IL4 and infection: Based on the previous knowledge that infections with helminths, such as S. mansoni, can induce a polarization of the immune response toward a Th2 phenotype with enhanced IL-4, IL-5, and IL-13 production (33) and that a soluble antigen from the S. mansoni egg may inhibit the production of IL-12 by dendritic cells (34), we hypothesized that concurrent infection with S. mansoni could be able to control or even neutralize the Th1 immune response induced by T. gondii infection.