This study characterized the activation of platelet integrin α bβ3 induced by two anti human platelet tetraspanin monoclonal antibodies（mAbs）

HI117 and SJ9A4. Methods.Using 125 I labeled human fibrinogen（Fg）

specific Fg binding to human platelets induced by HI117 and SJ9A4 was measured as indication of activation of platelet integrin αbβ3 by the two mAbs. Results.HI117 and SJ9A4（10μg/ml and 20μg/ml） induced evident specific Fg binding to human platelets

suggesting that the two mAbs evoked activation of platelet integrin αbβ3.Further study indicated that HI117 and SJ9A4 induced integrin αⅡbβ3 activation independent of platelet Fc receptors

and that HI117 and SJ9A4 induced integrin αbβ3 activation was inhibited by sphingosing

aspirin

apyrase

and/or PGI2. Conclusion.The anti platelet tetraspanin（CD9）mAbs

HI117 and SJ9A4

can induce platelet integrin αⅡbβ3 activation independent of Fc receptors.Three signaling pathways

i.e.thromboxane

secreted ADP

and cAMP pathways may be involved in the process

with protein kinase C activation presumably being the common step of the three pathways.