Abstract
The genetic control of susceptibility to two species of murine malarial parasites was investigated with recombinant inbred (RI) mouse strains as a model system. Initially, the nonlethal Plasmodium yoelii 17X strain was cloned by limiting dilution to minimize parasite variability. This cloned P. yoelii was used to infect C57BL and BALB/c mice, strains which are the progenitors of the CXB RI strains. Since these two strains displayed consistent differences in the kinetics of parasitemia, the seven CXB RI strains were compared for their susceptibility to the same parasite. The RI strains varied considerably when infected with P. yoelii and could be divided into susceptible and resistant groups based on mortality observed with this normally mild infection. This suggests a complex, multigenic inheritance determining susceptibility to this parasite. However, when the susceptible and resistant CXB RI mice were infected with another, unrelated plasmodial species, Plasmodium chabaudi adami, all the mice showed identical patterns of disease. Since susceptibility to different murine plasmodia does not cosegregate in the CXB RI mice, different mechanisms of resistance may be required for different plasmodial species.