Which statement best describes adaptive immunity?

Which statement best describes adaptive immunity?

• A. Relies on normally present body functions
• B. Involves only cellular immunity
• C. Response is similar for each exposure
• D. Specificity for each individual pathogen

Answer: (D)

Adaptive immunity is defined by its ability to recognize and respond to specific antigens on pathogens. It uses B cells and T cells that have receptors for particular molecules, so the response is directed toward a given pathogen rather than a general invader. This specificity arises as those lymphocytes that bind the antigen are selectively activated and proliferate, producing antibodies and T-cell–mediated attacks tailored to the invader. Importantly, adaptive immunity also forms memory cells, so subsequent exposures to the same pathogen provoke a faster and stronger response. This focus on precise antigen recognition and memory distinguishes adaptive immunity from nonspecific, innate defenses.

Adaptive immunity is defined by its ability to recognize and respond to specific antigens on pathogens. It uses B cells and T cells that have receptors for particular molecules, so the response is directed toward a given pathogen rather than a general invader. This specificity arises as those lymphocytes that bind the antigen are selectively activated and proliferate, producing antibodies and T-cell–mediated attacks tailored to the invader. Importantly, adaptive immunity also forms memory cells, so subsequent exposures to the same pathogen provoke a faster and stronger response. This focus on precise antigen recognition and memory distinguishes adaptive immunity from nonspecific, innate defenses.