title: Poly-guanosine motifs costimulate antigen-reactive CD8 T cells while bacterial CpG-DNA affect T-cell activation via antigen-presenting cell-derived cytokines.
abstract: Pathogen-derived pattern recognition ligands like lipopolysaccharide (LPS) and bacterial cytidine-guanosine (CpG)-DNA not only activate dendritic cells and macrophages but are also mitogenic for B cells. Less clear are the claimed effects of CpG-DNA on T cells, which range from direct activation, costimulation, or indirect transient activation via antigen-presenting cell (APC)-derived interferon type I (IFN type I). Here we demonstrate that CpG-DNA sequence specifically triggers macrophages to produce IFN type I, interleukin (IL)-12, IL-6 and tumour necrosis factor (TNF), but lacks the ability to directly costimulate T cells. Strikingly, poly-guanosine (poly-G) extensions to CpG-containing oligonucleotides (ODN) abolished the macrophage stimulatory potential yet generated T-cell costimulatory activities. In fact, independently of CpG-motifs, poly-G-ODN displayed the ability to costimulate T cells. Costimulation was operative on CD8 T cells but not CD4 T cells. Poly-G-mediated costimulation resulted in IL-2-driven T-cell proliferation and induced cytolytic T cells. Overall the data imply that poly-G motifs costimulate antigen reactive CD8 T cells, while CpG-DNA motifs fail to do so but may affect T-cell activation via APC derived cytokines such as IFN type I.
authors.affiliation: Institute of Medical Microbiology, Immunology and Hygiene, Technical University of Munich, Munich, Germany.
authors.forename: G B
authors.initials: GB
authors.lastname: Lipford
authors.forename: S
authors.initials: S
authors.lastname: Bendigs
authors.forename: K
authors.initials: K
authors.lastname: Heeg
authors.forename: H
authors.initials: H
authors.lastname: Wagner
mesh_terms: D000818:Animals; D000938:Antigen-Presenting Cells / Q000276:immunology*; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D018929:Cell Culture Techniques; D002455:Cell Division / Q000276:immunology; D002460:Cell Line; D003562:Cytidine / Q000276:immunology; D016207:Cytokines / Q000276:immunology; D004269:DNA, Bacterial / Q000276:immunology*; D005260:Female; D006151:Guanosine / Q000276:immunology; D008213:Lymphocyte Activation / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL; D011068:Poly G / Q000276:immunology*
chemical_list: D016207:Cytokines; D004269:DNA, Bacterial; D006151:Guanosine; D011068:Poly G; D003562:Cytidine