Resistance and Susceptibility to Malarial Infection: A Host De¬fense Strategy against Malaria

In an effort to understand what limits the virulence of malaria para­sites in relation to the host genetic and immunogenic background, we investi­gated the possibility that the parasite and host genotype crossover interac­tions constrain virulence. Two groups of mice from different genotypes were used (C57BL/6 (B6) and DBA/2 mice). The mice were infected with a virulent parasite line Plasmo­dium yoelii17XL (P. yoelii17XL). Parasitemia, hematocrit value and lympho­cytes yielded by livers and spleens were evaluated. Fluorescence Activated Cell Sorting (FACS) analysis illustrated phenotypic characterization of lymphocytes. Infection with P. yoelii17XL did not result in thedeath of DBA/2 mice. In contrast,B6 mice developed significantly high parasitemia and succumbed to death. Using (FACS) analysis, DBA/2 mice were found to experience a marked expansion of interleukin (IL)-2Rb+ CD3int cells and gd T cells in the liver, espe­cially in the recovery phase. The expansion of unconventional T cells (i.e. B220+ T cells) was also marked in DBA/2 mice. The outcome of murine malaria infections depends on the dynamic interplay between the immune-mediator and the genotype of the host.