Figure 4. IFNG stimulation increased acidification of chlamydial early inclusions, but not in hGBP1 or -2 knockdown macrophages. Empty (control), hGBP1 and hGBP2-stable knockdown THP1-derived macrophage monolayers were prestimulated for 24 h with 100 U/ml IFNG and then infected with C. trachomatis MOI 100 for 2 h. Confocal microscopy images of acidotropic dye LysoTracker (Red) and C. trachomatis (Blue) revealed that IFNG stimulated the acidification of chlamydial early inclusions in WT macrophages. By contrast, the acidification process is impaired in cells deficient in either hGBP1 or 2, in response to IFNG stimulation. Scale bars: 10 μm.