The workings of the immune system, in philosophical terms, follow integrity principle, which I regard as a sum of homeostatic (integrity preservation) and analytic (integration) functions of tissues within an organism. It states that damage of particular tissue is followed by restitution of integrity by interplay of positive and negative feedback loops. Such principle is seen as a driving force for evolution of the immune system from primordial integrity-repair mechanism. The most common disruption of integrity in vertebrates is caused by microorganisms, which can initiate the immune response. Natural selection favored the host/commensal rather than host/pathogen relationship, and consequently tolerance towards commensals co-evolved with the initiation of the immune response against pathogens (including host tolerance). However, the necessity of developing commensal tolerance by the immune system dissociated (evolutionarily) its analytic part (the afferent arm; started by disruption of tissue integrity) from its restorative part (the efferent arm) in space and time . The renewal process includes bio-destruction of an intruder and restoration of integrity. The analysis - renewal separation in space and time further necessitated evolution of characteristics such as immune specificities, chemotaxis and multicellular crosstalk. Due to various selective pressures, the immune systems of vertebrates exhibit diverse communications between cells of the afferent and efferent arms of the immune response. Diversification of the immune repertoire, in turn, facilitated the establishment of long-term memory. These mechanisms work to protect commensals (potential symbionts), reject harmful pathogens and neglect the rest of microbiota. Therefore, the role of the immune system is to dynamically maintain the integrity of a being, in a common effort with other tissues and with a little help from our tiny friends (commensals).
Proceedings of the 3rd International Scientific and Practical Conference.
"Immuniphysiology: Autoimmunity in health and disease. Contribution to predictive and preventive medicine" Moscow October 1-3, 2012.
Editors A.B. Poletaev, S.V. Skurydin. PP:64-76.
Posted with permission from the Organizing committee
