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Astrocyte gp130-expression is critical for the control of Toxoplasma encephalitis
© Drögemüller et al; licensee BioMed Central Ltd. 2008
Published: 23 September 2008
Toxoplasma (T.) gondii infects astrocytes, neurons and microglia cells in the CNS and, after acute encephalitis, persists within neurons. Robust astrocyte activation is a hallmark of Toxoplasma encephalitis (TE); however, the in vivo function of astrocytes is largely unknown. To study their role in TE, we generated C57BL/6 GFAP-Cre gp130fl/fl mice, which lack gp130, the signal transducing receptor for IL-6 family cytokines, in their astrocytes. In TE of wildtype mice, the gp130 ligands IL-6, IL-11, IL-27, LIF, oncostatin M, ciliary neurotrophic factor, B cell stimulating factor, and cardiotrophin-1 were upregulated. In addition, GFAP+ astrocytes of gp130fl/fl control mice were activated, increased in number, and efficiently restricted inflammatory lesions and parasites, thereby, contributing to survival from TE. In contrast, T. gondii-infected GFAP-Cre gp130fl/fl mice lost GFAP+ astrocytes in inflammatory lesions resulting in an inefficient containment of inflammatory lesions, impaired parasite control and, ultimately, a lethal necrotizing TE. Production of IFN-gamma and IGTP, which mediate parasite control in astrocytes, were even increased in GFAP-Cre gp130fl/fl mice indicating that instead of the direct anti-parasitic effect the immunoregulatory function of GFAP-Cre gp130fl/fl astrocytes was disturbed. Correspondingly, in vitro infected GFAP-Cre gp130fl/fl astrocytes inhibited growth of T. gondii efficiently after stimulation with IFN-gamma, whereas neighbouring non-infected and TNF-stimulated GFAP-Cre gp130fl/fl astrocytes became apoptotic. Collectively, these are the first experiments demonstrating a crucial function of astrocytes in CNS infection.
This article is published under license to BioMed Central Ltd.