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Infect. Immun., 03 1995, 751-756, Vol 63, No. 3
E Candolfi, CA Hunter and JS Remington
Suppressed splenocyte proliferation in response to mitogen and toxoplasma
lysate antigen (TLA) is observed in mice acutely infected with Toxoplasma
gondii. Recently, we reported that NG-monomethyl-L- arginine (NMMA), an
inhibitor of reactive nitrogen intermediate (RNI) production, partially
restored proliferative responses of splenocytes from infected mice. In the
present study we have examined the effect of NMMA on production of
cytokines by splenocytes from mice acutely infected with T. gondii and
assessed the role of gamma interferon (IFN- gamma) and interleukin-10
(IL-10) in the RNI-mediated suppression. Stimulation with concanavalin A
(ConA) or TLA of splenocytes from CBA/Ca mice infected for 7 days resulted
in increased production of IFN- gamma, IL-4, and IL-10 but reduced levels
of IL-2 when compared with cultures of splenocytes from uninfected mice.
Whereas addition of NMMA did not alter levels of cytokines produced by
splenocytes from uninfected mice, splenocytes from infected mice stimulated
with ConA produced significantly higher levels of IL-10 and reduced levels
of IL- 2 and IL-4. Addition of anti-IFN-gamma monoclonal antibodies to
cultures of spleen cells from mice infected for 7 or 14 days remarkably
decreased the levels of nitrite and resulted in a 47- and 4-fold increase
in proliferation induced by stimulation with ConA or TLA, respectively.
Anti-IL-10 did not reduce levels of nitrite produced in culture but did
result in a fourfold increase in the proliferative response of splenocytes
from mice infected for 14 days. In vivo administration of anti-IFN-gamma or
anti-IL-10 monoclonal antibodies to infected mice partially restored ex
vivo spleen cell proliferative responses by approximately 40 and 15%,
respectively. Our data indicate that IFN-gamma is important in inducing the
RNI-mediated immunosuppression, which, in turn, affects production of
cytokines by splenocytes. Our data also demonstrate that IL-10 is involved
in the suppression observed but that this activity is independent of RNI.
Copyright © 1995, American Society for Microbiology
Roles of gamma interferon and other cytokines in suppression of the spleen cell proliferative response to concanavalin A and toxoplasma antigen during acute toxoplasmosis
Department of Immunology and Infectious Diseases, Palo Alto Medical Foundation, California 94301.
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