Affiliation:
1. From the Department of Medicine, Cornell University Medical College, New York 10021
Abstract
Despite permitting uncontrolled intracellular visceral infection for 8 wk, interferon-γ (IFN-γ) gene knockout (GKO) mice infected with Leishmania donovani proceeded to reduce liver parasite burdens by 50% by week 12. This late-developing IFN-γ–independent antileishmanial mechanism appeared to be dependent largely on endogenous tumor necrosis factor-α (TNF-α): L. donovani infection induced TNF-α mRNA expression in parasitized GKO livers and neutralization of TNF-α reversed control at week 12. 7 d of treatment of infected GKO mice with interleukin-12 (IL-12) readily induced leishmanicidal activity and also partially restored the near-absent tissue granulomatous response, observations that for the first time expand the antimicrobial repertoire of IL-12 to include IFN-γ–independent effects. The action of IL-12 against L. donovani was TNF-α dependent and required the activity of inducible nitric oxide synthase. These results point to the presence of an IFN-γ–independent antimicrobial mechanism, mediated by TNF-α, which remains quiescent until activated late in the course of experimental visceral leishmaniasis. However, as judged by the effect of exogenous IL-12 this quiescent mechanism can readily be induced to rapidly yield enhanced intracellular antimicrobial activity.
Publisher
Rockefeller University Press
Subject
Immunology,Immunology and Allergy
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