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Biology · 2025 · 4 marks
CBSE 2025 · Region 2 · Set 1 · Q29
Immunity in our body is of two types: (i) Innate immunity and (ii) acquired immunity. Innate immunity is a non-specific defence mechanism, whereas…
Immunity in our body is of two types: (i) Innate immunity and (ii) acquired immunity. Innate immunity is a non-specific defence mechanism, whereas acquired immunity is pathogen-specific; it is called specific immunity too. Acquired immunity is characterised by memory. Antibodies are specific to antigens and there are different types of antibodies produced in our body: they are IgA, IgE, IgG and IgM. It shows primary response when it encounters the pathogen for the first time and secondary response during the subsequent encounters with the same Antigen/Pathogen.
(a)
Name the two types of specialised cells which carry out the primary and secondary immune response.
(b)
Why is the antibody-mediated immunity also called as humoral immune response ?
Attempt either sub-part (c) or (d) :
(c)
The organ transplants are often rejected if not taken from suitable compatible persons.
(i)
Mention the characteristic of our immune system that is responsible for the graft rejection.
(ii)
Name the type of immune response and the cell involved in it.
OR
(d)
How is active immunity different from passive immunity?
Marking-scheme solution
(a)
B-lymphocytes , and T-lymphocytes.
(b)
Because the antibodies are found in the blood hence antibody-mediated immunity is also called humoral immune response.
(c)(i)
Our immune system is able to distinguish between ‘self’ and ‘non-self’ cells/molecules.
(ii)
Cell-mediated immune response, T-lymphocytes are involved.
OR
(d)
| Active immunity | Passive immunity |
| When antibodies are produced by B-cells within the body | Preformed antibodies are injected into the body for defence. |
| It is comparatively slow | It provides quick response |
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CBSE Class 12 Biology past-paper question from the 2025 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.