Turbidimetric measurement of Bence-Jones proteins using antibodies against free light chains of immunoglobulins. An artifact caused by different polymeric forms of light chains.

The different polymeric forms of free kappa and lambda light chains from urines of two myeloma patients were separated by gel filtration. When samples containing kappa chains in equal protein concentration were quantified by turbidimetry with anti-free kappa chain antibodies, two out of three samples reacted much less sensitively than the third sample. When analysed with SDS-polyacrylamide gel electrophoresis in conditions dissociating non-covalent but not covalent linkages, these two samples contained monomeric light chains, whereas the third sample contained dimers.