What is the medical term for when a transplanted organ is attacked by the recipient's immune system?

• A. Rejection
• B. Infection
• C. Autoimmunity
• D. Allergy

Answer: (A)

Immune rejection of a transplanted organ occurs when the recipient’s immune system recognizes donor tissue as foreign and launches an immune attack against it. This reaction is driven by differences in donor antigens, especially HLA molecules, which activate T cells and antibodies that damage the graft and can impair its function. It’s distinct from infection (which is caused by pathogens), autoimmunity (where the immune system attacks the body’s own tissues), and allergy (an IgE-mediated response to environmental substances). In clinical care, immunosuppressive therapy is used to dampen the immune response and protect the transplanted organ from rejection.