Graft versus host disease

1 - DEFINITION

Graft versus host disease (GVHD) is a major complication of allogenic haematopoietic stem cell transplantation arising irrespective of the type of stem cells transplanted (bone marrow, peripheral stem cells or cord blood) and the relationship of the patient to the donor (family member = genoidentical transplant, or a registered HLA compatible donor = phenoidentical transplant) [1]. Prior to 2005, GVHD was known as "acute" (aGVHD) when it arose before day 100 of an allogenic transplant and chronic (cGVHD) after day 100. As signs of acute GVHD have been observed after day 100, particularly after a non-myeloablative transplant, a group of haematologists at the National Institute of Health (NYH) redefined GVHD on the basis of clinical rather than chronological criteria as follows : acute GVHD (classic before day 100, late onset after day 100, clinical signs summarized in Table I), chronic GVHD (clinical signs summarized in Table II) and overlap syndrome, which combines the clinical signs of aGVHD and cGVHD [2]. The validity of this classification has been confirmed in two recent studies [3, 4].

aGVHD arises when the donor’s immune cells, T lymphocytes, react against the recipient’s antigen-presenting cells, and is triggered by the inflammatory cascade and tissue damage resulting from pre-transplant conditioning. The main organs affected are the skin, gastrointestinal tract and liver [5]. cGVHD involves more complex immunologic phenomena including alloimmunity and autoimmunity as a result of donor T lymphocyte response and recipient antigen-presenting cell-deregulation leading to tissue inflammation and scarring.