Blood group-related antigen Le^y on human platelets and its involvement in platelet aggregation via a possible...

The Le^y antigen is a carbohydrate chain belonging to the ABH-Lewis blood group family. Le^y 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 Le^y antigen. This study aims to investigate the expression pattern and the function of Le^y in human platelets.

Flow cytometry, Western blot, and immunofluorescence assays were performed to determine Le^y 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 Le^y expression was evaluated again by flow cytometry. Blockade was performed with an anti-Le^y monoclonal antibody to verify the role of this epitope in platelet function. Finally, coimmunoprecipitation was performed to identify glycoproteins associated with Le^y .

Le^y was expressed on human platelets independent of ABO blood type. Le^y 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- Le^y mAb treatment increased alpha-granule release and neutralized the inhibitory effect of the anti-CD61 antibody on platelet aggregation. In addition, Le^y was proven to interact and colocalize with CD61.

These results demonstrate nondifferential expression of Le^y in platelets of different ABO blood types and suggest the involvement of Le^y in platelet function, possibly via interaction with CD61.