Previous studies have demonstrated that the delicate balance of a P. chabaudi-infected animal's life or death is regulated by CD4 T cells, as is the case in other persistent infections such as tuberculosis and toxoplasmosis (Caruso et al., 1999; Denkers and Gazzinelli, 1998; Stephens et al., 2005). Here, CD4 is linked to toxoplasmosis.