Human leukocyte antigen gene polymorphism and the histocompatibility laboratory

The human leukocyte antigens (HLA) encoded by genes within the major histoc ompatibility complex display an impressive degree of polymorphism. This var iability is apparently maintained in human populations through the need to successfully display a wide range of processed foreign peptides to the T ce ll antigen receptor. The large number of alleles at the Class I and Class I I loci pose a significant problem for molecular diagnosis. Knowledge of all ele groups and specific alleles present in individuals has important implic ations in organ and stem cell transplantation and in disease association st udies. Histocompatibility laboratories have transformed themselves during t he past decade as they have adapted the techniques of molecular diagnostics to the challenge of identifying HLA alleles.