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Purification and characterization of decay-accelerating factor (DAF) from Raji cells
Immunology
|July 1, 1988
Summary
Decay-accelerating factor (DAF) on nucleated cells protects them from complement-mediated damage. This membrane protein accelerates the decay of complement convertases, preventing cell lysis.
Area of Science:
- Immunology
- Complement System Biology
Background:
- Decay-accelerating factor (DAF) is a membrane protein regulating the complement system.
- DAF controls complement activation on cell surfaces.
Purpose of the Study:
- To investigate the role of DAF on nucleated cells in complement regulation.
- To compare the DAF from lymphoblastoid cells with that from erythrocytes.
Main Methods:
- Purification of DAF from Raji cells (DAF-R) and erythrocyte stroma (DAF-S).
- Assay of DAF's decay-accelerating activity on C3 convertases (classical and alternative pathways).
- Inhibition studies using a monoclonal anti-DAF antibody (1C6).
- Complement-mediated cell lysis assays with Raji cells.
Main Results:
- DAF-R and DAF-S share similar molecular weights but DAF-R exhibits higher decay-accelerating activity.
- Anti-DAF antibody (1C6) inhibited DAF activity and enhanced C3 binding to Raji cells.
- Blocking DAF activity led to efficient complement-mediated killing of Raji cells.
Conclusions:
- DAF on nucleated cells is crucial for protection against autologous complement-mediated damage.
- DAF's regulatory function is vital in preventing self-attack by the complement system.