Possible mechanisms for the maintenance of polymorphisms in Plasmodium populations.

There are two views on the origin and maintenance of the high levels of polymorphism found in antigenic Plasmodium proteins. Immune selectionists consider that mutations which avoid stimulating a host response are frequent and advantageous. Proponents of the random genetic drift of selectively equivalent mutations hold that Plasmodium antigens are relatively unconstrained and can tolerate considerable structural diversity. Both sides agree that antigenic diversity is advantageous although selectionists see benefits in individual mutations whereas the proponents of random genetic drift see the advantage in the parasite's capacity to tolerate diversity per se.