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Ingestion of yeast forms of Sporothrix schenckii by mouse peritoneal macrophages
Abstract:
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.
Insights
Phagocytosis of Sporothrix schenckii yeasts by macrophages is enhanced by concanavalin A (ConA) and inhibited by specific sugars. Neuraminidase treatment boosts yeast ingestion, suggesting macrophage receptors bind S. schenckii surface components.
Area of Science:
- Immunology
- Mycology
- Cell Biology
Background:
- Sporothrix schenckii is a fungus causing sporotrichosis.
- Macrophage phagocytosis is crucial for controlling fungal infections.
- Understanding fungal-macrophage interactions is key to developing treatments.
Purpose of the Study:
- To investigate the phagocytosis of Sporothrix schenckii yeast forms by mouse peritoneal macrophages.
- To determine the role of yeast surface components and macrophage receptors in phagocytosis.
- To explore the effects of lectins and specific sugars on fungal uptake.
Main Methods:
- Incubation of thioglycolate-elicited mouse peritoneal macrophages with S. schenckii yeast forms.
- Use of concanavalin A (ConA) for opsonization and assessment of phagocytic indexes.
- Treatment of yeast cells with neuraminidase and evaluation of phagocytosis.
- Inhibition studies using various monosaccharides, derivatives, and purified polysaccharides.
- Control experiments with latex particles and sheep erythrocytes.
Main Results:
- Concanavalin A (ConA) opsonization significantly increased yeast phagocytosis, dependent on ConA concentration and yeast surface receptors.
- Neuraminidase treatment of S. schenckii enhanced the ingestion of unopsonized yeasts by 7.7-fold.
- Specific monosaccharides (mannose, rhamnose, galactose, glucosamine, N-acetylglucosamine, N-acetylneuraminic acid) partially inhibited phagocytosis.
- Purified rhamnomannan and galactomannan inhibited phagocytosis, while certain peptidopolysaccharides showed toxicity or no effect.
- Macrophage pretreatment with inhibitory sugars did not affect phagocytosis of non-fungal particles.
Conclusions:
- Macrophage phagocytosis of S. schenckii is mediated by specific interactions with yeast surface carbohydrates.
- Lectins like ConA can enhance fungal uptake by binding to yeast surface receptors.
- Specific sugars and their derivatives act as inhibitors, suggesting the presence of corresponding receptors on macrophages.
- These findings indicate the existence of specific receptors on peritoneal macrophages that recognize and bind S. schenckii cell surface components, influencing phagocytosis.