Human recombinant soluble decay accelerating factor inhibits complement activation in vitro and in vivo

Area of Science:

• Immunology
• Biochemistry
• Pharmacology

Background:

• Complement (C) system activation contributes to inflammatory diseases.
• Human decay accelerating factor (DAF) is a regulator of complement activation.
• Controlling C activation is a therapeutic target for inflammatory conditions.

Purpose of the Study:

• To evaluate three forms of recombinant human decay accelerating factor (DAF) for their ability to inhibit complement activation.
• To investigate the mechanism of DAF interaction with cell membranes.
• To assess the in vivo anti-inflammatory potential of secreted DAF (seDAF).

Main Methods:

• Purification of three recombinant DAF forms (mDAF, sDAF, seDAF) from Chinese hamster ovary cells.
• Assays to test inhibition of classical and alternative complement pathways.
• Experiments to determine DAF reincorporation into red blood cell membranes.
• In vivo evaluation of seDAF in a guinea pig reversed passive Arthus reaction model.

Main Results:

• All three DAF forms (mDAF, sDAF, seDAF) inhibited both classical and alternative complement pathways.
• Membrane-bound DAF (mDAF) reincorporated into cell membranes via its GPI anchor and was a potent inhibitor of cell-surface C activation.
• Soluble DAF forms (sDAF, seDAF) inhibited fluid-phase C activation.
• Administered seDAF reduced inflammation in a reversed passive Arthus reaction model.

Conclusions:

• Membrane incorporation enhances DAF's efficiency in inhibiting cell-surface complement activation.
• Soluble DAF forms effectively inhibit fluid-phase complement activation.
• Secreted DAF (seDAF) demonstrates potential as an anti-inflammatory therapeutic agent.