Assertion-reason on tetanus antitoxin: active or passive immunity? Also what does each Ig class do?
Siddharth RaoDropper Sample
12 Sept 2026 Β· 1 min read
Second attempt, so I've done this chapter before, but I'm still losing marks on immunity assertion-reasons because I rush through. Here is the type I mean (written from memory, not an actual question):
Assertion: A person with a deep, rusty wound is given an injection of preformed antibodies against the tetanus toxin. This gives passive immunity. Reason: In active immunity the host's own cells produce antibodies in response to antigens.
I think both are true and the reason correctly explains the assertion, but I'd like someone to double-check the definitions. My second doubt is about immunoglobulins: NCERT lists IgA, IgM, IgE, IgG; I know an antibody is made of 4 chains (2 heavy, 2 light, H2L2), but I get the classes' functions wrong. Which is first in a primary response? Which appears in colostrum? Which one is for allergies?
And honestly, I keep treating "secondary response" as just "second dose of a vaccine". Is there more to it?
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[+][β]Tanvi Deshmukh12thSampleΒ· 1mo ago
Active immunity = host exposed to antigens (living or dead microbes, or other proteins) and the host's own immune system makes antibodies. It's slow and takes time, but memory cells are created. Passive immunity = ready-made antibodies given directly. In the tetanus example, since the situation needs a quick response, preformed antibodies (antitoxin) are injected. Snakebite is the same, antivenom is given. So both parts of your assertion-reason are true. The reason defines active immunity (not directly explaining passive, but true). If the exam question wants "does reason explain assertion?", it would be a no, actually; the reason describes the contrast.
[+][β]Siddharth RaoDropperSampleΒ· 1mo agoAuthor
thanks tanvi, I always doubt the reason when I see two true statements. I'll practise the "does it explain" check separately
[+][β]Mehak AroraDropperSampleΒ· 1mo ago
Anything where antibodies are given = active because the antibodies are active in the body. Vaccines are given to protect so passive. Right? That's how I remember it: active = action.
[+][β]Kavya NaikDropperSampleΒ· 1mo ago
Mehak, other way round. Vaccine (weakened/killed pathogen or its proteins) = active immunity, because the person's own immune system makes antibodies and also memory B and T cells. Antibodies injected directly (antitoxin, antivenom) = passive, no memory, protection fades. Also breast milk: the first milk, colostrum, has abundant IgA to protect the infant, which is passive. And the foetus gets some antibodies from the mother via the placenta, also passive.
[+][β]Mehak AroraDropperSampleΒ· 1mo ago
oh. active = your body does the work, not the antibodies being "active". I flipped vaccines. Thank you kavya, that's embarrassing but useful
[+][β]Pooja Iyer12thSampleΒ· 1mo ago
Ig classes (the ones I can recall):
- IgG: most abundant in blood, crosses the placenta
- IgM: first made in a primary response, a big pentamer
- IgA: in secretions (tears, saliva, mucus), and colostrum
- IgE: involved in allergic reactions, binds to mast cells which release histamine
- IgD: on the surface of B cells (NCERT doesn't list it) Mnemonic: "GAMED": G, A, M, E, D. Not elegant but useful.
[+][β]Nisha Verma12thSampleΒ· 1mo ago
Secondary response: when the same pathogen is encountered a second time, the body responds faster and much stronger because of memory cells from the first exposure. NCERT calls the first one primary response (low intensity) and the second secondary or anamnestic response (highly intensified). That's the basis of vaccination, and of the "booster" doses. Also B-cells do the antibody part (humoral), and T-cells do cell-mediated immunity, which is why graft rejection is T-cell mediated.
