Mechanism by which partial HLA matching can cause transfusion-associated graft-versus-host disease (ta-GVHD)

Partial HLA matching can cause ta-GVHD in a transfusion recipient of any blood product that contains viable lymphocytes. This occurs when donor lymphocytes share an HLA haplotype with the recipient, and the recipient has another HLA haplotype not shared by the donor. As a result, the donor lymphocytes recognize recipient cells as foreign, but recipient lymphocytes do not recognize donor cells as foreign. Donor cells can attack recipient tissues including bone marrow, skin, and gastrointestinal tract. Partial HLA matching is more common in genetically homogeneous populations and with directed donations. Refer to UpToDate for information on ta-GVHD and approaches to prevention.