Basic principles - Adpative immunity - IMMUNOLOGY

The mammalian immune response can be divided into two branches: innate immunity and adaptive immunity. Innate immunity is an immediate, non-specific response that cannot perfectly distinguish different pathogens. Furthermore, once the innate immune response is depleted, there is no memory left of the encounter with the pathogen. This is when adaptive immunity becomes crucial. Adaptive immunity recognizes specific components of specific pathogens and retains the information of the encounter.
This is due to the presence of billions of cells circulating, lymphocytes of adaptive immunity (often simply referred to as lymphocytes, being far more numerous and more important than those of innate immunity).