[Anti-leukemia immunity induced by dendritic cells fused with L615 tumor cells].

This study was aimed to investigate the specific anti-L615 leukemia cell immunity induced by L615/DC fused cell vaccine in vivo and in vitro. BM-derived DCs were generated from bone marrow of 615 mice by culturing for 9 - 10 days in culture medium supplemented with GM-CSF and IL-4. Irradiated L615 tumor cells were fused with DC by using PEG to form fused cell vaccine, with which 615 mice were immunized. After immunization, the specific proliferation ability and cytotoxicity against L615 leukemia cells in vitro were examined by MTT and LDH methods. Anti-leukemia effect of fused cell vaccine in vivo was studied by observing the immunotherapy effects on L615 tumor-bearing mice. The results showed that fully mature and functional bone marrow-derived DC were obtained. L615/DC fused cell vaccine could elicit potent specific proliferation response of spleen T cells from immunized mice when contacting with the same antigen at the second time, and could also elicit the effective cytotoxic activity against L615 leukemia cells in vitro, which were significantly different from other groups. In vivo the average survival time of the tumor-bearing mice received immunotherapy with L615/DC fused cell vaccine was 25.7 +/- 1 days, and one fourth of treated tumor-bearing mice survived for long time, but the mice of control group died all, their average of survival time was 17.5 +/- 1 days. The immunized mice survived with no evidence of recurrence when exposed to the second attack of lethal dose of living L615 cells 2 months later. It is concluded that L615/DC fused cell vaccine can improve the immunogenecity of L615 and induce effectively the specific anti-leukemia immunity against L615 leukemia cells to eliminate the residual leukemia cells, prolong the survival time and induce the immune memory to avoid the relapse. Thus, the fused cell vaccine may be an attractive strategy for malignance immunotherapy.