Graft-versus-host disease (GVHD) is a serious complication that can occur after a stem cell or bone marrow transplant. Understanding the causes and risk factors of GVHD is crucial for both patients and healthcare providers in managing this potentially life-threatening condition.
Causes:
GVHD occurs when the transplanted immune cells (the graft) recognize the recipient’s body (the host) as foreign and mount an immune attack. The transplanted stem cells contain immune cells, mainly T cells, which play a central role in the development of GVHD. These T cells are supposed to help the body fight infections and reconstitute the immune system after transplantation. However, in some cases, they can mistakenly attack the recipient’s tissues, leading to GVHD.
The immune response that causes GVHD can target various organs in the body, including the skin, liver, and gastrointestinal tract. For example, in skin GVHD, patients may experience rashes, itching, and skin thickening. Liver GVHD can lead to jaundice and abnormal liver function tests. Gastrointestinal GVHD can cause nausea, vomiting, diarrhea, and abdominal pain.
Risk Factors:
Several factors can increase the risk of developing GVHD. One of the main risk factors is the degree of mismatch between the donor and recipient. The closer the match between the donor and recipient in terms of human leukocyte antigen (HLA) typing, the lower the risk of GVHD. HLA molecules are proteins on the surface of cells that help the immune system distinguish between self and non-self. A greater mismatch in HLA types can lead to a stronger immune response and a higher risk of GVHD.
The source of the donor stem cells can also affect the risk of GVHD. Transplants from unrelated donors or cord blood have a higher risk of GVHD compared to transplants from related donors. Unrelated donors are less likely to have a perfect HLA match with the recipient, increasing the risk of immune rejection. Cord blood transplants may have a lower number of immune cells, which can also contribute to a higher risk of GVHD.
The conditioning regimen before transplantation is another risk factor. The conditioning regimen involves chemotherapy and/or radiation to destroy the patient’s diseased bone marrow and suppress the immune system to make room for the transplanted stem cells. A more intense conditioning regimen can increase the risk of GVHD by causing more damage to the recipient’s tissues and increasing the release of inflammatory cytokines.
Age is also a factor. Older patients are at a higher risk of developing GVHD compared to younger patients. This may be due to age-related changes in the immune system and a higher likelihood of having underlying health conditions that can increase the risk of complications.
Finally, certain genetic factors can predispose individuals to GVHD. Some genes have been identified that are associated with an increased risk of developing GVHD. These genetic variations can affect the immune response and the ability of the body to tolerate the transplanted cells.
In conclusion, GVHD is a complex condition caused by the immune response of transplanted cells against the recipient’s body. Several risk factors, including donor-recipient mismatch, donor source, conditioning regimen, age, and genetic factors, can increase the likelihood of developing GVHD. By understanding these causes and risk factors, healthcare providers can better assess the risk of GVHD in individual patients and develop personalized strategies to prevent and manage this complication.
