title: IFN-α is constitutively expressed in the human thymus, but not in peripheral lymphoid organs.
abstract: Type I interferons have been typically studied for their effects in the context of bacterial or viral infections. However in this report, we provide evidence that Interferon-alpha (IFN-α) expressing cells are present in the thymus in the absence of infection. We show that pDC express the highest level of IFN-α and that MxA, which is exclusively expressed after engagement of the type I IFN receptor by IFN-α/β, is expressed in normal fetal and post-natal thymus, but not in the periphery. The highest level of MxA is expressed in mature thymocytes and pDC located in the medulla and at the cortico-medullary junction. The anti-microbial peptide LL-37, which is expressed in the thymus, when complexed with eukaryotic nucleic acids, induces the secretion of IFN-α by thymic pDC. This results in the upregulation of MxA expression in responsive thymocytes. We propose that the secretion of IFN-α in the thymus may function to regulate the rate of T cell development and modulate the requirements for the selection of developing T cells.
authors: Department of Microbiology, Immunology, and Molecular Genetics, David E. Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America.
authors: Arnaud D
authors: AD
authors: Colantonio
authors: Marta
authors: M
authors: Epeldegui
authors: Maria
authors: M
authors: Jesiak
authors: Loes
authors: L
authors: Jachimowski
authors: Bianca
authors: B
authors: Blom
authors: Christel H
authors: CH
authors: Uittenbogaart
mesh_terms: D002478:Cells, Cultured; D005434:Flow Cytometry; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D050839:Interferon Regulatory Factor-7 / Q000235:genetics / Q000378:metabolism; D016898:Interferon-alpha / Q000378:metabolism* / Q000494:pharmacology; D008099:Liver / Q000378:metabolism; D008221:Lymphoid Tissue / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D064547:Myxovirus Resistance Proteins; D060888:Real-Time Polymerase Chain Reaction; D050794:STAT1 Transcription Factor / Q000235:genetics / Q000378:metabolism; D060168:Thymocytes / Q000187:drug effects / Q000378:metabolism*; D013950:Thymus Gland / Q000378:metabolism*
chemical_list: D050839:Interferon Regulatory Factor-7; D016898:Interferon-alpha; C579071:MX1 protein, human; D064547:Myxovirus Resistance Proteins; D050794:STAT1 Transcription Factor; D019204:GTP-Binding Proteins