Assertion (A): Injecting the microbes deliberately during immunisation induces passive immunity.
Reason (R): When a host is exposed to antigens, antibodies are produced in the host body; this type of immunity is called active immunity.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → (A) is false, but (R) is true.
Immunity is of two kinds. In active immunity the body meets an antigen and makes its own antibodies; it is slow to build up. In passive immunity ready-made antibodies are given to the body, so the protection is quick.
Assertion (A): Injecting the microbes deliberately during immunisation induces passive immunity. — False. In immunisation, microbes are injected deliberately. The body then makes its own antibodies against them, so immunisation of this kind induces active immunity, not passive immunity. Passive immunity comes only when ready-made antibodies are given directly.
Reason (R): When a host is exposed to antigens, antibodies are produced in the host body; this type of immunity is called active immunity. — True. R is the book’s definition of active immunity. The antigen may be living or dead microbes or other proteins; when the host meets it, antibodies are produced in the host body.
A is false and R is true.
NCERT Extract:
Active and Passive Immunity – “When a host is exposed to antigens, which may be in the form of living or dead microbes or other proteins, antibodies are produced in the host body. This type of immunity is called active immunity. Active immunity is slow and takes time to give its full effective response. Injecting the microbes deliberately during immunisation or infectious organisms gaining access into body during natural infection induce active immunity. When ready-made antibodies are directly given to protect the body against foreign agents, it is called passive immunity.”