Which immune system component builds memory of pathogens for a more effective response?

The adaptive immune system is responsible for building memory of pathogens, which allows for a more effective and faster response upon subsequent exposures to the same pathogen. This system includes specialized cells, such as B cells and T cells, that can remember previous infections. When the adaptive immune system encounters a pathogen for the first time, it responds by producing specific antibodies and activating T cells tailored to that pathogen. After the infection is cleared, some of these B and T cells become memory cells, which persist long after the initial infection has resolved.

Upon re-exposure to the same pathogen, these memory cells quickly recognize it and initiate a stronger and more efficient immune response compared to the first encounter. This is the principle behind vaccination, where a harmless version of a pathogen is introduced to stimulate the adaptive immune system and generate memory without causing disease.

In contrast, the innate immune system provides immediate but non-specific defense against pathogens and does not have the capacity to remember past infections. Cell-mediated immunity and humoral immunity are both facets of the adaptive immune system, but they do not directly pertain to the overall memory function of recognizing and responding to previously encountered pathogens.