The HLA molecules are important regulators of the immune response through mediating antigen presentation and interaction between key immune mediating cells. They are also the major histocompatibility barriers to transplantation, which is the clinical paradigm of the self versus non self concept. It is now recognized that this diverse range of gene systems involved in the control of the immune response have been shown to be important in many aspects of clinical practice. As a result many new molecular and cellular methods have been developed for identifying these genes and their...