INHIBITION OF CHLAMYDIA-PNEUMONIAE GROWTH IN HEP-2 CELLS PRETREATED WITH GAMMA-INTERFERON AND TUMOR-NECROSIS-FACTOR-ALPHA

An in vitro culture system was used to study the effects of increasing concentrations of human cytokines on the intracellular replication of Chlamydia pneumoniae. HEp-2 cell monolayers, pretreated for 24 h with 200 U of human recombinant gamma interferon (IFN-gamma) per mi restri cted the intracellular replication of C. pneumoniae. Tumor necrosis fa ctor alpha (TNF-alpha; 25 ng/ml) exhibited a synergistic effect with I FN-gamma by reducing the concentration of IFN-gamma necessary to restr ict intracellular growth to 100 U/ml. The addition of 200 mu g of tryp tophan per mi significantly reversed the inhibitory effects of IFN-gam ma, and TNF-alpha, suggesting involvement of the indoleamine-2,3 dioxy genase pathway in the restriction process.