Metchnikoff’s scientific ideas and modernity

Abstract

On May 15, 2015, we celebrated the 170th anniversary of the Ilya Metchnikoff, the author of the hypothesis about parenchymella, the father of cellular immunology and inflammation theory, founder of gerontology, aging and longevity science. He was at the vanguardof the probiotics use in elderly therapy. In his work “Essaysabout the Origin of Species” Metchnikoff critically reviewed the history of evolution ideas development.He rejected the idea that the struggle for existence occurs primarily among member of the same species and is the starting place of the new species development and complexity. There is still dispute about the mechanisms of speciation about whether evolution is punctuated rather than smoothly gradual about the role of natural selection in the new species creation and generation of life complexity.

Metchnikoff devoted many years to studying the comparative development of the embryonic layers of lower animals. He proved that in their development the lower animals follow a plan similar to that of the higher animals. Ilya Ilyich demonstrated that cnidarians gastrulate by introgression of cells which move from the blastula wall into the interior blastocoel and formed parenchymella or phagocytella. Also he assumed that invagination arose as a secondary mechanism of gastrulation. In the paper we discussed the contemporary views about parenchymella and multicellular animal origin. Metchnikoff is rightly famous for his theories of phagocytosis and inflammation. He proposed that macrophages evolved first to regulate development, and that these function are the stage for their evolution into the cells of innate immunity, He revealed of phagocytic cells functions in clearing infections and inflammation. He described of phagocytosis as an active process and its role in host defence, across a wide range of organisms digestion. It is very importantly that cells and microorganisms were taken up by an active process, involving living, and not only dead organisms. He demonstrated killing by leukocytic enzymes (‘cytase’). The humoral theory claimed that the phagocytes caused the spread of disease in the body and thus would harm the host, rather than defend it, against bacterial invasion. Metchnikoff devoted much of his scientific work to the development and defense of the role of phagocytosis in inflammation. He observed diapedesis through vessel walls, aggregation of leukocytes at sites of inflammation. Phagocytosis not only destructs of infectious microbes including bacteria, spirochaetes and yeasts, but uptake of host cells, e.g. erythrocytes, from diverse species as well. More broadly phagocytes are the cellswhich preserving the integrity and defining the identity of the organism. In the article we summarized the new data and concepts about the development and functions of phagocytes in innate immunity, inflammation, oncogenesis and tissues repair. Metchnikoff believed that the disabilities of old age are the work of phagocytes transformed from defenders against infection into destroyers of tissues by autotoxins derived from putrefactive bacteria residing in the colon. According to his concept, senile degeneration of the nervous system, for example, is the work of macrophages induced by autotoxins cause them to atrophy. Such degenerative changes, he believed were nearly always premature and potentially prevented by procedures directed against the putrefactive bacteria. Metchnikoff hypothesized that diminishing the number of putrefactive bacteria in the gut with probiotics could prolong life. Until recently it was generally assumed that phagocytic removal of neurons occurs only after neuronal death. But now it has been convincingly proved that stressed but viable neurons reversibly exposed the "eat-me" signal leading to their phagocytosis by microglia; this neuronal loss was prevented in the absence of microglia. As a result these data breathe life into the Metchnikoff ageing theory.