Usually human blood platelets or fresh blood are mixed with lymphocytes. When this blood or blood component with a large amount of immunologically active lymphocytes is introduced into a patient with low immunity, it can lead to "transfusion-associated graft-versus-host disease" (TA-GVHD) which can even lead to death. The irradiation of blood or blood products can effectively deactivate immunologically active T-lymphocytes. Infusion of irradiated blood or blood components can effectively prevent the occurrence of TA-GVHD and make blood transfusions safer.