Enhancement of granulocyte-endothelial cell adherence and granulocyte-induced cytotoxicity by platelet release products.

Abstract
Complement-stimulated [human] granulocytes adhere to and induce significant 51Cr release from endothelial cells in vitro. Platelts were stimulated to undergo release, and these release products significantly enhanced granulocyte-endothelial cell adherence and granulocyte-induced 51Cr release from endothelial cells. Platelet serotonin appeared to mediate these phenomena because serotonin antagonists [methysergide, imipramine] blocked the enhanced endothelial adherence and 51Cr release. Added serotonin mimicked the effect seen with the stimulted platelets granulocyte-endothelial cell adherence and cytotoxicity completely. This enhancement appeared to be due to serotonin effects on the granulocyte and endothelial cells. A released platelet constituent might modulate in vivo granulocyte-endothelial cell interactions in clinical disorders.