Remarks: Bence Jones protein is the free light chain component of antibodies. Antibodies are composed of heavy chains and light chains. In multiple myeloma patients, only one or the other is produced, or it may be produced in excess. The small size of Bence Jones protein allows it to pass through the kidneys and enter the urine. If screening test for BJ proteins is positive then immunofixation electrophoresis must be done, in order to assess the monoclonal gammopathies.