Interaction between Plasmodium chabaudi and C57Bl mice with particular reference to the immune response.

The parasitaemia consequent upon infection of normal, T cell-deprived, or nude mice with a strain of Plasmodium chabaudi was studied. In normal mice three waves of parasitaemia of successively diminishing magnitude were observed, the infected animals becoming aparasitaemic within 45 days. In most T cell-deprived and nude mice a sustained cyclicity of parasitaemia was observed. Slight evidence was adduced of increase in virulence of the parasite with increasing time of infection in deprived mice. No positive evidence could be obtained for modulation of antigenicity of the parasite although this is suspected to be present. The results seem to be in conflict with the notion that the transient diminishing cyclicity of parasitaemia observed in normal mice is due to suppression of the parasite by the host. In the absence of what could be regarded as part of the host defence mechanism the cyclicity far from disappearing was exaggerated and prolonged.