Evolution of the Human Immune System

Abstract Human immune system is an orchestra of various defence mechanisms functioning at different levels, from individual cells to the whole body. Specialised immune mechanisms can be subdivided into innate and adaptive immune systems. Innate immune mechanisms use receptors recognising conserved molecular patterns of pathogens. Adaptive immune system depends on the production of vast repertoires of immune receptors and selective expansion of pathogen‐specific ones. Some basic cellular functions such as ubiquitination and autophagy as well as stress response pathways also contribute to the immune defence. Various immune defence systems work autonomously but in communication with each other. All responses are coordinated at the body level by hormones and other mediators. Layered and redundant structure of the human immune system offers great efficiency in the detection and elimination of pathogens. All immune mechanisms evolve interactively in concordance with human environment and history. Key Concepts: Human immune system is a multilayered structure that includes various mechanisms. Basic cellular mechanisms may contribute to immune defence. Specialised immune mechanisms are subdivided into innate and adaptive based on the receptors used for antigen recognition. Immune mechanisms comprise those based on humoral factors and those based on cells. Most immune defence mechanisms work semiautonomously in interaction with other systems. Immune mechanisms can be controlled at the body level by hormones and other mediators. Immune receptors evolve by gene duplication, balancing selection, changes in coding and regulatory sequences, and other mechanisms. Human immune system continues to evolve. Individual immune mechanisms evolve in interaction with other mechanisms and basic cellular machinery.