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-γ) per ml restricted the intracellular replication of C- pneumoniae. Tumor necrosis factor alpha (TNF- α; 25 ng/ml) exhibited a synergistic effect with IFN-γ by reducing the concentration of IFN-γ necessary to restrict intracellular growth to 100 U/ml. The addition of 200 μg of tryptophan per ml significantly reversed the inhibitory effects of IFN-γ and TNF-α, suggesting involvement of the indoleamine-2,3-dioxygenase pathway in the restriction process.
ASJC Scopus subject areas
- Infectious Diseases