title: Immune suppression by gammadelta T-cells as a potential regulatory mechanism after cancer vaccination with IL-12 secreting dendritic cells.
abstract: In cancer patients undergoing immune therapy with lipopolysaccharides/interferon-gamma activated interleukin (IL)-12 secreting dendritic cells (DCs) we observed enhanced proliferative capacity of pyrophosphate-responsive peripheral blood (PB) gammadelta T-cells. This was not noted before as in other clinical trials DCs were used that were not enabled for IL-12 secretion and mice do not have a corresponding subset of PB gammadelta T-cells. In vitro examination of IL-12 DC/PB gammadelta T-cell interactions revealed a potential of PB gammadelta T-cells to negatively regulate the proliferative capacity of CD4 and CD8 T-cells. We further demonstrate that IL-12 is critical in the activation of PB gammadelta T-cells. In contrast, the regulatory activity of PB gammadelta T-cells in immune responses against strong recall antigens or alloantigens did not require activated DCs, but depended on pyrophosphate activation of PB gammadelta T-cells. Depletion of PB gammadelta T-cells abrogated the regulatory activity in IL-12 DC/peripheral blood mononuclear cell cocultures; adding back graded numbers of PB gammadelta T-cells restored it. Our observations revealed a potential PB gammadelta T cell-mediated negative regulatory feedback mechanism triggered by IL-12 DCs, which may critically impact on the design of DC cancer vaccines.
authors: Laboratory of Tumor Immunology, St Anna Children's Cancer Research Institute, Medical University Vienna, 1090 Vienna, Austria.
authors: Michael W
authors: MW
authors: Traxlmayr
authors: Daniela
authors: D
authors: Wesch
authors: Alexander M
authors: AM
authors: Dohnal
authors: Philipp
authors: P
authors: Funovics
authors: Michael B
authors: MB
authors: Fischer
authors: Dieter
authors: D
authors: Kabelitz
authors: Thomas
authors: T
authors: Felzmann
mesh_terms: D019496:Cancer Vaccines / Q000276:immunology; D017321:Clinical Trials, Phase I as Topic; D018920:Coculture Techniques; D003713:Dendritic Cells / Q000276:immunology / Q000378:metabolism / Q000637:transplantation*; D006801:Humans; D018664:Interleukin-12 / Q000276:immunology* / Q000378:metabolism; D008213:Lymphocyte Activation / Q000276:immunology*; D016692:Receptors, Antigen, T-Cell, gamma-delta / Q000276:immunology*; D016176:T-Lymphocyte Subsets / Q000276:immunology*
chemical_list: D019496:Cancer Vaccines; D016692:Receptors, Antigen, T-Cell, gamma-delta; D018664:Interleukin-12