Ilya Ilyich Mechnikov: life and work

Abstract

On May 15, 2020, we celebrated the 175th 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. The article discusses the main milestones in the life and scientific work of Ilea Metchnikoff. Ilya Metchnikoff working originally in Russia, later in Italy, and  then at the Pasteur Institute in Paris. His initial observations on phagocytic cells were made in the marine biology laboratories in Messina on starfish. Ilya Ilyich, as a result of observations of intracellular digestion in sponges, coelenterates and some flatworms, stretches a thread between phagocytosis and evolution (phagocytella), inflammation, cellular immunity, regeneration and the aging process. This thread is the quintessence of his work. Metchnikoff devoted many years to studying the comparative development of the embryonic layers of lower 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. According to Metchnikoff, the hypothetical ancestor of multicellular organisms was similar to phagocytella. 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. It is very importantly to aware that cells and microorganisms according to Metchnikoff were taken up by an active process, involving living, and not only dead organisms 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 revealing of the role of phagocytosis in inflammation. He observed diapedesis through vessel walls and aggregation of leukocytes at sites of inflammation. Phagocytosis not only destructs of infectious microbes but uptake of host cells, e.g. erythrocytes, from diverse species as well. More broadly phagocytes are the cells which preserving the integrity and defining the identity of the organism. 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. Such degenerative changes, he believed were nearly always premature and potentially prevented by procedures directed against the putrefactive bacteria. 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’s ageing theory. Metchnikoff’s hypothesis from the very beginning met with fierce criticisms. It required 25 years of in tense effort to achieve recognition of the phagocytosis theory. This struggle culminated in 1908 with the awarding of the Nobel Prize

DOI: 10.5281/zenodo.4038869