Immunogenetics is the study of the mechanisms of autoimmune diseases, tolerance in organ transplantation, and immunity to infectious diseases--with a special emphasis on the role of the genetic make-up of an organism in these processes. The immune system evolved essentially to protect vertebrates from a myriad species of potentially harmful infectious agents such as bacteria, virus, fungi and various eukaryotic parasites. However, the growing understanding of the immune system has influenced a variety of different biomedical disciplines, and is playing an increasingly important role in the study and treatment of many human diseases such as cancer and autoimmune conditions.

There are two broad types of immune systems. The innate immune system of defense depends on invariant receptors that recognize common features of pathogens, but are not varied enough to recognize all types of pathogens, or specific enough to act effectively against re-infection by the same pathogen. Although effective...