Objective　To explore the antitumor effect of interleukin 21 (IL-21) after transfected into in HeLa cells in severe combined immunodeficiency (SCID) mice or human  peripheral blood lymphocytes-SCID  (hu-PBL-SCID) mice. 　Methods　pcDNA4/HisMax-IL-21 was transfected into human cervical cancer cell line HeLa to produce HeLa-IL-21 cells. Totally 48 SCID mice were randomly and equally divided into SCID gr

oup (0.2 ml PBS

i.p.) and hu-PBL-SCID group (0.2 ml 2×10

7

/ml hu-PBL

i.p.). Then every group was further divided into 3 subgroups (n=6) to receive a subcutemeous implantation of HeLa

HeLa-vector or HeLa-IL-21 cells

and the rest 6 mice were intraperitoneally injected with anti-asialo GM

1

50 mg/animal 1 d before and 4 d after HeLa-IL-21 cells transplantation for NK cell depletion. The growth of the tumor mass was observed. Flow cytometry was used to detect CD8- and DX5-positive cells in hu-PBL from hu-PBL-SCID mice

and spleen NK cells from SCID mice or hu-PBL-SCID mice. The secretion of IFN-γ and cytotoxicity of splenic cells from HeLa/HeLa-IL-21-bearing SCID mice or hu-PBL-SCID mice were detected with double sandwich ELISA assay and LDH assay respectively. 　Results　Growth of HeLa-IL-21 tumors was significantly suppressed compared with that of HeLa cells

with a slow development and smaller volume. But this growth suppression was not observed in NK cell depletion groups

with SCID group more severe than hu-PBL-SCID group. hu-PBL-SCID mice bearing HeLa-IL-21 cells (16.55±4.53)had a higher toxicity in spleen cells than those SCID mice bearing HeLa-IL-21 cells (8.32±2.12) or HeLa cells (3.42±1.56) (P0.01)

and had larger production of IFN-γ than of hu-PBL-SCID mice bearing splenocyts from hu-PBL-SCID bearing HeLa cells (5.12±2.34) (P0.05). 　Conclusion　Expression of IL-21 in HeLa cells can produce T cell dependent and -independent antitumor effects in an NK cell-defective condition. 