Allogén

Allogén, often written allogène or allogénique in French, denotes a biological or medical entity originating from a donor who is of the same species as the recipient but genetically different. The term is primarily used in transplantation and tissue biology to distinguish from autogène (originating from the same individual) and from xenogène (originating from a different species).

In transplantation, allografts include solid organs such as the kidney, liver, heart, and lungs, as well as tissues like bone, skin, cornea, or hematopoietic stem cells. Because donor and recipient are not genetically identical, allografts trigger an immune response against donor antigens, raising the risk of rejection. Management relies on histocompatibility testing, notably human leukocyte antigen (HLA) matching, along with ABO blood group compatibility and crossmatching.

Immunosuppressive therapy is commonly used to prevent rejection, including calcineurin inhibitors, corticosteroids, and antimetabolites. In hematopoietic stem cell transplantation, allogeneic grafts can also exert a graft-versus-tumor effect but may cause graft-versus-host disease, a serious complication in which donor T cells attack the recipient’s tissues.

Outcomes depend on donor compatibility, organ quality, and recipient condition. Advances in immunology and donor matching have improved success rates, but risks remain, including rejection, infection, and complications from immunosuppression. The term allogén emphasizes the donor–recipient genetic difference within a species and is standard in clinical and research contexts.