title: Cutting Edge: A possible role for CD4+ thymic macrophages as professional scavengers of apoptotic thymocytes.
abstract: A vast majority of thymocytes are eliminated during T cell development by apoptosis. However, apoptotic thymocytes are not usually found in the thymus, indicating that apoptotic thymocytes must be eliminated rapidly by scavengers. Although macrophages and dendritic cells are believed to play such role, little is known about scavengers in the thymus. We found that CD4(+)/CD11b(+)/CD11c(-) cells were present in the thymus and that they expressed costimulatory molecules for T cell selection and possessed Ag-presenting activity. Moreover, these CD4(+)/CD11b(+) cells phagocytosed apoptotic thymocytes much more efficiently than thymic CD4(-)/CD11b(+) cells as well as activated peritoneal macrophages. CD4(+)/CD11b(+) cells became larger along with thymus development, while no such change was observed in CD4(-)/CD11b(+) cells. Finally, engulfed nuclei were frequently found in CD4(+)/CD11b(+) cells. These results strongly suggest that thymic CD4(+)/CD11b(+) cells are major scavengers of apoptotic thymocytes.
authors.affiliation: Institute of Molecular and Cellular Biosciences, University of Tokyo, Tokyo, Japan.
authors.forename: Eiji
authors.initials: E
authors.lastname: Esashi
authors.forename: Takashi
authors.initials: T
authors.lastname: Sekiguchi
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Ito
authors.forename: Shigeo
authors.initials: S
authors.lastname: Koyasu
authors.forename: Atsushi
authors.initials: A
authors.lastname: Miyajima
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000276:immunology*; D039481:CD11b Antigen / Q000096:biosynthesis; D015704:CD4 Antigens / Q000096:biosynthesis*; D002454:Cell Differentiation / Q000276:immunology; D002478:Cells, Cultured; D018920:Coculture Techniques; D008264:Macrophages / Q000166:cytology* / Q000276:immunology* / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D010587:Phagocytosis / Q000276:immunology*; D016176:T-Lymphocyte Subsets / Q000166:cytology* / Q000276:immunology; D013950:Thymus Gland / Q000166:cytology* / Q000276:immunology* / Q000378:metabolism
chemical_list: D039481:CD11b Antigen; D015704:CD4 Antigens