Interleukin-5 transgenic mice show enhanced resistance to primary infections with Nippostrongylus brasiliensis but not primary infections with Toxocara canis

In this study, interleukin-5 (IL-5) transgenic mice with lifelong eosinophi lia were assessed for resistance to primary infections with two tissue-inva ding nematodes, Nippostrongylus brasiliensis and Toxocara canis. Relative t o nontransgenic littermates, three lines of IL-5 transgenic mice with varyi ng degrees of eosinophilia all displayed enhanced resistance to N. brasilie nsis. Although the timing of final worm expulsion was similar in transgenic and nontransgenic hosts, intestinal worms in transgenic mice were fewer in number throughout infection, failed to increase in size over the course of the infection, and were much less fecund. In contrast, T. canis larvae wer e recovered in similar numbers from tissues of transgenic mice with "low" o r "high" eosinophilia and from nontransgenic mice. These results and other data suggest that eosinophils can contribute to host resistance to some par asite species. Parasite transit time through the host may correlate with re lative sensitivity to eosinophils.