allograft（同種移植）は同じ動物種間での臓器移植のこと。例えば、他人の腎臓を誰かに移植するなど。
enograft（異種移植）は異なる動物種間の臓器移植のこと。例えば、ブタの心臓を人に移植するなど。
isograft（同系移植）は遺伝学的なバックグラウンドが同一の個体間での移植のこと。例えば一卵性双生児の間での移植など。
Isografts are allografts in which organs or tissues are transplanted from a donor to a genetically identical recipient (e.g. an identical twin).
https://www.sciencedirect.com/topics/immunology-and-microbiology/isograft
歴史的には、isograftという単語は同種移植の意味で用いられたこともあるようです。
Transplants are classified as (1) autogenous transplants—tissue completely separated from its original site and implanted in another location in the same individual—and (2) heterogenous transplants—tissue taken from other individuals. The second class may be subdivided into (a) homogenous grafts (known as isografts)—tissue from the body of an individual of the same species—and (b) zoografts—tissue from animals of different species.
https://jamanetwork.com/journals/jamaotolaryngology/fullarticle/575670
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xenograft (26件）
allograft （39件）
isograft (0件）