IL2 and leukemia: Because our long-term cytotoxic T lymphocyte lines (CTLL) had been generated against allogeneic leukemia cells, and had demonstrable alloantigen cytolytic specificity as well as syngeneic tumor-specific cytolytic specificity, after 17 weeks of continuous culture in T cell growth factor (TCGF; IL-2) we cloned the cells using TCGF in liquid suspension culture in microtiter plates (Baker et al., 1979).