Abstract: Objective To establish leukemia cell lines expressing IL-21 constitutively, and analyze the activation function on lymphocytes by those cell lines. Methods Four leukemia cell lines were infected with lentivirus carrying IL-21 and RFP genes. Fluorescent microscope was used for observing the expression of RFP and flow cytometry was used for analyzing the percentage of RFP-positive cells. The concentration of IL-21 in the medium was detected by ELISA. After stimulation with the IL-21 stable-expressing leukemia cell lines, the amplification folds of PBMC were calculated by cell counter and the surface markers were analyzed by flow cytometry, while their cytotocicity towards different tumor cells were assessed with CCK8 test. Results Four leukemia cell lines stable-expressing IL-21 were established, namely, K562-IL-21, THP-1-IL-21, Jurkat E6-1-IL-21 and RPMI8226-IL-21. The lymphocytes amplification of 3 different samples varied from 1.147±0.057 to 2.725±0.345 times and the amplification folds of lymphocytes stimulated by different numbers of leukemia cells varied from 1.127±0.152 to 2.213±0.200. The percentage of CD3+T cell and CD56+ NK cell decreased（P<0.05）while CD19+ B cells increased（P<0.05） after stimulation. The killing rates of activated lymphocytes are much higher than the control. The activated lymphocytes had powerful killing capacity on their stimulating leukemia cells and 7 other tumor cells and the killing rates ranged from （28.68±9.31）% to （78.45±0.61）%. Conclusions Four leukemia cell lines stable-expressing IL-21 could activate PBMC to kill different tumor cells.

Key words: Leukemia cell lines, Interleukin-21, Tumor therapy