Granulocyte activation by endotoxin. II. Role of granulocyte adherence, aggregation, and effect of cytochalasin B, and comparison with formylated chemotactic peptide-induced stimulation.

PMN stimulation by endotoxin is heavily dependent on incubation conditions: although marked increase of PMN adhesiveness, enzyme release, and hexose monophosphate shunt activity, as well as superoxide production, occur when endotoxin-challenged cells are incubated in stationary petri dishes, absolutely no such response is observed with cells kept in suspension. Preincubation with cytochalasin B does not alter this reaction pattern. Hyperadhesiveness of endotoxin-challenged PMN is retained after thorough washing, eliminating the possibility that adhesion is due to absorption of endotoxin to petri dishes. In contrast to formylated chemotactic peptides that stimulate PMN adherence as well as aggregation, endotoxin elicits absolutely no aggregatory response (+/- cytochalasin B). Preexposure to endotoxin does not block the aggregatory response to subsequent addition of chemotactic peptides, whereas effects of endotoxin and formylated peptides on PMN in the stationary system are additive. These findings indicate that contact to surfaces is an essential primary event in PMN stimulation.