FIG. 2.

Effect of IFN-γ and IFN-γ-TNF-α-IL-1β-LPS on the growth of C. trachomatis L2 and C. muridarum MoPn (A and D) and on the expression of iNOS and IDO (B and C) in RT-4 cells. RT-4 cells were untreated or pretreated with IFN-γ (20 U/ml) for 24 h. Cells exposed to IFN-γ (20 U/ml)-TNF-α (20 ng/ml)-IL-1β (20 ng/ml)-LPS (20 ng/ml) were not pretreated. Following chlamydia infection, cells were incubated for a further 48 h in the complete medium described in Table 1 plus any indicated supplements. Final concentrations of tryptophan, indole, and NMMA were 500 μg/ml, 100 μM, and 1 mM, respectively. Cultures were harvested and processed for the various assays as described in the legend to Fig. 1. Growth data are presented as IFU (log₁₀) and represent the means ± standard errors of triplicate determinations. Intracellular tryptophan pools were measured by HPLC. Data are presented as pmol tryptophan/10⁷ cells and represent the means of two independent experiments with ranges shown. *, P < 0.0001 compared to the untreated control culture.