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

κ and λ urine free light chains: a new method for quantification

BACKGROUND

Immunofixation electrophoresis of urinary proteins, coupled with densitometric analysis, is the gold standard method for determining urinary monoclonal free light chains (FLCs), i.e. Bence Jones protein. Recently, immunochemical methods have been developed for Bence Jones protein quantification, but no such method has been widely adopted. This study evaluated a new antibody-based immunoturbidimetry method for urinary FLC quantification, using immunofixation electrophoresis as reference.

METHODS

κ and λ FLCs were measured in urine specimens from 95 (training cohort) and 103 (testing cohort) patients by both immunofixation electrophoresis and immunoturbidimetry.

RESULTS

There was almost perfect concordance in the training cohort between the new immunoturbidimetry assay and immunofixation electrophoresis and substantial agreement, with Cohen kappa of 0.85 and 0.75, for κ and λ FLC determination, respectively. Results were confirmed in the testing cohort, where Cohen kappa was 0.86 for κ and 0.94 for λ FLCs. The κ FLC assay had 88% sensitivity and 98%-100% specificity; the λ FLC assay had 94% and 96% sensitivity and 91% and 99% specificity in the training and testing cohorts, respectively.

CONCLUSIONS

The new immunochemical method has a satisfactory performance and almost perfect agreement with immunofixation electrophoresis and gives the advantage of FLC quantification.

Small intestinal development in suckling rats after enteral obestatin administration

This study investigated the effect of enteral administration of obestatin on the development of small intestine, as well as oxidative stress markers and trancriptomic profile of gastrointestinal genes. Suckling rats were assigned to 3 groups treated with: C-saline solution; OL-obestatin (125 nmol/kg BW); OH-obestatin (250 nmol/kg BW) administered twice daily, from the 14th to the 21st day of life. Enteral administration of obestatin in both studied doses had no effect neither on the body weight of animals nor the BMI calculated in the day of euthanasia. Compared to the control group (C), treatment with obestatin resulted in significant changes in the histometry of the small intestinal wall as well as intestinal epithelial cell remodeling. The observed changes and their possible implications for intestinal development were dependent on the dosage of peptide. The enteral administration of high dose (OH) of obestatin significantly decreased its expression in the stomach and increased markers of oxidative stress. The gene profile revealed MAPK3 (mitogen-activated protein kinase-3) as the key regulator gene for obestatin action in the gastrointestinal track. In conclusion, we have showed that enteral administration of obestatin influences the gut mucosa remodeling. It is also suggested that the administration of high dose (OH) has inhibitory effect on the intestinal maturation of suckling rats.

Urinary free light chain analysis by the Freelite immunoassay: a preliminary study in multiple myeloma

Evaluate the Freelite free light chain immunoassay for urine analysis in myeloma. Urine specimens from 20 patients were analyzed by Freelite (The Binding Site) and SDS-agarose gel electrophoresis (Hydragel protéinurie, Sebia). Using the kappa/lambda ratio, Freelite was more sensitive than electrophoresis to detect free light chains, but concentration was overestimated in 75% of cases. Despite high sensitivity and full automation, Freelite inaccurately measures monoclonal free light chains in urine.

Highly Sensitive, Automated Immunoassay for Immunoglobulin Free Light Chains in Serum and Urine

Background: Bence Jones proteins or monoclonal immunoglobulin κ and λ free light chains (FLCs) are important markers for identifying and monitoring many patients with B-cell tumors. Automated immunoassays that measure FLCs in urine and serum have considerable clinical potential.

Methods: Sheep antibodies, specific for FLCs, were prepared by immunization with pure κ and λ molecules and then adsorbed extensively against whole immunoglobulins. The antibodies were conjugated onto latex particles and used to assay κ and λ FLCs on the Beckman IMMAGETM protein analyzer.

Results: The unconjugated antibodies showed minimal cross-reactivity with intact immunoglobulins or other proteins. With latex-conjugated antibodies, κ and λ FLCs could be measured in normal sera and most normal urine samples. Patients with multiple myeloma had increased concentrations of the relevant serum FLC, whereas both FLCs were increased in the sera of patients with systemic lupus erythematosus.

Conclusions: We developed sensitive, automated immunoassays for κ and λ FLC measurements in serum and urine that should facilitate the assessment of patients with light chain abnormalities.

The estimation of free light chains of immunoglobulins in biological fluids

Methods for the estimation of the free light chains of immunoglobulins in serum, urine and cerebrospinal fluid are divided into two groups, electrophoretic and immunological, and the analytical performance of each method described. The problems associated with the accurate and precise determination of free light chains by the different methods are discussed and their complementary clinical roles emphasized. It is proposed that an International Reference Preparation for free light chains is established.