title: Fas ligand expression is restricted to nonlymphoid thymic components in situ.
abstract: The cell surface receptor Fas (Apo-1/CD95) and its ligand (FasL) are mediators of apoptosis that have been shown to be implicated in activation-induced death of mature T cells and in killing mediated by cytolytic T cells. The role of the Fas pathway in apoptosis associated with thymic selection events is, however, controversial. Although Fas and FasL are known to be expressed in the thymus, the nature and in vivo localization of FasL-expressing cells have not been determined. Using recently developed anti-FasL Abs in combination with in situ hybridization on tissue sections, we show in this work that FasL-expressing cells are present in the thymus, particularly within the medulla. FasL mRNA was detected readily in thymic stromal cell extracts, but not in isolated thymocytes. Moreover, immunohistochemical analysis of serial tissue sections stained with Abs against FasL in conjunction with epithelial and dendritic cell markers indicated that both thymic epithelial and dendritic cells express FasL in situ. The coexistence of FasL-expressing stromal cells and Fas-expressing thymocytes may have important implications for the role of the Fas pathway in apoptosis associated with thymic selection events.
authors.affiliation: Department of Dermatology, University of Geneva Medical School, Switzerland.
authors.forename: L E
authors.initials: LE
authors.lastname: French
authors.forename: A
authors.initials: A
authors.lastname: Wilson
authors.forename: M
authors.initials: M
authors.lastname: Hahne
authors.forename: I
authors.initials: I
authors.lastname: Viard
authors.forename: J
authors.initials: J
authors.lastname: Tschopp
authors.forename: H R
authors.initials: HR
authors.lastname: MacDonald
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D002454:Cell Differentiation; D017637:Clonal Deletion / Q000502:physiology*; D003238:Connective Tissue / Q000378:metabolism*; D053222:Fas Ligand Protein; D005786:Gene Expression Regulation; D017403:In Situ Hybridization; D008562:Membrane Glycoproteins / Q000096:biosynthesis* / Q000235:genetics; D051379:Mice; D008815:Mice, Inbred Strains; D009928:Organ Specificity; D012333:RNA, Messenger / Q000032:analysis; D013950:Thymus Gland / Q000166:cytology / Q000378:metabolism*; D019014:fas Receptor / Q000502:physiology
chemical_list: D053222:Fas Ligand Protein; C505658:Fasl protein, mouse; D008562:Membrane Glycoproteins; D012333:RNA, Messenger; D019014:fas Receptor