Induction of tryptophan catabolism is the mechanism for gamma-interferon-mediated inhibition of intracellular Chlamydia psittaci replication in T24 cells

G. I. Byrne, L. K. Lehmann, G. J. Landry

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    267 Scopus citations

    Abstract

    Human uroepithelial (T24) cells were incubated for 24 h in the presence of various concentrations of human recombinant gamma interferon (Hu-rIFN-γ) and then infected with the 6BC strain of Chlamydia psittaci. This resulted in a reduction of intracellular chlamydial inclusion development in proportion to the concentration of Hu-rIFN-γ present when Giemsa-stained cells were examined by light microscopy 24 h after infection. When tryptophan was added to Hu-rIFN-γ-treated cells just after infection, reversal of the Hu-rIFN-γ-mediated inhibition occurred in proportion to the concentration of tryptophan added. Addition of either isoleucine or lysine did not result in reversal of the antichlamydial state. Transport of L-[3H]tryptophan into acid-soluble intracellular pools was found to be greatly enhanced in Hu-rIFN-γ-treated T24 cells compared with the rates measured for untreated cells. Transport of [3H]leucine was not increased in treated cells. Cells treated with Hu-rIFN-γ also degraded L-[3H]tryptophan to catabolites that cochromatographed with N-formylkynurenine and kynurenine as measured by high-performance liquid chromatography. We conclude that Hu-rIFN-γ-mediated inhibition of intracellular C. psittaci replication in T24 cells occurs by depletion of the essential amino acid tryptophan, most likely via the induction of indoleamine-2,3-dioxygenase, the initial enzyme of tryptophan catabolism.

    Original languageEnglish (US)
    Pages (from-to)347-351
    Number of pages5
    JournalInfection and Immunity
    Volume53
    Issue number2
    DOIs
    StatePublished - 1986

    ASJC Scopus subject areas

    • Parasitology
    • Microbiology
    • Immunology
    • Infectious Diseases

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