title: Effective proliferation of human regulatory T cells requires a strong costimulatory CD28 signal that cannot be substituted by IL-2.
abstract: The strength of immune repression by regulatory T (Treg) cells is thought to depend on the efficiency of Treg cell activation. The stimuli and their individual strength required to activate resting human Treg cells, however, have so far not been elucidated in detail. We reveal here that induction of proliferation of human CD4(+)C25(+) Treg cells requires an extraordinary strong CD28 costimulatory signal in addition to TCR/CD3 engagement. CD28 costimulation, noteworthy, cannot be substituted by IL-2 to induce proliferation of Treg cells, which is in contrast to CD4(+)CD25(-) T cells. IL-2, in contrast, prevents spontaneous apoptosis of Treg cells, but does not initiate their amplification. IL-2 and CD28 costimulation clearly exhibit disparate effects on Treg cells which are in contrast to those on CD4(+)CD25(-) T cells. Moreover, the prerequisites for Treg cell proliferation differ strikingly from those for effector T cells, implying a balanced orchestration in initiating and limiting a T cell immune response. In addition, data are of relevance for the design of therapeutic strategies involving IL-2 administration and CD28 costimulation.
authors.affiliation: Zentrum für Molekulare Medizin Köln and Klinik I für Innere Medizin, Labor Tumorgenetik, Universität zu Köln, Köln, Germany. andreas.hombach@uk-koeln.de
authors.forename: Andreas A
authors.initials: AA
authors.lastname: Hombach
authors.forename: David
authors.initials: D
authors.lastname: Kofler
authors.forename: Anja
authors.initials: A
authors.lastname: Hombach
authors.forename: Gunter
authors.initials: G
authors.lastname: Rappl
authors.forename: Hinrich
authors.initials: H
authors.lastname: Abken
mesh_terms: D018106:CD28 Antigens / Q000502:physiology*; D017252:CD3 Complex / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D006801:Humans; D007376:Interleukin-2 / Q000502:physiology; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism; D015398:Signal Transduction / Q000276:immunology*; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*
chemical_list: D018106:CD28 Antigens; D017252:CD3 Complex; D007376:Interleukin-2; D011948:Receptors, Antigen, T-Cell