HLA and Antigen Receptor Biology

The human leukocyte antigen (HLA) complex has been implicated in key immune responses such as recognition of self versus nonself, susceptibility to autoimmune disease, drug hypersensitivity, and tolerance to organ transplantation. The peptide-HLA complex serves as the ligand for the antigen-specific T cell receptor (TCR) on T cells. The principal function of HLA molecules is to facilitate immune surveillance of the intracellular (class I) and extracellular (class II) environments by presenting antigens to T cells. Donor-specific antibodies (DSA) are antibodies against donor HLA molecules that are present in the recipient at any time before or after transplantation. The presence of preexisting DSA prior to lung transplantation, also known as allosensitization, is a major contributing factor to waitlist mortality. Anti-HLA antibodies play an important role in cardiac allograft injury.