Cambridge O Level Biology · Syllabus 5090 · Disease and Immunity
Passive Immunity
What is Passive Immunity?
Short-term defence against a pathogen provided by antibodies obtained from another individual. Because the antibodies are ready-made, protection is immediate, but the recipient's own lymphocytes have not responded and no corresponding memory cells are formed, so protection declines as the transferred antibodies are broken down.
This definition is part of the Disease and Immunity chapter in Cambridge O Level Biology.
Common mistakes with Passive Immunity
- "Vaccination gives passive immunity." A vaccine supplies antigens, not antibodies, and your own lymphocytes do the work. Write Vaccination stimulates active immunity: the person's own lymphocytes produce antibodies and memory cells are formed.
- "Passive immunity produces memory cells." The recipient's own lymphocytes never met the antigen, so there is nothing to remember. Write Passive immunity gives immediate protection but no memory cells are formed, so protection is short-term.
Questions students ask about Passive Immunity
Is passive immunity ever given deliberately?
Yes, ready-made antibodies can be given as a medical treatment when immediate protection is needed and there is no time to build a response. The syllabus examples you must know are the natural ones — antibodies crossing the placenta and antibodies in breast milk — and both share the same limitation: immediate protection, no memory cells, short duration.