Natural active immunity arises from:

Natural active immunity arises from:

• A. Infection
• B. Vaccination
• C. Serum injection
• D. Placental transfer

Answer: (A)

Natural active immunity is produced when the body encounters a real pathogen and mounts its own immune response, creating memory cells that ensure quicker, stronger protection upon future exposures. When infection occurs, B cells generate specific antibodies and memory B cells, while T cells also activate to target the pathogen; this lasting memory is what keeps you protected long-term. Vaccination also causes active immunity, but it’s artificial because it introduces a vaccine antigen rather than a natural infection. Serum injection provides antibodies directly, giving immediate but temporary protection without stimulating the body to make its own memory. Placental transfer delivers maternal antibodies to the fetus (natural passive immunity) but does not involve the offspring producing its own immune memory.

Natural active immunity is produced when the body encounters a real pathogen and mounts its own immune response, creating memory cells that ensure quicker, stronger protection upon future exposures. When infection occurs, B cells generate specific antibodies and memory B cells, while T cells also activate to target the pathogen; this lasting memory is what keeps you protected long-term.

Vaccination also causes active immunity, but it’s artificial because it introduces a vaccine antigen rather than a natural infection. Serum injection provides antibodies directly, giving immediate but temporary protection without stimulating the body to make its own memory. Placental transfer delivers maternal antibodies to the fetus (natural passive immunity) but does not involve the offspring producing its own immune memory.