FIG. 4.

IFN-γR expression up-regulated in response to Chlamydia does not contribute to increased IDO activity. (Top) HeLa 229 cells, stably transfected with the IDO reporter plasmid pGASinsIDO/EGFP-C1, were cultivated in complete medium, treated with IL-1β (100 ng/ml), or infected with C. psittaci for 12 h and then incubated in medium alone for 4 h before being induced with increasing concentrations of IFN-γ for an additional 12 h. The cells were harvested, and GFP expression was assessed using flow cytometric analysis (top panel), or the cells were analyzed for IDO enzymatic activity by HPLC (bottom panel). The results for one of three similar experiments (means ± standard deviations) are presented. MFI, mean fluorescent intensity.