Passive immunity can be achieved by which method?

• A. Exposing the body to antigens
• B. Injecting attenuated infectious agents
• C. Giving preformed antibodies
• D. Gradual exposure to the antigen

Answer: (C)

Passive immunity gives immediate protection by transferring ready-made antibodies to the recipient. Since the antibodies come from another immune source, the recipient’s own immune system doesn’t need to respond, and there’s little or no lasting memory—the protection fades as the antibodies are cleared from the body. This is achieved by giving preformed antibodies such as immune globulins, antiserum, or therapeutic monoclonal antibodies, or by maternal transfer of antibodies to the newborn.

The other options rely on the recipient’s immune system to respond to an antigen and develop active immunity, which takes time and creates memory for future encounters. Exposing the body to antigens or giving attenuated pathogens both stimulate the host to mount its own immune response, rather than providing immediate, passively acquired antibodies.