Platelets in malarial infection: Protective or pathological?

Platelets play an ambiguous role in a malarial infection. On the one hand, platelets have been implicated adversely in cerebral malaria. They stick to the cerebral endothelium and mediate the adhesion of infected erythrocytes, with the postulated outcome of increasing severity or of even mediating this disease. On the other hand, platelets bind to infected red cells in the periphery and activate and release the cytokine PF4. This, in turn, binds to the Duffy antigen on the red cell and is thought to be internalised and enters the parasite food vacuole which it then destroys, killing the parasites. The control of platelet levels during an infection is also discussed with a view to understanding the thrombocytopenia that frequently accompanies a malarial infection.