Nitric oxide-mediated suppression of T cell responses during Trypanosoma brucei infection: soluble trypanosome products and interferon-gamma are synergistic inducers of nitric oxide synthase
Abstract
African trypanosome infections result in lymphocyte unresponsiveness and anemia in the mammalian host. In murine infections, these effects are mediated by suppressor macrophages releasing nitric oxide (NO). We investigated the mechanism of activation of macrophages to produce NO during trypanosomiasis in vitro. A soluble component of trypanosome lysates induced NO synthesis in peritoneal macrophage cultures only when the macrophages were co-stimulated with interferon-gamma (IFN-gamma). The macrophage-activating factor was also released in a soluble form by live bloodstream-form trypanosomes, but not procyclic trypanosomes. When splenocyte cultures were exposed to IFN-gamma and trypanosomes, an NO-dependent suppression of T cell proliferation occurred. This is similar to the suppression observed in the spleens of trypanosome-infected mice, suggesting that a combination of trypanosome-released macrophage-activating factors and IFN-gamma are a trigger of immune dysfunction in trypanosomiasis.
References
Trypanosoma brucei is protected from the cytostatic effects of nitric oxide under in vivo conditions
Citations
Chemokines are produced in the brain early during the course of experimental African trypanosomiasis
In vitro induction of nitric oxide synthase in astrocytes and microglia by Trypanosoma brucei brucei
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