title: Inhibitor (IK) of IFN-gamma induced HLA class II antigens expression also inhibits HLA class II constitutive expression in the human Raji B cell line.
abstract: The expression of major histocompatibility complex (MHC) class II antigens is constitutive in professional antigen presenting cells (APCs) but can also be induced by interferon-gamma (IFN-gamma) on the majority of the non professional APCs (e.g. fibroblasts). We have recently characterised a new factor called IK which is an efficient inhibitor of IFN-gamma induction of MHC class II antigens expression. Here, we demonstrate a novel role for IK in MHC class II expression since over-expression of this protein by stable transfection into human B cells led to a total disappearance of constitutive MHC class II mRNA expression. The class II transactivator (CIITA) is necessary for both constitutive and IFN-gamma induced MHC class II expressions. Examination of CIITA mRNA in IK stably transfected clones revealed a marked reduction of CIITA mRNA transcription. Taken together these results demonstrate that the IK protein plays a key role in the constitutive expression of MHC class II antigens and that inhibition induced by IK is upstream of CIITA in this regulatory pathway.
authors.affiliation: INSERM U 396, Institut Biomédical des Cordeliers, Paris, France.
authors.forename: J
authors.initials: J
authors.lastname: Vedrenne
authors.forename: E
authors.initials: E
authors.lastname: Assier
authors.forename: R
authors.initials: R
authors.lastname: Pereno
authors.forename: H
authors.initials: H
authors.lastname: Bouzinba-Segard
authors.forename: B
authors.initials: B
authors.lastname: Azzarone
authors.forename: C
authors.initials: C
authors.lastname: Jasmin
authors.forename: D
authors.initials: D
authors.lastname: Charron
authors.forename: P
authors.initials: P
authors.lastname: Krief
mesh_terms: D001402:B-Lymphocytes; D002451:Cell Compartmentation; D016207:Cytokines / Q000502:physiology*; D003593:Cytoplasm / Q000378:metabolism; D005786:Gene Expression Regulation; D005802:Genes, MHC Class II; D006684:HLA-DR Antigens / Q000235:genetics*; D006801:Humans; D009687:Nuclear Proteins; D012333:RNA, Messenger / Q000235:genetics; D015534:Trans-Activators / Q000502:physiology*
chemical_list: D016207:Cytokines; D006684:HLA-DR Antigens; C090444:IK protein, human; C083728:MHC class II transactivator protein; D009687:Nuclear Proteins; D012333:RNA, Messenger; D015534:Trans-Activators