IL2 and leukemia: Dimeric IL-2 was cytotoxic to several cell types expressing the IL-2R, including human and rat kidney epithelial cells [12], [13], human and murine melanoma cells [14], [15], murine lymphocytes, murine lymphoma cells, human leukemia cells, and human colon carcinoma cells [16] (Figure 4B–D and not shown).