Objective To study if IL 15 or GM CSF, or their combination can activate NKT cells from the normal childhood peripheral blood; and if activated NKT cells can kill neuroblastoma cells. Methods T cells obtained from the normal childhood peripheral blood were activated by stimulation under IL 15 alone or GM CSF alone, or their combination. The proliferation of T cells was measured by MTT methods. NKT cells were identified and isolated on the basis of surface phenotype by two color flow cytometry. Cytotoxicity on neuroblastoma cell line LA N 6 mediated by NKT cells was investigated. Results The proliferation of T cells in the IL 15, GM CSF stimulation group and the combination group was higher than the non stimulated controls ( 1.25 fold, 1.2 fold, 1.4 fold, respectively; all P< 0.01 ); the surface antigen expression of NKT cells was up regulated compared with the controls (2.56 fold, 3.27 fold, 4.39 fold, respectively; P< 0.01 or <0.05 ). The cytotoxicity of NKT cells stimulated by GM CSF alone or by IL 15 plus GM CSF was enhanced compared with the controls (P< 0.01 ). There was no difference in the cytotoxicity between the IL 15 stimulation group and the controls. The proliferation of T cells was enhanced in the IL 15 plus GM CSF stimulation group compared with the GM CSF stimulation group; but there was no difference in the surface antigen expression and the cytotoxicity of NKT cells between the two experimental groups. The surface antigen expression and the cytotoxicity of NKT cells were higher in the IL 15 plus GM CSF stimulation group compared with the IL 15 stimulation group; but there was no difference in the proliferation of T cells between the two experimental groups. There was no difference in the proliferation of T cells, the surface antigen expression and the cytotoxicity of NKT cells between the IL 15 and GM CSF stimulation groups, either. Conclusions IL 15 and GM CSF could induce the proliferation of NKT cells of normal children and enhance its function; the synergistic effects of NKT cell proliferation will be achieved if IL 15 and GM CSF are combined. Objective To study if IL 15 or GM CSF, or their combination can activate NKT cells from the normal childhood peripheral blood; and if activated NKT cells can kill neuroblastoma cells. Methods T cells obtained from the normal childhood peripheral blood were activated by stimulation under IL 15 alone or GM CSF alone, or their combination. The proliferation of T cells was measured by MTT methods. NKT cells were identified and isolated on the basis of surface phenotype by two color flow cytometry. Cytotoxicity on neuroblastoma cell line LA N 6 mediated by NKT cells were investigated. Results The proliferation of T cells in the IL 15, GM CSF stimulation group and the combination group was higher than the non stimulated controls (1.25 fold, 1.2 fold, 1.4 fold, respectively; all P <0.01) ; the surface antigen expression of NKT cells was upregulated compared with the controls (2.56 fold, 3.27 fold, 4.39 fold, respectively; P <0.01 or <0.05). The c ytotoxicity of NKT cells stimulated by GM CSF alone or by IL 15 plus GM CSF was enhanced compared with the controls (P <0.01). There was no difference in the cytotoxicity between the IL 15 stimulation group and the controls. The proliferation of T cells was enhanced in the IL 15 plus GM CSF stimulation group compared with the GM CSF stimulation group; but there was no difference in the surface antigen expression and the cytotoxicity of NKT cells between the two experimental groups. The surface antigen expression and the cytotoxicity of NKT cells were higher in the IL 15 plus GM CSF stimulation group compared with the IL 15 stimulation group; but there was no difference in the proliferation of T cells between the two experimental groups. There was no difference in the proliferation of T cells, the surface antigen expression and the cytotoxicity of NKT cells between the IL 15 and GM CSF stimulation groups, either. Conclusions IL 15 and GM CSF could induce the prol iferation ofNKT cells of normal children and enhance its function; the synergistic effects of NKT cell proliferation will be if if 15 and GM CSF are combined.