Malaria and the immune system in humans.

Malaria infection gives rise to host responses which are regulated by both the innate and adaptive immune system as well as by environmental factors. Acquired immunity is both speciesand stage-specific. It is rarely sterile, but rather associated with low-grade parasitemia and episodes of clinical disease throughout life [1, 2]. In endemic areas, children born to immune mothers are protected against disease during their first half year of life by maternal antibodies. This passive immunity is followed by 1or 2 years of increased susceptibility before acquisition of active immunity [1]. In general, acquisition of active immunity to malaria is slow and requires repeated parasite exposure to be maintained. Genetic variability of both the human host and the parasite, parasite-induced immunosuppression and other reasons account for this instability [3]. In this chapter we will discuss the immune regulation of malaria blood-stage infection in humans, focussing on Plasmodium falciparum, the most widely spread and dangerous of the human parasites.