Answer:
1. IgA refers to the class of antibody, which is witnessed in very large concentrations in mucus secretions.
2. IgD refers to the class of antibody, which is not discharged by B cells, however, is expressed in the naive B cells' surface.
3. IgE refers to the class of antibody, which takes part in the defense against the infections caused by parasites, and also takes part in allergic reactions.
4. IgG refers to the class of antibody that can pass through the placenta.
5. IgM refers to the class of antibody that is the first to appear post-stimulation of B cells.