Blood group-related antigen Ley on human platelets and its involvement in platelet aggregation via a possible interaction with CD61.

Abstract

The Ley antigen is a carbohydrate chain belonging to the ABH-Lewis blood group family. Ley has been reported to be present on red blood cells (RBCs) and granulocytes, but its distribution and function in platelets remain unknown. There are a variety of glycoproteins on platelets, which may carry the Ley antigen. This study aims to investigate the expression pattern and the function of Ley in human platelets. Flow cytometry, Western blot, and immunofluorescence assays were performed to determine Ley expression on human platelets. ADP (1.25-10 μM) and thrombin (0.05-1 IU/mL) were used to activate platelets in the presence or absence of prostaglandin E1 (PGE1) and the Ley expression was evaluated again by flow cytometry. Blockade was performed with an anti-Ley monoclonal antibody to verify the role of this epitope in platelet function. Finally, coimmunoprecipitation was performed to identify glycoproteins associated with Ley . Ley was expressed on human platelets independent of ABO blood type. Ley expression was decreased in a dose-dependent manner after activation with either ADP or thrombin, and this effect could be partially reversed by PGE1. Anti- Ley mAb treatment increased alpha-granule release and neutralized the inhibitory effect of the anti-CD61 antibody on platelet aggregation. In addition, Ley was proven to interact and colocalize with CD61. These results demonstrate nondifferential expression of Ley in platelets of different ABO blood types and suggest the involvement of Ley in platelet function, possibly via interaction with CD61.