IL4 and B-cell chronic lymphocytic leukemia: Indeed, CLL cell viability could be increased by periodically changing the supportive cells from HS5-CD40L-IL4 (pro-proliferative stimulation) to HS5-WT or HS5-IL4 cells (non-proliferative stimulation, P < 0.0001; Supplementary Fig. 1Gi-ii).