Process by which various forms of radiation (usually ultraviolet or gamma rays) may be used to rid of bloodborn viruses in Ultraviolet Blood Irradiation (UBI) Therapy. Irradiation is also used to prevent Graft versus Host Disease (GVHD) in blood transfusions. GVHD is a disease in which the donor's white blood cells attack or "reject" the patient's tissues because the donor's white blood cells identify the patient's cells as "foreign." Irradiation prevents the white blood cells in the donor's blood donation from attacking the patient's tissues, but leaves the rest of the blood (red blood cells, platelets, plasma, etc.) intact.