FIG. 2.

Kinetics of the internalization of nongerminated E. cuniculi spores by various NPP cell lines and human MDM. Two million E. cuniculi spores were added to each well of confluent cells, and the monolayers were fixed after 0, 2, 4, 6, 10, and 24 h. Intracellular spores were identified using differential immunofluorescence staining. To account for the size difference between the cells studied, internalization rates are given as the number of intracellular spores per high-power field of view (magnification, ×1,000). In confluent monolayers every field covers approximately 11.5 MRC5 cells, 50 293 cells, 60 A549 cells, and 30 macrophages. Data shown are means ± SD for three independent experiments, except for time points of >6 h for 293 cells, where the results of a single experiment are given (monolayers of 293 cells tended to detach from the coverslip after >6 h). Differences between cell lines were significant at a P value of <0.0001 (two-way analysis of variance).