Inclusion-forming units (IFUs) of C. psittaci in THP-1 cells treated with iron sulfate, INP0007, or both. (a) Number of IFUs in each group. One million THP-1 cells were treated with 50 μM FeSO4, 50 μM INP0007, or both; the cells were then infected with C. psittaci. At 44 h p.i., the THP-1 cells were fixed and incubated with a rabbit anti-C. psittaci 6BC antibody and then incubated with a Cy2-labeled (green fluorescence) goat anti-rabbit IgG and DAPI. The inclusion bodies (green fluorescence) in the cells were counted under a fluorescence microscope (at 40x magnification). Five fields of each sample were counted. (b) Images of IFUs of C. psittaci in THP-1 cells. Cells infected with C. psittaci (A), cells infected with C. psittaci and pretreated with INP0007 (B), cells infected with C. psittaci and pretreated with FeSO4 (C), and cells infected with C. psittaci and pretreated with both INP0007 and FeSO4 (D) (40x magnification).