Upon further analysis, the M protein was determined to be Immunoglobulin G (IgG). Antibodies are given their class based on the molecule's heavy (larger) chain. Classes include IgA, D, E, M, and G.
Also, a serum-free light chain assay was performed, and the patient showed kappa light chains. Light chains can be either kappa or lambda.
The simplified image to the right shows the basic structure of an antibody (immunoglobulin) molecule.