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  • Title: Toxoplasma gondii inhibits MHC class II expression in neural antigen-presenting cells by down-regulating the class II transactivator CIITA.
    Author: Lüder CG, Lang C, Giraldo-Velasquez M, Algner M, Gerdes J, Gross U.
    Journal: J Neuroimmunol; 2003 Jan; 134(1-2):12-24. PubMed ID: 12507768.
    Abstract:
    Major histocompatibility complex (MHC) class II expression by microglia and astrocytes is critical for CD4+-mediated immune responses within the central nervous system. Here, we demonstrate that the obligate intracellular parasite, Toxoplasma gondii, down-regulates activation-induced MHC class II expression in human-derived glioblastoma cells as well as in primary astrocytes and microglia from cortices of rat fetuses. Down-regulation of MHC class II proteins was predominantly observed in parasite-positive, but not parasite-negative, host cells of T. gondii-infected cell cultures. MHC class II transcript levels induced by IFN-gamma alone or in combination with TNF-alpha were also clearly diminished after parasitic infection. Furthermore, T. gondii dose-dependently down-regulated the transcript levels of the class II transactivator CIITA. These results suggest that T. gondii partially evade CD4+-mediated intracerebral immune responses, a mechanism which may contribute to long-term persistence of the parasite within the CNS.
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