Question

Which immunoglobulin is first expressed when the body is attacked by an antigen?

Answer 1

Answer:

Explanation:

The first antibodies to be produced in a humoral immune response are always IgM, because IgM can be expressed without isotype switching (see Figs 4.20 and 9.8). These early IgM antibodies are produced before B cells have undergone somatic hypermutation and therefore tend to be of low affinity.

Answer 2

Answer:

IgM antibody appears first, followed by IgA on mucosal surfaces or IgG in the serum.

IgM is not only the first class of antibody to appear on the surface of a developing B cell. It is also the major class secreted into the blood in the early stages of a primary antibody response, on first exposure to an antigen.