Changes in CD36 receptor expression on sickle cell RBC before and while on HU therapy. Changes in CD36 expression are shown for the reticulocyte fraction (A), total RBC (B), and mature RBC (nonreticulocyte) fraction (C). Baseline = value at the time of the first measurement of adhesion receptor expression. On HU = value at the time of the last measurement of adhesion receptor expression while on HU therapy. Each paired data point represents one patient.