The innate immune system is the host’s first line of defense against harmful pathogens. It is composed of various physical, chemical, and cellular barriers that work together to protect the body from infection and attack invading pathogens. 

Characteristics of the innate immune system include the following:

• Rapid response: The components of the innate immune system respond to infection rapidly within minutes or hours unlike the adaptive immune system, which can take days or weeks to mount a specific response.
• Non-specificity: The innate immune system acts against all types of pathogens in the same way. 
• No immunological memory: The innate immune system does not develop immunological memory, which means it does not remember previous infections and is hence incapable of protection against reinfection.