Vascular occlusion in sickle cell disease may be a result of cellular interactions. Early sickle cells (reticulocytes that contain Hb SS) tend to be more "sticky" and adhere to endothelium. Abnormal receptors on these cells allow platelets to form a bridge between sickled RBCs and endothelial cells in post-capillary venules. Adding to this occlusive process are leukocytes that respond to tissue damage and inflammation. This will be discussed in more detail later in the course.