Restricted Electrophoretic Heterogeneity of Immunoglobulin LightChainsin Urine:a CauseforConfusion withBenceJonesProtein

The detection of Bence Jonesprotein,an importantpart of the investigation of suspected myeloma,is most commonly done by agaroseor cellulosenitrateelectrophoresis followedby immunofixation. Bence Jones proteinis recognized as singleor multiplebandsofonetypeof light chain.Unfortunately, improvements in sensitivity ofthese techniques(useof high-affinity antiseraand higherresolutionelectrophoresis) frequentlyallowdetectionof multiplelightchainbandsin the urineof patientswhodo not have a B-cell dyscrasia.The bands are usuallykappa, althoughthey may be accompanied by lambda bands. Thispatternmayleadto the misdiagnosis of BenceJones protein and oligoclonal lightchainproduction in patients. Here we showthatthispattern is produced by polyclonal lightchains;it is presentin the urine of all patientswitha tubularproteinunaof any etiologyand may be inducedin healthyindividualsby blockingtheirrenaltubularprotein reabsorption. PolyclonallightchainsseparateintomonomersanddimersonsodiumdodecylsuItate-polyacrylamide gel electrophoresis and into four major bands with manyminorbandsby isoelectric focusing. This difference inchargeand possibly size resultsin the bandingpattern seen on good-qualityelectrophoresis andimmunofixation.