Treatment of infected mice with exogenous IL-33 confirmed the protective effects of IL-33 and highlighted the impact on the recruitment of inflammatory monocytes to sites of infection and the subsequent upregulation of iNOS, a process required for the control of T. gondii (Yap and Sher, 1999b; Dunay et al., 2010; Serbina et al., 2003; Scharton-Kersten et al., 1997). This evidence concerns the gene NOS2 and infection.