FIG. 1.

Effect of IFN-γ on the growth of C. trachomatis L2 and C. muridarum MoPn (A) and on the expression of iNOS and IDO (B) in HeLa cells. HeLa cells were untreated or pretreated with IFN-γ (20 U/ml) for 24 h, infected with chlamydiae, and then incubated in the complete culture medium described in Table 1. After 48 h of incubation, the cultures were harvested and chlamydial growth was assessed by determination of IFU following passing onto fresh HeLa monolayers. Growth data are presented as IFU (log₁₀) and represent the means ± standard errors of triplicate determinations. *, P < 0.0001 compared to the untreated control culture. For RT-PCR and Western blot analyses, HeLa cells were untreated or pretreated with IFN-γ for 24 h and then left uninfected or infected with chlamydiae. Following incubation for a further 24 h, cells were harvested, RNA was isolated, cDNA was synthesized, and PCR was carried out using primers specific for human iNOS, IDO, and actin. For Western blot analyses, cells were harvested after 24 h and the cell pellets were resuspended in Laemmli sample buffer and proteins were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and blotted to nitrocellulose. See Materials and Methods for details.