FREE LIGHT-CHAINS OF IMMUNOGLOBULINS - CLINICAL LABORATORY ANALYSIS

The increased sensitivity of immunofixation electrophoresis (IFE) over prior electrophoretic methods has led to renewed interest in the stud y of free light chains. Here, we discuss problems associated with the identification of monoclonal free light chains (Bence Jones proteins) in urine. Besides reviewing the nature of the sample specimens and the assays themselves, we discuss the physiology, biochemistry, genetics, and immunological properties of these molecules. Direct measurement o f kappa/lambda ratios may ultimately be useful, but all commercial met hods available now lack sufficient sensitivity. IFE is the preferred m ethod because of its sensitivity and ease of interpretation. There are , however, difficulties associated with the interpretation of urinary IFE patterns, because the technique does not include an intrinsic mech anism for antibody-antigen titration and because of its great sensitiv ity in the absence of quantification. Problems of interpretation are d iscussed.