title: Major histocompatibility complex class II-positive cortical epithelium mediates the selection of CD4(+)25(+) immunoregulatory T cells.
abstract: CD4(+)25(+) T cells are a unique population of immunoregulatory T cells which are critical for the prevention of autoimmunity. To address the thymic selection of these cells we have used two models of attenuated thymic deletion. In K14-A(beta)(b) mice, major histocompatibility complex (MHC) class II I-A(b) expression is limited to thymic cortical epithelium and deletion by hematopoietic antigen-presenting cells does not occur. In H2-DMalpha-deficient mice, MHC class II molecules contain a limited array of self-peptides resulting in inefficient clonal deletion. We find that CD4(+)25(+) T cells are present in the thymus and periphery of K14-A(beta)(b) and H2-DMalpha-deficient mice and, like their wild-type counterparts, suppress the proliferation of cocultured CD4(+)25(-) effector T cells. In contrast, CD4(+)25(+) T cells from MHC class II-deficient mice do not suppress responder CD4(+) T cells in vitro or in vivo. Thus, development of regulatory CD4(+)25(+) T cells is dependent on MHC class II-positive thymic cortical epithelium. Furthermore, analysis of the specificities of CD4(+)25(+) T cells in K14-A(beta)(b) and H2-DMalpha-deficient mice suggests that a subset of CD4(+)25(+) T cells is subject to negative selection on hematopoietic antigen-presenting cells.
authors.affiliation: Department of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
authors.forename: S J
authors.initials: SJ
authors.lastname: Bensinger
authors.forename: A
authors.initials: A
authors.lastname: Bandeira
authors.forename: M S
authors.initials: MS
authors.lastname: Jordan
authors.forename: A J
authors.initials: AJ
authors.lastname: Caton
authors.forename: T M
authors.initials: TM
authors.lastname: Laufer
mesh_terms: D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D004847:Epithelial Cells / Q000276:immunology; D000949:Histocompatibility Antigens Class II / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL; D013950:Thymus Gland / Q000276:immunology*
chemical_list: D000949:Histocompatibility Antigens Class II