From the Guidelines
An allograft donor, an isograft donor, and a sibling graft donor differ significantly in terms of genetic compatibility, with allografts being the most genetically disparate, isografts being genetically identical, and sibling grafts falling in between, as evidenced by the importance of HLA-matched sibling donors in hematopoietic cell transplantation 1. The main difference between these types of donors lies in their genetic compatibility, which directly impacts the risk of immunological rejection.
- Allograft donors are genetically different from the recipient, leading to a higher risk of rejection.
- Isograft donors, typically identical twins, are genetically identical to the recipient, resulting in minimal rejection risk.
- Sibling graft donors, being relatives, share some genetic material with the recipient, placing them between allografts and isografts in terms of rejection risk. Key factors influencing the choice of donor include the patient's disease status, performance status, and the need for post-transplant cellular therapy, as outlined in the consensus on indications, conditioning regimen, and donor selection of allogeneic hematopoietic cell transplantation 1. In clinical practice, HLA-matched sibling donors are often the first choice for allo-HSCT due to their genetic similarity, which reduces the risk of graft-versus-host disease and improves transplantation outcomes, as recommended by the Chinese Society of Hematology 1. The genetic matching between donors and recipients is crucial, especially in hematopoietic stem cell transplantation, where HLA matching can significantly impact the success of the transplant and the patient's quality of life.
- The use of unrelated donors may be considered for patients with favorable-risk diseases, but this approach requires careful risk stratification and individualized management strategies 1.
- Ultimately, the choice of donor depends on various factors, including the patient's specific needs, the availability of suitable donors, and the potential risks and benefits associated with each type of transplant.
From the Research
Types of Grafts
- An allograft is a transplant between allogeneic (genetically not-identical) members of a given species 2
- An isograft is a transplant between genetically identical (syngeneic) individuals, such as monozygotic twins, and is readily accepted by the recipient's immune system 2
- There is no mention of a syblingraft (sibling graft) in the provided studies, however, it can be inferred that a transplant between siblings who are not monozygotic twins would be considered an allograft, as they are genetically not-identical
Graft Rejection and Immunological Response
- Allografts and xenografts provoke a strong immunological response, which can lead to rejection and graft loss unless suppressed by immunosuppressive therapy 2
- The immunological response to allografts involves both humoral (B-cell) and cellular (T-cell) components, and is influenced by the degree of genetic mismatch between the donor and recipient 2
Clinical Transplantation and Graft Outcomes
- The choice of immunosuppressive regimen can affect graft outcomes, with some studies suggesting that tacrolimus may be associated with improved graft survival and reduced risk of acute rejection compared to cyclosporine-based regimens 3, 4
- Genetic predispositions of the donor, such as polymorphisms in the stromal-derived factor-1 (SDF1) gene, can also influence graft outcomes, including the risk of acute rejection and long-term graft survival 5