Question

The adaptive immune response in an animal involves the generation of antibodies against an invading bacterial pathogen. The following graph represents antibody titer levels in a mammal exposed twice to the pathogen.
Which one of the following options correctly pairs antibodies to peak I and peak II in the graph?

• A. Peak I - IgG; Peak II - IgM
• B. Peak I - IgM; Peak II - IgG
• C. Peak I - IgE; Peak II - IgG
• D. Peak I - IgG; Peak II - IgG

Hint:

In a typical immune response, IgM is produced first in the primary response, while IgG predominates in the secondary response due to memory cells formed after the initial exposure.

Answer 1

The Correct Option is B

In the adaptive immune response, the antibody response to the first exposure to a pathogen typically involves an increase in IgM antibodies, which are produced first. These are followed by the production of IgG antibodies during the second exposure (secondary response), which is faster and more robust due to memory cells generated during the first exposure.
- Peak I corresponds to the primary response, which is characterized by the production of IgM antibodies first. This is the body's initial response to the pathogen.
- Peak II corresponds to the secondary response (after the second exposure), where the production of IgG antibodies predominates. This response is more rapid and robust compared to the primary response due to memory cells.
Thus, the correct pairing of antibodies to the peaks is:
- Peak I - IgM (first exposure)
- Peak II - IgG (second exposure)
Therefore, the correct answer is (B) Peak I - IgM; Peak II - IgG.