Genetics of the Immune System

The genetic organization and control of the immune system demonstrates several genetic phenomena that are shown less clearly or not at all by other systems: extensive polymorphism, linkage disequilibrium, an obvious evolutionary relationship between its various components, and, especially, a unique system of encoding great diversity within relatively few loci. The genes of the immune system not only are clinically important in relation to transplantation, autoimmune disease, and response to infection and as causes of a number of single-gene disorders, but they also provide excellent models for the analysis of human variation and gene expression. The application of molecular techniques has greatly expanded the understanding of the immune response while at thesame time revealing new layers of complexity that remain to be explored.

Higher organisms are unique in their ability to distinguish between "self" and "nonself" and to mount a reaction selectively against a very broad spectrum of foreign antigens. This reaction is mediated by the complex interactive network of cells and cellular cytokines of the immune system and is referred to as the immune response. Genetic factors play a key role not only in the generation of the normal immune response but also in the development of aberrant immune reactions and consequent immune-mediated disease.

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