Blood Irradiation Standards
The 29th edition of AABB Standards for Blood Banks and Transfusion Services specifies three conditions when cellular components shall be irradiated: (5.19.3.1.1) a patient is identified as being at risk for transfusion associated graft versus host disease (TA-GVHD), (5.19.3.1.2) the donor of the component is a blood relative of the recipient, and (5.19.3.1.3) the donor is selected for HLA compatibility by typing or crossmatching.
Patient factors that confer increased risk for TA-GVHD, include an immature immune system in the fetus or newborn and immune suppression due to genetic disease, malignancy, or immunosuppressive therapy.
The latter two conditions emphasize donor factors that may lead to TA-GVHD even in the absence of immune suppression. TA-GVHD has been reported to be relatively more prevalent among first-degree relatives and in populations with a higher incidence of homozygosity for HLA haplotypes. It seems to occur when the donor is homozygous for one of the recipient’s HLA haplotypes. For example, if a donor is homozygous for an HLA haplotype (e.g. HLA A2 A2, B7, B7) and a recipient is heterozygous (HLA A2, A19, B7, B57) the recipient would not recognize donor lymphocytes as foreign, but donor lymphocytes would recognize recipient lymphocytes as foreign. The recipient will not be able to reject lymphocytes from the donor, but donor lymphocytes can potentially attack the host if not treated by irradiation.
