What causes TA-GVHD?

TA-GVHD occurs when viable donor T-lymphocytes in transfused blood components engraft in the recipient and mount an immune response against tissue antigens. Normally, immunocompetent recipients quickly eliminate donor T-cells, which prevents TA-GVHD. However, a patient with a weakened immune system may not be able to clear donor T-cells, especially if those viable donor T-cells are sufficiently similar in human leukocyte antigen (HLA) expression to that of the recipient’s T-cells. In this case, the recipient’s immune system will not recognise the donor T-cells as foreign. Rather than being cleared, these donor T-cells may proliferate and attack recipient tissues and organs, resulting in TA-GVHD.

The primary risk factors in TA-GVHD include:

• Number of viable T-lymphocytes transfused
• Degree of recipient immunodeficiency
• Similarity in human leukocyte antigen (HLA) expression between the donor and recipient

Source: Corash and L Lin, Novel processes for inactivation of leukocytes to prevent transfusion-associated graft-versus-host disease, Bone Marrow Transplantation (2004) 33, 1–7