Schematic model of the different types of RSP-2–tagged nEs and rIEs and their adhesive tropism during the blood-stage cycle. (A) Parasites of the CSA-binding phenotype nE that carry RSP-2 on their surface cytoadhere to endothelial cells and placental syncytiotrophoblasts via an unknown receptor. RSP-2–tagged nEs are potential targets marked for destruction by the host immune response in the presence of anti–RSP-2 antibodies. (B) rIEs of parasites selected for CSA binding will cytoadhere, and during a short period of the blood-stage cycle (early trophozoites), both RSP-2 and PfEMP1 are present on the surface of IEs and can bind to 2 distinct host receptors at the same time. These parasites probably are not present in the peripheral blood circulation.