title: Early kinetic window of target T cell susceptibility to CD25+ regulatory T cell activity.
abstract: Peripheral tolerance is maintained in part by thymically derived CD25+CD4+ T cells (regulatory T cells (Tregs)). Their mechanism of action has not been well characterized. Therefore, to get a better understanding of Treg action, we investigated the kinetics of murine Treg activity in vitro. Tregs were suppressive within a surprisingly narrow kinetic window: necessary and sufficient only in the first 6-10 h of culture. Visualization of this time frame, using a sensitive single-cell assay for IL-2, revealed the early elaboration of target cell IL-2 producers in the first 6 h despite the presence of CD25+CD4+ Tregs. However, after 6 h, a rapid rise in the number of IL-2 producers in the absence of Tregs was dramatically abrogated by the presence of Tregs. Importantly, the timing of suppression was dictated by the kinetics of target T cell activation suggesting that early target T cell signals may alter susceptibility to suppression. Modulating target T cell activation signals with provision of CD28, IL-2, or high Ag dose all abrogated suppression of proliferation late in culture. However, only CD28 signals enabled target T cells to resist the early Treg-induced down-regulation of IL-2. Therefore the quality of early target T cell activation signals, in particular engagement of CD28, represents an important control point in the balance between vulnerability and resistance to Treg suppression.
authors.affiliation: David H. Smith Center for Vaccine Biology and Immunology, Aab Institute of Biomedical Sciences, Department of Microbiology and Immunology, University of Rochester, Rochester, NY 14642, USA.
authors.forename: Dorothy K
authors.initials: DK
authors.lastname: Sojka
authors.forename: Angela
authors.initials: A
authors.lastname: Hughson
authors.forename: Teresa L
authors.initials: TL
authors.lastname: Sukiennicki
authors.forename: Deborah J
authors.initials: DJ
authors.lastname: Fowell
mesh_terms: D000818:Animals; D018106:CD28 Antigens / Q000276:immunology; D049109:Cell Proliferation; D002478:Cells, Cultured; D005260:Female; D007108:Immune Tolerance / Q000276:immunology*; D007376:Interleukin-2 / Q000096:biosynthesis / Q000276:immunology; D008213:Lymphocyte Activation / Q000276:immunology*; D051379:Mice; D015375:Receptors, Interleukin-2 / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*; D013997:Time Factors
chemical_list: D018106:CD28 Antigens; D007376:Interleukin-2; D015375:Receptors, Interleukin-2