The innate immune system comprises the cells and mechanisms that defend the host from infection by other organisms, in a non-specific manner. This means that the cells of the innate system recognize, and respond to, pathogens in a generic way, but unlike the adaptive immune system, 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.
The major functions of the vertebrate innate immune system include:
Recruiting immune cells to sites of infection and inflammation, through the production of chemical factors, including specialized chemical mediators, called cytokines.
Activation of the complement cascade to identify bacteria, activate cells and to promote clearance of dead cells or antibody complexes.
The identification and removal of foreign substances present in organs, tissues, the blood and lymph, by specialized white blood cells.
Activation of the adaptive immune system through a process known as antigen presentation.
