Every day we are exposed to different viruses, fungi or bacteria, some of which can be harmful to our health. However, we rarely get sick, and this is due to the continuous and correct functioning of our immune system in which cells such as white blood cells or leukocytes participate. These travel through our blood vessels and tissues to feed on bacteria and damaged or dead cells through a digestive process called phagocytosis . In addition, macrophages, a type of leukocyte, are able to attract other white blood cells to the site of infection that will help defend against the pathogen.
Virtually all animals have phagocytic defender cells, and many single-celled organisms also possess the ability to phagocytic. A clear example of this are amoebae, microorganisms that move through soil and water in search of bacteria and yeasts to feed on by phagocytosis. In fact, some species of amoebae , such as Dictyostelium discoideum , group together to form a slug-like multicellular organism when faced with adverse environmental conditions such as lack of food. Inside said slug, and as if it were an immune system, cells called sentinels circulate that engulf bacteria and sequester toxins .
A common origin?
Although the mechanism of formation of a multicellular body in amoebae differs completely from animal embryogenesis, the molecular processes of development and communication between cells are common between amoebae and animals. In fact, in evolutionary terms, amoebas are very close to the common ancestor of professional protozoa and phagocytes such as the cells of our immune system . It has even been proposed that amoebas could be the ancestors of our white blood cells, since the molecular mechanisms they use to recognize and digest bacteria are very similar to those used by our macrophages.
Due to their great resemblance to white blood cells, some researchers use amoebas as a model to study defense mechanisms against infections such as bacteria that cause tuberculosis, salmonellosis, Legionnaires’ disease or cholera, among others. . Thus, whether or not they are our ancestors, amoebas are of great help to us in understanding the functioning of our immune system and how we defend ourselves against pathogens.
Elena Cardenal is a researcher in the Biochemistry department of the University of Geneva (Switzerland)
