Innate immunity is the first line of defense against infections

Innate immunity is the first line of defense against infections. It is oldest mechanism of defense against microbes. Innate immunity is present in all multicellular organisms. Innate in many cases can also eliminate microbes.It increases susceptibility to infections when the adaptive immune system is intact. Innate immunity stimulates the adaptive immune responses and make them active to act against adaptive immune responses.
Innate immunity can only recognize microbial pathogens. It cannot recognize non mammalian pathogens as adaptive immunity do.
The microbial target of innate immunity is called microbial pattern.These are the conserved structures and the receptors that bind to these receptors are called pattern recognition receptors. These receptors are present on the host cells. These receptors will recognize the different patterns of viruses, gram positive bacteria, gram negative bacteria,fungi.That’s why innate immunity can distinguish between self and non self.