INVESTIGATION OF PLATELET-NEUTROPHIL INTERACTIONS IN WHOLE-BLOOD BY FLOW-CYTOMETRY

Evidence is increasing that platelets can initiate and propagate infla mmatory processes by interacting with leucocytes and the vascular endo thelium, Platelets have been shown to bind to neutrophils, existing as platelet/neutrophil complexes (PNC) within the circulation. We descri be a simple flow cytometric method for assessing and investigating pla telet interactions with neutrophils in small volumes of whole blood. T wenty-five percent (sd 6%) of circulating neutrophils from healthy adu lts were associated with platelets. Formation of these platelet-neutro phil complexes was CD62P (P-selectin) and divalent cation dependent, P latelet activation (with ADP or thrombin) caused a rapid and sustained rise in %PNC which differed from the pattern of free platelet activat ion as assessed by CD62P expression. F-met-leu-phe induced neutrophil activation but did not increase the percentage PNC. Platelet activatio n also caused increased neutrophil CD11b/CD18 expression which was mos t marked on neutrophils complexed with platelets. This straightforward technique is simple, reproducible, and allows assessment of platelet- neutrophil interactions and activation of neutrophils. It may also pro vide a method for estimating platelet activation in whole blood. (C) 1 997 Elsevier Science B.V.