Monolayers were fixed daily from 1 day to 6 days p.i. The average fluorescence intensities of each effector were measured in the nuclei of host cells containing a single developing tissue cyst, ascertained by positive staining of either BAG1 (1 to 3 days p.i.)or SRS9 (4 to 6 days p.i.), both markers of bradyzoite differentiation (19, 20) (Fig. 3A to D). Here, BAG1 is linked to cyst.