Biology · Human Health and Diseases · NEET
In active immunity your own body is exposed to an antigen (a live/dead germ or a vaccine) and makes its own antibodies. In passive immunity, ready-made antibodies made by someone else (or another animal) are given straight to your body. So the real difference is: who made the antibodies. Active = you made them; passive = they were given to you.
A vaccine gives ACTIVE immunity. A vaccine puts an antigen (a weakened/attenuated or dead pathogen, or its proteins) into your body. Your body then reacts and makes its own antibodies and memory cells. Because your body does the work, it is active. NEET 2016 tested this: polio drops contain attenuated (weakened) pathogens, so they trigger active immunity, unlike antivenom which is passive.
Colostrum gives PASSIVE immunity. Colostrum is the yellowish first milk from the mother. It contains ready-made antibodies (mainly IgA). The baby does NOT make these antibodies; they are passed from the mother. Because the baby receives ready-made antibodies, it is passive immunity. This is a very common NEET question.
Antivenom (anti-venom / anti-toxin) gives PASSIVE immunity. It contains preformed (ready-made) antibodies against snake venom. These antibodies act immediately to neutralise the venom. Because the antibodies are given ready-made and not made by the patient, it is passive immunity. Speed matters here: in a snake bite you need protection NOW, so passive is used.
Passive immunity is FASTER. Ready-made antibodies are already there and act at once. Active immunity is SLOWER because your body needs time to recognise the antigen and produce antibodies. But remember the trade-off: passive is fast but short-lived, while active is slow but long-lasting (because it forms memory cells).
No. Passive immunity does NOT form memory cells. You only receive antibodies, so once they are used up or broken down, the protection ends and there is no lasting record. Only active immunity forms memory cells (B and T memory cells), which is why active immunity gives long-term protection and a fast secondary response.
It is PASSIVE immunity. During pregnancy, IgG antibodies pass from the mother to the foetus through the placenta. The foetus does not make them, so it is passive (natural passive immunity). NEET 2020 confirmed this statement is correct.
Identify the wrong statement with reference to immunity.
Antivenom injection contains preformed antibodies while polio drops that are administered into the body contain:
Try the real previous-year questions from this chapter — each with the answer and a full solution.
(1) Colostrum / mother's first milk (IgA antibodies) given to the newborn. (2) Antivenom injection (preformed antibodies) for a snake bite. Also, IgG antibodies passing from mother to foetus through the placenta. All three are ready-made antibodies given to the body.
(1) Getting an infection and recovering (natural active immunity). (2) Taking a vaccine like the polio drops or a tetanus vaccine (artificial active immunity). In both, your body meets an antigen and makes its own antibodies and memory cells.
Active immunity forms memory cells, so the body remembers the antigen and protects you for a long time. Passive immunity only supplies ready-made antibodies with no memory cells, so once those antibodies break down, protection ends within weeks to a few months.
Passive immunity (antivenom). A snake bite needs protection immediately. Passive immunity is fast because ready-made antibodies act at once. There is no time to wait for the body to make its own antibodies, which is what active immunity would need.
Both active and passive immunity are types of acquired immunity, because both involve antibodies. Active immunity is fully acquired by the person. Passive immunity uses antibodies made elsewhere. Both differ from innate immunity, which is non-specific and present at birth.
