STAT1 and infection: To determine if there are strain differences in the effect of infection on IFNγ-induced STAT1 phosphorylation and localization, we infected HFFs for one hour with either RH(I), Pru(II), or CEP(III) parasites, subsequently stimulated the cells for two hours with IFNγ, and quantified STAT1 tyrosine phosphorylation and nuclear translocation by immunofluorescence (Fig. 2A, B).