Characterization of platelet antigen for CD45RA monoclonal antibodies

CD45RA monoclonal antibodies recognize the higher molecular weight isoforms (220 and 205 kDa) of leukocyte common antigen family (CD45), which are typically expressed on B cells and unstimulated T cells. We have found that there are at least three distinct CD45RA monoclonal antibodies which react with platelet 42 kDa (P42) intracellular protein antigen, which seems to be different from any to date described platelet proteins with similar molecular weight. This platelet antigen is a single chain protein, very likely not a glykoprotein, with isoelectrical point between 6.8 and 7.5. P42 does not seem to be a membrane protein and is not associated with platelet cytoskeleton. Results of immunofluorescence assay suggest that P42 may be redistributed to platelet surface after platelet aggregation.