MODIFICATION OF PLATELET-AGGREGATION BY LEUKOCYTES IN ACUTE ISCHEMIC STROKE

Background and Purpose Platelet aggregation plays an important role in the pathogenesis of thromboembolic cerebrovascular disease. Leukocytes can efficiently stimulate as well as inhibit platelet aggregability. We studied the influence of leukocytes on collagen-induced platelet aggregation in patients with acute ischemic stroke. Methods We investigated 23 patients within 2 days after stroke and 23 healthy age- and sex-matched control subjects and determined collagen-induced platelet aggregation in platelet-rich plasma with or without addition of polymorphonuclear or mononuclear leukocytes. Results Platelet aggregation without leukocytes tended to be lower in patients than in control subjects (P=.06). Mononuclear leukocytes reduced (P=.018) and polymorphonuclear leukocytes tended to reduce (P=.06) platelet aggregation in patients. Leukocytes did not significantly alter platelet aggregation in control subjects. In the presence of either mononuclear or polymorphonuclear leukocytes, platelet aggregation was significantly lower in patients than in control subjects (P=.004 and P=.008). The ratio of polymorphonuclear leukocytes to platelets in venous blood was higher in patients than in control subjects (P<.001). Conclusions Mononuclear-and less clearly polymorphonuclear-leukocytes possess a platelet aggregation-inhibiting potential in the early stages after ischemic stroke, a feature with possible antithrombotic effects.