Overview on HLA and DNA typing methods

The term HLA refers to the Human Leukocyte Antigen System, which is controlled by genes on the short arm of chromosome six. The HLA loci are part of the genetic region known as the major histocompatibility complex (MHC). The MHC has genes (including HLA) that form part of the normal function of the immune response. The essential role of the HLA antigens lies in the control of self-recognition and thus defense against microorganisms. The HLA loci, by virtue of their extreme polymorphism ensure that few individuals are identical and thus the population at large is well equipped to deal with attacks. Because some HLA antigens are recognized on all body tissues (rather than just blood cells), the identification of HLA antigens is described as “Tissue typing”. In the last twenty years there has been an exponential growth in the application of DNA technology to the field of Histocompatibility and Immunogenetics. The development and application of several different DNA methods by many laboratories has resulted in that nearly every Histocompatibility and Immunogenetics laboratory performs some DNA typing to detect HLA alleles.