Induction of Cytokine Expression in Leukocytes by Binding of Thrombin-Stimulated Platelets

Background Activated platelets tether and activate myeloid leukocytes. To investigate the potential relevance of this mechanism in acute myocardial infarction (AMI), we examined cytokine induction by leukocyte-platelet adhesion and the occurrence of leukocyte-platelet conjugates in patients with AMI. Methods and Results We obtained peripheral venous blood samples in 20 patients with AMI before and daily for 5 days after direct percutaneous transluminal coronary angioplasty (PTCA) and in 20 patients undergoing elective PTCA. Throughout the study period, CD41 immunofluorescence of leukocytes (flow cytometry) revealed increased leukocyte-platelet adhesion in patients with AMI compared with control patients (mean±SE of fluorescence [channels] before PTCA: 77±16 versus 35±9; Pequals;.003). In vitro, thrombin-stimulated fixed platelets bound to neutrophils and monocytes. Within 2 hours, this resulted in increased mRNA for interleukin (IL)-1β, IL-8, and monocyte chemoattractant protein (MCP)-1 in unfractionated ...