Type: Term Definitions: 1. a type III transmembrane protein found on platelets, megakaryocytes, monocytes, pre-B cells, eosinophils, basophils, and activated T cells; plays a role in signal transduction leading to platelet activation and aggregation; expressed in some T-cell acute lymphocytic leukemias and some acute nonlymphocytic leukemias. &nb..... Found on http://www.medilexicon.com/medicaldictionary.php?t=18329