Stage-specific cross-resistance between Nippostrongylus brasiliensis and Strongyloides ratti (Nematoda) in rats.

Stage-specificity of cross-resistance between Nippostrongylus brasiliensis and Strongyloides ratti was investigated. Results showed that immunization with tissue-migrating larvae was sufficient to generate cross-resistance and that host defense mechanisms operating in the cross-resistance were directed against tissue-migrating larvae but not against intestinal adult worms. In addition, no significant potentiation of the cross-resistance was observed after multiple immunization. These observations suggest that host defense mechanisms against heterologous challenge infection were qualitatively and/or quantitatively different from those against homologous challenge infection.