Final answer:
IgG is the main antibody of both primary and secondary immune responses, IgA protects mucosal barriers, IgE is involved in allergies, and IgM is the first antibody to peak during a primary immune response.
Step-by-step explanation:
IgG is the main antibody of both primary and secondary immune responses in the blood. It is a monomeric antibody that clears pathogens from the blood and can activate complement proteins. IgG is also the antibody that crosses the placenta to protect the developing fetus from disease.
On the other hand, IgA is the antibody that protects mucosal barriers, such as the digestive and respiratory tracts. It can pass immunity to an infant through breastfeeding. IgE is involved in allergies and binds to mast cells, causing antigen-specific degranulation during an allergic response.
IgM is the first antibody to peak during a primary immune response and is a B cell receptor along with IgD.