Fig. 6. Internalized exogenous anti-CD63 antibody disrupted intracellular chlamydial development. HEp-2 cells were infected with C. trachomatis E and cultured in the presence of exogenous anti-CD63 from 24 hours to 48 hours post infection. (Left panels) TOPRO-3-labeling was used to analyze morphological changes in inclusion development. TOPRO-3 labeled intracellular bacteria and the host-cell nuclei, with the chlamydial inclusions colorized blue (Photoshop 7.0) in obtained black and white images. 0.5-µm-thick optical sections revealed that the addition of exogenous anti-CD63 antibody resulted in reduced inclusion-size relative to untreated controls. (Center panels) Electron micrographs of the intracellular bacteria revealed primarily EBs in the untreated control cells, but predominantly RBs delayed in re-differentiation to infectious EBs in infected cells treated with exogeneous anti-CD63. Arrowheads indicate representative EBs. (Right panel) A reduction in recovery of infectious Chlamydia was observed in cells cultured in the presence of anti-CD63 antibody. Data are presented as the mean infectious-forming units of triplicate cultures ± s.e.m.