IL2 and melanoma: Finally, even though therapeutically active TIL from melanoma patients are more reliably expandable in culture than peripheral blood T-cells, it has not proved possible to reliably expand even TIL unless they are propagated in exceedingly high concentrations of IL-2 (6,000 IU/ml) [1, 2], a maneuver which has not proved to be successfully adaptable to peripheral blood T-cells.