IgG antibodies are large globular proteins composed of four peptide chains with a molecular weight of about 150kDa. "It contains two identical heavy chains of about 50kDa(γ) and two identical light chains of about 25kDa and is therefore a tetrameric quaternary structure." Studies have shown that IgG antibodies can be used to evaluate renal biopsies, autoimmune diseases, and to identify plasma cell tumors and non-Hodgkin's lymphoma.