allotransplantation

Allotransplantation is the transplantation of organs, tissues, or cells between genetically non-identical individuals of the same species. It contrasts with autotransplantation (within the same person) and with syngeneic transplantation (between genetically identical individuals).

Solid organs such as kidney, liver, heart, and lung; pancreas; as well as tissues including cornea, bone, skin, and hematopoietic stem cells, can be transferred through allotransplantation. Successful outcomes require careful donor–recipient matching, including blood type compatibility and HLA typing, as well as crossmatching to detect preformed antibodies. Immunologic rejection remains the principal obstacle and occurs in several forms: hyperacute rejection due to preformed antibodies, acute cellular rejection, and chronic rejection. Immunosuppressive therapy is used to prevent rejection, typically combining induction therapy with maintenance regimens based on calcineurin inhibitors, antiproliferative agents, steroids, and sometimes mTOR inhibitors. Antibody-directed treatments may be needed for difficult cases. Ongoing monitoring includes clinical assessment, laboratory tests, imaging, and tissue biopsy when appropriate.

Donor sources include deceased and living donors. Living donation is common for kidneys and segments of liver and other tissues, guided by ethical and medical evaluations. Organ allocation systems aim to balance fairness and medical urgency, using matching, waiting lists, and allocation rules specific to each country or region.

Outcomes have improved substantially with modern immunosuppression, but long-term management carries risks, including infection, malignancy, drug toxicity, metabolic complications, and cardiovascular disease. The field is regulated by national and international authorities to ensure safety, ethics, and informed consent.