Question

The graph given below shows the level of antibodies in the blood after exposure to a pathogen.

1. What types of responses of the immune system do the peaks A and B represent?
2. Name the type of antibody that is at the highest level in the 7^th week.

Answer 1

(a)

• Peak A represents the primary immune response, which is of lower intensity and has a longer lag period as it occurs during the first exposure to the antigen.
• Peak B represents the secondary (anamnestic) immune response, which is faster and more intense due to the presence of immunological memory cells.

(b) IgM appears first in the primary response, but IgG reaches the highest level by the 7^th week. It remains in the body for a longer duration and provides sustained immunity.