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Original Article |
Correspondence to: Walter Reith, Department of Genetics and Microbiology, University of Geneva Medical School, CMU, 1 rue Michel-Servet, 1211 Geneva, Switzerland. Tel:41-22-702-56-66 Fax:41-22-702-57-02 E-mail:walter.reith{at}medecine.unige.ch.
Cell surface expression of major histocompatibility complex class II (MHCII) molecules is increased during the maturation of dendritic cells (DCs). This enhances their ability to present antigen and activate naive CD4+ T cells. In contrast to increased cell surface MHCII expression, de novo biosynthesis of MHCII mRNA is turned off during DC maturation. We show here that this is due to a remarkably rapid reduction in the synthesis of class II transactivator (CIITA) mRNA and protein. This reduction in CIITA expression occurs in human monocyte-derived DCs and mouse bone marrowderived DCs, and is triggered by a variety of different maturation stimuli, including lipopolysaccharide, tumor necrosis factor
, CD40 ligand, interferon
, and infection with Salmonella typhimurium or Sendai virus. It is also observed in vivo in splenic DCs in acute myelin oligodendrocyte glycoprotein induced experimental autoimmune encephalitis. The arrest in CIITA expression is the result of a transcriptional inactivation of the MHC2TA gene. This is mediated by a global repression mechanism implicating histone deacetylation over a large domain spanning the entire MHC2TA regulatory region.
Key Words: MHC class II, class II transactivator, experimental autoimmune encephalitis, bare lymphocyte syndrome, histone deacetylation
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