Francisco et al. Increase of reactive oxygen species by desferrioxamine during experimental Chagas’ disease through Fenton-type mechanisms since iron is an essential catalytic agent in such reactions. The use of this chelator may provoke a release of iron from ferritin as ‘free iron’ that was used in this reaction. It must be concluded, therefore, that the action of DFO increases the protection of the host against infection and also acts directly on the parasite itself, thus explaining the reductions in parasitemia and the rate of mortality in DFO-treated animals that have been reported earlier.8,9 However, DFO also delayed increased production of nitrate/nitrite until 21 dpi, and this could be the reason why mortalities of infected animals treated with DFO have been observed by our group.9 Conclusions On the basis of the results presented herein, it is concluded that DFO possesses the capacity to increase antioxidant defense systems in the host, particularly by up-regulating SOD, as well as promoting a measured increase in oxidative stress that exerts pressure on the parasite. This suggests that DFO offers a balance of effects with respect to its capacity to promote protection in the host. 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