Active immunity is characterized by which of the following?

• A. Active Immunity
• B. Passive Immunity
• C. Innate Immunity
• D. Adaptive Immunity

Answer: (A)

Active immunity is defined by the body's own immune system actively responding to an antigen and forming immunological memory. When you’re exposed to a pathogen or receive a vaccine, B and T cells mount a specific response, producing antibodies and generating memory cells that confer long-lasting protection. This contrasts with passive immunity, where antibodies are simply transferred from another source and no lasting memory is formed. Innate immunity is the non-specific first line of defense that acts quickly but without antigen-specific memory, while adaptive immunity refers to the specific, learned immune responses that can be either active or passive. The key feature of active immunity is that the host actively generates a targeted, memory-based response.