TAP-deficient human iPS cell-derived myeloid cell lines as unlimited cell source for dendritic cell-like antigen-presenting cells.

We previously reported a method to generate dendritic cell (DC)-like antigen-presenting cells (APC) from human induced pluripotent stem (iPS) cells. However, the method is relatively complicated and laborious. In the current study, we attempted to establish a method through which we could obtain a large number of functional APC with a simple procedure. We transduced iPS cell-derived CD11b(+) myeloid cells with genes associated with proliferative or anti-senescence effects, enabling the cells to propagate for more than 4 months in a macrophage colony-stimulating factor (M-CSF)-dependent manner while retaining their capacity to differentiate into functional APC. We named these iPS cell-derived proliferating myeloid cells 'iPS-ML', and the iPS-ML-derived APC 'ML-DC'. In addition, we generated TAP2-deficient iPS cell clones by zinc finger nuclease-aided targeted gene disruption. TAP2-deficient iPS cells and iPS-ML avoided recognition by pre-activated allo-reactive CD8(+) T cells. TAP2-deficient ML-DC expressing exogenously introduced HLA-A2 genes stimulated HLA-A2-restricted MART-1-specific CD8(+) T cells obtained from HLA-A2-positive allogeneic donors, resulting in generation of MART-1-specific cytotoxic T lymphocyte (CTL) lines. TAP-deficient iPS-ML introduced with various HLA class I genes may serve as an unlimited source of APC for vaccination therapy. If administered into allogeneic patients, ML-DC with appropriate genetic modifications may survive long enough to stimulate antigen-specific CTL and, after that, be completely eliminated. Based on the present study, we propose an APC-producing system that is simple, safe and applicable to all patients irrespective of their HLA types.