allogeneic
Meaning of allogeneic: A word describing where donated material came from: another person of the same species, neither the recipient nor an animal.
Definition of allogeneic
Allogeneic means taken from a different individual of the same species. In transplantation it describes cells, tissue or an organ donated by another person, as opposed to material taken from the recipient. Because donor and recipient carry different tissue markers, allogeneic material can be attacked by the recipient's immune system, and in a marrow graft it can attack the recipient in turn.
How does it compare with the related words?
| Term | Source | Immune conflict |
|---|---|---|
| Autologous | The same individual | None |
| Syngeneic | An identical twin | Effectively none |
| Allogeneic | Another person | Yes, in both directions |
| Xenogeneic | Another species | Severe |
Why does the immune system object?
Every cell displays a set of surface markers known as HLA, inherited as a block from each parent. Immune cells are trained to accept the markers they grew up with and to treat anything else as foreign. Donor and recipient are therefore matched at as many HLA positions as possible, which is why siblings are checked first and why unrelated registries need to be very large. Even a close match is not a perfect one, so medicines that damp the immune response are needed alongside.
What is graft versus host disease?
This is the reversal that makes marrow and stem cell grafts different from solid organs. The transplanted material contains the donor's immune cells, and those cells inspect the new surroundings and find them foreign. They attack the recipient's tissues, most often the skin, the gut and the liver, producing rash, diarrhea and jaundice. The same reaction has a useful side: donor immune cells also recognize any remaining tumor cells as foreign and destroy them, an effect called graft versus tumor. Much of the value of allogeneic bone marrow transplantation rests on that, and the difficulty lies in keeping one effect while limiting the other.
Is the spelling fixed?
Two forms circulate. Allogenic is a shortened variant of the same word and means the same thing, though the longer spelling is standard in transplantation writing.
Also known as
Used in a sentence
The plan proceeded to an allogeneic transplant once a matched donor was identified.
Good to know
In marrow and stem cell grafts the immune reaction runs both ways, so donor cells can attack the recipient as well as being attacked, which does not occur with material from the recipient.
Word origin
Where “allogeneic” comes from
From the Greek allos, meaning other, and genos, meaning kind or race.