Which immune response is characterized by a faster reaction upon second exposure to an antigen?

The adaptive immune response is the correct choice because it develops a memory for specific antigens after the initial exposure. When the body encounters a particular pathogen, the adaptive immune system generates specialized cells, such as memory T cells and B cells, that remember the antigen. Upon subsequent exposures to the same antigen, these memory cells enable a much quicker and more effective immune response compared to the first encounter. This rapid reaction is crucial for preventing reinfection and is the underlying principle of how vaccinations work, as they prepare the adaptive immune system for future encounters with the actual pathogen.

Other immune responses, such as the innate immune response, do not develop memory and react similarly to all pathogens regardless of previous exposures. The inflammatory response is a part of both innate and adaptive responses but does not specifically provide a faster reaction upon later exposures. The allergic response involves an exaggerated reaction to benign substances and is not characterized by a faster immune response to previously encountered pathogens.