Bence Jones proteins are composed of:

Bence Jones proteins are immunoglobulin free light chains excreted in the urine of patients with multiple myeloma. During antibody synthesis a small excess of light chains are produced and are excreted. Hypergammaglobulinemic states such as rheumatoid ahritis and chronic infection are associated with the excretion of polyclonal free light chains. Monoclonal free light chains are seen in myeloma. Bence jones proteinuria occurs in myeloma, leukemia, and Hodgkin's disease. They can be detected by positive Bradshaw's test, heat test and electrophoresis. Ref: Immunology: Understanding The Immune System By Klaus D. Elge page 119.Oxford Handbook of Clinical and Laboratory Investigation edited by Drew Provan page 317. Jaypee's Review of Med. Biochemistry By S. M. Raju page 261