Mimicry in Trypanosoma cruzi: fantasy and reality.

Chronic infection of mammals by Trypanosoma cruzi often results in severe autoimmune and inflammatory pathology. Extensive antigen cross-reactivity between the parasite and its mammalian hosts has also been reported. These findings have stimulated speculation that Trypanosoma cruzi uses antigenic mimicry as a mechanism for escaping the host immune system. This may not be the case and the observed antigen cross-reactivity may be a result of perturbations of the immune system such that common, normally tolerated antigens are recognized in infected animals. The parasite, however, does appear to use functional mimicry to survive in the immune competent host.