Immune memory is the cornerstone of vaccine efficacy.
The principle of vaccination is based on the immune system's property of Memory.
(A) Memory - Correct: Vaccines stimulate immunological memory via memory B-cells and T-cells.
(B) Specificity - Incorrect: While important, this isn't the basis of vaccination.
(C) Diversity - Incorrect: Refers to antigen receptor variety, not vaccine mechanism.
(D) Plasticity - Incorrect: Describes immune adaptability, not vaccine function.
The correct answer is (D) Memory, enabling rapid response upon pathogen re-exposure.
The principle of vaccination is based on the immune system’s ability to remember previous encounters with pathogens. When a person is vaccinated, they are exposed to a harmless form of a pathogen (e.g., killed bacteria or attenuated viruses). This triggers the immune system to produce antibodies and memory cells.
These memory cells allow the immune system to mount a rapid and effective response if the body encounters the real pathogen in the future.
Option (A) is correct because vaccination relies on the immune system's memory.
Match the hypersensitivity type with its example. 
Match the cells in Column I with their primary function in Column II. 
Match the following:
In the following, \( [x] \) denotes the greatest integer less than or equal to \( x \). 
Choose the correct answer from the options given below:
For x < 0:
f(x) = ex + ax
For x ≥ 0:
f(x) = b(x - 1)2