title: Foxp3+ natural regulatory T cells preferentially form aggregates on dendritic cells in vitro and actively inhibit their maturation.
abstract: Naturally occurring CD4(+)CD25(+) regulatory T cells (Treg) suppress in vitro the proliferation of other T cells in a cell-contact-dependent manner. Dendritic cells (DCs) appear to be a target of Treg-mediated immune suppression. We show here that, in coculture of dye-labeled Treg cells and CD4(+)CD25(-) naïve T cells in the presence of T cell receptor stimulation, Treg cells, which are more mobile than naïve T cells in vitro, out-compete the latter in aggregating around DCs. Deficiency or blockade of leukocyte function-associated antigen-1 (LFA-1) (CD11a/CD18) abrogates Treg aggregation, whereas that of cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) (CD152) does not. After forming aggregates, Treg cells specifically down-regulate the expression of CD80/86, but not CD40 or class II MHC, on DCs in both a CTLA-4- and LFA-1-dependent manner. Notably, Treg exerts this CD80/86-down-modulating effect even in the presence of strong DC-maturating stimuli, such as GM-CSF, TNF-alpha, IFN-gamma, type I IFN, and lipopolysaccharide. Taken together, as a possible mechanism of in vitro Treg-mediated cell contact-dependent suppression, we propose that antigen-activated Treg cells exert suppression by two distinct steps: initial LFA-1-dependent formation of Treg aggregates on immature DCs and subsequent LFA-1- and CTLA-4-dependent active down-modulation of CD80/86 expression on DCs. Both steps prevent antigen-reactive naïve T cells from being activated by antigen-presenting DCs, resulting in specific immune suppression and tolerance.
authors.affiliation: Department of Experimental Pathology, Institute for Frontier Medical Sciences, Kyoto University, Kyoto 606-8507, Japan.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Onishi
authors.forename: Zoltan
authors.initials: Z
authors.lastname: Fehervari
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Yamaguchi
authors.forename: Shimon
authors.initials: S
authors.lastname: Sakaguchi
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D018122:B7-1 Antigen / Q000378:metabolism; D051940:B7-2 Antigen / Q000378:metabolism; D060908:CTLA-4 Antigen; D002449:Cell Aggregation; D002454:Cell Differentiation; D003713:Dendritic Cells / Q000166:cytology* / Q000276:immunology* / Q000378:metabolism; D005260:Female; D051858:Forkhead Transcription Factors / Q000378:metabolism*; D016169:Lymphocyte Function-Associated Antigen-1 / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D018448:Models, Immunological; D010047:Ovalbumin / Q000235:genetics / Q000276:immunology; D011948:Receptors, Antigen, T-Cell / Q000235:genetics / Q000378:metabolism; D050378:T-Lymphocytes, Regulatory / Q000166:cytology* / Q000276:immunology* / Q000378:metabolism
chemical_list: D015703:Antigens, CD; D018122:B7-1 Antigen; D051940:B7-2 Antigen; D060908:CTLA-4 Antigen; C497965:Cd86 protein, mouse; C556707:Ctla4 protein, mouse; D051858:Forkhead Transcription Factors; C498833:Foxp3 protein, mouse; D016169:Lymphocyte Function-Associated Antigen-1; D011948:Receptors, Antigen, T-Cell; D010047:Ovalbumin