Constituents of late endocytic multivesicular compartments localized to the chlamydial inclusion by indirect immunofluorescence. HEp-2 cells were infected with C. trachomatis E for 36 hours, immunlabeled with the indicated MVB-specific antibodies and analyzed by confocal microscopy. (Upper panels) 0.5-μm-thick optical sections of infected cells, immunolabeled with antibodies against CD63, MLN64, LBPA and LAMP-1, followed by the appropriate secondary antibody conjugated to Alexa Fluor 594. (Middle panels) TOPRO-3 labeling of the equivalent confocal slice to reveal intracellular bacteria and host-cell nuclei. (Lower panels) Merged images. Arrows indicate representative chlamydial inclusions, arrowheads indicate representative nuclei. CD63, MLN64 and LBPA localized to the TOPRO-3-positive chlamydial inclusions. Bar, 20 μm.