Natural active immunity occurs when exposure to a live pathogen leads to what?

Natural active immunity occurs when the body is exposed to a live pathogen, which leads to the activation of the immune system. In this process, specific immune cells recognize the foreign pathogen and initiate a response by producing antibodies. This immune response not only helps to eliminate the pathogen but also leads to the formation of memory cells, which provide long-term immunity against future infections from the same pathogen.

The key aspect of natural active immunity is that the body itself generates the antibodies in response to the pathogen. This differs from passive immunity, where antibodies are transferred from another individual, or from immediate antibody transfer that does not involve the immune system's own response. Therefore, the generation of antibodies by the immune system in response to a pathogen is fundamental to the concept of natural active immunity. This immune response is critical for the establishment of lasting protection against infections.