In general, distinguished by the type of heavy chains in the molecule, there are five primary classes of immunoglobulins (Ig), which are IgG, IgM, IgA, IgD, and IgE. IgG molecules have heavy chains known as γ-chains; IgMs have μ-chains; IgAs have α-chains; IgEs have ε-chains; and IgDs have δ-chains. Learn more: igm services