Answer: Receiving pre-formed antibodies from another source (e.g., antiserum, breast milk).
- A Becoming vaccinated with a weakened or killed pathogen preparation administered each season
- B Receiving pre-formed antibodies from another source (e.g., antiserum, breast milk)
- C Recovering naturally after successfully surviving a prior natural infection episode
- D Taking a long prescribed course of broad-spectrum antibiotic medication
Correct answer: B. Receiving pre-formed antibodies from another source (e.g., antiserum, breast milk)
Explanation: Passive immunity: receiving ready-made antibodies from another source. Examples: maternal antibodies across placenta (IgG), breast milk (IgA), antivenom/antitoxin injections. It is immediate but short-lived (no memory cells formed).
An antibody is Y-shaped, with two identical antigen-binding sites at the tips of the variable regions - each shaped to recognise one specific antigen - while the constant (Fc) region at the base is recognised by immune cells to trigger further responses.
Concept context
Innate and adaptive immunity, B cells, T cells, antibodies, vaccines, and immune disorders. Critical for NEET.