The Blood and Bone Marrow Neutrophil Response to Graded Doses of Endotoxin in Mice. ∗

Summary

Studies were undertaken to characterize more definitively the effect of endotoxin upon neutrophil kinetics. The data presented herein indicate that the neutrophil response to endotoxin in the mouse is dose related. With relatively small doses of endotoxin, neutrophilia appeared earlier, was of greater magnitude and was not preceded by neutropenia. After larger doses, neutropenia persisted for several hours and was later followed by neutrophilia.

The response in marrow neutrophils was determined at 6 and 16 hours following the injection of endotoxin in order to correlate changes occurring in the marrow with those observed in the blood. Smaller doses of endotoxin resulted in an earlier and greater degree of blood neutrophilia than did larger doses but fewer cells were released from the marrow after small doses than after large doses.

At least 2 dose related kinetic events explain the neutrophil changes occurring after the administration of endotoxin. With small doses of endotoxin, the acceleration of release rate from the marrow exceeds the rate of loss from the blood. Larger doses have a more profound effect than small doses in accelerating the rate of release of neutrophils from the marrow but they have an even greater effect on acceleration of the outflow of neutrophils from the blood.