The present invention comprises a method of protecting organs or tissue susceptible to reperfusion-induced dysfunction after ischemia. The method comprises parenterally administering to a patient a therapeutical composition containing natural alpha-1 acid glycoprotein, natural alpha-1 antitrypsin or a mixture thereof. Alternatively, organ or tissue transplants can be contacted with natural alpha-1 acid glycoprotein, natural alpha-antitrypsin or mixtures by perfusing or flushing them with a solution containing natural alpha-1 acid glycoprotein, natural alpha-1 antitrypsin or mixtures thereof in a concentration of 0.1 to 5 g/l.