The cHtrA but not other chlamydial periplasmic proteins are secreted into host cell cytosol. HeLa cells infected with C. trachomatis organisms were processed and co-labeled with mouse antibodies against various periplasmic proteins (red) and a rabbit antibody against IncA (green) as described in Figure 1 legend. The Hoechst dye was used to visualize DNA (blue). The triple labeling was analyzed under a conventional fluorescence microscope (A) and confocal microscope (B). Under the confocal microscope, a series of four images were taken along the Z-axis by varying 1 μM between each. Note that cHtrA (red arrows) but none of the other periplasmic proteins including CT067, CT539 & CT783 was detected outside of the inclusion membrane (green arrows) by either immunofluorescence microscopy or confocal microscopy.