Immunoglobulin light-chain immunoblots of urine proteins from patients with tubular and Bence-Jones proteinuria

Electrophoretic analysis of Bence Jones proteinuria

The electrophoresis of Bence Jones proteinuria (BJP) by urinary protein electrophoresis (UPE), immunoelectrophoresis (IE), immunofixation electrophoresis (IFE), sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), isoelectric focusing (IEF), two-dimensional electrophoresis (2-DE) and capillary electrophoresis (CE) is described. UPE, IE and IFE are briefly discussed as clinical laboratory methods for the detection and typing of free light chain (LC) whilst the high resolution electrophoretic methods (SDS-PAGE, IEF, 2-DE and CE) are considered in greater detail as research tools for molecular characterisation of free LC and its association with nephrotoxicity. Refinements of sample processing designed to improve the standardisation of analysis of BJP by high resolution electrophoretic methods are reported.

Clinical analysis of human urinary proteins using high resolution electrophoretic methods

The application of isoelectric focusing (IEF), sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), two-dimensional electrophoresis (2-DE) and capillary electrophoresis (CE) for high resolution electrophoretic analysis of human urinary proteins is reviewed. In each case, the information is tabulated chronologically with details of sample preparation, electrophoretic system, detection method and clinical application. The text includes an historical perspective of the use of each method for urinalysis and a detailed review of the application of the methods to the investigation of renal disease, renal transplantation, Bence Jones proteinuria (BJP), diabetes mellitus, cadmium toxicity, nephrolithiasis and cancers of the urogenital tract.

Sodium dodecyl sulfate-agarose gel electrophoresis of urinary proteins: application to multiple myeloma

We evaluated a new sodium dodecyl sulfate-agarose gel electrophoresis (SDS-AGE) for urinary protein analysis in patients with multiple myeloma (MM; n = 47; ages, 62 ± 2 years, mean ± SE). Abnormal proteinuria (mean = 1872 ± 360 mg/24 h) was present in 95% of the samples; 75% of the patients had some sign of renal dysfunction (glomerular and/or tubular) according to their SDS-AGE pattern. A band suggesting Bence Jones proteinuria (BJP) was detected in 40 vs 33 specimens by routine AGE. Immunofixation identified BJP in 38 patients; the calculated sensitivity of SDS-AGE for BJP was 97%. Excellent correlation (P <0.0001) was obtained with routine AGE (r = 0.994) and immunonephelometry (r = 0.963) for light chain quantification. SDS-AGE allows easy evaluation of renal dysfunction and shows high sensitivity for BJP detection. In a specialized laboratory, it is useful for following the progress of MM patients through the semiquantification of BJP.

Detection of Bence-Jones protein in serum by immunoblotting

To detect Bence-Jones protein (BJP) in serum we precipitated intact immunoglobulins (Ig) using polyethylene glycol (PEG) and subjected the BJP in solution to electrophoresis in agarose gel, followed by transfer to a polyvinylidene difluoride membrane, and immunoenzymatic staining (successively using rabbit anti-human light/heavy chain of Ig, biotinylated swine anti-rabbit Ig, and alkaline phosphatase-conjugated streptavidin). Treatment with PEG effectively reduced background staining of polyclonal Ig in the immunoblots, although intact monoclonal Ig was not always completely removed. To compare the present method with immunoelectrophoresis (IEP), we selected samples from patients demonstrating BJP by IEP in both serum and urine (n = 40), serum only (n = 18), and urine only (n = 32); 21 of these patients had BJP alone and 69 had BJP in addition to intact monoclonal Ig. Efficiency of detection of BJP in serum was increased by the present method: serum BJP was detected in 70 patients by the present method versus 58 by IEP. The present method demonstrated single BJP bands in the samples from 16 patients (kappa, n = 7; lambda, n = 9) and multiple BJP bands (range: 2-9) in the samples from 54 patients (kappa, n = 31; lambda, n = 23). This method could be useful for detecting BJP in serum from patients suspected of having light chain gammopathy (without the need for urine testing) and may complement urine testing in patients excreting polyclonal free light chains of Ig.

Patient-specific microheterogeneity patterns of monoclonal immunoglobulin light chains as revealed by high resolution, two-dimensional electrophoresis

Preliminary observations have indicated that both heavy and light chains of monoclonal immunoglobulin exhibit diagnostically useful microheterogeneity patterns when examined with high resolution two-dimensional electrophoresis (2DE) and silver staining (Clin Chem 1990; 36: 993). The present study is a survey of the distribution and types of monoclonal light chain isoforms as observed with 2DE in a group of 68 sera and urine specimens from a cohort of 41 patients with monoclonal gammopathy. The light chain patterns were patient-specific and varied in both the type (kappa, lambda, charge or mass or both) and the number of isoforms present (one to six). A large proportion (31 of 41 cases, 75.6%) exhibited significant microheterogeneity, i.e., distribution of light-chains among two or more isoforms. Charge-based microheterogeneity alone occurred in 17 cases and both charge and mass isoforms were observed in 14 cases. The distribution of charge isoforms of the light chains corresponded qualitatively to the densitometric profiles of agarose gel and immunofixation electrophoresis studies. There was no correlation between heavy chain type and light chain pattern. A carbamylation assay was used to demonstrate that the chemical charge differences between the isoforms were unitary. Ascertainment of this light-chain microheterogeneity has not only proved useful in resolving some diagnostic immunoglobulin typing dilemmas but also is germane to understanding the molecular basis of neoplastic B-cell paraprotein metabolism.

A sandwich enzyme-linked immunosorbent assay for beta 2-glycoprotein I

A solid-phase sandwich enzyme-linked immunosorbent assay for determining beta 2-glycoprotein I in urine has been developed. It has a working concentration range of 5-40 micrograms/L and a detection limit of approximately 1.4 micrograms/L. The within-plate coefficient of variation (CV) falls between 1.4% and 2.1%, and the between-batch CV ranges from 5.2 to 6.0%. Recovery of beta 2-glycoprotein I added to urine varies between 96 and 110%. The assay can also be used for determining beta 2-glycoprotein I in serum.

Immuno-isotachophoretic determination of monoclonal immunoglobulin light chains produced by neoplastic B-cells: use in diagnosis, monitoring and detection of residual disease

We suggest that countercurrent isotachophoresis performed on cellulose acetate membranes (ITP-CAM) should be used for detecting trace amounts of Bence-Jones protein (BJP) in urine of patients with chronic lymphocytic leukemia (CLL), non-Hodgkin's lymphoma (NHL) and related diseases. ITP-CAM allows simultaneous concentration and electrophoretic separation of proteins present in highly diluted solutions, as well as easy immunological detection of separated substances. BJP was found in 24 out of 42 patients with CLL, 33 of 56 with NHL and 3 of 3 with Waldenström macroglobulinemia. Twenty-three patients were followed during the course of chemo- or radiotherapy. In 19 cases the BJP findings correlated well with clinical status. In no case of partial or complete clinical response did BJP completely disappear from the urine.

Renal impairment in myeloma: negative association with isoelectric point of excreted Bence-Jones protein

The isoelectric point (pI) of the major form of Bence-Jones protein excreted by 62 patients with myeloma and six with macroglobulinaemia was measured by combining isoelectric focusing with immunoblotting techniques. The distribution of the pI values for both kappa and lambda type proteins was bimodal, most falling in the ranges 5.0-6.0 and 7.0-7.5. Plasma creatinine and creatinine clearance and the urine excretion of alpha-1-microglobulin and beta-2-microglobulin were measured in 24 of the patients. These patients, who were free of additional factors known to have an association with the development of renal impairment, were followed up for a mean period of 16 months (range three to 28 months). It was found that renal impairment was not related to the pI of the Bence-Jones protein excreted.