Anti-human Leukocyte Antigen Immune Sensitization Effects of Cryopreserved Allograft and Blood Transfusion

Do allografts present a risk to burn patients? Allografts and HLA-sensitization

OBJECTIVE

This meta-analysis aimed to quantify sensitization rates following allograft usage and determine whether allografts have an increased risk of long-term sensitization compared to alternative therapies in burn patients.

METHODS

Systematic review, meta-analysis and meta-regression of post-operative sensitization in burn patients were performed following Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidance (Prospero registration: CRD42024497137). Database searches were conducted on MEDLINE, Embase, CENTRAL using ProQuest Dialog. We included all studies reporting post-operative sensitization in burn patients that were not case series or singular case reports. Meta-analysis was used to compare the risk of sensitization for allograft versus alternative therapies.

RESULTS

Six studies (Allograft Patients: 71; Non-Allograft Patients: 95) were included (n = 166). Overall, 73 % (CI: 39 %-92 %) of burn patients were sensitized following allograft. Patients receiving allograft were at a significantly increased risk of sensitization (OR 13.14 [95 % CI: 1.32-131.00]). However, on sub-group analysis, when directly comparing patients who received allograft and transfusion versus those who received transfusion alone, there was not a significantly increased risk of sensitization (OR 7.68 [95 % CI:.61-95.86]).

CONCLUSION

Allograft is associated with a significantly increased risk of sensitization in burn patients. However, it is not clear whether burn patients already receiving transfusion will have an increased risk of sensitization from adding allograft. Further studies are required to demonstrate the multifactorial causes of sensitization within the burned population to explain the significance of the contribution from allograft and/or transfusion reported within the literature. Clinicians must carefully weigh the immediate benefits of allografts against the potential long-term challenges of sensitization, especially where alternative wound therapies are possible.

Sensitization and Desensitization in Vascularized Composite Allotransplantation

Vascularized composite allotransplantation (VCA) is a field under research and has emerged as an alternative option for the repair of severe disfiguring defects that result from severe tissue loss in a selected group of patients. Lifelong immunosuppressive therapy, immunosuppression associated complications, and the effects of the host immune response in the graft are major concerns in this type of quality-of-life transplant. The initial management of extensive soft tissue injury can lead to the development of anti-HLA antibodies through injury-related factors, transfusion and cadaveric grafting. The role of antibody-mediated rejection, donor-specific antibody (DSA) formation and graft rejection in the context of VCA still remain poorly understood. The most common antigenic target of preexisting alloantibodies are MHC mismatches, though recognition of ABO incompatible antigens, minor histocompatibility complexes and endothelial cells has also been shown to contribute to rejection. Mechanistically, alloantibody-mediated tissue damage occurs primarily through complement fixation as well as through antibody-dependent cellular toxicity. If DSA exist, activation of complement and coagulation cascades can result in vascular thrombosis and infarction and thus rejection and graft loss. Both preexisting DSA but especially de-novo DSA are currently considered as main contributors to late allograft injury and graft failure. Desensitization protocols are currently being developed for VCA, mainly including removal of alloantibodies whereas treatment of established antibody-mediated rejection is achieved through high dose intravenous immunoglobulins. The long-term efficacy of such therapies in sensitized VCA recipients is currently unknown. The current evidence base for sensitizing events and outcomes in reconstructive transplantation is limited. However, current data show that VCA transplantation has been performed in the setting of HLA-sensitization.