Permalink : http://hdl.handle.net/2115/78720

JaLCDOI : 10.14943/ouyourin.11.3

脳疾患に対する他家／異種細胞移植( 他人や動物の細胞が脳内に入り込む) に関して現状を分析し、Derek Parfit 著『理由と人格 非人格性の倫理へ』で言及される〈R 関係〉に基づいて考察を行う。実際に他家／異種細胞が脳内に長期生着しキメラ状態となっている患者が多数存在しているが、人格の同一性については深く検討されてこなかった。我が国では自家細胞を用いた治療が先行してきたが、最近他家細胞に関する臨床研究も開始され、今後増加すると予想される。自家細胞と異なり、他家／異種細胞移植では回復した意識や認知機能は新たに生じたキメラ状態の脳に由来し、そこに〈R 関係〉は存在しない。患者らに漠たる違和感が生じるとすれば、〈R 関係〉を有しないことに（無意識的ながら）根ざしているように思われる。移植によるキメラ状態は、臓器移植や骨髄移植など日常診療としてありふれているが、キメラ状態の臓器の問題は脳とそれ以外で倫理学上の重要性が異なる。
A recent breakthrough in cell therapy is expected to cure the neurological symptoms　associated with various brain disorders. However, the issue concerning patients' personal identity, especially those who undergo allogeneic/xenogeneic cell transplantation, was hardly considered at all. The aim of the present study is to analyze the status quo about allogeneic/xenogeneic cell transplantation. Moreover, the personal identity of patients who undergo cell transplantation is discussed from an ethical point of view based on "Relation R" from "Reasons and Persons" written by Derek Parfit. Since the late 1980s, there have been lots of patients with chimeric brain because of allogeneic/xenogeneic cell transplantation to the brain. In Japan, although studies on autologous cell transplantation have preceded, clinical trials for allogeneic cell transplantation have increased in number. If a patient with severe disturbance of consciousness or dementia is treated with allogeneic/xenogeneic cell transplantation, but not autologous cell transplantation, the reason behind the improved consciousness or cognitive function would be the patient's chimeric brain and any "Relation R" would not exist before and after the treatment. If vague sense of incongruity occurs in the patient, it would come from the absence of "Relation R." In conclusion, although the chimeric state is as common as medical treatment including organ and bone marrow transplantation, brain is in a unique position in terms of ethics as an organ with a chimeric state.