Innate immune system.
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 (which is only found in vertebrates), that is specific for single pathogens, it does not confer long-lasting or protective immunity to the host. It provide immediate defense against infection and is the dominant immune system found in plants, fungi, insects, and in primitive multicellular organisms.
- 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 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.
- Acting as a physical and chemical barrier to infectious agents.The epithelial surfaces form a physical barrier that is very impermeable to most infectious agents. In the gastrointestinal and respiratory tract, movement due to peristalsis or cilia, respectively, helps remove infectious agents. Also, mucus traps infectious agents, produced by Goblet cells (in picture).
(Source: Peter Parham, The Immune System; wikipedia).