IL2 and melanoma: Interleukin-15 (IL-15) and IL-2 bind to IL-15 receptors (IL-2Rβ/γ) to induce immune cell proliferation and survival as well as enhance cytotoxic and cytokine-secreting effector functions of lymphocytes.6, 7, 8, 9, 10, 11 Recently, IL-2 (aldesleukin) was approved for use in metastatic renal cell carcinoma (RCC) and melanoma,12 whereas in a clinical trial evaluating recombinant human IL-15, dose-limiting toxicities (DLTs) stopped dose escalation without any objective responses.13