Fig. 5. U937 cells were incubated with L. pneumophila for two hours, then washed, scrapped off the petri plates and homogenized. A low-speed pellet of unbroken cells or large cell fragments was removed by centrifugation. The supernatant was then centrifuged on a tabletop centrifuge and the pellet fixed. It contains L. pneumophila enclosed in its phagosome, and still attached to the surface of the phagosome are mitochondria and ER vesicles. (a) Since the ER is continuous with the outer nuclear membrane (NM), L. pneumophila-containing phagosomes can also be found attached to the nucleus (N) as well as to the outer ER vesicles (b).
