A quantitative approach to the determination of antigen in immune complexes

Distinctive aspects of the immune status of the Kola Saami and Russians living in the Far North

OBJECTIVE

The level of immunological reactivity of the indigenous inhabitants of the Far North may depend on the extreme-discomfort factors of the climatic environment and genetic traits of the population. Therefore, the aim of this study was to identify the distinctive elements of the immune status of the Kola Saami and Russians living in the Far North (Murmansk Region).

METHODS

A complex immunological study of peripheral venous blood composition was performed and involved 67 Saami and 81 Russian inhabitants of the Far North (Murmansk Region) who were aged 21-55. Blood was collected from the cubital vein on an empty stomach in the morning. For the peripheral venous blood, we obtained a hemogram and phagocytic activity of neutrophils, determined the content of lymphocytes with CD4, CD8, CD16, and CD71 phenotypes by indirect immunoperoxidase reaction and flow cytometry using an Epics XL apparatus (Beckman Coulter, United States), obtained concentrations of IL-6, IFN-γ, IL-10, IgA, M, G, E, sCD54, and sCD62L, transferrin, and sCD71 by enzyme immunoassay using the "Evolis" enzyme immunoassay analyzer from Bio-RAD (Germany), and obtained circulating immune complexes by precipitation using 3.5%, 4.0%, and 7.5% PEG-6000. The sIgA content was determined in morning saliva, urine, and gastrointestinal tract secretions. The results were analyzed using descriptive statistics, independent sample t-criterion, and Pearson correlation coefficient.

RESULTS

A decrease in the total number of leukocyte cells in the Saami was associated with a high incidence of leukopenia, lymphopenia, and neutropenia. Deficiency in active phagocytes and serum IgA and sIgA concentrations was revealed as well as increased contents of CD4+ and CD8+ receptor lymphocytes, membrane and free adhesion molecules, and transferrin. Leukocytosis, lymphocytosis, neutrophilia, monocytosis, and eosinophilia with increased contents of natural killer cells, IL-6, and IL-10 were recorded more frequently in the Russians. High levels of IgE and IFN-γ, which have the most pronounced cytotoxicity and are indicative of strained immune mechanisms, were characteristic of the Saami and Russians.

CONCLUSION

The distinctive aspects of the immune status of the Kola Saami is related to the deficit in the active phagocyte and serum IgA and sIgA concentrations as well as the increase in the contents of cytotoxic lymphocytes, intercellular adhesion molecules, transferrin, and IFN-γ proinflammatory cytokines. The Russian inhabitants of the Far North are characterized by an adaptive response manifested by an increase in antibody-dependent cytotoxicity, involving IL-6 and IL-10.

Circulating immune-complexes of IgG/IgM bound to B2-glycoprotein-I associated with complement consumption and thrombocytopenia in antiphospholipid syndrome

Background

Antiphospholipid syndrome (APS) is a multisystemic autoimmune disorder characterized by thrombotic events and/or gestational morbidity in patients with antiphospholipid antibodies (aPL). In a previous single center study, APS-related clinical manifestations that were not included in the classification criteria (livedo reticularis, thrombocytopenia, leukopenia) were associated with the presence of circulating immune-complexes (CIC) formed by beta-2-glycoprotein-I (B2GP1) and anti-B2GP1 antibodies (B2-CIC). We have performed a multicenter study on APS features associated with the presence of B2-CIC.

Methods

A multicenter, cross-sectional and observational study was conducted on 303 patients recruited from six European hospitals who fulfilled APS classification criteria: 165 patients had primary APS and 138 APS associated with other systemic autoimmune diseases (mainly systemic lupus erythematosus, N=112). Prevalence of B2-CIC (IgG/IgM isotypes) and its association with clinical manifestations and biomarkers related to the disease activity were evaluated.

Results

B2-CIC prevalence in APS patients was 39.3%. B2-CIC-positive patients with thrombotic APS presented a higher incidence of thrombocytopenia (OR: 2.32, p=0.007), heart valve thickening and dysfunction (OR: 9.06, p=0.015) and triple aPL positivity (OR: 1.83, p=0.027), as well as lower levels of C3, C4 and platelets (p-values: <0.001, <0.001 and 0.001) compared to B2-CIC-negative patients. B2-CIC of IgM isotype were significantly more prevalent in gestational than thrombotic APS.

Conclusions

Patients with thrombotic events and positive for B2-CIC had lower platelet count and complement levels than those who were negative, suggesting a greater degree of platelet activation.

Detection of Novel Urine Markers Using Immune Complexome Analysis in Bladder Cancer Patients: A Preliminary Study

BACKGROUND/AIM

Little is known on urine biomarkers that are associated with malignant behavior in patients with bladder cancer (BC). Our aim was to identify BC-related factors in urine samples using our original method "immune complexome analysis", based on detecting the immune complex (IC).

PATIENTS AND METHODS

Immune complexome analysis was performed using urine samples from 97 BC patients, including 67 with non-muscle invasive BC (NMIBC).

RESULTS

Eight IC-antigens were recognized as candidates for BC-related factors from 20,165 proteins. IC-serum albumin, -fibrinogen γ chain, -hemoglobin subunit α, -hemoglobin subunit β, -ceruloplasmin, and fibrinogen β chain were significantly associated with either pathological features and/or outcome. IC-ceruloplasmin was most widely associated with pathological features in all BC patients and lamina propria invasion and urinary tract recurrence in NMIBC.

CONCLUSION

Based on detection of IC-antigens it was demonstrated that six IC-antigens, especially IC-ceruloplasmin, are potential urine biomarkers in BC.

State of humoral immunity in lactating sows and suckling piglets

The state of humoral immunity in lactating sows and its formation in suckling piglets in the conditions of a pig-breeding complex were studied. In sows after farrow, a high content of total immunoglobulins, the main classes of IgG, IgM and IgA, the concentration of which decreased in a day, followed by an increase in serum as lactation continued was detected in the serum and colostrum. In piglets at birth, the content of total immunoglobulins and the main Ig isotypes was insignificant, and at the age of twenty-four hours, as a result of absorption of colostral immunoglobulins in the small intestine, their amount in the serum was the highest, followed by a decrease in the concentration of IgG and IgA until the end of the suckling period, and IgM - up to day 14 with a further increase in its content, indicating the formation of a primary immune response. It has been detected that the dominant class of immunoglobulins in the serum and colostrum of sows and the serum of piglets is IgG, and in milk - IgA. An increase in the level of medium-dispersed circulating immune complexes (C4%) and their relation to giant (C3%) CICs was revealed, associated with an increase of the antigenic load in sows in the second half of lactation as a result of immunization, in milk - with a decrease in the content of the main classes of immunoglobulins, and in piglets, due to this, with a decrease in passive immunity.

Immune-Complexome Analysis Identifies Immunoglobulin-Bound Biomarkers That Predict the Response to Chemotherapy of Pancreatic Cancer Patients

Pancreatic Ductal Adenocarcinoma (PDA) is an aggressive malignancy with a very poor outcome. Although chemotherapy (CT) treatment has poor efficacy, it can enhance tumor immunogenicity. Tumor-Associated Antigens (TAA) are self-proteins that are overexpressed in tumors that may induce antibody production and can be PDA theranostic targets. However, the prognostic value of TAA-antibody association as Circulating Immune Complexes (CIC) has not yet been elucidated, mainly due to the lack of techniques that lead to their identification. In this study, we show a novel method to separate IgG, IgM, and IgA CIC from sera to use them as prognostic biomarkers of CT response. The PDA Immune-Complexome (IC) was identified using a LTQ-Orbitrap mass spectrometer followed by computational analysis. The analysis of the IC of 37 PDA patients before and after CT revealed differential associated antigens (DAA) for each immunoglobulin class. Our method identified different PDA-specific CIC in patients that were associated with poor prognosis patients. Finally, CIC levels were significantly modified by CT suggesting that they can be used as effective prognostic biomarkers to follow CT response in PDA patients.

Revisiting immune complexes: Key to understanding immune-related diseases

Immune complexes (ICs) formed by foreign or self-antigens and antibodies in biological fluids affect various tissues and are thought to cause several diseases. Biological and physical properties of IC, abnormal IC amounts, IC deposition and their relationships with disease pathogenesis had been studied. However, the relationship between ICs and each disease is not well understood and little is known of what determined ICs deposition in particular organ and why different organs are affected in different diseases. Recent technological advance enables identification of ICs in particular its antigens in tissues and body fluids, which may provide a key to discover an important trigger for immunological abnormality occurrence. Further identification of their epitopes, that are the exact origin of antigenicity, is developing and may be useful for diagnosis, elucidation of pathogenesis and treatment against IC-induced diseases. Here, we first make an overview of clearance of ICs, IC-induced pathogenesis and biological properties of ICs. Then, we introduce various methods developed to recover ICs from biological fluids or to identify antigens incorporated into ICs. Furthermore, several methods that can be used in epitope mapping for IC antigens are also documented.

Comprehensive immune complexome analysis detects disease-specific immune complex antigens in seminal plasma and follicular fluids derived from infertile men and women

BACKGROUND

Autoimmune reactions and subsequent inflammation may underlie spermatogenic dysfunction and endometriosis-related infertility. The aim of this study is to identify disease-specific antigens in immune complexes (ICs) in seminal plasma (SP) and in follicular fluid (FF).

METHODS

Immune complexome analysis, in which nano-liquid chromatography-tandem mass spectrometry is employed to comprehensively identify antigens incorporated into ICs in biological fluids, was performed for specimens collected from infertile couples undergoing assisted reproduction. Forty-two male patients consisting of subjects with oligozoospermia (n = 6), asthenozoospermia (n = 8), and normal semen analysis (n = 28). Fifty-eight female patients consisting of subjects with ovarian endometriosis (n = 10) and control women without disease (n = 48).

RESULTS

Four disease-specific antigens were identified in subjects with oligozoospermia, while five disease-specific antigens were detected in subjects with asthenozoospermia, some of which are involved in sprematogenesis. Eight antigens were detected only in subjects with endometriosis.

CONCLUSION

Functional characteristics of disease-specific antigens were found to correspond to the pathogenesis of male and female infertility. The formation of ICs may contribute to spermatogenic dysfunction and endometriosis-related infertility via loss of function of the related proteins. Immune complexome analysis is expected to be a valuable tool for the investigation of novel diagnostic methods and treatment strategies for infertility.

Identification of Antigens in Immune Complexes

Comprehensive identification and profiling of antigens in immune complexes (IC-antigens) is useful to provide insights into pathophysiology and could form the basis for novel diagnostic and treatment strategies for many immune-related diseases. Immune complexome analysis is the method for comprehensively identifying and profiling IC-antigens in biological fluids (such as serum and cerebrospinal fluid). Here, we describe an IC-antigen detection method; specifically, ICs in biological fluids are captured by using protein G- or protein A-coated beads, are subjected to papain-digestion, elution, and tryptic digestion, and are analyzed by nano-liquid chromatography-tandem mass spectrometry (nano-LC-MS/MS).

Selective, sensitive and comprehensive detection of immune complex antigens by immune complexome analysis with papain-digestion and elution

Comprehensive identification and profiling of antigens in immune complexes (ICs) in biological fluids, such as serum and cerebrospinal fluid, is useful for developing early diagnostic markers and specific treatments for many diseases. We have developed a method, designated "immune complexome analysis", to comprehensively identify the antigens in ICs. In this method, we first purify ICs from biological fluid by using Protein G- or Protein A-coated beads, then these ICs are subjected to tryptic digestion on the beads and subsequent analysis using nano-liquid chromatography-tandem mass spectrometry (nano-LC-MS/MS). We previously used this method to find specific antigens in circulating ICs (CIC-antigens) in serum for autoimmune diseases, infectious disease and cancers. However, this method detects not only CIC-antigens but also antibodies and proteins bound non-specifically to the beads, which restricts the detection of minor peptides released by the digestion of CIC-antigens whose amounts are generally much less than antibodies and the proteins. To selectively detect CIC-antigens with enhanced sensitivity, in this study we compared three methods (Method A, direct tryptic digestion on the beads; Method B, low-pH elution and tryptic digestion; Method C, papain-digestion, elution, and tryptic digestion) and examined which method selectively elutes CIC-antigens from CICs bound to the beads and selectively detects CIC-antigens using nano-LC-MS/MS. We also compared three types of CIC-capturing beads (Protein G-coated magnetic beads, Protein A-coated magnetic beads and Proceptor™-sepharose beads) to examine if parallel use of these beads aids the comprehensive detection of CIC-antigens in immune complexome analysis. Comparison showed that Method C provided the most selective and sensitive detection of CIC-antigens, without interference by antibodies and proteins non-specifically bound to the beads. In addition, using three types of beads allowed the examination of a wide range of CIC-antigens in immune complexome analysis. Therefore, combining Method C with three types of beads should allow the selective and sensitive identification of IC-antigens present in biological fluids from patients with a variety of diseases. The identification of IC-antigens may lead to the development of diagnostic methods and protocols for specific treatments for these diseases.

Peculiarities of the formation and subsequent removal of the circulating immune complexes from the bloodstream during the process of digestion

Background: Large protein aggregates, known as circulating immune complexes (CICs), are formed in biological fluids as a result of the development of the body's immune response to various provoking factors. The kinetic characteristics of the formation and removal of immune complexes (ICs), their physical parameters, the isotypic composition of immunoglobulins (Igs) and the antigenic component of the CICs may reflect certain aspects of certain pathological and metabolic processes taking place in humans and animals. The aim of this study is to assess the kinetic characteristics of the formation and removal of the CICs that form in blood after eating. We also analyze the changes in the isotypic composition of Igs of ICs that accompany this biological process in rodents and humans. Methods: We identified the CICs, which differed in size and class of Igs, using dynamic light scattering. To remove ICs from the plasma, we used immune-affinity sedimentation. Monoclonal antibodies for the Igs of different isotypes were added to the plasma samples to determine the isotypic composition of the ICs. Results: A large number of ICs were formed in the blood of rats and humans after eating (food CICs). In rats, food ICs are almost immediately filtered in the liver, without circulating in the bloodstream through the body. In humans, the level of food ICs in the blood increases for 3.5 h after ingestion, then within 7-8 h their gradual removal takes place. It was found that in the process of digestion in humans, the isotypic composition of Igs in the CICs changes and becomes more diverse. Conclusions: The molecular-cellular mechanisms of the formation and utilization of food CICs in humans and rodents do not match completely.

WITHDRAWN: Diversity of immunoglobulin G functions

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Plasma anti-α-galactoside antibody binds to serine- and threonine-rich peptide sequence of apo(a) subunit in Lp(a)

Lipoprotein(a) immune complexes [Lp(a) IC] of varying particle density obtained by ultracentrifugation of plasma from normal healthy donors were markedly dominated by IgG. Lp(a) and immunoglobulins were liberated from plasma Lp(a) IC by treatment with melibiose, a sugar specific for circulating anti-α-galactoside antibody (anti-Gal). Upon incubation with plasma lipoprotein fraction anti-Gal but not the α-glucoside-specific antibody from human plasma formed de novo IC with Lp(a). Binding of Lp(a) sugar-reversibly enhanced the fluorescence of FITC-labeled anti-Gal as did binding of α-galactoside-containing glycoproteins. This effect apparently due to conformational shift in the Fc region of the antibody was also produced by apo(a) subunit separated from Lp(a) and de-O-glycosylated apo(a) but not by any other plasma lipoproteins or by Lp(a) pre-incubated with the O-glycan-specific lectin jacalin. O-Glycans and their terminal sialic acid moieties in apo(a) of circulating Lp(a)-anti-Gal IC, in contrast to those in pure Lp(a), were inaccessible to jacalin and anion exchange resin, respectively. Unlike other plasma lipoproteins, Lp(a) inhibited Griffonia simplicifolia isolectin B4 which also accommodates serine- and threonine-rich peptide sequence (STPS) as surrogate ligand to α-galactosides at its binding site. Results suggest that anti-Gal recognizes STPS in the O-glycan-rich regions of apo(a) subunit in Lp(a) which contains no α-linked galactose.

Human plasma anti-α-galactoside antibody forms immune complex with autologous lipoprotein(a)

Anti-α-galactoside antibody (anti-Gal) from human plasma that bound to α-galactoside-bearing guar galactomannan gel and was eluted with specific sugar (affinity-purified anti-Gal ; APAG) invariably contained apo(a) and apo B subunits in a proportion close to that in plasma lipoprotein(a) [Lp(a)]. Since LDL does not contain apo(a), result suggested Lp(a) as a component of APAG. Lp(a) in APAG was complexed with anti-Gal since plate-coated anti-apo(a) captured Lp(a) along with the antibody. Association of Lp(a) with anti-Gal in APAG was considerably lower in presence of anti-Gal-specific sugar, suggesting that Lp(a) occupied the sugar-binding site of anti-Gal. Content of Lp(a)-bound anti-Gal in APAG, though a minor fraction of total antibody, increased steadily with total Lp(a) content of plasma. Further, Lp(a) released from immune complex-rich fraction of plasma by anti-Gal- specific sugar was proportional to total plasma Lp(a). Anti-Gal titre decreased with increasing Lp(a) concentration among 114 plasma samples. Results indicate the potential of anti-Gal molecules with its binding site partially occupied by Lp(a) molecule(s) to a) use the remaining binding site(s) to recognize other macromolecules or cells and b) transport Lp(a) across Fc receptor-bearing cells.

Circulating levels of chromatin fragments are inversely correlated with anti-dsDNA antibody levels in human and murine systemic lupus erythematosus

Anti-dsDNA antibodies represent a central pathogenic factor in Lupus nephritis. Together with nucleosomes they deposit as immune complexes in the mesangial matrix and along basement membranes within the glomeruli. The origin of the nucleosomes and when they appear e.g. in circulation is not known. Serum samples from autoimmune (NZBxNZW)F1 mice, healthy BALB/c mice, patients with SLE, RA and normal healthy individuals were analyzed for presence and amount of circulating anti-dsDNA antibodies and nucleosomal DNA. Here we use a quantitative PCR to measure circulating DNA in sera. We demonstrate an inverse correlation between anti-dsDNA antibodies and the DNA concentration in the circulation in both murine and human serum samples. High titer of anti-DNA antibodies in human sera correlated with reduced levels of circulating chromatin, and in lupus prone mice with deposition within glomeruli. The inverse correlation between DNA concentration and anti-dsDNA antibodies may reflect antibody-dependent deposition of immune complexes during the development of lupus nephritis in autoimmune lupus prone mice. The measurement of circulating DNA in SLE sera by using qPCR may indicate and detect the development of lupus nephritis at an early stage.

Anti-dsDNA antibodies bind to mesangial annexin II in lupus nephritis

Production of anti-dsDNA antibodies is a hallmark of lupus nephritis, but how these antibodies deposit in organs and elicit inflammatory damage remains unknown. In this study, we sought to identify antigens on the surface of human mesangial cells (HMC) that mediate the binding of human anti-dsDNA antibodies and the subsequent pathogenic processes. We isolated anti-dsDNA antibodies from patients with lupus nephritis by affinity chromatography. We used multiple methods to identify and characterize antigens from the plasma membrane fraction of mesangial cells that crossreacted with the anti-dsDNA antibodies. We found that annexin II mediated the binding of anti-dsDNA antibodies to HMC. After binding to the mesangial cell surface, anti-dsDNA antibodies were internalized into the cytoplasm and nucleus. This also led to induction of IL-6 secretion and annexin II synthesis, mediated through activation of p38 MAPK, JNK, and AKT. Binding of anti-dsDNA antibodies to annexin II correlated with disease activity in human lupus nephritis. Glomerular expression of annexin II correlated with the severity of nephritis, and annexin II colocalized with IgG and C3 deposits in both human and murine lupus nephritis. Gene silencing of annexin II in HMC reduced binding of anti-dsDNA antibody and partially decreased IL-6 secretion. In summary, our data demonstrate that annexin II mediates the binding of anti-dsDNA antibodies to mesangial cells, contributing to the pathogenesis of lupus nephritis. This interaction provides a potential target for therapeutic intervention.

Circulating non-immune IgG complexes in health and disease

IgG molecules possess a well-defined ability to form complexes with various proteins at interaction sites composed of residues of the constant domains. Such non-immune complexes (non-ICs) were recently identified in the circulatory system of healthy people, as well as patients suffering from various pathologies. By forming non-ICs, attached proteins that are harmful to the organism (anaphylatoxins, for example) are removed from the circulation. Non-immune IgG complexes can react simultaneously with two cell receptors-one specific for IgG, and another specific for an associated protein. Such double reactions augment cellular responses. The attachment of a protein to an IgG site may induce structural changes in neighboring areas of IgG molecules. The formation of non-ICs helps proteins with low molecular mass to escape glomerular filtration, as well as enzymatic degradation and cell uptake. Non-immune IgG complexes have been found in commercial immune globulin preparations used for the treatment of various diseases. Among the IgG-attached proteins, there are specific disease biomarkers used for clinical diagnostics and understanding disease processes. Therefore, in order to identify potential biomarkers, not only proteins that are free in the liquid phase of serum but also proteins associated with abundant proteins such as IgG must be investigated.

Immune complex binding by immunocamouflaged [poly(ethylene glycol)-grafted] erythrocytes

Immune complexes (IC) are constantly formed at low levels in normal individuals. In humans, the red blood cell (RBC) complement receptor 1 (CR1) plays the dominant role in the IC binding and clearance. Over the last several years, we have investigated the potential utility of immunocamouflaged (methoxypoly(ethylene glycol) [mPEG] grafted) RBC to attenuate the risk of alloimmunization. Because the grafted polymer nonspecifically camouflages membrane proteins, its effects on CR1 detection and IC binding were assessed. The dose dependent (0-2.5 mM) effects of activated mPEG (CmPEG, 5 kDa; and BTCmPEG, 5 and 20 kDa) on CR1 detection and the binding of artificially generated IC [C3b coated alkaline phosphatase and antialkaline phosphatase complexes] to control and pegylated RBC was investigated by flow cytometry. In contrast to selected non-ABO blood group antigens, grafted mPEG did not effectively camouflage CR1. Surprisingly, however, even very low grafting concentrations of mPEG (>or=0.3 mM) resulted in a >or=95% loss in IC binding. Further reductions in grafting concentration (0.15 and 0.03 mM mPEG) still yielded decreased IC binding of approximately 60 and 40%, respectively. Importantly, unactivated mPEG had minimal effects on IC binding. These data demonstrate that even small amounts of grafted mPEG interfere with the multivalent CR1-IC interaction necessary for high affinity IC binding, hence large volume transfusions of mPEG-RBC may be contraindicated in patients with pre-existing IC disease. Whether this concern is of clinical significance in healthy humans is less clear due to dilutional effects and the presence of secondary clearance pathways.

Proteomic-based discovery and characterization of glycosylated eosinophil-derived neurotoxin and COOH-terminal osteopontin fragments for ovarian cancer in urine

PURPOSE

The objective was to identify and characterize low molecular weight proteins/peptides in urine and their posttranslational modifications that might be used as a screening tool for ovarian cancer.

EXPERIMENTAL DESIGN

Urine samples collected preoperatively from postmenopausal women with ovarian cancer and benign conditions and from nonsurgical controls were analyzed by surface-enhanced laser desorption/ionization mass spectrometry and two-dimensional gel electrophoresis. Selected proteins from mass profiles were purified by chromatography and followed by liquid chromatography-tandem mass spectrometry sequence analysis. Specific antibodies were generated for further characterization, including immunoprecipitation and glycosylation. Quantitative and semiquantitative ELISAs were developed for preliminary validation in patients of 128 ovarian cancer, 52 benign conditions, 44 other cancers, and 188 healthy controls.

RESULTS

A protein (m/z approximately 17,400) with higher peak intensities in cancer patients than in benign conditions and controls was identified and subsequently defined as eosinophil-derived neurotoxin (EDN). A glycosylated form of EDN was specifically elevated in ovarian cancer patients. A cluster of COOH-terminal osteopontin was identified from two-dimensional gels of urine from cancer patients. Modified forms EDN and osteopontin fragments were elevated in early-stage ovarian cancers and a combination of both resulted to 93% specificity and 72% sensitivity.

CONCLUSIONS

Specific elevated posttranslationally modified urinary EDN and osteopontin COOH-terminal fragments in ovarian cancer might lead to potential noninvasive screening tests for early diagnosis. Urine with less complexity than serum and relatively high thermodynamic stability of peptides or metabolites is a promising study medium for discovery of the novel biomarkers which may present in many non-urinary tract neoplastic diseases.

Detection of immune-complexed 9-O-acetylated sialoglycoconjugates in the sera of patients with pediatric acute lymphoblastic leukemia

Although childhood acute lymphoblastic leukemia (ALL) is highly responsive to chemotherapy, reliable techniques are needed to determine treatment outcome. Over expression of 9-O-acetylated sialoglycoconjugates (9-OAcSGs) on lymphoblasts and concomitant anti-9-OAcSGs was found to have a diagnostic and prognostic potential. However, the presence of circulatory immune-complexed antigens remains unknown. The present study was aimed to evaluate whether immune-complexed 9-OAcSGs can be harnessed for better disease management. Immune-complexed antigens were evaluated in ALL sera (n=262) by a Dot-blot using a 9-OAcSAalpha2-6GalNAc-specific lectin, Achatinin-H. Using three serum samples, the inter- and intra-assay imprecision was evaluated as 11-13% and 7-11%, respectively. The recovery of spiked 9-OAcSGs was 84.2-95.4%. The central 95% reference interval for immune-complexed 9-OAcSGs in normal human sera (NHS, n=144) was 2.9-3.4 mug/ml irrespective of sex and age. At disease presentation, the immune-complexed 9-OAcSGs were fivefold higher than NHS, decreased with remission induction and importantly, reappeared with clinical relapse. Sera from patients with other hematological disorders (n=86) showed negligible levels. The Dot-blot demonstrated the potential application of immune-complexed antigen as a disease-specific marker and its efficacy as a sensitive and specific method that could serve as an economical yet effective index for monitoring disease status.

Mesangial cell-binding anti-DNA antibodies in patients with systemic lupus erythematosus

The mechanisms by which anti-DNA antibodies contribute to the pathogenesis of lupus nephritis (LN) remain to be elucidated. This study investigates the binding of polyclonal anti-DNA immunoglobulins from patients with systemic lupus erythematosus (SLE) to human mesangial cells (HMC) in vitro. Testing of cross-sectional serum samples from 280 LN patients (108 during active disease; 172 during remission), 35 SLE patients without renal involvement, 72 patients with non-lupus primary glomerular diseases, and 37 healthy subjects with a cellular enzyme-linked immunosorbent assay showed significant IgG mesangial cell-binding activity in patients with SLE, particularly those with active LN (P < 0.0001). Significant HMC-binding activity was demonstrated in 83.9%, 42.8%, and 47.1% of patients with active LN, inactive LN, and non-renal SLE, respectively. This was predominantly attributed to binding by anti-DNA antibodies, and immune complex binding accounted for 4.6%, 3.5%, and 2.8% of seropositive samples in the respective groups. Longitudinal studies in 27 LN patients demonstrated correlation between serial levels of anti-DNA antibodies, serum HMC-binding activity, and disease activity in 18 patients (66.7%). Affinity-purified polyclonal IgG anti-DNA antibodies from sera with HMC-binding activity showed significant binding to cultured HMC, and to a lesser extent glomerular and proximal tubular epithelial cells and human umbilical vein endothelial cells, but not tumor cell lines, peritoneal mesothelial cells, bronchial epithelial cells, or fibroblasts. The binding of anti-DNA antibodies to HMC was increased 1.47-fold (P = 0.0059) after the removal of Ig-associated DNA by DNase treatment, but it was unaffected by DNase treatment of HMC membrane. Controlled trypsinization of membrane proteins in HMC resulted in a 1.26-fold (P = 0.0025) increase in their binding by anti-DNA antibodies. In conclusion, subsets of anti-DNA antibodies from patients with SLE are capable of binding to HMC. The association of such binding with renal involvement and disease activity and its modulation by DNA concentration suggest that Ig binding to HMC can be a potential marker for disease activity in selected patients and that the binding of anti-DNA antibodies to HMC may be a pathogenetic mechanism in LN.

Sensitivity and specificity of isolated antigen fromPlasmodium falciparum culture supernatant

Immunological sensitivity and specificity properties of isolated Plasmodium falciparum (GPL) antigen from culture supernatant have been measured and compared with malarial antigens and non malarial filtered paper blood sera for potency and efficacy. Latex bead coded GPL, Pf and RESA antigens immunoreaction properties of human filter paper blood samples (FPB) were studied by laser light scattering immunoassay (LIA) and Enzyme linked immunoabsorbent assay (ELISA) techniques. Results of GP. antigen sensitivity study by LIA method showed a very high malaria antibody binding response (MABR) i.e. 6% compared with 78% with RESA and 88% Pf antigens. Malaria detection by ELISA method also found similar results. Specificity study of GPL antigen for different non malarial filter paper blood sera (NMFS) showed no immunoreaction however Pf and RESA antigen showed few positive immunological responses. These results suggest that sensitivity and specificity properties of isolated GPL antigen is better than other antigens.

Autoantibodies Associated with Rheumatic Diseases

The identification of circulating autoantibodies contributes to the correct diagnosis as well as to the follow-up of rheumatic diseases. Some autoantibodies are even included in diagnostic and classification criteria for these types of autoimmune diseases. There are several relatively specific screening and identification methods for the measurement of autoantibodies available. The type of assay crucially influences the diagnostic value of the parameters. In general, routine laboratories should prefer enzyme immunoassays (ELISA) using well characterized antigens, although ELISA tests tend to produce more false-positive and true weakly positive results, which reduce their positive predictive value. Therefore one should be aware that laboratory results can only be properly interpreted when there is a correlation with the clinical situation and when the limitations of the technologies used for autoantibody identification have been taken into consideration. A diagnostic algorithm consisting of screening and identification steps should be established by each laboratory in order to create a rational, evidence-based and cost-effective basis for the diagnosis of rheumatic diseases.