hostversusgraft

Host-versus-graft (HvG), also written as host-versus-graft reaction, is an immune response in which the recipient’s immune system recognizes and attacks a transplanted graft, leading to rejection or impaired graft function. It is the counterpart of graft-versus-host disease (GVHD), where donor immune cells attack the host. HvG is a consideration in solid organ transplantation and, to a lesser extent, in hematopoietic stem cell transplantation, particularly when donor–recipient compatibility is imperfect.

Immunological basis and mechanisms involve recognition of donor antigens by the recipient’s T cells. Direct and indirect pathways of allorecognition contribute to HvG, with human leukocyte antigen (HLA) mismatches and disparities in minor histocompatibility antigens increasing risk. Antibody-mediated HvG can occur when recipient antibodies target donor antigens, causing vascular injury and graft dysfunction. Unlike GVHD, HvG results in rejection or failure of the graft rather than widespread damage to host tissues.

Clinical presentation and diagnosis depend on the transplanted organ or tissue. HvG presents as signs of graft dysfunction, such as reduced organ function or rising laboratory markers of injury. Diagnosis relies on graft biopsy when feasible, which may show lymphocytic infiltration and tissue injury, and laboratory tests detecting donor-specific antibodies or reactive T cells.

Prevention and management focus on maximizing donor–recipient compatibility and appropriate immunosuppression. Practices include careful donor selection, HLA matching, and tailored immunosuppressive regimens. Treatment of HvG may involve intensified immunosuppression, corticosteroids, anti-T cell therapies, and procedures to remove antibodies (e.g., plasmapheresis or IVIG) in antibody-mediated cases. In some settings, adjustments to conditioning or tolerance-promoting strategies may be pursued to reduce the risk of HvG.