During the second half of the 19th century, doctors and biologists of that time actively studied the role of pathogenic microorganisms in the development of infectious diseases, as well as the ability to form an artificial immunity to them. These studies led to the study of facts about the body's natural defense against infections. Pasteur proposed to the scientific community the idea of the so-called "exhausted strength." According to this theory, viral immunity is a condition in which the human body is not a beneficial nutrient medium for infectious agents. However, this idea could not explain a number of practical observations.
Mechnikov: cellular theory of immunity
This theory appeared in 1883. The creator of the cellular theory of immunity relied on the teachings of Charles Darwin and was based on the study of digestion processes in animals, which are located at various stages of evolutionary development. The author of the new theory found some similarities in the intracellular digestion of substances in endoderm cells, amoebas, tissue macrophages and monocytes. Actually, the well-known Russian biologist Ilya Mechnikov created the cellular theory of immunity. His work in this area continued for a long time. They started back in the Italian city of Messina, in which the microbiologist observed the behavior of sea fleas and starfish larvae .
The pathologist found that the wandering cells of the observed creatures are surrounded by foreign bodies, and then absorb them. In addition, they dissolve and then destroy those tissues that the body no longer needs. He put a lot of effort into developing his concept. The creator of the cellular theory of immunity introduced, in fact, the concept of “phagocytes”, derived from the Greek words “phages” - to eat and “kitos” - a cell. That is, the new term literally meant the process of eating cells. The scientist came to the idea of such phagocytes a little earlier when he studied intracellular digestion in various cells of connective tissue in invertebrates: sponges, amoebas and others.
In representatives of the higher fauna, the most typical phagocytes can be called white blood cells, that is, white blood cells. Later, the creator of the cellular theory of immunity proposed to divide such cells into macrophages and microphages. The correctness of this division was confirmed by the achievements of the scientist P. Ehrlich, who differentiated different types of white blood cells by staining. In his classic works on the pathology of inflammation, the creator of the cellular theory of immunity was able to prove the role of phagocytic cells in the elimination of pathogens. Already in 1901, his fundamental work on the immunity to infectious diseases entered the world. In addition to Ilya Mechnikov himself, I.G. made a significant contribution to the development and dissemination of the theory of phagocytic immunity. Savchenko, F.Ya. Chistovich, L.A. Tarasevich, A.M. Birch, V.I. Isaev and a number of other researchers.