occurs in biological_process heart heart transplant rejection A body response in rejection to a heart transplant. Your immune system will see your donor heart as a foreign object that's not supposed to be in your body. Your immune system will try to attack your donor heart. Although all people who receive a heart transplant receive immunosuppressants — medications that reduce the activity of the immune system — nearly 25 percent of heart transplant recipients still have some signs of rejection during the first year after transplantation. Sirarat Sarntivijai MedDRA:10019315 http://www.mayoclinic.org/tests-procedures/heart-transplant/basics/risks/prc-20014050 Tomasz Adamusiak