Induction of antitumor cytotoxic activity using CD34+ cord blood cell-derived and irradiated tumor cell-primed dendritic cells.

Dendritic cells (DCs) are the most powerful antigen-presenting cells in the immune system. They can activate immunologically naive T cells and improve the efficacy of immunotherapy against tumors. In the present study we investigated whether CD34+ cord blood cell-derived DCs are capable of inducing antitumor cytotoxic cells, such as cytotoxic T lymphocytes (CTLs), NK cells, and monocytes. Cord blood T cells stimulated by DCs pulsed with irradiated K562 major histocompatibility complex (MHC) class I+ cells were highly effective in eliciting a selective killing response against K562 class I+ cells. This killing activity was almost completely abrogated by antibodies to CD8 or MHC class I, but not to CD4. This suggests that tumor cell-pulsed DCs generated from CD34+ cord blood cells are able to induce tumor specific CTLs against corresponding tumor cells from cord blood T cells, and that these CTLs are CD8+ T cells which may recognize tumor cells via MHC class I molecules. This observation has potentially important implications for the use of DCs in clinical immunotherapy in cord blood transplantation.