Within 12 h of infection, Toxoplasma increased activation of PERK as measured by its self-phosphorylation (PERK-P), induced expression of ATF6 and formation of its cleavage product ATF6-N, and increased levels of the IRE1-derived spliced variant of XBP1 (XBP1s) (Fig. 1A). This evidence concerns the gene XBP1 and infection.