The innate immune system is an ancient host defense mechanism found in almost every multicellular organism from plants to humans.
In invertebrates it is the sole mechanism of defense against pathogens but in higher vertebrates constitutes the first line of defense.
The role of the innate immune system is not an insignificant one; not only must it discriminate between self and non-self as well as
distinguish between pathogenic and non-pathogenic microbes, it also plays an important role in triggering and optimizing the adaptive immune response.
This remarkable system allows an immediate non-specific response against microorganisms whereas the adaptive immunity mounts a specific
response against the invading pathogen during the late phase of the infection.
(from CliniSciences newsletter 06/10/08)