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Non-specific immunity, or innate immunity, is the immune system with which you were born, made up of phagocytes and barriers. Phagocytosis , derived from the Greek words phagein , meaning to eat, kytos or cell, and “osis” meaning process, was first described by Élie Metchnikoff , who won the Nobel Prize 100 years ago.
Some products of the coagulation system can contribute to non-specific defenses via their ability to increase vascular permeability and act as chemotactic agents for phagocytic cells. In addition, some of the products of the coagulation system are directly antimicrobial.
Mechnikov proposed that phagocytes were a primary defense against invading organisms. [15] In 1903, Almroth Wright discovered that phagocytosis was reinforced by specific antibodies that he called opsonins, from the Greek opson, "a dressing or relish". [19]
Innate immune defenses are non-specific, meaning these systems respond to pathogens in a generic way. [19] This system does not confer long-lasting immunity against a pathogen. The innate immune system is the dominant system of host defense in most organisms, [2] and the only one in plants. [20]
Phagocytosis is one main mechanisms of the innate immune defense. It is one of the first processes responding to infection, and is also one of the initiating branches of an adaptive immune response. Although most cells are capable of phagocytosis, some cell types perform it as part of their main function. These are called 'professional phagocytes.'
Each antibody recognizes a specific antigen unique to its target. By binding their specific antigens, antibodies can cause agglutination and precipitation of antibody-antigen products, prime for phagocytosis by macrophages and other cells, block viral receptors, and stimulate other immune responses, such as the complement pathway .
Cell-mediated immunity is directed primarily at microbes that survive in phagocytes and microbes that infect non-phagocytic cells. It is most effective in removing virus-infected cells, but also participates in defending against fungi, protozoans, cancers, and intracellular bacteria.
The mononuclear phagocyte system is part of both humoral and cell-mediated immunity. The mononuclear phagocyte system has an important role in defense against microorganisms, including mycobacteria, fungi, bacteria, protozoa, and viruses. Macrophages remove senescent erythrocytes, leukocytes, and megakaryocytes by phagocytosis and digestion.