Complement receptor 1 and malaria.

Plasmodium falciparum malaria is an intracellular parasite that is transmitted by Anopheles mosquitoes. It is responsible for approximately 1 million deaths per year. Most deaths occur as a result of complications such as severe anaemia or cerebral malaria (coma). The complement receptor 1 is a key complement regulator found on the surface of red cells and most leucocytes. A growing body of evidence suggests that this molecule plays a critical role in the pathogenesis of P. falciparum malaria. Initial reports showed that CR1 enables the binding of infected red cells to uninfected red cells to form rosettes, which can potentially obstruct small capillaries. However, further evidence suggests that CR1 is also important in the control of complement activation and immune complex formation during malaria infection. Most recently, CR1 has also been shown to be a receptor for the invasion of red cells by the parasite. Its polymorphic nature almost certainly has allowed the selection of variants that have helped humankind survive the scurge of malaria. The finding of conflicting reports about the exact role of these variants in severe disease underlies the complexity of the parasite-host interactions and highlights the need for further studies.