Question

Human IgM ______.

Options

• crosses the placenta

• consists of 3 subunits linked together by a J chain

• is largely restricted to the circulation

• is the antibody produced by high affinity plasma cells

Answer 1

Human IgM is largely restricted to the circulation.

Explanation:

Human IgM is a pentamer composed of five monomeric units linked together by disulfide bonds and a joining (J) chain, not three subunits. IgM does not cross the placenta due to its large size. It is largely confined to the bloodstream (circulation) because of its size and structure. IgM is the first antibody produced during an immune response, but it is generally produced by plasma cells early in the response, not specifically by high-affinity plasma cells, which usually produce IgG, a type of antibody that has a higher affinity for antigens.