A spleen is not necessary to resolve infections with Plasmodium yoelii

The role of the spleen in resistance to infections with nonlethal Plasmodium yoelii 17x is dependent upon the genotype of the host. Thus, DBA/2 (D2) mice infected with P. yoelii 17x were not adversely affected by removal of the spleen, while splenectomized C57BL/6 (B6) or Balb/c mice failed to resolve their infections and eventually died. The levels of parasitemia were lower in splenectomized mice compared to intact controls; however, splenectomized mice became as anemic as did spleen-intact controls. Splenectomy resulted in the appearance of large aggregates of mononuclear cells in the livers of infected mice and also altered the liver/body weight ratios. These results indicate that D2 mice have a spleen-independent mechanism of clearing parasites which is lacking in B6 and Balb/c mice.