Summary We analysed endothelial cell membrane microparticles (ECMP) in the peripheral blood of patients with paroxysmal nocturnal haemoglobinuria (PNH) (n = 9), aplastic anaemia (AA) (n = 10), sickle cell disease (SCD) (n = 8), and healthy donors (HD) (n = 11). There was no clinically manifested thrombosis in the PNH or AA group, except one cured thrombophlebitis (PNH), while all SCD patients had a history of vaso‐occlusive crises. We used three‐colour flow cytometry with blood cell‐specific antibodies and antibodies to endothelial antigens CD105 and CD144. Phosphatidylserine‐positive microparticles were detected using the annexin V‐binding (AVB) assay. The population of CD105+AVB+ ECMP was significantly (P < 0·05) higher in SCD (median: 0·568 × 109/l; 25–75th percentile range: 0·351–0·976 × 109/l) and PNH (0·401 × 109/l ; 0·19–0·441 × 109/l) patients when compared with AA (0·122 × 109/l; 0·061–0·172 × 109/l) or HD (0·180 × 109/l; 0·137–0·217 × 109/l) group. Even more pronounced differences were observed in ECMP exhibiting a marker of inflammatory stimulation CD54 (CD105+CD54+). Similarly, ECMP that exhibited endothelial specific and proteolysis‐sensitive antigen CD144 were increased in SCD and PNH, but not in AA. Elevated CD54+ ECMP may reflect the inflammatory status of endothelial cells in SCD and PNH, while CD144+ ECMP could indicate continuous endothelial stimulation and/or injury. Analysis of circulating ECMP appears promising to provide useful information on the status of the vascular endothelium in PNH and SCD.

To elucidate a mechanism of prothrombotic effects of carbon nanotubes (CNTs), we report here that multiwalled CNTs activate blood platelets by inducing extracellular Ca(2+) influx that could be inhibited by calcium channel blockers SKF 96365 and 2-APB. We also demonstrate platelet aggregating activity of different single-walled and multiwalled CNTs. In addition, we show that CNT-induced platelet activation is associated with a marked release of platelet membrane microparticles positive for the granular secretion markers CD62P and CD63.