Immune System: Evolutionary Pressure of Infectious Agents

Abstract

AbstractLike all other biologic systems, the immune system emerged as a consequence of evolution. A major force that has driven the evolution of the immune system and shaped its current organisation was the needs to fight pathogens. Key elements of adaptive immunity, such as antigen receptors and major histocompatibility complex molecules, show evidence of selective pressures exerted by pathogens. Conversely, immune responses mounted by the host have also imposed strong selective pressures on pathogens. To escape immune attack from the host, pathogens have developed immune evasion tactics such as antigenic variation (as typically seen in influenza viruses) and the production of immune evasion proteins (as typically seen in herpesviruses). Mutation is the key genetic mechanism underlying the co‐evolution of the immune system and pathogens.Key Concepts:The immune system of vertebrates has evolved to fight pathogens.Pathogens have exerted intense selective pressures on the evolution of the immune system.Key elements of the adaptive immune system, such as antigen receptors and major histocompatibility complex molecules, show evidence of such selective pressures.Immune responses by the host exert strong selective pressures on pathogens.To escape immune attack, pathogens change their antigenicity or produce immune evasion proteins.Mutation is the key genetic mechanism underlying the co‐evolution of the immune system and pathogens.