[Trypanolytic factor of human serum]

African trypanosomes (prototype : Trypanosoma brucei) are protozoan flagellates that infect a wide range of different mammals. In humans these parasites have to counteract innate immunity because, unlike other mammals, human serum possesses efficient trypanolytic activity. Resistance to this activity has arisen in two T. brucei subspecies, termed T. b. rhodesiense and T. b. gambiense, allowing them to infect humans where they cause sleeping sickness in East and West Africa respectively. The study of the mechanism by which T. b. rhodesiense escapes lysis by human serum led to the identification of the trypanolytic factor, which turned out to be an ionic pore-forming apolipoprotein associated with some HDL particles.