Distinguish between active and passive immunity with examples. Explain the principle of vaccination.

1. 1 · Define both. Active immunity: the host makes its own antibodies after exposure to antigens. Passive immunity: ready-made antibodies are given.
2. 2 · Compare.
   • Active: slow to develop, long-lasting, memory cells form.
   • Passive: immediate, short-lived, no memory.
3. 3 · Give examples. Active: natural infection, vaccination. Passive: IgA in colostrum, antibodies through the placenta, tetanus antitoxin, snake antivenom.
4. 4 · Explain vaccination. Vaccine (antigenic proteins or inactivated or weakened pathogen) causes antibody production and memory B and T cells; on real infection, a quick massive response neutralises the pathogen.
5. 5 · Add the modern method. Recombinant DNA technology makes antigens in bacteria or yeast for large-scale vaccines, e.g. hepatitis B vaccine from yeast.
6. 6 · Link to daily life. Colostrum feeding and the immunisation schedule protect Indian children.
7. 7 · Close in one line. So vaccines build active immunity in advance, while passive immunity is an emergency shield.

Scoring tip: Name the antibody in colostrum (IgA) and say that vaccination works because of memory. Both are scoring points.