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Background and Purpose: Interleukin-15 (IL-15) is important in the activation and proliferation of lymphocytic cell populations and is implicated in inflammatory disease. We report the characterization of a novel monoclonal antibody DISC0280 which is specific for human IL-15.Experimental Approach: DISC0280 was characterized in a direct binding assay of IL-15 with IL-15 receptor α (IL-15Rα) and by its ability to alter IL-15 mediated proliferation of a range of cell lines (cytotoxic T lymphocyte line-2, M-07e, KIT225). A pharmacodynamic model injecting male C57/BL6 mice with IL-15 or IL-15/IL-15Rα, with or without DISC0280, and assessing changes in lymphocytic cell populations and serum cytokines was utilized.Key Results: DISC0280 inhibited the binding of IL-15 to IL-15Rα and also potently inhibits IL-15 dependent proliferation of cells expressing IL-15Rα, shared interleukin 2/ interleukin 15 receptor β chain (IL-15Rβ) and common gamma chain (γ(c) ). DISC0280 also inhibited the IL-15 dependent proliferation of M-07e cells that only express IL-15Rβ/γ(c) subunits. Human IL-15 injected into mice caused an increase in NK1.1(+) and CD3(+) cells in the spleen and peripheral blood and these effects were unexpectedly potentiated by giving DISC0280 with human IL-15. This increase in cells caused by DISC0280/IL-15 co-administration was greater than that observed when IL-15 was administered complexed with soluble IL-15Rα.Conclusions and Implications: The ability of DISC0280 to bind to the IL-15Rα-binding site on IL-15 allows trans-presentation of IL-15 by DISC0280 in vivo, similar to the trans-presentation by soluble IL-15Rα. DISC0280 may be therefore suitable as a clinical substitute for IL-15. [ABSTRACT FROM AUTHOR]