Irradiated blood is used to prevent transfusion-associated graft-versus host disease (TA-GvHD) in people who received bone marrow transplants or transfusions of blood components. The disease can also affect a person who receives a blood transfusion from a close relative who is homozygous for certain human leukocyte antigens (HLA).
The risk of developing TA-GvHD is small, but patients who should take the precaution of using irradiated blood include those with a weakened immune system due to Hodgkin’s disease, people who have taken certain chemotherapy drugs, unborn babies, and babies who need exchange transfusions. Other indications include non-Hodgkin’s lymphoma, multiple myelomas, Waldenstrom’s macroglobulinemia, severe combined immunodeficiency (SCID), and Wiskott-Aldrich syndrome
The irradiation process kills the donor’s T-lymphocytes which are the main cause of TA-GvHD. Unless the T-lymphocytes are destroyed, they will graft themselves in the recipient’s tissues. If the person’s own immune system is incapable of mounting an immune response to them, the T-lymphocytes get the upper hand and attack the recipient’s body as if it were a foreign invader.
Between 4 and 30 days after transfusion, the resulting cascading immune response causes fever, rash, diarrhea, hepatitis, and reduced levels of red blood cells, white blood cells, and platelets (pancytopenia). Experts describe attempts to treat TA-GvHD as “difficult to futile.” The disease is fatal about 90% of the time, and death occurs due to an infection the patient can’t fight off or hemorrhaging caused by the pancytopenia.
How Blood is Irradiated
Blood is irradiated by exposing the bags to gamma radiation from cobalt-60 or cesium-137 using an instrument called an irradiator. The minimum radiation dose to kill the T-lymphocytes of 25 Gy10. Another method uses X-rays generated by a linear accelerator. When irradiating just red blood cells, they should be treated within 14 days of their expiration date and stored for a maximum of 28 days or until their expiration, whichever comes first.
Blood does not become radioactive after it is irradiated, and it does not present a danger to the recipient or their family members. The process does not damage healthy blood cells or platelets, but it does shorten the shelf life slightly because the cells lose some of their salt content.
- Alter, H. J., & Klein, H. G. (2008). The hazards of blood transfusion in historical perspective. Blood, 112(7), 2617–2626. https://doi.org/10.1182/blood-2008-07-077370
- Anwar, M., & Bhatti, F. A. (n.d.). Transfusion-Associated Graft Versus Host Disease. Retrieved May 3, 2018, from http://www.ayubmed.edu.pk/JAMC/PAST/15-3/masood.htm