Abstract
Peritoneal macrophages from T. cruzi-immune mice were resistant to infection in vitro with culture forms of the parasite. Macrophage resistance appeared in infected mice about 21 days postinfection when parasitemia was still rising. Resistance in vitro was nonspecific since macrophages from BCG-immune mice were resistant to T. cruzi, and since macrophages from T. cruzi-immune mice were resistant to infection in vitro with Listeria were not resistant to challenge with T. cruzi even when the parasites were opsonized.