Activated platelets and leukocyte activations in young patients with β-thalassemia/HbE following bone marrow transplantation

Bone marrow transplantation (BMT) is the only curable option for thalassemia major, β-thalassemia/HbE. However, some patients still have the risk of hypercoagulable complications. We used a whole blood flow cytometric analysis to measure the circulating microparticle (MP) levels, activated platelets, and leukocyte-platelet aggregates in 59 young β-thalassemia/HbE patients compared with 20- and 28-matched healthy and patients receiving regular blood transfusion (RT), respectively. Results from the studies showed that blood samples from BMT group contained a significantly higher numbers of circulating MPs originated from platelets (ann-V⁺CD41a⁺), leukocyte (ann-V⁺CD45⁺) and endothelial cells (ann-V⁺CD146⁺) when compared to samples from healthy subjects and RT patients. In contrast, the percentages of activated/procoagulant platelets (CD62P and CD142 expressing platelets) were decreased in BMT group. In addition, monocytes forming microaggregates were the major population among other leukocyte-platelet complexes. Different patterns of CD11b, CD62P and CD142 expression on platelet-leukocyte microaggregate surface were also found. These data suggest that circulating MPs together with leukocyte-platelet aggregates may be responsible, in part, in pathogenesis of hypercoagulable state in β-thalassemia/HbE patients who undergone BMT.