Analysis of immunoglobulins by two-dimensional gel electrophoresis

Cryoglobulin/albumin complexes in a patient with severe autoimmune syndrome

We describe the case of a 30-year-old man with a severe autoimmune disease characterized by cryoglobulinaemia, pulmonary hypertension, Raynaud's phenomenon, lymphadenopathy, and glomerulonephritis. Despite initial remission following autologous stem cell transplantation, his disease relapsed and he died from pulmonary hypertension. At presentation the patient had hypergammaglobulinaemia and a number of autoantibodies, including rheumatoid factor (1:10240). The most striking feature was the extremely high level of cryoglobulins. The cryoprecipitate consisted of polyclonal IgM, IgG and albumin. Interestingly, the albumin in the cryoprecipitate was exclusively present in SS-bonded oligomeric forms, and contained an abnormal acidic component as judged by 2D gel electrophoresis. Oxidized albumin was also present in serum, and represented a small but significant fraction. None of the many known albumin variants have so far been associated with a particular disease; thus our results may represent the first description of an altered albumin associated with severe disease.

Methods for human CD8(+) T lymphocyte proteome analysis

T lymphocytes, including cytotoxic CD8(+) T cells, are important cells involved in immunology, as they can destroy infected or tumor cells. We describe here a detailed protocol starting from CD8(+) T lymphocytes isolation for T cell culture followed by total protein extraction or subcellular fractionation, like nuclei isolation. We also describe well-defined biochemistry and cell biology methods adapted to T lymphocytes, showing the importance of using the method best suited to answering the question addressed. All these techniques would be very helpful to immunologists willing to study underlying biological processes related to T lymphocytes.

A better understanding of molecular mechanisms underlying human disease

This review summarises and discusses the degree to which proteomics is contributing to medical care, providing examples and signspots for future directions. Why do genomic approaches provide a limited view of gene expression? Because of the multifactorial nature of many diseases, proteomics enables us to understand the molecular basis of disease, not only at the organism, whole-cell or tissue levels, but also in subcellular structures, protein complexes and biological fluids. The application of proteomics in medicine is expected to have a major impact by providing an integrated view of individual disease processes. This review describes several proteomic platforms and examines the role of proteomics as a tool for clinical biomarker discovery, the identification of prognostic and earlier diagnostic markers, their use in monitoring the effects of drug treatments and eventually find more efficient and safer therapeutics for a wide range of pathologies.

Proteomic analyses of amniotic fluid: Potential applications in health and diseases

Amniotic fluid (AF) is a potential source of biomarkers for many disorders which may occur during pregnancy. The purpose of this study was to evaluate the place of two-dimensional gel electrophoresis (2-DE) technologies to compare AF in both normal and pathological situations. Two-dimensional fluorescence difference gel electrophoresis (2D-DIGE; Ettan DIGE) as well as two-dimensional gel electrophoresis and silver staining followed by image analysis were used. Differentially expressed proteins were identified by mass spectrometry. This approach was used to study electrophoregrams of normal AF obtained at 17 weeks of gestation and at term, as well as AF from fetuses presenting with congenital diaphragmatic hernia. Finally, the potential of two-dimensional electrophoresis was assessed by studying the protein profile of plasma containing AF proteins in a model of premature rupture of the membranes (PROM). Our results clearly show that two-dimensional electrophoresis technologies still have place for analyzing biological fluids such as AF.

Nonreducing two-dimensional gel electrophoresis for the detection of Bence Jones proteins in serum and urine

Nonreducing two-dimensional gel electrophoresis (2-DE) is described for the study of immunoglobulin disorders with asynchronous production of single chains. Unlike classical reducing 2-DE, this method can distinguish between complex intact molecules and their free single chains (with different degrees of polymerization) and will thus be helpful for diagnosis of this type of disease. Examples are taken from canine patients, but the method may also be applied to both urine and serum specimens from other species. Nonreducing 2-DE thus represents a useful tool complementary to classical 2-DE, when further information about the appearance of free subunits or modifications of proteins are required, even in the presence of intact molecules.

New approach based on fuzzy logic and principal component analysis for the classification of two-dimensional maps in health and disease. Application to lymphomas

Two-dimensional (2D) electrophoresis is the most wide spread technique for the separation of proteins in biological systems. This technique produces 2D maps of high complexity, which creates difficulties in the comparison of different samples. The method proposed in this paper for the comparison of different 2D maps can be summarised in four steps: (a) digitalisation of the image; (b) fuzzyfication of the digitalised map in order to consider the variability of the two-dimensional electrophoretic separation; (c) decoding by principal component analysis of the previously obtained fuzzy maps, in order to reduce the system dimensionality; (d) classification analysis (linear discriminant analysis), in order to separate the samples contained in the dataset according to the classes present in said dataset. This method was applied to a dataset constituted by eight samples: four belonging to healthy human lymph-nodes and four deriving from non-Hodgkin lymphomas. The amount of fuzzyfication of the original map is governed by the sigma parameter. The larger the value, the more fuzzy theresulting transformed map. The effect of the fuzzyfication parameter was investigated, the optimal results being obtained for sigma = 1.75 and 2.25. Principal component analysis and linear discriminant analysis allowed the separation of the two classes of samples without any misclassification.

Generalized crystal-storing histiocytosis associated with monoclonal gammopathy: molecular analysis of a disorder with rapid clinical course and review of the literature

Crystal-storing histiocytosis (CSH) is a rare event in disorders associated with monoclonal gammopathy. The intracellular crystal formation is almost always accompanied by the expression of κ light chains. However, the exact mechanism for the storage has not been clarified until now. We report a case of generalized CSH in a 73-year-old man who presented with IgA κ paraproteinemia and paraproteinuria. The initially observed CSH in the bone marrow biopsy was associated with the clinical and pathomorphologic features of a monoclonal gammopathy of undetermined significance. The progression of disease could not be affected by steroid therapy and the patient died of septic shock 7 months after detection of CSH. At the time of autopsy there was evidence for multiple myeloma and generalized CSH. Two-dimensional gel electrophoresis of liver tissue combined with immunoblotting revealed the massive storage of heavy chains of α type and light chains of κ type, each in a monoclonal pattern. Analysis of the stored κ light chain by nanoelectrospray-ionization mass spectrometry indicated that it belongs to the variable κI variability subgroup. We identified some unusual amino acid substitutions including Leu59, usually important for hydrophobic interactions within a protein, at a position where it has never been previously described in plasma cell disorders. In conclusion, we present the first case of CSH with molecular identification of the stored κ subgroup and detection of unusual amino acid substitutions. Our results suggest that conformational alterations induced by amino acid exchanges represent a crucial pathogenic factor in CSH.

Electrophoretic characteristics of monoclonal immunoglobulin G of different subclasses

Monoclonal IgG are commonly observed in various B cell disorders, of which multiple myeloma is the most clinically relevant. In a series of serum samples, we identified by immunofixation 73 monoclonal IgG, including 63 IgG(1), 4 IgG(2), 5 IgG(3), and 1 IgG(4). The light chains were of kappa type in 45 cases, and of lambda type in 28 cases. These monoclonal IgG were further characterized by high resolution two-dimensional polyacrylamide gel electrophoresis (2-DE) in various isoelectric focusing conditions, as well as by 3-DE (2-DE of the proteins extracted from agarose after serum protein agarose electrophoresis). After 2-DE, 38 out of 73 monoclonal gamma chains (52%) were visualized using immobilized pH 3-10 gradients for isoelectric focusing. In 6 cases (8%), gamma chains were only detected using alkaline immobilized pH 6-11 gradients. In 3 cases (4%), 3-DE revealed monoclonal gamma chains hidden by polyclonal gamma chains. Finally, in 26 cases (36%), no monoclonal gamma chains were clearly visualized. Sixty-one monoclonal light chains (84%) were detected using immobilized pH 3-10 gradients, whereas 12 (16%) were not. Monoclonal gamma chains and light chains were highly heterogeneous in terms of pI and M(r). However, a statistically significant correlation (P<0.05) was observed between the position of the monoclonal IgG in agarose gel and the pI of their heavy and light chains (R=0.733, multiple linear regression). Because of the extreme diversity of their heavy and light chains, it appears that a classification of monoclonal IgG based only on their electrophoretic properties is not possible.

The diversity of antigen-specific antibodies in humans and in two xenochimeric SCID mouse models

We applied two-dimensional gel electrophoresis (2-DE) to study the repertoire of tetanus toxoid (TT)-specific antibodies produced after TT immunization in healthy humans and in severe combined immunodeficient mice xenotransplanted with either human peripheral blood leukocytes (PBLe) or with human adult tonsil (hu-ton) pieces. Specific anti-TT antibodies, as well as total immunoglobulins (Ig), were purified by affinity chromatography on TT-Sepharose or Protein G-Sepharose, respectively. 2-DE unambiguously allowed us to differentiate between the specific humoral responses produced either by humans or by the two xenochimeric mouse models. Anti-TT antibodies produced by humans were polyclonal with a superimposed oligoclonality that was donor-dependent and that did not change upon time. By contrast, immunized hu-PBLe-SCID mice exhibited an evident clonal restriction of the Ig, which increased with time after boosting. Hu-ton-SCID mice showed a clonal diversity which was intermediate between those observed in humans and in hu-PBLe-SCID mice, and which was stable over time. In addition, information was gained by 2-DE, correlating with data obtained by enzyme-linked immunosorbent assay (ELISA), on the isotype composition of the anti-TT IgM response. Altogether, our results clearly demonstrated that the clonal diversity of monospecific antibodies can be appreciated by 2-DE, and that the largest diversity was found in humans when compared to that in xenochimeric models. In addition, mice implanted with pieces of lymphoid organs had the broadest anti-TT Ig diversity, an observation supporting the use of this model for the generation of antibodies with restricted specificity.

Micropurification and two-dimensional polyacrylamide gel electrophoresis of immunoglobulins for studying the clonal diversity of antigen-specific antibodies

Presented here is a simplified method for purifying antigen-specific antibodies and analysing them by two-dimensional polyacrylamide gel electrophoresis (2D-PAGE). For this procedure, specific immunoglobulins (Ig) are bound to resin beads coated with antigen and, in the presence of sodium dodecyl sulphate and dithioerythritol, loaded directly onto isoelectric focusing strips for 2D-PAGE analysis. This technique bypasses antigen-specific Ig elution and concentration and therefore minimises antibody loss and simplifies sample preparation. Because of its high sensitivity, this technique permits clonal analysis of samples containing small quantities of Ig. We studied Ig anti-tetanus toxoid (TT) and IgG in sera from several sources. The resulting oligoclonal Ig anti-TT patterns contrasted with the polyclonal patterns of total IgG visualised after 2D-PAGE analysis of the respective serum samples.

Two-dimensional electrophoretic analysis of cryoproteins: a report of 335 samples

Cryoproteins are defined as proteins precipitating at low temperature. Most frequently, the precipitate contains immunoglobulins (Igs), and are therefore called cryoglobulins. Three types of cryoglobulins have been described: type I contains a single monoclonal Ig, whereas type II is a mixture of a monoclonal Ig with polyclonal Igs, and type III is a mixture of polyclonal Igs of different isotypes, most frequently IgG and IgM. Type II and type III are also called mixed cryoglobulins. A new type of cryoglobulins, containing polyclonal IgG associated with a mixture of polyclonal and monoclonal IgM has recently been described after two-dimensional polyacrylamide gel electrophoresis (2-DE). This type of cryoglobulin has been called type II-III cryoglobulin. In this study, we report on 2-DE analysis of 335 cryoproteins from patients with heterogeneous clinical conditions. In 69 out of 335 samples (20.7%), 2-DE revealed patterns that were inadequate to characterize the cryoproteins. Out of 335 (79.3%) cryoproteins, 266 were identified according to their two-dimensional patterns: 265 samples contained Igs and were diagnosed as cryoglobulins, and one sample consisted of fibrinogen, and was identified as cryofibrinogen. Among the 265 cryoglobulins, types I, II, and III were observed in 9 (3.4%), 69 (26%), and 116 (43.8%) cases, respectively, whereas type II-III was detected in 71 (26.8%) cases. Eleven of the latter consisted of oligoclonal Igs (IgM in 10 cases, IgA in 1 case) mixed with traces of polyclonal IgG. These cryoproteins were tentatively named type II-IIIvariant cryoglobulins. Taken together, our result clearly show that 2-DE is a suitable technique to analyze cryoproteins.

Electrophoretic analyses in a case of monoclonal gamma chain disease

Abnormal low molecular weight immunoglobulin heavy chain can be detected in serum samples from patients with heavy chain disease. In this paper, we report the characterization of a gamma heavy chain in a patient suffering from a lymphoplasmocytic disorder, using immunofixation analysis and two-dimensional polyacrylamide gel electrophoresis. We demonstrate that the combination of serum protein agarose electrophoresis and two-dimensional electrophoresis (three-dimensional electrophoresis) can be used to further characterize abnormal protein bands detected by immunofixation.

Analysis of Bence Jones proteinuria by high resolution two-dimensional electrophoresis

Analysis of Bence Jones proteinuria by high resolution two-dimensional electrophoresis (2-DE) and immunoblotting reveals a complex pattern of light chain (LC) isoforms corresponding to the free monoclonal Bence Jones protein and its fragments. Replica blotting gives duplicate blots for LC typing (lambda, chi) and, under the conditions employed, leaves sufficient protein for Coomassie Blue staining of the urinary protein profile and pIIMr determination of the LC isoforms. Carrier ampholytes (CAs, in our "simplified" 2-DE system) and immobilised pH gradients (IPGs, in the Multiphor 2-DE system) give similar LC isoform patterns. Artifacts, including cone-like distortions and trailing "piggyback" spots, are visualised with both 2-DE systems. IPGs are advantageous as they allow reproducible detection of strongly basic LC isoforms by isoelectric focusing (under equilibrium conditions) without recourse to CA nonequilibrium pH gradient electrophoresis.

Role of two-dimensional electrophoretic analysis in the diagnosis and characterization of IgD monoclonal gammopathy

Over a period of 5 years, an isolated light chain (kappa = 9, lambda = 12) was detected in 21 sera by immunofixation electrophoresis. Further analysis with anti-delta- and anti-epsilon-specific antisera identified four delta heavy chains, all associated with a lambda light chain, and no epsilon heavy chains. For evaluation of the role of two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) in the diagnosis of IgD paraproteins, as a possible alternative or complement to immunofixation, IgD paraproteins were retrospectively analyzed by 2D-PAGE. Delta Heavy chains migrated to gel areas clearly distinguishable from other heavy chains alpha, gamma, or mu, and in a wide range of isoelectric points (pI: 5.4-8). In one serum, the monoclonal delta chain had a pI range comparable to that of albumin and was undetectable. However, all four delta chains were easily identified when analyzed from affinity-purified immunoglobulin fractions. These observations showed the following: 1) IgD paraproteins are not rare among apparently isolated monoclonal light chains detected by routine immunofixation, strongly confirming the need for further analysis with anti-delta antisera, before assumption of a light-chain disease. 2) 2D-PAGE analysis of affinity-purified immunoglobulin fractions allowed correct identification of IgD monoclonal gammopathies in all cases. 3) However, although 2D-PAGE analysis is now easy to perform, well standardized, and highly sensitive, this technique remains time-consuming and expensive, and does not appear suitable for routine practice as a first-line diagnostic procedure. 2D-PAGE should find its place as a complement to immunofixation and in the definitive demonstration, in selected ambiguous cases, of the clonal pattern of a suspected gammopathy at immunofixation.