<unk>  occurs when the immune system of the recipient of a<unk>  attacks the<unk> ed organ or tissue. This is because a normal healthy human immune system can distinguish foreign tissues and attempt to destroy them, just as it attempts to destroy infective organisms such as bacteria and viruses.
Transplant rejection
Graft-versus-host disease
Immunosupression
Radiation fibrosis
Injection fibrosis
Graft versus host
Injection site reaction
Posttransplantation lymphoproliferative disorder