Which type of immunity involves a quick response from the immune system upon re-exposure to a pathogen?

Adaptive immunity is characterized by its ability to recognize and respond more rapidly to pathogens that the body has encountered before. When the immune system is exposed to a specific pathogen, it creates a memory of that encounter in the form of memory cells. Upon re-exposure to the same pathogen, these memory cells enable a swift and robust immune response, often preventing the onset of illness.

This feature distinguishes adaptive immunity from other types. Innate immunity, for instance, is the body's first line of defense and responds to all pathogens in a generalized way, lacking the specificity and memory component of adaptive immunity. Natural immunity refers to the immunity acquired through natural exposure to pathogens, but it does not necessarily involve the rapid reactivation seen in adaptive immunity. Cell-mediated immunity is a component of adaptive immunity that specifically involves T cells targeting infected cells, but it is a subset rather than the overall concept of adaptive immunity.