Human leukocyte antigen gene polymorphism and the histocompatibility laboratory.

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