What is active immunity?

What is active immunity?

• A. The immune response to an attack by a foreign substance
• B. The autoimmune response to a chronic infection
• C. The inflammatory response
• D. The transfer of immunity from one animal to another

Answer: (A)

Active immunity happens when the body’s own immune system responds to a foreign substance, such as a pathogen or vaccine antigen, by activating B and T cells and building memory. This exposure triggers an adaptive, antigen-specific defense that remains ready for future encounters, providing long-lasting protection. The description of responding to a foreign substance reflects this process, since it centers on the body's own activation of adaptive defenses after exposure. This differs from passive immunity, which is simply the transfer of antibodies from another source and is temporary; the inflammatory response, which is part of innate immunity and not specifically memory-based; and autoimmune responses, which misdirect the immune system against the body's own tissues.

Active immunity happens when the body’s own immune system responds to a foreign substance, such as a pathogen or vaccine antigen, by activating B and T cells and building memory. This exposure triggers an adaptive, antigen-specific defense that remains ready for future encounters, providing long-lasting protection. The description of responding to a foreign substance reflects this process, since it centers on the body's own activation of adaptive defenses after exposure. This differs from passive immunity, which is simply the transfer of antibodies from another source and is temporary; the inflammatory response, which is part of innate immunity and not specifically memory-based; and autoimmune responses, which misdirect the immune system against the body's own tissues.