Bence-Jones proteins and light chains of immunoglobulins (second of two parts)

The Increasing Role of Kappa Free Light Chains in the Diagnosis of Multiple Sclerosis

Free light chains (FLC) are a promising biomarker to detect intrathecal inflammation in patients with inflammatory central nervous system (CNS) diseases, including multiple sclerosis (MS). The diagnostic use of this biomarker, in particular the kappa isoform of FLC ("KFLC"), has been investigated for more than 40 years. Based on an extensive literature review, we found that an agreement on the correct method for evaluating KFLC concentrations has not yet been reached. KFLC indices with varying cut-off values and blood-CSF-barrier (QAlbumin) related non-linear formulas for KFLC interpretation have been investigated in several studies. All approaches revealed high diagnostic sensitivity and specificity compared with the oligoclonal bands, which are considered the gold standard for the detection of intrathecally synthesized immunoglobulins. Measurement of KFLC is fully automated, rater-independent, and has been shown to be stable against most pre-analytic influencing factors. In conclusion, the determination of KFLC represents a promising diagnostic approach to show intrathecal inflammation in neuroinflammatory diseases. Multicenter studies are needed to show the diagnostic sensitivity and specificity of KFLC in MS by using the latest McDonald criteria and appropriate, as well as standardized, cut-off values for KFLC concentrations, preferably considering non-linear formulas such as Reiber's diagram.

Kinetic stability and sequence/structure studies of urine-derived Bence-Jones proteins from multiple myeloma and light chain amyloidosis patients

It is now accepted that the ability of a protein to form amyloid fibrils could be associated both kinetic and thermodynamic protein folding parameters. A recent study from our laboratory using recombinant full-length (encompassing the variable and constant domain) immunoglobulin light chains found a strong kinetic control of the protein unfolding for these proteins. In this study, we are extending our analysis by using urine-derived Bence Jones proteins (BJPs) from five patients with light chain (AL) amyloidosis and four patients with multiple myeloma (MM). We observed lower stability in κ proteins compared to λ proteins (for both MM and AL proteins) in agreement with previous studies. The kinetic component of protein stability is not a universal feature of BJPs and the hysteresis observed during refolding reactions could be attributed to the inability of the protein to refold all domains. The most stable proteins exhibited 3-state unfolding transitions. While these proteins do not refold reversibly, partial refolding shows 2-state partial refolding transitions, suggesting that one of the domains (possibly the variable domain) does not refold completely. Sequences were aligned with their respective germlines and the location and nature of the mutations were analyzed. The location of the mutations were analyzed and compared with the stability and amyloidogenic properties for the proteins in this study, increasing our understanding of light chain unfolding and amyloidogenic potential.

Evolutionary redefinition of immunoglobulin light chain isotypes in tetrapods using molecular markers

The phylogenetic relationships of Ig light chain (IGL) genes are difficult to resolve, because these genes are short and evolve relatively fast. Here, we classify the IGL sequences from 12 tetrapod species into three distinct groups (kappa, lambda, and sigma isotypes) using conserved amino acid residues, recombination signal sequences, and genomic organization of IGL genes as cladistic markers. From the distribution of the markers we conclude that the earliest extant tetrapods, the amphibians, possess three IGL isotypes: kappa, lambda, and sigma. Of these, two (kappa and lambda) are also found in reptiles and some mammals. The lambda isotype is found in all tetrapods tested to date, whereas the kappa isotype seems to have been lost at least in some birds and in the microbat. Conservation of the cladistic molecular markers suggests that they are associated with functional specialization of the three IGL isotypes. The genomic maps of IGL loci reveal multiple gene rearrangements that occurred in the evolution of tetrapod species. These rearrangements have resulted in interspecific variation of the genomic lengths of the IGL loci and the number and order of IGL constituent genes, but the overall organization of the IGL loci has not changed.

Chicken Anti-Protein L for the Detection of Small Amounts of Protein L in the Presence of IgG

Protein L is a cell surface protein, expressed by Peptostreptoccocus magnus, which binds to the variable light chains of immunoglobulins without interfering with antigen binding. It can be used for purification of mammalian antibodies of all classes in contrast to the Ig-binding proteins protein A and protein G. Detection of protein L leakage into antibody preparations is important, since protein L could interfere in immunological assays and cause adverse reactions in vivo. Here we have developed a sandwich ELISA for detection of protein L in the presence or absence of mouse IgG utilizing specific chicken IgY antibodies. Protein L does not react with chicken IgY light chains, and it is therefore possible to make an antigen-specific assay. The assay can be used to detect protein L at a concentration of 0.3 ng/mL in the presence of IgG.

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.

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

Immunoglobulin excretion by patients with monoclonal gammopathies and tubular proteinuria has been analysed by agarose gel isoelectricfocussing of untreated urine and immunoblotting. About three-quarters of the Bence-Jones proteins detected occurred as multiple bands on isoelectricfocussing; in about half of these cases the multiple forms were due to polymerisation or fragmentation of the light chains. In specimens with tubular proteinuria, a characteristic light chain pattern of three broad bands covering the pI ranges 7.1-7.3, 7.8-8.0 and 8.3-8.5 was found. This pattern also occurred in 53% of specimens with Bence-Jones proteinuria and was identical to that found in concentrated normal urine. Intact monoclonal immunoglobulin usually appeared as three or more evenly spaced bands of similar intensity whereas polyclonal intact immunoglobulins produced diffuse staining from pI 5.0-8.5. A scheme for the qualitative analysis of urinary immunoglobulin excretion using this technique has been developed.

Multiple myeloma, IgA kappa type, accompanying crystal-storing histiocytosis and amyloidosis

An autopsy case of multiple myeloma, IgA kappa type, accompanying systemic crystal-storing histiocytosis and generalized amyloidosis, is reported. Besides multiple destructive lesions in the skeletal bones, nodular myeloma cell infiltrates were scattered in the liver, spleen, and both kidneys. Not only in these lesions but also in the reticuloendothelial organs, crystal-storing macrophages appeared dispersively or in clusters. Electron microscopically, numerous crystalline inclusions contained in the cytoplasm of macrophages were membrane-bound and of variable configuration, comprising of a homogeneous electron-lucid material. Enzyme cytochemically, almost all of the inclusions showed acid phosphatase activity. On the basis of the results obtained from the immunohistochemical, immunofluorescent and immunoelectron microscopic studies, it was considered that the crystalline inclusions stored in the macrophages were derived from IgA kappa immunoglobulin secreted from the myeloma cells and were formed within secondary lysosomes by crystallization during lysosomal digestion and degradation of the ingested immunoglobulin by macrophages. Generalized amyloidosis developed in different sites from those of the crystal-storing histiocytosis and were proven immunohistochemically to belong to AL amyloidosis probably derived from a certain group of A kappa precursor protein.

Human anti-F(ab')2 antibodies and pepsin agglutinators react with Fv determinants

Affinity-purified human IgG anti-tetanus antibody was subjected to papain and then pepsin digestion, and residual fragments retaining antibody activity were re-isolated by adsorption and elution from Sepharose-tetanus toxoid columns. Both Fab' and Fv fragments isolated by gel filtration showed strong reactivity with anti-F(ab')2 antibodies. Failure of tetanus toxoid to completely block reactivity of anti-F(ab')2 antibody with anti-tetanus Fv fragments indicates that these antibodies react with framework antigens within variable antibody regions.

Detection of Bence-Jones protein by isoelectric focussing of unconcentrated urine followed by nitrocellulose blotting and immunoperoxidase staining

Urine specimens from 164 patients sent to the laboratory for testing for Bence-Jones proteinuria were investigated using a new procedure. The protein in the untreated urine was subjected to isoelectric focussing in an agarose gel, transferred to a nitrocellulose membrane by blotting, and then stained by an immunoperoxidase technique for either immunoglobulin kappa or lambda chains. This technique was compared with a routine procedure for the detection of immunoglobulin light chains involving concentration by ultrafiltration, electrophoresis and then immunofixation. The new technique achieved a much increased rate of detection of Bence-Jones proteinuria. Among 51 patients known to have myeloma or macroglobulinaemia, Bence-Jones proteinuria was detected in 35 cases with the new procedure and in only 27 by the conventional method. In 28 patients with paraproteinaemia without other evidence of myeloma, macroglobulinaemia, leukaemia or lymphoma, 12 instances of Bence-Jones proteinuria were discovered with the new procedure, 10 of which were missed by the conventional method. The improved efficiency of detection is attributed to the high resolution of isoelectric focussing and the avoidance of protein loss from adsorption on to ultrafiltration membranes.

Novel arrangement of immunoglobulin variable domains: X-ray crystallographic analysis of the lambda-chain dimer Bence-Jones protein Loc

We have characterized and crystallized a human lambda I light-chain dimer, Bence-Jones protein Loc, which has variable (V) region antigenic determinants characteristic for the lambda I subgroup and constant (C) region determinants of the C lambda I gene Mcg. The crystal structure was determined to 3-A resolution; the R factor is 0.27. The angle formed by the twofold axes of the V and C domains, the "elbow bend", is 97 degrees, the smallest found so far for an antibody fragment. The antigen-binding site formed by the two V domains of the Loc light chain differs significantly from those of other immunoglobulin molecules (light-chain dimers and Fab fragments) for which X-ray crystallographic data are available. Whereas, in other antibody fragments, the V domains are related by a local twofold axis, a local twofold screw axis with a translational component of 3.5 A relates the V domains in protein Loc. In contrast to the classic antigen binding "pocket" formed by V domain interactions in the previously characterized antibody structures, the V region associations in protein Loc result in a central protrusion in the binding site, with grooves on two sides of the protrusion. The structure of protein Loc indicates that immunoglobulins are physically capable of forming a more diverse spectrum of antigen-binding sites than has been heretofore apparent. Moreover, the unusual protruding nature of the binding site may be analogous to structures required for some anti-idiotypic antibodies. Further, the complementarity-determining residues form parts of two independent grooves.(ABSTRACT TRUNCATED AT 250 WORDS)

Thin layer gel filtration immunofixation: identification of abnormal molecular weight immunoglobulins or related fragments

A simple procedure is described to identify immunoglobulin (Ig) fragments without isolation from biological fluids. It involves an initial separation based on molecular weight (MW) by thin layer gel filtration (TLG) followed by immunofixation (IF) in cellulose acetate strips with monovalent antisera. TLG-IF permits detection of differences about 10,000 Da MW and specific immunological typing, making it a useful tool in the accurate identification of protein fragments.

Simple method for the screening of polymeric Bence Jones proteins

The author tested the electropherograms of previously identified, concentrated urine samples in agarose gel. Before electrophoresis, the gel plate containing the samples was covered with a cellulose-acetate membrane soaked with 0.1 M 2-mercaptoethanol, and it was incubated for 10 min in a moist chamber, at room temperature. If the polymeric Bence Jones protein is present, the electropherogram of the sample changes. In the following, a quick and easy method of recognizing this rare structural anomaly is recommended.

Urinary protein profiles in patients with urothelial bladder tumours

Urinary protein profiles were studied in 32 patients with urothelial bladder tumours, using immunonephelometry. In patients without residual or recurrent tumours a glomerular type of proteinuria was demonstrated. In patients with grade III-IV transitional cell carcinoma the glomerular proteinuria was more severe than in patients with grade I-II tumours. Increased excretion of low molecular weight proteins was observed only in patients with grade III-IV tumours. The use of the increased relative clearance of albumin, transferrin, and haptoglobin as a diagnostic test was attempted in detecting residual or recurrent tumours. In patients with grade III-IV tumours the predictive value of a positive or negative test was 92% and 100% respectively, whereas the relative protein clearance was without predictive value in patients with grade I-II tumours.

Multiple myeloma: current concepts in diagnosis and management

The basic pathologic process in multiple myeloma is the neoplastic proliferation of a single clone of plasma cells. Although the events which trigger autonomous cell growth are not well understood, the secretion of an M component, a serum or urinary immunoglobulin molecule or a light chain fragment by the vast majority of myeloma cells has provided a biologic marker which has greatly facilitated the study of this disease Some of the more recent clinical concepts which have evolved from studies on the plasma cell and the immunoglobulin molecule are discussed.

Plasmapheresis in the treatment of acute renal failure in multiple myeloma

Three patients with multiple myeloma and severe acute renal failure were treated by repeated plasmapheresis. Recovery of renal function was observed in all. The pathogenetic role of light chains and the possible mechanisms responsible for renal damage are discussed. It is suggested that the removal of light chains by plasmapheresis may be of therapeutic value in this condition.