Anti-Myeloma Effects Induced by Myeloma Idiotype Pulsed Dendritic Cells In Vitro.

As the most potent antigen-presenting cells, Dendritic cells (DCs), capable of inducing immune responses from naive T cells, are operative tools for tumor immunotherapy. Derived DCs are extremely effective in capturing and presentation of antigens to T cells and play a key role in the induction of cytotoxic T lymphocytes (CTLs). In vitro culture system containing the combination of GM-CSF, IL-4 and TNF-α cytokine can affect CD14 ⁺ progenitor cells from mononuclear cells (MNCs) of peripheral blood (PB) developing into functional DCs, which have enough quantities for application in vitro researches and clinical practices. Multiple myeloma cells(MM)are able to secrete a great quantity of immunoglobulin (Ig) expressing idiotypic antigen called idiotype (Id) in its mutational hotspot. This kind of idiotypic structure regions also expressing on the surface of MM cells are high specific autologous tumor associated antigen (TAA). The combination use of DCs and tumor specific antigen can improve the immunogenicity of MM cells and stimulate specific anti-tumor immunological response effectively, so by using this new kind of DC tumor vaccine, following high dose chemical therapy, the tiny residual pathological changes might be cleared totally in the future.

To investigate the specific antitumor immune response induced by Id-pulsed dendritic cells(DCs) in vitro. DCs were generated from peripheral blood monocytes of the multiple myeloma(MM) patients using GM-CSF, IL-4, and TNF-α. pulsed with idiotype protein at the immature stage, DCs could activate T cells to become tumor specific cytotoxic T lymphocytes (CTLs). The morphologic characteristics of those cells were observed with light and electron microscopes. The phenotypic figures were analyzed with FACS analysis. Methy-thiazoly-Tetrazolium (MTT) assay was employed to evaluate the effect of proliferation of autologous T cells and the inhibition rate of CTL on MM cells. DCs precursors in peripheral blood could be induced to typical mature DCs in medium containing GM-CSF, IL-4 and TNF-α. Mature DCs with Id could operatively increase proliferation of the autologous T cells and active naive T cells to become tumor specialized CTLs. Any doses of CTLs had significant inhibition or killing ability on autologous MM cells. These results suggest in suitable cytokine environment, the precursors in peripheral blood of MM patients could be induced to functional DCs, and vaccination with Id-pulsed DCs could induce active antitumor immune response. Multiple cycles of immunization using DC as APC in vitro can be beneficial in generating antigen- specific T cells from normal PBMC, and Id an auto-specific tumor antigen, can be got with ammonium sulfate four-step precipitated method, By digestion of pepsin and affinity chromatography so as to stimulate MM specific immunological responce, and Id-pulsed mature DCs from MM patients can stimulate not only the proliferation of autologous T cells, but also the specific CTL immune response against autologous MM cells. In addition, in vitro immunization may provide an alternative approach to in vivo immunization of MM. We believe that DCs vaccine can bring the breakthrough of therapy to MM in the near future.