resistance and susceptibility to malarial infection: a host de¬fense strategy against malaria

background: 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. methods: 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 yoelii 17xl ( p. yoelii 17xl) . parasitemia, hematocrit value and lympho­cytes yielded by livers and spleens were evaluated. fluorescence activated cell sorting (facs) analysis illustrated phenotypic characterization of lymphocytes. results: infection with p. yoelii 17xl 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 + cd3 int 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. conclusion: the outcome of murine malaria infections depends on the dynamic interplay between the immune-mediator and the genotype of the host.