FIG 7.

Limited association of M. tuberculosis bacilli with neuronal phagolysosomes. Murine primary neuron cultures were established from hippocampi of 17-day-old C57BL/6 embryos and infected with H37Rv-GFP bacilli (green) at a multiplicity of infection of 30:1. The neurons were stained with the phagolysosome marker Lysotracker (red) after 24 h (A) and 48 h (B). Cell nuclei were labeled with DAPI (blue) and analyzed by confocal microscopy. The images represent 3-dimensional data sets and provide a view of the x-y and z dimensions of the original z-stack. A colocalized signal (yellow) resulting from the association of the bacilli (green) with the phagolysosome, labeled with Lysotracker (red), is rarely observed in neurons at 24 h (A) and 48 h (B) postinfection, and most internalized bacilli appear disassociated from the phagolysosome. Scale bars, 5 μm.