TAIL7 cells and their parental leukemia T cells proliferate in response to IL-7 and IL-4. TAIL7 cells (A) and patient's peripheral blood blasts (B) were cultured for 96 hours in medium alone or the indicated cytokine or mitogens (Mito.), and proliferation was measured by ³H-thymidine incorporation. Insets: Proliferation index (described in “Materials and methods”) for each condition at 72 and 96 hours. Results are expressed as mean ± SD of triplicates and are representative of 2 independent experiments for the primary leukemia cells and 3 independent experiments for the TAIL7 cell line.