Flow cytometry and Western blot of human and murine megakaryocytes and platelets. (A) Representative examples of flow cytometry of murine bone marrow–derived megakaryocytes (top) stained with a biotin labeled anti-hLRP1 antibody known to cross-react with mouse LRP1³¹  and then stained with streptavidin, PE–Alexa 647 secondary antibody. The gray line represents unstained cells. The broken black line represents secondary antibody alone. The solid black line is megakaryocytes with both antibodies. The bottom graph shows flow cytometry of platelets similarly performed. (B) As in panel A but for human cultured megakaryocytes and human peripheral blood platelets. LRP1 antibody was directly labeled with Alexa 647 for these experiments. As in panel A, the solid gray line represents unstained cells. The broken black line represents cells with isotype control antibody. The solid black line represents cells stained with the LRP1 antibody. (C) Western blot for LRP1 and actin as a control for protein loading. (1) Megakaryocytes, (2) platelets, and (3) WBCs. LRP1 band is expected at approximately 85 kDa and actin at approximately 25 kDa.