Activation of microglia by aggregated beta-amyloid or lipopolysaccharide impairs MHC-II expression and renders them cytotoxic whereas IFN-gamma and IL-4 render them protective.

Department of Neurobiology, The Weizmann Institute of Science, 76100 Rehovot, Israel.
Molecular and Cellular Neuroscience (Impact Factor: 3.73). 08/2005; 29(3):381-93. DOI: 10.1016/j.mcn.2005.03.005
Source: PubMed

ABSTRACT 'Protective autoimmunity' refers to a well-controlled anti-self response that helps the body resist neurodegeneration. The response is mediated by autoimmune T cells, which produce cytokines and growth factors. Using an in vitro assay of hippocampal slices, we show that the cytokines interferon-gamma and (especially) interleukin-4, characteristic of pro-inflammatory and anti-inflammatory T cells, respectively, can make microglia neuroprotective. Aggregated beta-amyloid, like bacterial cell wall-derived lipopolysaccharide, rendered the microglia cytotoxic. Cytotoxicity was correlated with a signal transduction pathway that down-regulates expression of class-II major histocompatibility proteins (MHC-II) through the MHC-II-transactivator and the invariant chain. Protection by interleukin-4 was attributed to down-regulation of tumor necrosis factor-alpha and up-regulation of insulin-like growth factor I. These findings suggest that beneficial or harmful expression of the local immune response in the damaged CNS depends on how microglia interpret the threat, and that a well-regulated T-cell-mediated response enables microglia to alleviate rather than exacerbate stressful situations in the CNS.


Available from: Adolfo Talpalar, Mar 05, 2015
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