Transfusion can cause Graft Versus Host Disease. TA GvHD causes tissue and organ damage that is usually fatal. There is an intensive immunologic reaction mediated by transfused immunocompetent lymphocytes directed against an immunocompromised recipient, or one who shares an HLA haplotype with the donor.

The risk of TA-GVHD can be avoided by irradiation of cellular blood components or by treating platelet components with amotosalen. This inactivates T lymphocytes remaining in the component so that they are unable to engraft (PMID 18544121, 17655584, 15744235)

Irradiation may employ Gamma irradiation using a Cs137 or Co59 source, or special X-ray equipment that is now available for this purpose.