages treated with 50 microgram/ml of thiabendazole. Thiabendazole was lethal for some intracellular H. capsulatum.     

Inhibition of growth of Histoplasma capsulatum by lymphokine-stimulated macrophages

Peritoneal cells from mice immunized by sublethal infection inhibit the intracellular growth of Histoplasma capsulatum in vitro. Lymphokines generated in cultures of immune splenocytes stimulated with Histoplasma antigen activate normal macrophages to inhibit the intracellular growth of the fungus. Such lymphokines may inhibit the intracellular growth of H. capsulatum by 60 to 80% but have no direct effect on the viability of the fungus extracellularly. The lymphokine preparations have high interferon activity that is heat stable and acid labile. The cells in the spleen that are responsible for lymphokine production are T lymphocytes, but the help of other cells such as macrophages is essential for maximal production.     

Digestion of Histoplasma capsulatum yeasts by human macrophages.

The strategies used by Histoplasma capsulatum yeasts to survive and multiply within human macrophages (M phi) are unknown. To better understand these strategies we studied the intracellular fate of viable vs heat-killed (HK) yeasts in human monocyte-derived M phi. Initial studies demonstrated that phagolysosome fusion was present in M phi ingesting either viable or HK yeasts. Viable yeasts multiplied within M phi phagolysosomes, whereas M phi completely digested intracellular FITC-labeled HK yeasts within 24 h after ingestion. This observation was confirmed by electron microscopy. M phi that had ingested colloidal gold-labeled HK yeasts contained gold particles but no visible yeasts at 24 h. Digestion of HK yeasts was evident as early as 4 h after phagocytosis, and was complete by 24 h. M phi digestion of HK yeasts was blocked completely when M phi were cultured for 24 h in the presence of chloroquine. In M phi simultaneously ingesting both viable and HK yeasts, viable yeasts multiplied, but HK yeasts were digested within the same cell. M phi that had ingested viable yeasts digested them completely when M phi were cultured for 24 h in the presence of cycloheximide or amphotericin B. Coculture of infected M phi with nystatin or ketoconazole resulted in inhibition of growth, but the yeasts were not digested. These data indicate that: 1), HK Hc yeasts are easily digested by preformed M phi lysosomal hydrolases; 2), viable Hc yeasts survive and multiply within M phi phagolysosomes, but the yeasts do not secrete a factor(s) that affects the ability of other phagolysosomes within the same M phi to digest killed yeasts; and 3), inhibition of yeast protein synthesis or cell wall biosynthesis is sufficient to render viable yeasts susceptible to digestion by human M phi.     

Effect of low-frequency ultrasound on the chemotactic and phagocytic activity of peritoneal macrophages in rats

The influence of low-frequency ultrasound on the chemotactic, ingestive and digestive activity of peritoneal macrophages in rats was studied. The intraoperative treatment of the peritoneum with ultrasound enhanced chemotactic activity 3.3-fold in comparison with that in the control animals. The digestive function of peritoneal macrophages considerably increased, the stimulation of their ingestive capacity also occurred. The activation of the phagocytic function of macrophages was observed within 7 days after a single sonar treatment. The authors believe that the stimulation of the macrophage system is probably one of the mechanisms of the sanative action of ultrasound which is used at present in purulent surgery.     

Influence of termolabile enterotoxin of Enterobacter cloacae on phagocytic activity of mice peritoneal macrophages

Influence of termolabile enterotoxin (LT-enterotoxin) of Enterobacter cloacae on functional activity of mice peritoneal macrophages was studied and following combinations were used: LT-enterotoxin-producing E. cloacae, its isogenic pair--LT-enterotoxin non-producing E. cloacae, supernatantof broth culture containing LT-enterotoxin, and physiological salt solution (in control group). Data showing decrease in phagocytic and lysosomal activity, disorder in functions of hexosemonophosphate shunt enzymes in peritoneal phagocytes were obtained.     

Human macrophages do not require phagosome acidification to mediate fungistatic/fungicidal activity against Histoplasma capsulatum

Histoplasma capsulatum (Hc) is a facultative intracellular fungus that modulates the intraphagosomal environment to survive within macrophages (Mphi). In the present study, we sought to quantify the intraphagosomal pH under conditions in which Hc yeasts replicated or were killed. Human Mphi that had ingested both viable and heat-killed or fixed yeasts maintained an intraphagosomal pH of approximately 6.4-6.5 over a period of several hours. These results were obtained using a fluorescent ratio technique and by electron microscopy using the 3-(2,4-dinitroanilo)-3'-amino-N-methyldipropylamine reagent. Mphi that had ingested Saccharomyces cerevisae, a nonpathogenic yeast that is rapidly killed and degraded by Mphi, also maintained an intraphagosomal pH of approximately 6.5 over a period of several hours. Stimulation of human Mphi fungicidal activity by coculture with chloroquine or by adherence to type 1 collagen matrices was not reversed by bafilomycin, an inhibitor of the vacuolar ATPase. Human Mphi cultured in the presence of bafilomycin also completely degraded heat-killed Hc yeasts, whereas mouse peritoneal Mphi digestion of yeasts was completely reversed in the presence of bafilomycin. However, bafilomycin did not inhibit mouse Mphi fungistatic activity induced by IFN-gamma. Thus, human Mphi do not require phagosomal acidification to kill and degrade Hc yeasts, whereas mouse Mphi do require acidification for fungicidal but not fungistatic activity.     

In vitro antifungal activity of ajoene on five clinical isolates of Histoplasma capsulatum var. capsulatum

BackgroundThe number of histoplasmosis cases have considerably increased since the advent of AIDS, and the therapy for this mycosis is not always effective, as well as having adverse effects.AimsTo evaluate the inhibitory effect of ajoene on five clinical isolates of Histoplasma capsulatum, on the mycelial form, using Sabouraud dextrose broth (SDB) and RPMI-1640 culture media.MethodsGrowth curves and inhibitory activity of the drug (at concentrations of 1.25 ug/ml to 20 μg/ml) were performed at room temperature, under mechanical agitation, and the turbidimetric readings (540 nm) were recorded every 48 h for 14 days, in both culture media. Generation times (GT) were calculated and graphs were constructed to estimate Minimal Inhibitory Concentrations (MIC) and Inhibitory Concentration 50% (IC₅₀). The fungicidal minimal concentrations (FMC) were determined by plate cultures. The U-Mann-Whitney and t-test with a significance level of 0.05 were used to evaluate the statistical significance between culture media and GT, MIC, IC₅₀ MFC and fungistatic effect (FE).ResultsIn both media and for all isolates, growth curves showed a GT of 43 to 67 hrs, an FE at 1.25-2.5 μg/ml, and a MFC at 5-10 μg/ml of ajoene. Values of MIC were 2.5-5 in SDB and in RPMI medium these values were 1.25-5 μg/ml of ajoene. For IC₅₀, in SDB, the values were 1.9-2.6 ug/ml and in RPMI medium, they were of 3.8-4.3 μg/ml of ajoene. There were no significance differences between culture media for GT, FE, MIC, IC₅₀ and MFC (p > 0.05).ConclusionsThese findings corroborate that ajoene inhibits the growth of the mycelial form of H. capsulatum.     

Stimulation of the phagocytic function in guinea pig peritoneal macrophages by physical activity stress.

A study was made of all the different stages of the phagocytic function in peritoneal macrophages from male guinea pigs [3 (SD 1) months old] before, immediately after, and 24 h after being subjected to stress from physical activity (swimming until exhaustion). The early (10 min) and late (40 min) adherence to tissue substrates, chemotaxis, attachment and phagocytosis of Candida albicans, ingestion of inert particles (latex beads), and basal oxidative metabolism [measured by nitroblue tetrazolium (NBT) reduction] were significantly stimulated by the physical activity. After 24 h, late adherence, attachment capacities, and basal oxidative metabolism returned to basal values, whereas early adherence, chemotaxis, phagocytosis of cells and inert particles, and microbicidal capacity (production of superoxide anion measured by NBT reduction in presence of ingested material) remained significantly increased. The stress produced by physical activity, reflected in increased serum corticosterone values, led to a global stimulation of the phagocytic function.     

Changes in the phagocytic activity of the peritoneal macrophages of white mice caused by alcoholic intoxication

Observations made on white mice showed that doses of alcohol had a stimulating effect on the indices of macrophage acitivity (pagocytic number and phagocytic index), while longer administration of 40% ethyl alcohol solution (in doses of 0,1 ml for 21--30 days) suppressed the functional activity of macrophages. In vitro experiments in which macrophages were subjected to the action of ethyl alcohol showed that alcohol, depending on its concentration, had a direct effect on the cells of the microphage system.     

Danazol action on 5'-nucleotidase activity in mouse peritoneal macrophages]

The paper reports the results of danazol action in vivo and in vitro on 5'-nucleotidase activity of mouse peritoneal macrophages. The results showed, that danazol at a concentration of 10 M (the pharmacologic level in women taking 600 mg/day) significantly stimulated the enzyme activity.     

Ultrastructure and phagocytic activity of rat peritoneal macrophages exposed to low temperatures in vitro

Hypothermia affects various components of the immune system, leading to impaired immune resistance. To examine the in vitro effect of low temperature on the ultrastructure and phagocytic function of rat peritoneal macrophages, cells were incubated at 4, 10, 24, and 37 degrees C for 60 min. Subsequently, their ultrastructure and capacity to engulf latex particles and generate superoxide anions were evaluated. The results showed a close inverse relationship between incubation temperature and ultrastructural changes, i.e., the lower the temperature, the higher the number of altered cells. In addition, at lower temperatures the number of cells capable of phagocytosis was reduced; the cells engulfed fewer particles per cell and generated less superoxide anions. These findings may be relevant for explaining the increased susceptibility to bacterial infections under hypothermic conditions.     

Functional activity of mouse peritoneal macrophages contaminated with gram-positive bacteria

The analysis of the functional and enzymatic activity of mouse peritoneal macrophages contaminated with Staphylococcus aureus and Listeria monocytogenes virulent strains is presented. The low bactericidal and digestive activity of these cells with respect to the above-mentioned microorganisms was determined. In this study a decrease in the activity of plasmatic membrane enzymes (5'-nucleotidase and ATP-ase) of macrophages contaminated with S. aureus and L. monocytogenes was observed, which was indicative of the stimulation of phagocytes. A rise in the activity of the oxygen-dependent system of macrophages contaminated with S. aureus and L. monocytogenes was detected by means of the nitro blue tetrazolium test. At the same time a decrease in the intracellular content of nitrogen oxide end metabolites in macrophages was detected with a rise in content of nitrogen oxide in the supernatants.