Question
Graft – versus – host ( GVH ) reaction
Answer
Graft-versus-host (GVH) reaction is an immunological complication in which immunocompetent donor T lymphocytes present within a transplanted graft recognize and attack the recipient’s (host’s) tissues as foreign — the reverse direction from ordinary graft rejection (where the host’s immune system attacks the graft).
Conditions required for GVH reaction (Billingham’s criteria):
- The graft must contain immunocompetent lymphoid cells (donor T cells).
- The recipient must express tissue (histocompatibility) antigens that the graft lacks, i.e., there must be genetic/HLA disparity between donor and recipient.
- The recipient must be incapable of mounting an effective immune response against the graft (immunologically compromised/immunosuppressed), so that the donor’s attacking lymphocytes are not themselves rejected/eliminated before they can act.
Clinical settings: classically seen after allogeneic haematopoietic stem cell (bone marrow) transplantation, where donor T cells within the graft attack the immunosuppressed recipient’s tissues; can also occur after transfusion of non-irradiated blood products containing viable lymphocytes to a severely immunocompromised recipient (transfusion-associated GVHD), and rarely in solid organ transplants containing substantial passenger lymphocytes (e.g., liver, small bowel).
Clinical features:
- Acute GVHD (within the first ~100 days) — predominantly affects skin (maculopapular rash, can progress to desquamation), gastrointestinal tract (diarrhoea, abdominal pain), and liver (cholestatic jaundice, deranged liver function).
- Chronic GVHD (later) — a more multisystem, sclerodermatous-like process affecting skin, mucous membranes, lungs, liver, and other organs, resembling autoimmune connective-tissue disease.
Prevention/management: HLA matching between donor and recipient to minimize disparity; prophylactic immunosuppression (e.g., calcineurin inhibitors, methotrexate); T-cell depletion of the graft; irradiation of blood products given to severely immunocompromised patients to inactivate donor lymphocytes and prevent transfusion-associated GVHD.