Macrophage mediated resistance to Babesia microti in Nematospiroides dubius--infected mice.

Infection with the gastrointestinal nematode, Nematospiroides dubius, induced resistance to a concurrent infection with Babesia microti in mice. This enhanced resistance to B. microti occurred during infection with the larval, rather than the adult stages of N. dubius. Splenectomy or the injection of carrageenan or silica abrogated the protective effect against B. microti induced by infection with N. dubius. Peritoneal macrophages harvested from infected mice produced inhibition of the development of B. microti in vitro. This inhibition was greatest using macrophages harvested from mice recovered from infection with B. microti and from mice infected with the larval stages of N. dubius. Also, supernatants harvested from cultures of macrophages from N. dubius-infected mice suppressed B. microti development in vitro.