IFN‐γ has been implicated in the pathogenesis of experimental cerebral malaria (ECM). We have used mice lacking the α chain of the IFN‐γ receptor (KO mice) to define its role in the pathogenesis of ECM. Infected KO mice did not develop ECM and showed no leukocyte or parasite sequestration in the brain, and no hemorrhages. The resistance of KO mice to ECM was associated with the absence of any increases of TNF‐α and ICAM‐1 proteins in the brain, which are both essential for ECM. Wild‐type (WT) mice which do not develop ECM, despite increased local production of TNF‐α protein, showed no leukocyte accumulation in the brain and this was correlated with the absence of ICAM‐1 protein from brain microvessels. KO mice infected with 106 parasitized erythrocytes (PE) of Plasmodium berghei ANKA (PbA) did not develop ECM, but they had high parasitemia and died earlier than WT mice which did not develop ECM. However, KO mice did not develop higher parasitemia than WT mice when both groups were infected with a lower dose (5×105 PE) of PbA‐infected red blood cells. This indicates that different doses of PE may trigger different IFN‐γ responses and that there may be a threshold concentration for protection against parasitemia.

Infection with Plasmodium berghei ANKA is usually lethal. The parasite causes in some mouse strains a neurovascular syndrome, experimental cerebral malaria (ECM), involving immunopathological reactions. The effects on the development of ECM of the mouse genetic background have been clearly demonstrated, but nothing is known about the effects of the clonal diversity of the parasite. We showed that various cloned lines derived from a polyclonal line of P. berghei ANKA caused ECM but that the extent of ECM induction was dependent on the amount of inoculum. Subtle differences in ECM characteristics (survival time and hypothermia) were also observed. We also confirmed, using the 1.49L cloned line, that the mouse genetic background strongly affects ECM.

Infection with Plasmodium berghei ANKA is usually lethal. The parasite causes in some mouse strains a neurovascular syndrome, experimental cerebral malaria (ECM), involving immunopathological reactions. The effects on the development of ECM of the mouse genetic background have been clearly demonstrated, but nothing is known about the effects of the clonal diversity of the parasite. We showed that various cloned lines derived from a polyclonal line of P. berghei ANKA caused ECM but that the extent of ECM induction was dependent on the amount of inoculum. Subtle differences in ECM characteristics (survival time and hypothermia) were also observed. We also confirmed, using the 1.49L cloned line, that the mouse genetic background strongly affects ECM.