Describe the basic structure of an antibody and detail the function of each of the 5 antibody classes

Question

What will be an ideal response?

Answer 1

Each antibody molecule is made up of four protein chains: two identical "light" chains and two identical "heavy" chains. The four chains are held together by covalent disulfide bonds. The antibody shape can be approximately thought of as a "Y". At the tip of each branch at the top of the "Y" is the site where the antibody binds to its antigen. The five antibody classes in order of abundance are IgG, IgM, IgA, IgE, and IgD. IgG is found in blood and all body fluids. It has strong neutralization, complement activation, and opsonization activity, and is the only antibody to cross the placenta to protect the fetus. IgA may occur as a monomer or dimer, and is abundant in mucous secretions and coating the mucous membranes. IgA has strong neutralizing capability, and is secreted in breastmilk; it is also resistant to stomach acid. IgM is the first antibody made during a primary immune response. It occurs as a monomer or pentamer. It has strong complement activation and agglutination/precipitation activity. IgE is relatively rare. Its key role is fighting parasite infections by encouraging mast cells and basophils to release histamine and other inflammatory mediators. This also explains its role in allergic responses. IgD is the least abundant antibody. It is primarily found bound to B cells and it specific function is poorly understood.