Major histocompatibility complex : Polymorphism from coevolution

Abstract

There are many examples of pathogens adapting toward evasion of immune responses. Viruses, such as influenza, rapidly alter their genetic make-up, and each year there appear to be sufficient susceptible hosts that lack memory lymphocytes from previous influenza infections to give rise to a new epidemic. During human immunodeficiency virus (HIV) infection, such alterations occur at an even faster rate, enabling the virus to escape repeatedly from the immune response within a single host. Hosts, on the other hand, are selected for counteracting immune evasive strategies by pathogens. Since the generation time of hosts is typically much longer than that of pathogens, these host adaptations are expected to evolve much more slowly.