Blood
-
Children with sickle cell anemia (HbSS) are at high risk for neurologically overt cerebral infarcts associated with stroke and neurologically silent cerebral infarcts correlated with neuropsychometric deficit. We used complete magnetic resonance imaging (MRI) histories from 266 HbSS children, aged 6 through 19 years, who were enrolled in the Cooperative Study of Sickle Cell Disease (CSSCD) to examine silent infarct prevalence, localization, recurrence, and progression. We report a baseline prevalence of 21.8%, marginally higher than previously reported due to improved imaging technologies. ⋯ Both events were substantially less frequent than the risk of stroke recurrence among children not provided chronic transfusion therapy. Although chronic transfusion is known to decrease occurrence of new silent infarcts and strokes in children with elevated cerebral arterial blood flow velocity, further study is required to determine its risk-benefit ratio in children with silent infarct and normal velocities. Until safe and effective preventive strategies against infarct recurrence are discovered, MRI studies are best reserved for children with neurologic symptoms, neuropsychometric deficits, or elevated cerebral artery velocities.
-
CD40 ligand (CD40L) is expressed on activated CD4(+) T lymphocytes and at the activated platelet surface. A circulating soluble form of CD40L (sCD40L) is generated by the way of a proteolytic cleavage. We measured sCD40L in the plasma of either healthy subjects; patients with inflammatory disorders and low, normal, or high platelet count (reactive thrombocytosis); or patients with essential thrombocythemia (ET). ⋯ Platelet-associated CD40L was released upon platelet activation. In conclusion, platelets appear as a reservoir of CD40L that may be a major contributor to circulating sCD40L. Platelet-associated CD40L may be a potential marker of platelet regeneration.