At the first signs of an infection or an injury, the innate immune system is the one that kicks into action first to try and stave off rapid bacteria growth. It is less of specific response — the innate system that can sense patterns that could warrant an immune response.
One of the most important elements when it comes to “sensing danger” by the innate immune system is the presence of these pattern recognition receptors, also known as PRRs — proteins which can identify molecules in pathogens as well as molecules that are released due to damaged cells. These patterns are more specifically known as damage-associated molecular patterns (DAMPs) that are caused by injury, and pathogen-associated molecular patterns (PAMPs) that respond to infections.
The adaptive immune system is secondary and is more specific at targeting the pathogen that it has “learned” from previous encounters. But while the innate immune system is not as effective in identifying individual threats (antigen-specific), it can detect what doesn’t belong there. Furthermore, many microorganisms recognized by innate response are due to repeating patterns in terms of structure, which differ from host cells — which is important in preventing healthy cell destruction when fighting off a threat.
