The non-specific, first line of defense against a potential pathogen in the immune system.
The immune system is the first line of defense against pathogens. The most obvious example is the skin. However, the two main differences between the Innate and Adaptive immune responses are:
Innate immunity is non-specific
Innate immunity does not confer long-term immunity
For example, Phagocytes are non-specific innate immune cells which engulf pathogens or particles. They are non-specific because they do not need to recognize their target.
An example of a Phagocyte are the Dendritic cells , which play a key role in antigen presentation. They destroy the potential pathogen and display part of its antigen outside its membrane.
This links the innate immune system to the adaptive as antigen presentation leads to the production of the correct antibodies and also memory cells which remember the pathogen, thus adaptive immunity results in long-term immunity.