Inclusion of plasma from patients with RCC and MM patient plasma in cytotoxic T-lymphocyte leukaemic (CTLL) cell/IL-2 assays inhibited the ability of CTLL cells to respond to IL-2, and an inverse correlation was found between the concentration of sIL-2R and the growth response of CTLL cell to IL-2 (r = -0.86, P = 0.003). Here, IL2 is linked to renal cell carcinoma.