Free Light Chain Concentrations Research Articles

Serum Reference Intervals and Diagnostic Ranges for Free κ and Free λ Immunoglobulin Light Chains: Relative Sensitivity for Detection of Monoclonal Light Chains

The detection of monoclonal free light chains (FLCs) is an important diagnostic aid for a variety of monoclonal gammopathies and is especially important in light-chain diseases, such as light-chain myeloma, primary systemic amyloidosis, and light-chain-deposition disease. These diseases are more prevalent in the elderly, and assays to detect and quantify abnormal amounts of FLCs require reference intervals that include elderly donors. We used an automated immunoassay for FLCs and sera from a population 21-90 years of age. We used the calculated reference and diagnostic intervals to compare FLC results with those obtained by immunofixation (IFE) to detect low concentrations of monoclonal kappa and lambda FLCs in the sera of patients with monoclonal gammopathies. Serum kappa and lambda FLCs increased with population age, with an apparent change for those >80 years. This trend was lost when the FLC concentration was normalized to cystatin C concentration. The ratio of kappa FLC to lambda FLC (FLC K/L) did not exhibit an age-dependent trend. The diagnostic interval for FLC K/L was 0.26-1.65. The 95% reference interval for kappa FLC was 3.3-19.4 mg/L, and that for lambda FLC was 5.7-26.3 mg/L. Detection and quantification of monoclonal FLCs by nephelometry were more sensitive than IFE in serum samples from patients with primary systemic amyloidosis and light-chain-deposition disease. Reference and diagnostic intervals for serum FLCs have been developed for use with a new, automated immunoassay that makes the detection and quantification of monoclonal FLCs easier and more sensitive than with current methods. The serum FLC assay complements IFE and allows quantification of FLCs in light-chain-disease patients who have no detectable serum or urine M-spike.

Serum free light-chain measurements for identifying and monitoring patients with nonsecretory multiple myeloma

AbstractUsing sensitive, automated immunoassays, increased concentrations of either κ or λ free light chains (and abnormal κ/λ ratios) were detected in the sera of 19 of 28 patients with nonsecretory multiple myeloma. Four other patients had suppression of one or both light chains, and the remaining 5 sera had normal or raised free light-chain concentrations with substantially normal κ/λ ratios. Six of the patients with an elevated single free light chain, who were studied during follow-up, had changes in disease activity that were reflected by the changes in free light-chain concentrations. It is concluded that quantification of free light chains in serum should prove useful for the diagnosis and monitoring of many patients with nonsecretory myeloma.

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

Bence Jones proteins or monoclonal immunoglobulin kappa and lambda 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. Sheep antibodies, specific for FLCs, were prepared by immunization with pure kappa and lambda molecules and then adsorbed extensively against whole immunoglobulins. The antibodies were conjugated onto latex particles and used to assay kappa and lambda FLCs on the Beckman IMMAGE protein analyzer. The unconjugated antibodies showed minimal cross-reactivity with intact immunoglobulins or other proteins. With latex-conjugated antibodies, kappa and lambda 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. We developed sensitive, automated immunoassays for kappa and lambda FLC measurements in serum and urine that should facilitate the assessment of patients with light chain abnormalities.

Sensitive competitive‐binding elisas for quantifying free kappa and lambda light chains in cerebrospinal fluid

Simple, sensitive, and fully standardized solid-phase enzyme-linked competitive binding immunoassays to quantify free kappa and lambda immunoglobulin light chains are described. The assays were developed to measure the concentration of free light chains in cerebrospinal fluid (CSF), in part because elevated levels of free kappa light chains have utility as a diagnostic marker for multiple sclerosis (MS). Polyclonal rabbit antibodies raised against pooled Bence Jones proteins are bound to solid-phase Staphylococcal protein A and used as the primary antisera in this assay. A pool of Bence Jones proteins isolated from the urine of 10 individuals with multiple myeloma are used as a biotin-labeled ligand and to develop a standard curve. The assays as described are sensitive to the low nanogram range and are specific for free kappa or lambda light chains. The assays were found to have acceptable precision, and results correlated highly with concentrations determined using competitive-binding radioimmunoassays previously described.

Is IgD Myeloma a Separate Clinical Entity? Report of Six Cases Investigated by Isoelectric Focusing.

Six IgD myeloma patients whose monoclonal components were identified by isoelectric focusing are presented. They represented 4% of all patients with myeloma seen at our institute between 1982 and 1986. The patients did not display many of the features described as typical for IgD myeloma: in particular younger age group, decreased survival and increased incidence of lymphadenopathy, hepatosplenomegaly, extraosseous disease, anemia, renal failure and hypercalcemia. However males predominated, the concentrations of circulating monoclonal IgD were low and concentrations of serum and urinary monoclonal free light chains were high, findings previously reported in IgD myeloma. The concentrations of circulating IgD were at the lower end of ranges reported previously. The hypothesis that our patients represent the malignant equivalent of the normal "low secretory phenotype", possibly associated with improved survival, is discussed. The belief that IgD myeloma is a separate clinical entity is questioned. The sensitive, high-resolution technique of isoelectric focusing is recommended as the investigation of choice for the detection of monoclonal gammopathies in body fluids.

Estimation of free light chains of immunoglobulins by enzyme immunoassay

In the urine of about half the patients with multiple myeloma, immunoglobulin light chains, referred to as Bence Jones protein, can be detected. About 20% of all myeloma patients have monoclonal light chains in their urine as the only detectable paraprotein. These proteins can serve as biological markers for activity of disease and response to therapy. Serial quantitative measurements of these tumor cell products can provide an effective and rational basis for the administration of chemotherapy [l]. It has been shown that an increase in the concentration of such proteins presages incipient relapse and that the restarting of chemotherapy should not necessarily await the development of symptomatic multiple myeloma [2]. Several immunochemical methods for estimating free light chain concentrations have been developed in which the free chains had to be separated from those bound to the heavy chains by gel filtration [3] or membrane filtration [4], because antisera to light chains react with both free and immunoglobulin-bound chains. Such separation steps can be circumvented now because of the availability of antisera that are specific for .free light chains. Robinson et al [2] have described radioimmunoassays in which such antisera were used. These assays are sufficiently sensitive to measure the free light chain concentrations in unconcentrated normal urines. In this paper, we describe competitive enzyme immunoassays (EIA) for free kappa and lambda chains in which only stable reagents have been used. The assay is sensitive enough to estimate concentrations in unconcentrated urines. Reference intervals have been established in normal urines for the concentrations of free kappa and lambda and the kappa : lambda ratios.

Serum concentrations of immunoglobulins and free light chains before and after vascular events in essential hypertension.

Serum concentrations of immunoglobulins (Ig) and free light chains (LC) of Ig have been determined at regular intervals during five years in patients with essential hypertension and correlated to development of vascular complications. In 6 cardiac event patients serum IgG increased by 11.9% (p less than 0.05) and LC by 19.8% (p less than 0.05). IgG levels correlated positively with LC levels (r = 0.59, p less than 0.001) and changes in IgG correlated positively with changes in LC (r = 0.46, p less than 0.01). The post-event increments in IgG persisted up to 21 months. No significant changes in serum concentrations of IgA, IgM, albumin and creatinine were found. In 10 cerebral event patients and in matched groups of 15 uncomplicated hypertensive patients, no significant changes in the above parameters could be demonstrated. It is concluded that heart tissue damage in essential hypertension induces a long-lasting stimulation of B-lymphocytes, and it is suggested that the high Ig levels found in as yet uncomplicated hypertensive patients may reflect an ongoing damage of the vascular bed.

Free light chains of immunoglobulins in serum from patients with leukaemias and multiple myeloma.

The serum concentration of free kappa and lambda light chains of immunoglobulins were measured in 114 patients with myelo- and lymphoproliferative disorders including multiple myeloma. Increased concentrations of a single light chain type, suggesting monoclonal origin, were found with high frequency in B-cell diseases only. Thus 6 out of 9 patients with chronic lymphatic leukaemia and 24 of 28 patients with multiple myeloma had increased concentrations of a single chain type. The highest values reported in chronic lymphatic leukaemia were approximately 10 and in multiple myeloma 1000 times normal mean. Cytostatic treatment of chronic lymphatic leukaemia was followed by a decrease in the light chain levels. The levels were, however, not correlated to the number of circulating lymphocytes, the lymphatic infiltration of tissue or clinical activity. Increased concentrations of both chain types, suggesting a polyclonal origin, were found in both of 2 patients with acute monocytic leukaemia, 6 of 7 with acute myelomonocytic leukaemia, 2 of 23 with acute myeloid leukaemia and 1 of 7 with acute lymphoblastic leukaemia. The highest levels of light chains in these groups were 5 times normal mean. All patients with myeloproliferative disorders revealed normal values of both light chain types.

Normal values for free light chains in serum in different age groups

The concentration of free light chains from the immunoglobulins was measured in twelve paired sera from mothers and newborns and from 149 sera from normal individuals in various age groups. Variations in concentration during life are correlated to the variations in the concentration of 'regular' immunoglobulins. A concentration of light chains in cord blood of 35% of mean normal adult level (MNA) together with a rapid passage of light chains across the placenta is interpreted as indicating catabolization of maternal light chains in the fetus. This is further supported by the finding of a lower concentration of light chains in maternal serum than in normal adult serum. The investigation shows that the concentration of light chains falls rapidly from 35 to 24% of MNA during the first few days of life. From the first week of life the concentration of light chains increases and low normal adult values are attained by one year of age. Except for difference in concentration, the elution pattern for light chains from Sephadex G-100 columns was similar for normal, adult and cord blood. The relationship between kappa and lambda chains--the K/L ratio--is 1.2 for normal and maternal serum and 1.0 for cord serum.