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The innate immune system, also known as the nonspecific immune system, is an important subsystem of the overall immune system that comprises the cells and mechanisms that defend the host from infection by other organisms. The cells of the innate system recognize and respond to pathogens in a generic way, but, unlike the adaptive immune system (which is found only in vertebrates), it does not confer long-lasting or protective immunity to the host. Innate immune systems provide immediate defense against infection, and are found in all classes of plant and animal life. They include both humoral immunity components and cell-mediated immunity components. The innate immune system is an evolutionarily older defense strategy, and is the dominant immune system found in plants, fungi, insects, and primitive multicellular organisms.〔.〕 The major functions of the vertebrate innate immune system include: * Recruiting immune cells to sites of infection, through the production of chemical factors, including specialized chemical mediators, called cytokines * Activation of the complement cascade to identify bacteria, activate cells, and promote clearance of antibody complexes or dead cells * The identification and removal of foreign substances present in organs, tissues, the blood and lymph, by specialised white blood cells * Activation of the adaptive immune system through a process known as antigen presentation * Acting as a physical and chemical barrier to infectious agents. ==Anatomical barriers== Anatomical barriers include physical, chemical and biological barriers. The epithelial surfaces form a physical barrier that is impermeable to most infectious agents, acting as the first line of defense against invading organisms.〔 Desquamation of skin epithelium also helps remove bacteria and other infectious agents that have adhered to the epithelial surfaces. Lack of blood vessels and inability of the epidermis to retain moisture, presence of sebaceous glands in the dermis provides an environment unsuitable for the survival of microbes.〔 In the gastrointestinal and respiratory tract, movement due to peristalsis or cilia, respectively, helps remove infectious agents.〔 Also, mucus traps infectious agents.〔 The gut flora can prevent the colonization of pathogenic bacteria by secreting toxic substances or by competing with pathogenic bacteria for nutrients or attachment to cell surfaces.〔 The flushing action of tears and saliva helps prevent infection of the eyes and mouth.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「innate immune system」の詳細全文を読む スポンサード リンク
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