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Decay-accelerating factor functions as a signal transducing molecule for human monocytes
Insights
Monoclonal antibody 1C6 activates human monocytes by blocking decay-accelerating factor (DAF), enhancing glucose consumption and phagocytosis. This DAF-mediated monocyte activation involves signaling pathways, including inositol trisphosphate generation.
Area of Science:
- Immunology
- Cell Biology
Background:
- Decay-accelerating factor (DAF) is a membrane protein protecting cells from complement-mediated damage.
- Monoclonal antibodies (mAbs) can modulate cellular functions by targeting specific membrane proteins.
Purpose of the Study:
- To investigate whether human monocytes are activated through decay-accelerating factor (DAF) molecules.
- To identify the signaling pathways involved in DAF-mediated monocyte activation.
Main Methods:
- Incubation of human monocytes with anti-DAF mAbs (1C6 and 5B2) and their fragments.
- Measurement of glucose consumption and phagocytosis of latex beads.
- Analysis of monokine production (TNF-alpha, IL-1 alpha, IL-1 beta).
- Treatment with phosphatidylinositol-specific phospholipase C (PI-PLC) and measurement of inositol trisphosphate generation.
Main Results:
- Monocyte incubation with 1C6 mAb resulted in significant glucose consumption and enhanced phagocytosis, indicating activation.
- 1C6-mediated monocyte activation was dependent on the F(ab')2 fragment but not the Fab fragment.
- PI-PLC treatment reduced 1C6-induced glucose consumption and phagocytosis.
- 1C6 stimulated the generation of inositol trisphosphate in monocytes.
Conclusions:
- The signal transmitted via decay-accelerating factor (DAF) can activate human monocytes.
- DAF-mediated monocyte activation involves phosphatidylinositol-specific phospholipase C-sensitive signaling pathways and inositol trisphosphate generation.
Abstract:
Decay-accelerating factor (DAF) is a glycosylphosphatidylinositol-anchored membrane protein that protects cells from damage by autologous complement activation. Of the four mAb against DAF prepared in our laboratory, 1C6 completely blocked DAF function, whereas 5B2 partially blocked it. Using these mAb, we investigated whether human monocytes were activated via DAF molecules. When monocytes were incubated with 1C6 alone, glucose was consumed in significant amounts and phagocytosis of latex beads was enhanced, indicating that the monocytes had been activated. However, 1C6 did not enhance the production of monokines, TNF-alpha, and IL-1 alpha and -beta. The F(ab')2 fragment of 1C6 also activated monocytes, whereas 5B2 and the Fab fragment of 1C6 could not. To further examine monocyte activation, these cells were treated with phosphatidylinositol-specific phospholipase C. Increased glucose consumption and enhanced phagocytic activity by 1C6 were considerably reduced in monocytes treated with phosphatidylinositol-specific phospholipase C. In addition, we found that 1C6 stimulated the generation of inositol trisphosphate. These results demonstrate that the signal transmitted via the DAF molecule is capable of stimulating monocytes.