The foremost function of the immune system is to protect organisms from exogenous agents that cause infection using layered defenses, namely the physical barriers, the innate immune system, and, on the last line of defense, the adaptive immune system. Each of the three has a critical role to play if the organism is to be protected from harmful pathogens such as bacteria and viruses. Although current research has revealed that both innate and adaptive systems work in a flexible continuum, this paper will focus attention on elucidating their differences in addition to shedding light on the organization of the immune system and the role each part plays to protect organisms from infection.
The first difference, according to Palm & Medzhitov, is that while innate immunity only provides an immediate non-specific response once a pathogen breaches the physical barriers and enters the organism, the adaptive immune system provides a pathogen and antigen-specific response. This implies that while innate immunity may be compromised by the invading microorganisms due to the non-specific response, the adaptive immunity adapts its response when the microorganisms have violated the barriers to improving their recognition of the microorganisms. The second difference is that while innate immunity is found in all plants and animals, adaptive immunity is only found in jawed vertebrates.
The third distinctive difference between the two immune systems is that while exposure to pathogens in innate immunity leads to the immediate maximal response, researchers have observed a lag time between exposure to pathogens and maximal response in the adaptive immune system. The fourth difference is that “…in innate immunity, signaling is through germ-like receptors of limited repertoires that respond by pattern recognition of exogenous agents and antigens while the adaptive immune system is composed of cells bearing rearranged cell surface receptors, generating an almost unlimited diversity of recognition response elements”.
Lastly, it has been noted that while the innate immune system does not form any immunological memory upon exposure to pathogens, the adaptive immune system forms a distinctive immunological memory upon exposure. The immunological memory creates an enabling environment for the adaptive immunity to mount speedy and stronger attacks each time the same microorganism enters the organism.