Interaction of B henselae with ECs and CD34⁺ HPCs. (A) Adherence and invasion rates of B henselae obtained with CD34⁺ HPCs and ECs (100 000 cells each, respectively). The number of adherent B henselae was assessed 30 minutes after infection and invasion of B henselae was quantified after 2 hours. (B) Detection of adherent and intracellular B henselae by CLSM 24 and 72 hours after infection (left: ECs; right: HPCs). Green signal indicates extracellular bacteria; blue signal, intracellular bacteria; and red signal, filamentous actin. (C) Detection of B henselae by FISH 24 hours after infection of ECs and HPCs. Overlay of FISH using a universal eubacterial oligonucleotide probe (EUB338-Cy-3, red signal) and DAPI staining (light blue) of the host cell nucleus. (D) TEM of HPCs 24 hours after infection with B henselae (arrows). Membrane ruffling (ii,iii) can be observed following adherence (i) of the bacteria to the host cells. Intracellular bacteria are located in vacuoles (iv). (E) Detection of B henselae by IEM using anti-BadA– and 10 nm gold-conjugated goat anti–rabbit IgG antibodies. The enlargement illustrates the interaction of B henselae with HPCs by immunogold staining of B henselae (see arrows).