MHC diversity in Individuals and Populations

Abstract

The genes encoding the major histocompatibility (MHC) molecules are among the most polymorphic genes known in vertebrates. Since MHC molecules play an important role in the induction of immune responses, this polymorphism is probably due to selection for increased protection of hosts against pathogens. In contrast to the large population diversity of MHC molecules, each individual expresses only a limited number of different MHC molecules. This is widely believed to represent a trade-off between maximizing the detection of foreign antigens, and minimizing the loss of T cell clones during self tolerance induction in the thymus.