Idiotypic Specificities Research Articles

Reactivity Graph Yields Interpretable IgM Repertoire Signatures as Potential Tumor Biomarkers.

Combining adaptive and innate immunity induction modes, the repertoire of immunoglobulin M (IgM) can reflect changes in the internal environment including malignancies. Previously, it was shown that a mimotope library reflecting the public IgM repertoire of healthy donors (IgM IgOme) can be mined for efficient probes of tumor biomarker antibody reactivities. To better explore the interpretability of this approach for IgM, solid tumor-related profiles of IgM reactivities to linear epitopes of actual tumor antigens and viral epitopes were studied. The probes were designed as oriented planar microarrays of 4526 peptide sequences (as overlapping 15-mers) derived from 24 tumor-associated antigens and 209 cancer-related B cell epitopes from 30 viral antigens. The IgM reactivity in sera from 21 patients with glioblastoma multiforme, brain metastases of other tumors, and non-tumor-bearing neurosurgery patients was thus probed in a proof-of-principle study. A graph representation of the binding data was developed, which mapped the cross-reactivity of the mixture of IgM (poly)specificities, delineating different antibody footprints in the features of the graph-neighborhoods and cliques. The reactivity graph mapped the major features of the IgM repertoire such as the magnitude of the reactivity (titer) and major cross-reactivities, which correlated with blood group reactivity, non-self recognition, and even idiotypic specificities. A correlation between an aspect of this image of the IgM IgOme, namely, small cliques reflecting rare self-reactivities and the capacity of subsets of the epitopes to separate the diagnostic groups studied was found. In this way, the graph representation helped the feature selection in its filtering step and provided reduced feature sets, which, after recursive feature elimination, produced a classifier containing 51 peptide reactivities separating the three diagnostic groups with an unexpected efficiency. Thus, IgM IgOme approaches to repertoire studies is greatly augmented when self/viral antigens are used and the data are represented as a reactivity graph. This approach is most general, and if it is applicable to tumors in immunologically privileged sites, it can be applied to any solid tumors, for instance, breast or lung cancer.

Commentary: Rapid steps forward in environmental epigenetics: Implications for epidemiologic investigation of chronic disease

Epidemiology relies heavily on a sister discipline, biology, to understand origins of human disease. This reliance serves two important functions. The first is fundamental and constant: over the entire arc of the research process, from formulating and addressing new questions to interpreting each emerging result, epidemiology looks to biology, asking ‘What is plausible?’ The second occurs when discoveries in biology lead to new measures that can be employed in epidemiologic research. These developments enable epidemiologists to move a compelling hypothesis into the realm of scientific enquiry, when new measures provide a means of testing hypothetical predictions. The choices epidemiologists have made regarding samples to place in bio-repositories have changed over time, illustrating how emerging biological measures brought successive sets of hypotheses within reach of epidemiologic research. Once antibodies of specific idiotype could be assayed to measure exposure to specific infectious agents, large collections of human sera were assembled to address hypotheses relating these agents to disease. Epidemiologists who came of age in the era of recombinant DNA marvel that nucleated cells did not routinely enter these collections. This generation created collections of genomic DNA to test hypotheses relating inherited sequence variants to the increased risk of hundreds of diseases. These DNA collections used cells readily collected by minimally invasive means as the source of DNA, since sequence is quite uniform between nucleated cell types of the body. Now, newer measures of epigenetic state—which varies with cell type—are motivating collection of tissues directly involved in disease processes. 1 These measures have emerged from epigenetics, the biological discipline addressing processes whereby stable molecular characteristics other than DNA nucleotide sequence influence gene expression. 2

A Small-molecule Screen Yields Idiotype-specific Blockers of Neuromyelitis Optica Immunoglobulin G Binding to Aquaporin-4

Neuromyelitis optica (NMO) is an inflammatory demyelinating disease of the central nervous system caused by binding of anti-aquaporin-4 (AQP4) autoantibodies (NMO-IgG) to AQP4 on astrocytes. A screen was developed to identify inhibitors of NMO-IgG-dependent, complement-dependent cytotoxicity. Screening of 50,000 synthetic small molecules was done using CHO cells expressing human AQP4 and a human NMO recombinant monoclonal antibody (rAb-53). The screen yielded pyrano[2,3-c]pyrazoles that blocked rAb-53 binding to AQP4 and prevented cytotoxicity in cell culture and spinal cord slice models of NMO. Structure-activity analysis of 82 analogs yielded a blocker with IC(50) ∼ 6 μm. Analysis of the blocker mechanism indicated idiotype specificity, as (i) pyrano[2,3-c]pyrazoles did not prevent AQP4 binding or cytotoxicity of other NMO-IgGs, and (ii) surface plasmon resonance showed specific rAb-53 binding. Antibody structure modeling and docking suggested a putative binding site near the complementarity-determining regions. Small molecules with idiotype-specific antibody targeting may be useful as research tools and therapeutics.

Organization and evolution of synthetic idiotypic networks

We introduce a class of weighted graphs whose properties are meant to mimic the topological features of idiotypic networks, namely, the interaction networks involving the B core of the immune system. Each node is endowed with a bit string representing the idiotypic specificity of the corresponding B cell, and the proper distance between any couple of bit strings provides the coupling strength between the two nodes. We show that a biased distribution of the entries in bit strings can yield fringes in the (weighted) degree distribution, small-world features, and scaling laws, in agreement with experimental findings. We also investigate the role of aging, thought of as a progressive increase in the degree of bias in bit strings, and we show that it can possibly induce mild percolation phenomena, which are investigated too.

Idiotypic Vaccination of Patients with Relapsed Follicular Lymphoma Using a Novel Vaccine Formulation Including a Tobacco Plant-Produced Tumor Specific Idiotype

Abstract 1649Idiotypic vaccination has shown evidence of biological efficacy, clinical efficacy and clinical benefit in some subsets of patients with follicular lymphoma. A phase-I clinical trial is currently being conducted to assess safety and immunogenicity of a novel, recombinant idiotype vaccine in which the idiotype protein is produced in tobacco plants. Previous animal and clinical studies with plant-produced single-chain variable fragment lymphoma vaccines have demonstrated specific immunogenicity and safety. However, the expression levels of such fragments were highly variable and required complex engineering of the linkers. Moreover, the downstream processing could not be built around standard methods like protein A affinity capture. Our novel vaccine manufacturing process by magnICONR technology is devoid of such shortcomings and allows consistent and efficient expression in plants of idiotype-containing, whole immunoglobulins. Safety and tolerability of the novel vaccine formulation is the subject of this report.Patients eligible for the study are those with relapsed follicular lymphoma whose prior treatment has included rituximab. Patients receive salvage therapy with bendamustine and prednisone. Use of rituximab is prohibited on this trial due to the prolonged B-cell depletion that characteristically follows its administration. Subjects enrolled in the study who achieve and maintain either a complete (CR) or partial (PR) response for at least 4 months following BP therapy undergo idiotype vaccination.Six patients have received a variable number of monthly doses of the novel, first-in-human, magnICONR produced idiotype vaccine. Each dose includes a conjugate of 0.5 mg of idiotype and 0.5 mg of keyhole limpet hemocyanin on day 1. A dose of 0.125mg of GM-CSF is administered with the idiotype vaccine on day 1 and alone subcutaneously at the same injection site on day 2 through 4. Each vaccination cycle is repeated every four weeks. The vaccination schedule as defined by the protocol outlines eight monthly vaccination cycles followed by four bi-monthly vaccination cycles for a total of 12 vaccinations. No patient has yet completed the entire vaccination protocol and no patient has relapsed/progressed while receiving vaccine.Two patients have received eight vaccinations. The remaining four patients have received five, four, two and one vaccination, respectively. The patient who received two vaccinations was removed from the study after the development of progressive multifocal leukoencephalopathy Undefined symptoms had appeared prior to the initiation of vaccine and PML was subsequently attributed to previous, prolonged maintenance treatment with rituximab received prior to the enrollment in this clinical trial.Toxicity data are available for 28 doses of idiotype vaccine. There has been no grade 4–5 hematologic and non-hematologic toxicity. Grade 3 non-hematologic toxicity was recorded in 1/6 (17%) patients and in 1/28 (4%) cycles, respectively, consisting of generalized pain during one day. Grade 1–2 non-hematologic toxicities were recorded in all six patients and virtually in all cycles. The most common of them were fatigue, pain at the injection site, myalgia, diarrhea, headache and generalized pain. Grade 3 hematologic toxicity was recorded in 2/6 (33%) patients and in 2/28 (7%) cycles, respectively, and consisted predominantly of leucopenia. Grade 1–2 hematologic toxicities were common, most often consisting of anemia and thrombocytopenia.These preliminary data indicate that this novel idiotype vaccine is well tolerated in patients with relapsed follicular lymphoma following chemotherapy with BP. Studies of vaccine-induced humoral and cellular immune responses are ongoing. Results will be updated at the time of the meeting.The authors wish to acknowledge Drs. Ralph Heaven, Larry Barker, Jairo Olivares, Thomas Anderson, Carl Chakmakjian, Barry Cooper, Amir Faridi, Vinay Jain, Pankaj Khandelwal, Janice Marshall, Anton Melnyk, Robert Mennel, James Turner. Disclosures:No relevant conflicts of interest to declare.

Immunization with peptides derived from the idiotypic region of lupus-associated autoantibodies delays the development of lupus nephritis in the (SWR × NZB)F 1 murine model

Systemic lupus erythematosus (SLE) is a multiorgan autoimmune disease affecting 40–50/100,000 Americans. Although most of the research on pathogenic antibodies focuses on antigenic specificity, there is increasing evidence that specific immunoglobulin idiotypes may mediate lupus nephritis independent of autoantigen specificity. In previous work, our laboratory characterized a set of nephritogenic monoclonal antibodies with substantial idiotypic cross-reactivity, produced by the spontaneous SLE model (SWR × NZB)F 1 (SNF 1), termed Id LNF 1. Peptides derived from one of these antibodies, Id540, was previously shown to stimulate pathogenic T-cells from prenephritic SNF 1 mice, similar to what has been seen for pathogenic A6.1 antibody produced by the (NZB × NZW)F 1 model. In this study, we immunized pre-nephritic SNF 1 mice with p62–73, a peptide derived from the variable region of Id540 and, in separate experiments, with p58–69, a peptide derived from the variable region of A6.1. In both cases, immunization resulted in increased survival and delayed nephritis; however, while both peptides affected levels of anti-DNA antibodies, immunization with p62–73 only affected levels of Id LNF 1 antibodies. These findings confirm the roles of pathogenic idiotypes in the pathogenesis of lupus nephritis and suggest that therapies that target specific idiotypes might be a potential tool in the management of SLE.

Are Anti–Oxidized Low-Density Lipoprotein Antibodies Pathogenic or Protective?

Despite a recent decline, atherosclerosis remains the most common cause of death in the Western world. The disease course of atherosclerosis is characterized by its chronicity, with progression in its initial stages being particularly insidious. Chronic inflammation is the pathological hallmark of atherosclerosis,1–4 and inflammatory processes are instrumental at all stages of this disease. Even before the development of detectable intimal lesions, the expression pattern of the endothelium has been shown to be inflammatory in nature, conforming to the response-to-injury hypothesis first postulated by the late Russell Ross.5 Thus, in lesion-prone sites of the arterial tree, the endothelial expression of adhesion molecules is upregulated, reflecting endothelial dysfunction secondary to unfavorable blood rheology6 and/or hypercholesterolemia.7–9 Atherosclerosis is known today to be associated with the burden of infection as well.10 The presence of infectious/inflammatory pathogeneses raises the autoimmune aspect of the condition.11–14 Anti–oxidized LDL (oxLDL) antibodies are exceptional among the autoantibodies prevalent in atherosclerosis: on the one hand, a correlation was found between the existence and titers of anti-oxLDL antibodies and the extent of atherosclerosis and cardiovascular disease (CVD) (Table 1). On the other hand, experimental data indicate that anti-oxLDL antibodies may be protective. View this table: TABLE 1. Correlation Between Titers of Anti-oxLDL Abs and Atherosclerosis and CVD oxLDL frequently presents in the sera of patients with autoimmune conditions, acute coronary syndrome, or stable coronary artery disease (CAD).15–18 OxLDL has been associated with both subclinical atherosclerosis and inflammatory variables.19 A large amount of oxLDL accumulates in atherosclerotic plaques,20–22 and the serum concentrations of circulating oxLDL may correlate with the severity of CAD23 and acute coronary syndrome.24 OxLDL seems to be an immunogenic molecule that stimulates the induction of anti-oxLDL antibodies. Thus, it is not surprising that an association was found between the presence …

Monoclonal antibodies to amoxicillin express different idiotypes determined by anti-idiotype antibodies production.

Penicillins are beta-lactam antibiotics able to generate several antigenic determinants that are recognized by the immune system. To study the differences in the antigen binding site of two monoclonal antibodies (Mab) specific to amoxicillin, polyclonal rabbit anti-idiotypic antibodies were produced. One Mab, AO3.2 (IgG2a), specific to a structure formed by the acyl-side chain structure and a part of the nuclear region of amoxicillin. The second one, AO6.2 (IgE), is specific to the side chain of amoxicillin, although it also recognizes the side chain of other penicillins (penicillin G and ampicillin). These antibodies were used to immunize rabbits in order to produce polyclonal anti-idiotypic antibodies, which were purified in several steps by affinity chromatography. The specificity and cross-reactivity studies were made by ELISA and ELISA inhibition. The results suggest that the anti-Id antibodies produced are the internal image of the antigen, since the binding to their specific idiotype is blocked mainly by the original hapten (amoxicillin): in 98% of the cases with anti-id-1 (induced against AO3.2) and in 59% with anti-id-2 (induced against AO6.2). The absence of cross-reactivity of each anti-idiotypic antibody with the different Mabs specific to amoxicillin shows that the idiotypes induced by the same hapten have differences that are reflected by the nonrecognition of these anti-idiotypes. We conclude that such a small molecule as amoxicillin can present several antigenic determinants that induce a panel of antibody specificities especially directed against the side chain.

Determination of idiotype-specific T cells in idiotype-vaccinated mice

Immunoglobulin idiotypes (Id) of malignant B lymphocytes and plasma cells are tumor-specific antigens that were extensively used in immunotherapy studies. The effector mechanisms, involved in resistance to tumor following Id vaccination, are a controversial issue. Since cell-mediated responses, rather than antibody responses, constitute powerful effectors against tumors, recent studies focused on the generation of Id-specific T cells. Traditional methods for assessment of cellular responses in murine models of Id vaccination are inadequate because of their low sensitivity and because they do not determine actual frequency of antigen-reactive T cells. Here, we use the highly sensitive enzyme-linked immunospot (ELISPOT) assay for enumeration of interferon gamma (IFN-γ)—secreting cells in Id-vaccinated mice. Our experimental model consists of the murine B-lymphocyte tumor 38C-13, which expresses surface IgM, and the plasma cell tumor D2, which secretes IgM with idiotypic specificity identical to that of 38C-13. Vaccination of mice with purified 38C-13 IgM induced resistance to 38C-13 as well as to D2 tumor cells. Although immunized mice produced high levels of anti-Id antibodies that bound to 38C-13 cells, no binding of antibodies to D2 occurred, suggesting that cellular mechanisms mediated resistance to the plasma cell tumor. ELISPOT assays revealed that immunization induced a significant increase in the frequency of Id-specific IFN-γ-secreting T cells. Depletion of T cell subsets demonstrated that both CD4 + and CD8 + T cells were involved in the response to Id. This is the first report on application of the ELISPOT assay for enumeration of Id-reactive T cells in a murine model of Id vaccination, providing a tool to study Id-specific T cell responses and to evaluate the efficacy of Id vaccines.

Immunoglobulin GM and KM allotypes and vaccine immunity

Immunoglobulin (Ig) GM and KM allotypes are genetic markers of γ and κ-type light chains, respectively. The striking qualitative and quantitative differences in the distribution of these determinants among different races raise questions concerning the nature of the evolutionary selective mechanism that maintains this variation. Associations between Ig allotypes and specific antibody responses could be a selective force for the maintenance of various haplotypes and their frequencies. Data from several studies reporting significant associations between certain GM and KM allotypes and immune responsiveness to polysaccharide vaccines and to particular infectious pathogens support this hypothesis. Possible ways in which constant (C)-region allotypes could contribute to the antibody specificity include the following: (i) certain alleles coding for allotypes may be in linkage disequilibrium with particular variable (V)-region determinants associated with immune responsiveness; (ii) they could directly contribute to the formation of specific idiotypes, as shown for the T15 system in mice; and (iii) allotype-associated structural variability in the C-region could modulate the kinetic competence of the antigen binding sites.

Selection of peptidic mimics of digoxin from phage-displayed peptide libraries by anti-digoxin antibodies

Since the initial report of the development of methodology to generate high-affinity digitalis-specific (digoxin) antibodies, these antibodies have proven extremely useful tools to monitor digoxin levels in digitalized patients and, as Fab fragments, to reverse toxic digoxin effects in life-threatening digoxin overdoses. These antibodies (both digoxin-specific and ouabain-specific) have been used extensively by investigators for the identification and characterization of putative endogenous digitalis-like factors. In this study, we used two well-characterized mouse anti-digoxin monoclonal antibodies (mAbs), designated 26–10 and 45–20, as binding templates with which to select short bacteriophage-displayed (pIII protein inserted) peptides that are capable of binding to these mAbs and mimicking the conformational structure of digoxin. Selective enrichment from two phage-displayed random peptide libraries enabled us to isolate and identify distinct 15 and 26 amino acid residue peptide inserts that bind with high avidity and idiotypic specificity to the selecting mAbs. Among these displayed inserts a subset was identified whose mAb binding is inhibited by digoxin and whose corresponding synthetic peptides inhibit phage binding. They, therefore, appear to bind at the mAbs digoxin-binding sites. These data provide the first clear evidence that short polypeptides can serve as surrogates for the low molecular mass hapten digoxin.

Rejection of tumors of the B cell lineage by idiotype-vaccinated mice.

Idiotypic determinants of immunoglobulins of malignant B lymphocytes and plasma cells are tumor-specific antigens and have been used extensively in immunotherapy studies. The mechanisms involved in resistance to tumor challenge following idiotype vaccination are poorly understood. Although a predominant role has been attributed to anti-idiotype antibodies, both humoral and cellular immune responses are probably involved. Cell-mediated responses may be particularly effective against tumor cell variants that do not express the idiotype on the cell surface and are therefore resistant to anti-idiotype antibodies but continue to produce one of the original immunoglobulin polypeptides that may be processed and presented to T cells. In this report we describe two experimental models of idiotype vaccination in which antibodies are unlikely to play a role, and hence tumor immunity is attributed to cell-mediated responses. One model consists of the murine B lymphocyte tumor 38C-13 and its idiotype-negative variant DB2, which has lost the idiotypic specificity of the parental 38C-13 cell line through the production of a different light chain but expresses the original heavy chain. Vaccination of mice with the purified IgM of 38C-13 induced resistance to 38C-13 tumor cells as well as to the variant cells. Although immunized mice produced high levels of anti-idiotype antibodies that bound to 38C-13 cells, no binding of antibodies to DB2 cells occurred. The finding that idiotype-vaccinated mice were resistant to idiotype-negative DB2 cells suggested that cellular mechanisms are involved in mediating resistance. The second model consists of the two plasma cell line JLmu s and JLmu m, which produce IgM with an identical specificity. Whereas one of them (JLmu s) secretes the IgM, the other one (JLmu m) can neither secrete nor deposit it on the cell surface. Immunization against JLmu s IgM followed by tumor challenge resulted in prolonged survival of both JLmu s- and JLmu m-challenged mice. Although sera of immunized mice contained high levels of anti-idiotype antibodies, they did not react with the plasmacytoma cells. Similarly to the results obtained in the 38C-13 experimental model, these results suggest that a non-antibody-mediated mechanism was involved in the resistance of mice to tumor growth.

Specific detection of myeloma plasma cells using anti-idiotypic single chain antibody fragments selected from a phage display library.

Bone marrow plasma cells constitute the bulk of malignant cells in multiple myeloma patients. B-lymphocytes having immunoglobulin heavy chain gene rearrangements identical to those of the malignant clone (clonally related B-lymphocytes) may function as malignant plasma cell precursors. We and others proposed the use of anti-idiotypic antibodies to isolate and study clonally related B-lymphocytes. This strategy failed until now because anti-idiotypic antibodies raised by conventional hybridoma techniques proved to react frequently with epitopes shared by different idiotypes. Recently, we succeeded in selecting specific single chain Fv antibodies from phage libraries. To select single chain Fv bearing phages specifically directed against the immunoglobulin idiotype expressed by myeloma tumor cells we panned a semisynthetic phage library against purified myeloma paraprotein Fab fragments. The selection was performed in the presence of soluble polyclonal immunoglobulin as a competitor. Three independent selections for three myeloma patients yielded 10-26 clones. Between two and seven of the selected clones were reactive with patient Fab and not with polyclonal immunoglobulin in enzyme-linked immunosorbent assays. Five out of six anti-idiotypic single chain Fvs were able to specifically stain fixed monoclonal plasma cells in myeloma bone marrow. Idiotype specificity of these single chain Fvs was confirmed by flow cytometry since they did not react with monoclonal plasma cells of other patients, a panel of nine myeloma cell lines, isolated polyclonal bone marrow plasma cells and cultured B-lymphocytes. Using these anti-idiotypic reagents we were able to detect 25 myeloma plasma cells in a background of 50000 immunoglobulin isotype-matched cells of the myeloma cell line UM-1 or 50000 donor bone marrow cells (sensitivity 0.05%). This paper shows that highly specific anti-idiotypic single chain Fv antibody fragments selected from a phage display library can be used to detect rare idiotypic cells in patient samples.

Cross-Reacting Idiotypes on Anti-insulin Autoantibodies in Autoimmune Diseases, Identified by Monoclonal Antibodies

Investigations on the specific idiotypes of autoantibodies are supposed to help with the understanding of the control mechanisms participating in the pathogenesis of autoimmune diseases. This study describes three monoclonal antibodies (Mabs) that recognize distinct idiotypic determinants on anti-insulin autoantibodies. The preabsorption by IAA-positive sera of insulin inhibits their subsequent binding to the anti-Id, thus suggesting that the Mabs recognize epitopes located at or near the binding site of insulin autoantibodies (IAA). These idiotypes are detected in sera from patients with insulin-dependent diabetes mellitus (IDDM), which are IAA-negative, also. It is possible that the expression of the idiotypes recognized might generally be associated with induction of autoantibodies, since they were found in sera from patients with rheumatoid arthritis (RA), autoimmune thyroid disease (AITD), and cataract (K). It can be assumed that the corresponding idiotypes of these Mabs, or similar structures (sequential or conformational), are expressed on autoantibodies with various antigen-binding specificities. These data suggest that some autoimmune diseases are preceded by the secretion of autoantibodies which express a common or similar pathological idiotype.

The prognostic significance of T cell receptor beta gene rearrangements and idiotype-reactive T cells in multiple myeloma.

Clonal T cell populations with idiotype specificity are present in the peripheral blood of a proportion of patients with multiple myeloma. We have identified the presence of both T cell subpopulations with a specificity for autologous immunoglobin fragments and T cell receptor beta gene rearrangements in peripheral blood samples of patients with myeloma. T cell receptor beta gene rearrangements were detected in 38 of 119 patient samples (32%) and were more common in progressive disease (70%), than at diagnosis (25%) or in stable disease (23%). The 38 patients who had T cell receptor beta gene rearrangements detected at any time had a better overall survival (median not yet achieved) than the patients who never had rearrangements detected (median 45 months, n = 49; chi2 = 6.2, P < 0.01). All 12 patients with T cell receptor beta gene rearrangements at diagnosis are still alive whereas the median survival for 28 patients with a germline configuration at diagnosis was 40 months (chi2 = 5.8, P > 0.01). The presence of T cell receptor beta gene rearrangements even conferred a survival advantage during progressive disease (median survival 44 months vs 19 months; chi2 = 8.7, P < 0.003). Two colour flow cytometry with biotinylated autologous immunoglobulin fragments demonstrated idiotype-reactive T cells in the peripheral blood of five out of 15 patients all of whom had T cell gene rearrangements. The remaining 10 patients had neither idiotype-reactive T cells nor a detectable T cell receptor beta gene rearrangement in concurrent samples. Thus in patients with myeloma there was a good correlation between the presence of T cell receptor beta gene rearrangements and idiotype-reactive T cells. Patients with a rearranged T cell receptor beta gene had a significantly better prognosis.

Characterization of anti-Thymoglobulin, anti-Atgam and anti-OKT3 IgG antibodies in human serum with an 11-min ELISA

Patients treated with OKT3 may become resistant to OKT3 therapy following induction of anti-idiotypic antibodies. Antirabbit or antihorse antibodies following Thymoglobulin (rabbit antihymocyte globulin (ATG)) or Atgam (hores ATG) theraphy may not similarly inhibit drug efficacy due to an insufficient anti-idiotypic response against the multiple idiotypic specificities of the polyclonal anti-T cell preparations. However, no standardized assay had been developed to monitor antihorse and antirabbit antibodies. To address this issue, we developed three rapid (11-min) and standardized semiquantitative plate enzyme-linked immunoassays (ELISAs) to monitor human serum immunoglobulin-G (IgG) antibodies to Orthoclone OKT3 IgG2a, Atgam and Thymoglobulin. The format was identical for the three assays, with the exception of the immunoglobulin antigen coated on the ELISA plates. As OKT3 is a monoclonal antibody, OKT3 itself is used as the capture antigen. However, for antibody responses against the polyclonal antibody preparations Atgam and Thymoglubulin, it was found tht horse IgG and rabbit IgG respectively were equivalent to Atgam and Thymoglobulin as capture antigens. Excellent correlation with a 3.5-h format was demonstrated ( r values between 0.986 and 0.845). Specificity was demonstrated by inhibition experiments. Correlation between endpoint titres calculated from serial dilutions and 1:50 dilution OD values were 0.821, 0.983 and 0.937 respectively for the mouse, horse and rabbit assay. High titre sera were selected to asess their ability to block in vitro the binding of OKT3, Thymoglobulin or Atgam to T cells, using flow cytometry. None of the sera containing antihorse ( n = 9) or antirabbit ( n = 8) antibodies blocked T cell binding of Atgam or Thymoglobulin. In contrast, OKT3 binding was blocked by the four highest titre sera of the 13 anti-OKT3 sera tested. Consequently, prospective monitoring of treated patients using standardized 11-min assays may allow a better assessment of the effect of presentization to OKT3, Atgam or Thymoglobulin.

Molecular mapping of the 8.12 sle-associated idiotype specificity at the single amino acid level

The 8.12 idiotype is expressed in elevated titer in the serum of patients with systemic lupus erythematosus and is a marker for a subpopulation of anti-DNA antibodies that possess a VλII encoded light chain. This study utilized a eukaryotic expression system to identify the structural basis for expression of this idiotype. Reversion of the 8.12 + DSC light chain to the hs1v215.23/DPL11 germline gene reveals that the 8.12 idiotype is encoded in the germline. The 8.12 + DSC and the 8.12 − AS17 light chains, both belonging to the VλII family, were subjected to site directed mutagenesis, to localize amino acids important for expression of the 8.12 idiotype. Point mutations were performed in CDR1, CDR2, FR3 and CDR3, in positions where the 8.12 + DSC differs from the 8.12 − AS17. Amino acids in CDR1 and the CDR2 proximal region of FR3, but not the J proximal region of CDR3, play a crucial role in 8.12 reactivity. The 3-D structure of Mcg, a human IgG1, with which DSC shares a sequence homology of 92.3% has been examined to visualize the effect of each of the mutations and to identify the surface on DSC that comprises the idiotype.

Study of Anti-Idiotype Antibodies to the Monoclonal Antibody HGT3a and its Relation to the 38 kDa Antigen of Mycobacterium tuberculosis

The hypervariable regions of the immunoglobulins which function as the antigen binding sites are capable of provoking an antibody response and are referred to as anti-idiotypic antibodies. Antisera were raised in rabbits against the idiotypes of a mouse monoclonal antibody HGT3a which binds only to the 38 kDa antigen of the M. tuberculosis complex group of organisms. Idiotype specificity in these antisera was determined by dot ELISA, Western blot and solid phase inhibition assays. In vivo administration of this rabbit anti-idiotypic antibody to Swiss mice evoked an anti-anti-idiotypic antibody response, further confirming the internal antigen mimicry by the anti-idiotypic antibodies of the 38 kDa antigenic epitope and its potential use as a surrogate antigen. Antibody response to the anti-idiotypic antibodies in the sera of patients with pulmonary tuberculosis showed significant correlation with the antibody response to the 38 kDa antigen studied in the same clinical samples indicating a close similarity of the 38 kDa antigen of M. tuberculosis and the rabbit andi-idiotypic antibody produced against MoAb HGT3a.

Primary structure of the variable regions encoding antibody to NG2, a tumour-specific antigen on the rat chondrosarcoma HSN. Correlation of idiotypic specificities with amino acid sequences

Eight syngeneic rat monoclonal antibodies that recognize structurally overlapping epitopes on the chondroitin sulphate proteoglycan NG2, a tumour-specific antigen on the chemically induced rat chondrosarcoma HSN, have been analysed for the sequence of their immunoglobulin heavy (H) and light (L) chain variable (V) regions. This analysis defined five groups of antibodies which are very similar for both the H and L chains and revealed that a wide range of different V regions are capable of binding to the same antigenic determinant. However, three mAbs, 11 160 , ALN/12/17 and ALN/9/94, which recognize a sequential epitope, were found to use almost identical heavy (V-D-J) and light (V-J) chains in regions demonstrating an exclusivity in specific protein-protein interaction for this particular epitope. Two other mAbs, ALN/11/53 and AL/3/12, used similar V and J segments but totally different D regions. With the exception of the pair ALN/11/53 and AL/3/12, this grouping of antibodies matches that derived from the idiotypic specificity study we have reported previously. The reactivity pattern of Ab1 11 160 , ALN/12/17 and ALN/9/94 with six anti-idiotopic mAbs raised against 11 160 demonstrated that the idiotope recognized by Ab2 HIM/3/41 was defined by a single amino acid, Asn, at position 52 within the CDR2 loop of the V H region; whereas the D region of Ab1 ALN/11/53 was implicated as the structural correlate of idiotypy. The substitution of Asn H52 influenced the Id recognition but Ag binding was not affected suggesting that Ab2 HIM/3/41 did not mimic the NG2 Ag.

Immunoglobulin idiotypic specificity of AIDS‐associated lymphomas and their experimental model

B cell non-Hodgkin's lymphoma (B-NHL) occurring in immunocompromised hosts, such as acquired immune deficiency syndrome (AIDS) patients, is a high-grade malignancy resistant to regular chemotherapy. To determine whether immunotherapy with public anti-Ig idiotype antibodies can be used to treat these NHL, the Ig idiotype specificity of six NHL in AIDS patients (AIDS-ML) and 23 B-NHL experimentally induced in immunocompromised mice (SCID mice) was investigated. One of the six AIDS-ML and two of the 23 experimental B-NHL reacted monoclonally with a single public antibody, while one AIDS-ML and three experimental B-NHL reacted polyclonally with two or three different antibodies. The presence of Ig idiotypic polyclonality requires special consideration with regard to the introduction of anti-Ig idiotype immunotherapy in these cases.