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J Infect Dis. 1992 Dec;166(6):1354-61.

Recombinant murine interferon-gamma reversibly activates rat alveolar macrophages to kill Legionella pneumophila.

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Medical Research Service, VA Medical Center, Seattle, WA 98108.


The interaction of interferon (IFN)-gamma, rat alveolar macrophages, and Legionella pneumophila was studied in vitro to define the effector cell potential of alveolar macrophages against an intracellular pathogen in a model in which the efficacy of IFN-gamma could be tested in vivo. Alveolar macrophages preincubated with IFN-gamma up-regulated Ia antigen and killed 0.5-4 logs of L. pneumophila over 4 days compared with 1-2 logs of bacterial growth in untreated cells. The bactericidal effect was dose dependent, evident over a wide range of bacterial inocula, and not suppressed by hydrocortisone. Preincubation with IFN-gamma was unnecessary and insufficient, as intracellular replication was reversed by exposure to IFN-gamma up to 48 h after infection, and neutralization of IFN-gamma after infection permitted bacterial growth. IFN-gamma thus converts alveolar macrophages from target cells to effector cells in host defense against L. pneumophila and may be of therapeutic benefit in legionellosis.

[Indexed for MEDLINE]

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