In vivo endotoxin exposure increases neutrophil counts without maintenance of primed superoxide anion release in short-term cultures of sheep bone marrow.

A short-term bone marrow culture was established to determine the functional and proliferative responses of neutrophils sampled from sheep exposed to endotoxin in vivo. Iliac crest bone marrow was drawn from surgical control animals and from sheep given a 12-h infusion of endotoxin. In these bone marrow aspirates, neutrophils from endotoxin-treated sheep showed primed superoxide anion release compared with controls when stimulated with phorbol myristate acetate. Priming was no longer present in neutrophils tested after 2 days in culture. The neutrophil cell count, however, was higher after 2 days in culture than in controls. Increased neutrophil production/viability was reproduced in naive bone marrow cultures by replacing part of the normal serum medium with plasma taken from sheep several hours after endotoxin infusion. These data suggest that a dissociation exists between priming and increased neutrophil production/viability in response to endotoxin.