Immune activation of erythroleukemia cells induced by interleukin 12

To investigate the antitumor activity of IL 12, the induction of differentiation of IL 12 was observed using erythroleukemia cells (FBL 3) as model. After incubation with 200 U/mL IL 12 for 48 h, DNA synthesis of FBL 3 cells in S phase decreased significantly; the expression of CD14 which is the specific marker of monocyte increased, the rate of NBT + cells was apparently higher than that of the untreated FBL 3 cells. After treating FBL 3 cells with IL 12 for 72 h, the expression of 33D1 and NLDC145 which are the specific markers of dendritic cells increased markedly, the surface molecules such as MHC II,B7 1, B7 2, and VCAM 1 were up regulated; morphological observation showed two kinds of cells: some cells had a ruffled surface and plentiful lysosome; the others had many dendritic projections on the surface, and contained numerous mitochondria. Functionally, the IL 12 treated FBL 3 cells could apparently stimulate the proliferation of allogeneic and autologous T lymphocytes, and improve the specific cytotoxic activity of CTL on FBL 3 cells. These results indicated that erythroleukemia cells were induced by IL 12 to differentiate into the monocytes and dendritic cells, then exhibited the antigen presenting function. The data outline a new mechanism for IL 12 to treat leukemia.