title: Murine liver antigen presenting cells control suppressor activity of CD4+CD25+ regulatory T cells.
abstract: CD4(+)CD25(+) regulatory T cells (Treg) are important mediators of peripheral immune tolerance; however, whether Treg participate also in hepatic immune tolerance is not clear. Therefore, we tested the potential of Treg to suppress stimulation of CD4(+) T cells by liver sinusoidal endothelial cells (LSEC), Kupffer cells (KC), or hepatocytes. In the absence of Treg, all 3 types of liver cells could stimulate CD4(+) T cell proliferation; in the presence of Treg, however, CD4(+) T cell proliferation was suppressed. Interaction with KC even stimulated the expansion of the Treg population; LSEC or hepatocytes, in contrast, could not induce proliferation of Treg. Because liver inflammation can be induced by infection, we tested the potential of liver cells to modify Treg suppressor activity in the presence of microbial signals. In the presence of immune-stimulatory CpG-oligonucleotides, LSEC, KC, and hepatocytes could indeed overcome Treg-mediated suppression; in the presence of lipopolysaccharide (LPS), however, only KC and hepatocytes, but not LSEC, could overcome Treg suppressor activity. Hepatocytes from mice with deficient toll-like receptor-4 signaling failed to abrogate Treg suppression in response to LPS, indicating that overcoming Treg suppressor activity was indeed a response of the liver cell and not of the Treg. In conclusion, Treg can suppress CD4(+) T cell stimulation by liver cells. However, in response to microbial signals, the liver cells can overcome the suppressive activity of Treg. Thus, liver cells may facilitate the transition from hepatic immune tolerance to hepatic inflammation by controlling Treg suppressor activity.
authors.affiliation: Department of Internal Medicine I, University Hospital Hamburg-Eppendorf, Germany.
authors.forename: Christiane
authors.initials: C
authors.lastname: Wiegard
authors.forename: Christian
authors.initials: C
authors.lastname: Frenzel
authors.forename: Johannes
authors.initials: J
authors.lastname: Herkel
authors.forename: Karl-Josef
authors.initials: KJ
authors.lastname: Kallen
authors.forename: Edgar
authors.initials: E
authors.lastname: Schmitt
authors.forename: Ansgar W
authors.initials: AW
authors.lastname: Lohse
mesh_terms: D000818:Animals; D000938:Antigen-Presenting Cells / Q000502:physiology*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D049109:Cell Proliferation; D042783:Endothelial Cells / Q000276:immunology; D022781:Hepatocytes / Q000276:immunology; D007108:Immune Tolerance / Q000276:immunology*; D007249:Inflammation; D007728:Kupffer Cells / Q000276:immunology; D008099:Liver / Q000166:cytology / Q000276:immunology*; D051379:Mice; D015375:Receptors, Interleukin-2 / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D015375:Receptors, Interleukin-2