IL2 and renal cell carcinoma: Immunotherapy with cytokines, notably subcutaneous recombinant interleukin-2 (s.c. IL-2) alone or in combination with subcutaneous recombinant interferon-α2a (s.c. IFN-α2a) at doses far below the maximum tolerated dose, yields significant therapeutic efficacy in RCC patients (Atzpodien et al, 1990; Sleijfer et al, 1992).