In the in vitro model described normal serum or plasma alone does not detoxify endotoxin, as determined by the response of the thorotrast-primed rabbit to the injection of the reaction mixture after 1 hour of incubation at 37°C. Partial detoxification, however, is achieved by serum or plasma after 3 hours of incubation of the same reaction mixture, as determined by the chick embryo test.
Macrophages in serum or plasma do detoxify endotoxin, as determined by both tests. Granulocytes, which are also able to detoxify endotoxin in the presence of serum, are less potent than macrophages.
Immune serum alone is much more potent than normal serum alone. Macrophages in immune serum are more potent than immune serum alone.
The relevance of the anti-endotoxic properties of these in vitro systems to the processes in the living animal are in doubt, and must await the results of comparable observations in the living animal.