title: CD25+CD4+ T cells contribute to the control of memory CD8+ T cells.
abstract: Previously we demonstrated that IL-15 and IL-2 control the number of memory CD8+ T cells in mice. IL-15 induces, and IL-2 suppresses the division of these cells. Here we show that CD25+CD4+ regulatory T cells play an important role in the IL-2-mediated control of memory phenotype CD8+ T cell number. In animals, the numbers of CD25+CD4+ T cells were inversely correlated with the numbers of memory phenotype CD8+ T cells with age. Treatment with anti-IL-2 caused CD25+CD4+ T cells to disappear and, concurrently, increased the numbers of memory phenotype CD8+ T cells. This increase in the numbers of CD8+ memory phenotype T cells was not manifest in animals lacking CD4+ cells. Importantly, adoptive transfer of CD25+CD4+ T cells significantly reduced division of memory phenotype CD8+ T cells. Thus, we conclude that CD25+CD4+ T cells are involved in the IL-2-mediated inhibition of memory CD8+ T cell division and that IL-2 controls memory phenotype CD8+ T cell numbers at least in part through maintenance of the CD25+CD4+ T cell population.
authors.affiliation: Howard Hughes Medical Institute, Integrated Department of Immunology, National Jewish Medical and University of Colorado Health Sciences Center, Denver, CO 80206, USA.
authors.forename: Masaaki
authors.initials: M
authors.lastname: Murakami
authors.forename: Akemi
authors.initials: A
authors.lastname: Sakamoto
authors.forename: Jeremy
authors.initials: J
authors.lastname: Bender
authors.forename: John
authors.initials: J
authors.lastname: Kappler
authors.forename: Philippa
authors.initials: P
authors.lastname: Marrack
mesh_terms: D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology / Q000276:immunology*; D018414:CD8-Positive T-Lymphocytes / Q000166:cytology / Q000276:immunology*; D002455:Cell Division; D007156:Immunologic Memory; D019409:Interleukin-15 / Q000502:physiology; D007376:Interleukin-2 / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D015375:Receptors, Interleukin-2 / Q000276:immunology*
chemical_list: D019409:Interleukin-15; D007376:Interleukin-2; D015375:Receptors, Interleukin-2