Detection of intracellular B henselae in differentiated erythroid cells. Freshly isolated HPCs were infected with B henselae gfp_mut2 (MOI 100) and were subsequently cultivated for 16 days. (A) Flow cytometric detection of intracellular B henselae gfp_mut2 (green fluorescence, x-scale) in erythroid cells 9 days (left) and 16 days (right) after infection (control: uninfected erythroid cells). Data for 50 000 cells per time point were analyzed. Percentages shown in histogram analysis refer to B henselae gfp_mut2–infected cells. In total, 25% of all cells at day 9 and 41% at day 16 were positive for intracellular B henselae. Cells harboring GFP-expressing B henselae are given right of the dotted line (upper fluorescence limit of uninfected control cells). (B) Detection of intracellular B henselae gfp_mut2 (green) by CLSM 9 (left) and 16 (right) days after infection. Cells are counterstained by GPA (red signal). Scale bar: 20 μm. (C) TEM of an erythroid differentiated cell (day 9) containing intracellular B henselae. The enlargement illustrates that B henselae is located in a vacuolic compartment in differentiated erythroid cells.