Fig. 1.

The concept of “iPS Cell Stock Project” and remaining immunological issues. a The concept of the “iPS Cell Stock Project”. iPSCs established from monocytes of HLA-homo healthy volunteers can be applied not only to the recipient who has the same HLA in both alleles, but also the one who has it in one allele. No T cell-mediated immune response in the recipient takes place against HLA-homo regenerated graft because the graft has the same HLA as the recipient. b Immunological issues in homo-to-hetero transplantation. Issue 1: the mismatch of minor histocompatibility antigens. Minor histocompatibility antigens expressed in grafts do not match to the recipients except in the case of monozygotic twins. Immune rejection may take place when immune cells recognize these antigens in either HLA-homo or HLA-hetero recipients. Issue 2: NK cell-mediated immune reaction. NK cells in the HLA-hetero recipient may recognize HLA-homo regenerated graft and exert cytotoxic activity