The immune system of the body generally functions by seeking out and mobilizing all foreign particles for destruction. In the same way every circulating red blood cell infected with malaria parasites is mobilized and destroyed in the spleen. Unfortunately, most malaria parasites particularly P. falciparum often averts this fate by displaying adhesive proteins on the surface of the infected blood cells, causing them to stick to the walls of the small blood vessels, thereby sequestering the parasites from passage through the general circulation and the spleen (Chen et al., 2000). Again owing to the fact that for most of its human life cycle, the parasite resides within the liver and red blood cells, they are relatively invisible to immune surveillance.
Although the red blood cell surface adhesive proteins (called PfEMP1) are exposed to the immune system, they do not serve as good immune targets because of their extreme diversity; there are 60 variations of the proteins within a single parasite and perhaps limitless versions within parasite populations (Chen et al., 2000)
. So like a thief changing disguises or a spy with multiple passports the parasite switches between a broad repertoire of PfEMP1 surface proteins, thus staying one step ahead of the pursuing immune system
Perhaps these peculiar behaviours of the parasite are the reason why nobody in the endemic areas has been able to acquire complete immunity to malaria. However, the partial or semi-immunity conferred on those living in malaria endemic regions is quite helpful as it reduces significantly, the severity and fatality of the disease compared to non-immune individuals.
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