Circulating soluble CD40 ligand mediates the interaction between neutrophils and platelets in acute coronary syndrome

Following plaque rupture, activated platelet will induce subsequent inflammatory process including neutrophil recruitment. In vitro study demonstrated an interaction between neutrophils and platelets via a mechanism involving CD40-CD40 ligand. However, whether this mechanism exists in the clinical setting remains unknown. Fifty-four patients with acute myocardial infarction (AMI) and 25 with unstable angina of pain onset of < or = 24 h were enrolled consecutively. Acute myocardial infarction was diagnosed from three diagnostic criteria, i.e., anginal pain, electrocardiogram ST-T changes, and cardiac enzyme elevation. Unstable angina was diagnosed in patients without elevated cardiac enzymes. Peripheral venous blood was drawn at admission for routine blood count and soluble CD40 ligand (sCD40L) measurement. Neutrophil count was determined by an automated blood cell counter. Circulating sCD40L was measured using a standard enzyme-linked immunosorbent assay. Neutrophil count was significantly higher in AMI as compared with unstable angina (P < 0.001), whereas circulating sCD40L did not significantly differ. Despite marked elevation, no correlation was observed between neutrophil count and circulating sCD40L in AMI. Interestingly, we observed a strong and positive significant correlation between neutrophil count and circulating sCD40L level (r = 0.607, P = 0.002) in unstable angina. Circulating sCD40L is associated with neutrophil count and may mediate interaction between neutrophils and platelets in acute coronary syndrome, particularly in unstable angina.