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J. Exp. Med.,
Volume 189, Number 2, January 18, 1999 219-230
,
Nitric Oxide, and Apoptosis
By

From the * Laboratory of Immunology and Pathogenic effector T cells in experimental autoimmune uveitis (EAU) are T helper type 1-like,
and interleukin (IL)-12 is required for their generation and function. Therefore, we expected that IL-12 administration would have disease-enhancing effects. Mice were immunized with a
uveitogenic regimen of the retinal antigen interphotoreceptor retinoid-binding protein, treated
with IL-12 (100 ng/d for 5 d), and EAU was assessed by histopathology. Unexpectedly, IL-12
treatment failed to enhance EAU in resistant strains and downregulated disease in susceptible
strains. Only treatment during the first, but not during the second, week after immunization
was consistently protective. High levels of interferon
Laboratory of Retinal Cell and Molecular Biology of the
National Eye Institute, and the § Howard Hughes Medical Institute-NIH Research Scholars Program,
National Institutes of Health, Bethesda, Maryland 20892
(IFN-
) were present in the serum during IL-12 treatment, but subsequent antigen-specific IFN-
production in protected mice was
diminished, as were IL-5 production, lymph node cell proliferation, and serum antibody levels.
Treated mice had fewer cells and evidence of enhanced apoptosis in the draining lymph nodes.
Unlike wild-type mice, IFN-
-deficient, inducible nitric oxide synthase (iNOS)-deficient, and
Bcl-2lck transgenic mice were poorly protected by IL-12, whereas IL-10-deficient mice were
protected. We conclude that administration of IL-12 aborts disease by curtailing development
of uveitogenic effector T cells. The data are compatible with the interpretation that IL-12 induces systemic hyperinduction of IFN-
, causing activation of iNOS and production of NO,
which mediates protection at least in part by triggering Bcl-2 regulated apoptotic deletion of
the antigen-specific T cells as they are being primed.
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