Naturally acquired passive immunity occurs when

• A. Antibodies are from mother to fetus
• B. When your body makes antibodies
• C. Vaccination
• D. Injecting antibiotics

Answer: (A)

Natural passive immunity occurs when antibodies are transferred from the mother to the child, giving immediate protection without the infant having to make those antibodies itself. The key mechanism is maternal IgG crossing the placenta during pregnancy, and after birth, protective IgA from breast milk helps shield mucosal surfaces. This protection is temporary because the maternal antibodies fade over time and the infant doesn’t develop its own antibody-producing memory from this transfer. In contrast, making antibodies or vaccination involve the individual’s own immune system producing responses (active immunity), and antibiotics do not confer immunity.