The rate of release of leukocyte pyrogen from rabbit blood incubated with endotoxin.

The time course of leukocyte pyrogen liberation from whole rabbit blood incubated at 37 degrees C with various concentrations of proteus endotoxin was studied. The kinetics of the process provide further evidence for the view that leukocyte pyrogen is an independent entity. It was shown that complete liberation of all available leukocyte pyrogen from blood is too slow a process to account for the fevers seen when rabbits are injected with endotoxin. However, very small quantities of leukocyte pyrogen were demonstrated after short periods of incubation which are adequate to account for endotoxin fevers. It was also found that small, but definite, quantities of leukocyte pyrogen are liberated from rabbit blood incubated without endotoxin.