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Ganglioside identification on human monocyte membrane with Clostridium perfringens delta-toxin
Abstract:
Clostridium perfringens delta-toxin was first described as a hemolysin with a restricted lytic spectrum. A selective cytotoxicity of the delta-toxin was then found on rabbit leukocytes: peritoneal and alveolar macrophages were uniformly killed, whereas thymocytes were essentially resistant. The toxin was shown to be specific for GM2 ganglioside or a GM2-like structure. In the present study we report the interaction of delta-toxin with human monocytes. A specific, saturable, and irreversible binding of 125I-delta-toxin was demonstrated. Binding was inhibited by preincubation of the radiolabeled toxin with GM2 and with high amount of GM1 ganglioside. As judged by dye exclusion, no cytotoxicity was observed on freshly isolated monocytes, but when added at the beginning of a culture of human adherent cells, the cytotoxic effect was detected after 48 hours of culture. Taken together, these data indicate the presence of monosialoganglioside(s) at the surface of human monocytes, and suggest a possible reorganisation of such structure into the cell membrane when monocytes mature in vitro toward macrophage-like cells.
Insights
Clostridium perfringens delta-toxin specifically binds to human monocytes. This toxin shows cytotoxicity after monocytes mature into macrophages, indicating ganglioside structure changes during cell differentiation.
Area of Science:
- Microbiology
- Immunology
- Cell Biology
Background:
- Clostridium perfringens delta-toxin is a hemolysin with selective cytotoxicity.
- It targets rabbit leukocytes, killing macrophages but not thymocytes.
- The toxin specifically binds to GM2 ganglioside or similar structures.
Purpose of the Study:
- To investigate the interaction of delta-toxin with human monocytes.
- To determine if human monocytes express target structures for delta-toxin.
- To explore the cytotoxic effects of delta-toxin on human monocytes and their differentiation.
Main Methods:
- Radiolabeling of delta-toxin with 125I.
- Assessing binding of radiolabeled toxin to human monocytes.
- Evaluating cytotoxicity using dye exclusion assays.
- Culturing human adherent cells for 48 hours to observe differentiation.
Main Results:
- Demonstrated specific, saturable, and irreversible binding of 125I-delta-toxin to human monocytes.
- Binding was inhibited by GM2 and GM1 gangliosides.
- No immediate cytotoxicity was observed on fresh monocytes.
- Cytotoxicity was evident after 48 hours of culture, coinciding with monocyte maturation.
Conclusions:
- Human monocytes possess monosialoganglioside(s) on their surface.
- These ganglioside structures may reorganize during in vitro differentiation from monocytes to macrophages.
- This suggests a mechanism for delta-toxin's selective cytotoxicity during monocyte maturation.