What best defines natural immunity?

Natural immunity is best described as immunity that is developed from environmental exposure, primarily through the body's own immune responses to pathogens it encounters in nature. This form of immunity occurs when the immune system is activated by pathogens such as viruses, bacteria, and other foreign invaders that enter the body. Upon exposure, the immune system produces antibodies and memory cells that recognize the pathogen, enabling the body to respond more effectively upon subsequent exposures.

While genetic inheritance does play a role in determining an individual's overall immune capacity and predisposition to certain diseases, it does not define the process by which immunity is acquired. Natural immunity is characterized by the active engagement of the immune system in response to real-world exposures rather than inherited traits. Consequently, acquired immunity from vaccinations, immunity developed from environmental exposure, and immunity transferred from other individuals all differ from the concept of natural immunity, as they do not involve the body's direct encounter with pathogens acquired through typical environmental interactions.