Question

Statement 1: First antibody to be produced is IgM; it is monomeric on the surface of B cell receptor and it crosses the placenta to the foetus.

Statement 2: Concentration of IgM is higher than IgG in subsequent attacks by the similar antigen.

• A. Both the statements are correct
• B. Statement 1 is correct and statement 2 is incorrect
• C. Statement 1 incorrect and statement 2 is correct
• D. Both the statements are incorrect

Answer 1

The correct option is D Both the statements are incorrect

IgM is the first antibody to be produced in the humoral immune response, which is generally pentameric in the blood but on the surface of the B-cell receptor it is monomeric. IgM cannot diffuse through the placenta, only IgG passes through the placenta to the foetus.

When the antigen is recognized for the first time by the B-cell, IgM in high concentration followed by IgG in low concentration in the primary immune response. But when the same antigen is recognised for the second time, the main type of antibody produced is IgG, although small amounts of IgM are sometimes produced.