Bence Jones proteins identified by immunofixation electrophoresis of concentrated urine.

addressed some recently recognized problems in testing concentrated urine for monoclonal free light chains of immunoglobulins, i.e., Bence Jones protein (BJP), by high-resolution elec-trophoresis (lIRE) and immunofix-ation electrophoresis (IFE). When BJP is present in low concentrations, poly-clonal free light chains can interfere with identification of the protein either by causing a dense background pattern, which may obscure weak bands, or by exhibiting the so-called " ladder light chain " or " pseudo-oligo-clonal " pattern (2-4), which reflects differences in the charge and size of molecules and results in multiple banding on IFE when good-quality electrophoresis is used. By performing IFE on serial dilutions of their patient's concentrated urine, Hess et al. obviated the interference of the dense background staining of polyclonal K free light chains and demonstrated the presence of a A-BJP. Their suggestion of diluting the samples to improve the sensitivity of WE is in agreement with our own laboratory's practice since 1980, when we introduced WE in combination with agarose lIRE (5-7) for the investigation of monoclonal proteins in serum and concentrated urine. As Hess et al. correctly stressed, dilution of the samples provides a means for titrating antigen and antibody concentrations that is otherwise lacking in WE; we previously (6) recommended the routine use of at least two different dilutions of the same sample for each an-tiserum used. To minimize the expense and time that would be required to repeat IFE trials for each case being studied, we usually perform preliminary agarose HRE of concentrated urine at the time we test the patient's serum. Then, after examining the electrophoretogram, and depending both on the amount of protein in the particular specimen and the characteristics of the antisera we use routinely, we determine the proper serial dilutions for WE. Some of the modifications we have made to the original IFE technique (5, 6) may make it possible to produce a much clearer background staining without overdiluting the samples, which could result in failure to detect faint bands of BJP. The addition of polyethylene glycol to high-quality commercial an-tisera improves the definition of the precipitin bands while allowing use of smaller amounts of antiserum and a shorter time for fixation. Compared with thick gels, thin gels prepared from good-quality agarose, besides improving electrophoresis resolution, require shorter washing periods to re