Innate Immunity

Innate immunity encompasses a host organism's nonspecific barriers to microbes. Innate immunity consists of a first line of defense, and a second line of defense.

First Line of Defense
The first line of defense is composed of physical and chemical barriers and the host's normal flora. In general, it encompasses the surfaces of a host organism. The first line of defense functions in preventing entry of microbes.

Second Line of Defense
The second line of defense is composed of chemical and biological barriers, which constitute a nonspecific response. The second line of defense functions in preventing disease.