The primary cause of GVHD is the immune response initiated by the donor T-cells present in the graft. These cells can recognize the recipientâs tissues as foreign due to differences in human leukocyte antigens (HLAs). The severity and occurrence of GVHD are influenced by the degree of HLA mismatch, the source of the graft (e.g., bone marrow, peripheral blood, or cord blood), and the intensity of the conditioning regimen used prior to transplant.
