Interrelationships of immunoconglutinin, immune complexes, and complement in anemia, thrombocytopenia, and parasitemia of acute and chronic malaria in rats.

Anemia, thrombocytopenia and reduction in parasitemia in P. chabaudi infection of rats were associated with appearance in blood of soluble immune complexes, immunoconglutinin (IK), and by reductions in titers of lytic complement. With reduction of parasitemia to subpatent levels, anemia, but not thrombocytopenia, persisted and erythrocyte counts did not return to preinfection levels for several weeks. This chronic anemia was accompanied by elevated amounts of soluble immune complex, depressed titers of lytic complement and persistence of IK. Evidence was presented indicating that the infections of the rats persisted in a chronic form. It was thus indicated that immune interactions, related to anemia and clearance of parasitemia, persisted in absence of microscopically evident parasitemia, and may have been in part responsible for the persistent anemia. Based on the evidence cited, it is suggested that complement-fixing immune complexes attach to blood cells, infected as well as uninfected, and that these cells are sequestered and phagocytized in the spleen after immunoconglutination by IK. It is also suggested that this interaction continued after the clearance of patent parasitemia and accounted for the persistence of anemia in the chronic phase of infection.