Severe malaria is characterized by the sequestration of Plasmodium falciparum-infected erythrocytes (IEs). Because platelets can affect tumor necrosis factor (TNF)-activated endothelial cells (ECs), we investigated their role in the sequestration of IEs, using IEs that were selected because they can adhere to endothelial CD36 (IE(CD36)), a P. falciparum receptor that is expressed on platelets. The results of coincubation studies indicated that platelets can induce IE(CD36) binding to CD36-deficient brain microvascular ECs. This induced cytoadhesion resisted physiological shear stress, was increased by EC stimulation with TNF, and was abolished by anti-CD36 monoclonal antibody. Immunofluorescence and scanning electron microscopy results showed that platelets serve as a bridge between IEs and the surface of ECs and may therefore provide receptors for adhesion to microvascular beds that otherwise lack adhesion receptors. This novel mechanism of cytoadhesion may reorient the sequestration of different parasite phenotypes and play an important role in the pathogenesis of severe malaria.
