Question

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R
Assertion A: Normally, the influenza virus changes its structure slightly for each passing year. Although, we are being exposed to these “modified” or slightly mutated and evolving influenza strains every year, we do not always come down with the flu disease even if we have not received the yearly influenza vaccine. However, sometimes, we do get a really bad case of the flu, despite the fact that we have memory cells left from previous infections with the influenza virus.
Reason R: This is a concept of original antigenic sin, which suggests that we only mount a primary response once we have exhausted the potential to use our memory cells to eradicate the infection. Since most of our first encounters with influenza will vary, the years in which “all” of the key influenza epitopes are significantly “new” to each of us will also vary. It is only in these years that we experience a new primary response to influenza virus, and therefore symptoms of the flu are most severe.
In the light of the above statements, choose the correct answer from the options given below

• A. Both A and R are true and R is the correct explanation of A
• B. Both A and R are true but R is NOT the correct explanation of A
• C. A is true but R is false
• D. A is false but R is true

Hint:

• Influenza → Antigenic drift
• Original antigenic sin → Immune memory bias

Answer 1

The Correct Option is A

Concept: Influenza virus undergoes antigenic drift, leading to gradual changes in viral surface proteins.
• Immune system relies on memory cells from previous infections
• However, new strains may partially escape immune recognition

Step 1: Evaluating Assertion A.

• Influenza virus changes slightly every year → True
• Memory cells often protect, but sometimes fail → True Thus, Assertion A is correct.

Step 2: Evaluating Reason R.

• Original antigenic sin explains reliance on existing immune memory
• When epitopes are significantly different → new primary response → severe symptoms Thus, Reason R is correct.

Step 3: Linking A and R.
Reason R explains why sometimes severe infection occurs despite memory cells—because immune response is biased toward previous strains and may not effectively recognize new variants.

Step 4: Selecting the correct answer.
Hence, both statements are true and R correctly explains A.