ⓘ Phagocyte

                                     

ⓘ Phagocyte

Phagocytes are cells that protect the body by ingesting harmful foreign particles, bacteria, and dead or dying cells. Their name comes from the Greek phagein, "to eat" or "devour", and "-cyte", the suffix in biology denoting "cell", from the Greek kutos, "hollow vessel". They are essential for fighting infections and for subsequent immunity. Phagocytes are important throughout the animal kingdom and are highly developed within vertebrates. One litre of human blood contains about six billion phagocytes. They were discovered in 1882 by Ilya Ilyich Mechnikov while he was studying starfish larvae. Mechnikov was awarded the 1908 Nobel Prize in Physiology or Medicine for his discovery. Phagocytes occur in many species, some amoebae behave like macrophage phagocytes, which suggests that phagocytes appeared early in the evolution of life.

Phagocytes of humans and other animals are called "professional" and "unprofessional", depending on how effective they are at phagocytosis. Professional phagocytes include many types of white blood cells. The main difference between professional and non-professional phagocytes is that the professional phagocytes have molecules called receptors on their surfaces that can detect harmful objects, such as bacteria that do not normally occur in the body. Phagocytes are crucial in fighting infections, as well as in maintaining healthy tissues by removing dead and dying cells that have reached the end of their lives.

During infection, chemical signals attract phagocytes to places where the pathogen to enter the body. These chemicals may come from bacteria or from other phagocytes already present. In phagocytes move a method called chemotaxis. When phagocytes come into contact with bacteria, receptors on the surface of phagocytes will be tied to them. This binding will lead to the uptake of bacteria by phagocytosis. Some phagocytes kill the ingested pathogen with oxidants and nitric oxide. After phagocytosis, macrophages and dendritic cells can also participate in antigen presentation, the process in which a phagocyte moves parts of the ingested material back to its surface. This material is then shown to other cells of the immune system. Some phagocytes then travel to the bodys lymph nodes and display the material to white blood cells called lymphocytes. This process plays an important role in building immunity, many pathogens have evolved methods to evade attacks by phagocytes.