Acquired Immunity: Memory and Response — NEET Biology
📚 Practice ConceptAcquired immunity, on the other hand is pathogen specific. It is characterised by memory. This means when our body encounters a pathogen for the first time it produces a response called primary response which is of low intensity. Subsequent encounter with the same pathogen elicits a highly intensified secondary or anamnestic response. This is ascribed to the fact that our body appears to have memory of the first encounter.
Which of the following statements regarding immune responses and vaccination are NOT correct? S1: Vaccination works by inducing a low-intensity primary immune response and subsequent memory cell formation. S2: The primary immune response is generally characterized by a slower onset and lower antibody production compared to a secondary response. S3: The secondary immune response is slower but more prolonged than the primary response due to the rapid proliferation of memory cells. S4: Memory B and T-cells, once formed, enable the body to elicit a highly intensified anamnestic response upon re-exposure to the same pathogen. S5: Passive immunisation, such as antitoxin injection, directly stimulates the production of memory cells against specific toxins for long-term protection.
View solution & NCERT explanation
Correct answer: B — S3 and S5 only
This question assesses understanding of primary and secondary immune responses and the mechanism of vaccination. S1: Vaccination works by inducing a primary immune response and memory cell formation. The primary response itself is of low intensity. This statement is correct. S2: The primary immune response is indeed of low intensity and takes more time to develop. This statement is correct. S3: The secondary immune response (anamnestic response) is not slower; it is highly intensified and faster than the primary response. Therefore, S3 is NOT correct. S4: Memory B and T-cells are generated during the primary response and are responsible for the highly intensified secondary (anamnestic) response upon subsequent exposure. This statement is correct. S5: Passive immunisation involves directly injecting preformed antibodies, providing immediate protection without inducing the host's immune system to produce memory cells. Memory cell formation is characteristic of active immunity. Therefore, S5 is NOT correct. Thus, statements S3 and S5 are NOT correct.
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