IL21 and B-cell chronic lymphocytic leukemia: CLL cells in HS5-CD40L-IL4 co-cultures achieved significantly better long-term survival than HS5-CD40L-IL4-IL21 co-cultures (P = 0.03 at 1 month; Fig. 1J, Supplementary Fig. 1Q), despite the higher proliferation rate induced by HS5-CD40L-IL4-IL21 cells (Supplementary Fig. 1R).