The HLA system: an update and relevance to patient-donor matching strategies in clinical transplantation.

In recent years the development of recombinant DNA and sequencing techniques has led to a greatly increased understanding of the genetic complexity, structure and function of the human major histocompatibility complex. This system may be subdivided into the "classical' HLA (human leukocyte antigen) class I and II transplantation antigens and novel HLA and non-HLA genes, involved in antigen processing and presentation to T cells. Parallel technological developments in HLA DNA typing in the clinical laboratory have resulted in a more precise awareness of the role of HLA matching for the classical HLA antigens in bone marrow and solid organ transplantation, while alternative strategies and techniques for donor selection are currently under evaluation. This review offers a current perspective on the genetics, structure and function of the HLA system, its relevance to clinical transplantation and future prospects for improvements in donor selection.