The source of complement, a major contributor to the pathology of diseases such as multiple sclerosis (MS) and experimental allergic encephalomyelitis (EAE), is unclear. Despite this lack of information, the role of complement in demyelinating disease has been extensively studied. These studies have shown 1) the presence of the terminal components of complement which form the lytic membrane attack complex, 2) activation of complement by myelin and myelin basic protein and 3) the destructive effects of complement activation specifically inflammation, demyelination and tissue destruction. Our preliminary data demonstrate that astrogliomas and primary rat astrocytes synthesize several components of the complement system and that synthesis can be markedly upregulated by the cytokine, interferon-gamma (IFN-gamma). The regulation of complement synthesis by IFN-gamma is of particular interest as all other cell types known to synthesize complement are refractory to the effect of this cytokine. We hypothesize that local complement production, enhanced in astrocytes by the effects of cytokines such as IFN-gamma, participates in the pathogenesis of neural autoimmune diseases such as MS or EAE. Because of the potential for complement-mediated tissue destruction and inflammation in neural autoimmune diseases, we feel it is important to more fully understand the production and regulation of complement by astrocytes. We will focus on components involved in the activation of the alternative pathway of complement (C3, factors B and D) as all of these components are synthesized by astroglioma cells and rat primary astrocytes, and on one of the regulatory molecules in the complement system, decay accelerating factor. We will characterize the biosynthesis and functionality of these components as produced by the astroglioma cell line D54-MG, which we have found to be a representative cell type with respect to synthesis of complement. We will also examine the induction of complement genes by IFN- gamma by the analysis of transcription rates, steady-state mRNA levels, mRNA stability and protein expression. Further, we will delineate the tissue-specific cis and trans-acting transcriptional control structures involved in regulation of C3 gene expression in astrogliomas and rat primary astrocytes. The studies proposed in this application will contribute to understanding the role played by complement in the central nervous system. In addition, this information will form the basis for comparing the production and regulation of other complement by these cell types, as well as in specific neural disease states such as MS and EAE.
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