The significance of HLA-DR in transplantation compatibility stems from its role as a major component of the immune response. HLA-DR is part of the class II major histocompatibility complex (MHC), which is crucial for presenting antigens to CD4+ T helper cells. In the context of transplantation, matching HLA-DR alleles between donor and recipient is particularly important because a significant portion of the immune response against transplanted tissues is mediated by CD4+ T cells.
When there is a mismatch in HLA-DR, it can lead to a more robust immune response against the transplanted organ, increasing the risk of graft rejection. Therefore, the compatibility of HLA-DR is pivotal for the success of organ transplants, as it directly influences the recipient's immune tolerance to the donor organ.
While other alleles such as HLA-A, HLA-B, and HLA-C also play important roles in immune recognition and graft acceptance, the class II alleles, particularly HLA-DR, are deemed the most critical in the context of transplantation due to their direct involvement in orchestrating the immune response.