What is the definition of active immunity?

What is the definition of active immunity?

• A. The immediate response of the immune system
• B. Immunity acquired through vaccination
• C. The stimulation of the immune system to produce antigen-specific immunity
• D. Immunity gained through passive transfer of antibodies

Answer: (C)

Active immunity is defined as the stimulation of the immune system to produce antigen-specific immunity. This type of immunity occurs when an individual's immune system is exposed to a pathogen and responds by producing antibodies and memory cells specifically tailored to that pathogen. This can happen through natural infection or through vaccination, where a harmless form or component of the pathogen is introduced to provoke an immune response.

When the immune system recognizes the antigen, it activates different types of immune cells, leading to a robust and long-lasting defense against future infections by the same pathogen. This development of memory cells ensures that if the same pathogen invades again, the immune system is prepared to respond more rapidly and effectively.

In contrast, immediate responses of the immune system (as mentioned in the first option) refer more to innate immunity, which acts quickly but is not antigen-specific. Vaccination refers to a method of acquiring active immunity, but it is the act of stimulation and the resulting immune response that define active immunity more comprehensively. Passive transfer of antibodies provides temporary immunity and does not involve the immune system's own response, distinguishing it from active immunity.