Figure 4.

The bacterial density in vacuoles that contained LAMP-1 (black bars) or lacked LAMP-1 (white bars). (A) Macrophages infected for the period indicated were fixed and processed for microscopic localization of LAMP-1 and L. pneumophila. At the times indicated, vacuoles were scored for the presence of LAMP-1 and the number of bacteria. As it was not possible to count accurately >20 bacteria in one compartment, these were scored as >20. (B) After a 1-h infection, macrophages were treated with the proton ATPase inhibitor BFA, incubated for the times indicated, then processed as described above. In each of three independent experiments, 50 vacuoles were analyzed for each condition at the times indicated. The population of vacuoles analyzed for A was the same as that depicted in Fig. 1 B; the population of vacuoles analyzed for B was the same as that represented by Fig. 7.