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Selective costimulation by IL-15R/IL-15, but not IL-2R/IL-2, allows the induction of high numbers of tumor-specific CD8+ T cells by human dendritic cells matured in conditions of acute inflammation
  1. Morten Hansen1,
  2. Eva Wieckowski2,
  3. Inge Marie Svane3,
  4. Robert P Edwards2 and
  5. Pawel Kalinski2
  1. Aff1 grid.4973.90000000406467373Copenhagen University Hospital Herlev Denmark
  2. Aff2 grid.21925.3d0000000419369000University of Pittsburgh Pittsburgh PA USA
  3. Aff3 grid.5254.6000000010674042XCenter for Cancer Immune Therapy, Herlev HospitalCopenhagen University Herlev Denmark

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Meeting abstracts

Conventional dendritic cells (DC) are believed to rely on membrane-bound IL-2Rα to trans-present soluble IL-2 and costimulate T cell activation and expansion. In contrast, Langerhans cells have been shown to use membrane-bound IL-15Rα/IL-15 complex to activate T cells. Here we show that, while the expansion of tumor-specific CD8+ T cells by DC matured in the presence of chronic inflammatory mediators (PGE2, TNFα IL-1β, IL-6) fully depends on expression of IL-2Rα, CD8+ T cell expansion induced by IL-12p70-producing DC matured by interferon's and Toll-Like receptor ligands (type-1-polarized; DC1) is both more effective and independent of IL-2Rα expression. While DC1-expressed IL-15Rα promotes the expansion of tetramer-specific CD8+ T cells, their secreted levels of IL-12p70 determines the degree of CD8+ T cell functionality as evidenced by tumor antigen-specific release of IFNγ and TNFα. In accordance with the in vivo advantage of utilizing an IL-2-independent pathway of costimulation of tumor-specific T cells, in a retrospectively analyzed cohort of patients with metastatic malignant melanoma treated with cyclophosphamide and tumor-antigen transfected DCs (NCT00978913) we observed a highly significant inverse relation between overall survival and expression of IL-2Rα on DC vaccine products (p = 0.009). The differential usage of IL-2Rα/IL-2 versus IL-15Rα/IL-15 pathways by subsets of DCs helps to explain the role of different types of inflammation in memory formation, exhaustion of CD8+ T cell responses and progression of cancer. Furthermore, ex vivo induction of IL-15Rα/IL-15 dependent signaling might improve adoptive T cell therapies targeting tumors with well-defined and undefined tumor rejection antigens.