BACKGROUND: It has been reported that the cytokine released from the white blood cells (WBC) in the stored platelet concentrates may induce febrile nonhemolytic transfusion reactions. Few studies, however, have examined the effects of cytokine on platelet activation. METHODS: The platelets from healthy donors were incubated with interleukin (IL) at the final concentration of IL-8 0.5 ng/mL, 3 ng/mL, 5 ng/mL, 10 ng/mL, 1000 ng/mL, and IL-6 0.1 ng/mL, 0.5 ng/mL, 1 ng/mL, 5 ng/mL, respectively. The activated platelets were stained with monoclonal antibodies of PAC-1 and CD62, and were analyzed by flow cytometry. RESULTS: The ranges of mean percent of PAC-1 and CD62 expressions on platelets were 61.1-71.4% and 9.0-12.5% by incubating with IL-8, and 69.0-73.4% and 13.0-13.9% with IL-6, respectively. There were no significant differences of PAC-1 and CD62 expressions on platelets among the various concentrations of IL-8 nor IL-6. In 0.5 ng/mL concentration, the mean percentage of CD62 expressions on platelets by incubating with IL-6 (13.8%) were greater than that of IL-8 (9.0%). CONCLUSION: During the period of the storage of platelet concentrates, the IL-6 and IL-8 secreted by WBC can activate platelets and thus the suppression of the cytokine secretion may be important for increasing post-transfusional survival of platelets.