How is transfusion-associated graft-versus-host disease similar to, yet different from, organ transplantation-associated graft-versus-host disease?

Graft-versus-host disease (GVHD) is a rare, usually fatal complication following blood transfusion or organ transplantation, namely transfusion-associated GVHD (TA-GVHD) and organ transplantation-associated GVHD (OA-GVHD). The dominant mechanism of GVHD is exposure to viable donor lymphocytes that are not recognized as foreign by, but able to respond to, the recipient. The clinical features and relative risk factors of either TA-GVHD or OA-GVHD are yet to be fully understood. The current review article aims to discuss and summarize the similarities and differences between TA-GVHD and OA-GVHD to gain a deeper understanding of the pathogenesis. It is evident that the shared human leukocyte antigens (HLA) between donor and recipient and immunocompromised status of the recipient are the two main risk factors for the development of both TA-GVHD and OA-GVHD. In particular, the homozygous donor with donor-dominant one-way matching at the three loci HLA-A, -B, and -DR has a high risk of developing GVHD following liver transplantation, and such donors should be excluded to prevent it. However, the development of GVHD is thought to be related to a combination of several risk factors, and the contribution of each risk factor remains unknown. Further studies are warranted to determine the important contributing factors that lead to an accurate prediction of GVHD development.