Studies of anti-F(ab')2 antibodies and possible immunologic control mechanisms in systemic lupus erythematosus

Natural autoimmunity in oligoarticular juvenile idiopathic arthritis

BACKGROUND

Oligoarticular juvenile idiopathic arthritis (oligo-JIA) is considered as an antigen-driven lymphocyte-mediated autoimmune disease. Natural antibodies (NAbs) are pre-immune antibodies produced in the absence of exogenous antigen stimulation, participating in both, innate and adaptive immunity. Considering their major immunoregulatory role in homeostasis and autoimmune pathogenesis, we designed this study to further elucidate their role in oligo-JIA pathogenesis.

METHODS

Seventy children with persistent oligo-JIA and 20 healthy matched controls were enrolled in the study. Serum IgM and IgA antibodies against human G-actin, human IgG F(ab΄)2 fragments and the hapten TriNitroPhenol (TNP) as well as the total concentration of serum IgM and IgA were measured by in-house enzyme-immunoassays. Kolmogorov-Smirnov normality test, Kruskal-Wallis H and Mann-Whitney tests were used to assess data distribution, and significant differences of non-parametric data between groups of the study. Backward regression analysis was used to analyze the effect of multiple factors (age, gender, disease activity, anti-nuclear antibody positivity, presence of uveitis) on continuous dependent variables (activities and activity/ concentration ratios of IgM and IgA NAbs).

RESULTS

The ratios of IgA anti-TNP, anti-actin and anti-F(ab΄)₂ levels to total serum IgA concentration were found to be significantly increased in patients with oligo-JIA compared to healthy subjects. Significantly elevated levels of IgM anti-TNP antibodies were also found in children with inactive oligo-JIA compared to those of children with active disease and of healthy controls. In the presence of anterior uveitis, IgM anti-TNP levels were significantly higher than in patients without uveitis or in healthy controls. Backward regression analysis revealed that the disease activity and the presence of anterior uveitis independently affect IgM anti-TNP levels.

CONCLUSUIONS

Our findings are in accordance with the hypothesis that NAbs contribute to the pathogenesis of autoimmune diseases and provide additional evidence that disturbances in natural autoimmunity may contribute to the as yet unclarified pathogenesis of oligo-JIA.

Immunomodulatory potential of anti-idiotypic antibodies for the treatment of autoimmune diseases

The immune system is a complex network of specialized cells and organs that recognises and reacts against foreign pathogens while remaining unresponsive to host tissues. This ability to self-tolerate is known as immunological tolerance. Autoimmune disease occurs when the immune system fails to differentiate between self and non-self antigens and releases autoantibodies to attack our own cells. Anti-idiotypic (anti-ID) antibodies are important in maintaining a balanced idiotypic regulatory network by neutralising and inhibiting the secretion of autoantibodies. Recently, anti-ID antibodies have been advanced as an alternative form of immunotherapy as they can specifically target autoantibodies, cause less toxicity and side effects, and could provide long-lasting immunity. This review article discusses the immunomodulatory potential of anti-ID antibodies for the treatment of autoimmune diseases.

The immune system protects the body against infections and diseases, such as by producing antibodies. Usually, these antibodies only attack pathogens, leaving healthy cells unharmed. However, autoimmune disease may develop when the immune system mistakenly recognises part of the body as foreign and produces antibodies to attack them. Antibodies that attack our own cells are called autoantibodies. Anti-idiotypic antibodies could be utilized to stop autoantibodies from attacking self cells with minimal side effects and long-lasting immunity. This review discusses anti-idiotypic antibodies usage as an alternative form of immunotherapy to inhibit autoantibodies in autoimmune disease.

B-CD8+ T Cell Interactions in the Anti-Idiotypic Response against a Self-Antibody

P3 is a murine, germline, IgM mAb that recognizes N-glycolylated gangliosides and other self-antigens. This antibody is able to induce an anti-idiotypic IgG response and B-T idiotypic cascade, even in the absence of any adjuvant or carrier protein. P3 mAb immunization induces the expression of activation markers in a significant percentage of B-1a cells in vivo. Interestingly, transfer of both B-1a and B-2 to BALB/Xid mice was required to recover anti-P3 IgG response in this model. In fact, P3 mAb activated B-2 cells, in vitro, inducing secretion of IFN-γ and IL-4, although this activation was not detected ex vivo. Interestingly, naïve CD8+ T cells increased the expression of activation markers and IFN-γ secretion in the presence of B-1a cells isolated from P3 mAb-immunized mice, even without in vitro restimulation. In contrast, B-2 cells were able to stimulate CD8+ T cells only if P3 was added in vitro. Using bioinformatics, a MHC class I-binding peptide from P3 VH region was identified. P3 mAb was able to induce a specific CTL response in vivo against cells presenting this peptide. Both humoral and CTL anti-idiotypic responses could be mechanisms to protect against the self-reactive antibody, contributing to keeping the tolerance to self-antigens.

Decline in titers of anti-idiotypic antibodies specific to autoantibodies to GAD65 (GAD65Ab) precedes development of GAD65Ab and type 1 diabetes

The humoral Idiotypic Network consisting of antibodies and their anti-idiotypic antibodies (anti-Id) can be temporarily upset by antigen exposure. In the healthy immune response the original equilibrium is eventually restored through counter-regulatory mechanisms. In certain autoimmune diseases however, autoantibody levels exceed those of their respective anti-Id, indicating a permanent disturbance in the respective humoral Idiotypic Network. We investigated anti-Id directed to a major Type 1 diabetes (T1D)-associated autoantibody (GAD65Ab) in two independent cohorts during progression to disease. Samples taken from participants of the Natural History Study showed significantly lower anti-Id levels in individuals that later progressed to T1D compared to non-progressors (anti-Id antibody index of 0.06 vs. 0.08, respectively, p = 0.02). We also observed a significant inverse correlation between anti-Id levels and age at sampling, but only in progressors (p = 0.014). Finally, anti-Id levels in progressors showed a significant decline during progression as compared to longitudinal anti-Id levels in non-progressors (median rate of change: -0.0004 vs. +0.0004, respectively, p = 0.003), suggesting a loss of anti-Id during progression. Our analysis of the Diabetes Prediction in Skåne cohort showed that early in life (age 2) individuals at risk have anti-Id levels indistinguishable from those in healthy controls, indicating that low anti-Id levels are not an innate characteristic of the immune response in individuals at risk. Notably, anti-Id levels declined significantly in individuals that later developed GAD65Ab suggesting that the decline in anti-Id levels precedes the emergence of GAD65Ab (median rate of change: -0.005) compared to matched controls (median rate of change: +0.001) (p = 0.0016). We conclude that while anti-Id are present early in life, their levels decrease prior to the appearance of GAD65Ab and to the development of T1D.

Mechanisms involved in the p62-73 idiopeptide-modulated delay of lupus nephritis in SNF(1) mice

The F(1) progeny of the (SWR × NZB) cross develop a lupus-like disease with high serum titers of autoantibodies, and increased frequency and severity of immune complex-mediated glomerulonephritis in females. In previous work, we found that an idiotypic peptide corresponding to aa62-73 (p62-73) of the heavy chain variable region of autoantibody 540 (Id(LN)F(1)) induced the proliferation of p62-73 idiotype-reactive T cell clones. Further, monthly immunization of pre-nephritic SNF(1) female mice with p62-73 resulted in decreased nephritis and prolonged life spans. Here we show that this treatment modulated proliferative responses to Id(LN)F(1) antigen, including a reduction in the population of idiopeptide-presenting antigen-presenting cells (APCs), as early as two weeks after immunization (10 weeks of age). Th1-type cytokine production was increased at 12 weeks of age. The incidence and severity of nephritis was reduced by 14 weeks compared to controls. Clinical indicators of nephritis, specifically histological evidence of glomerulonephritis and urine protein levels, were reduced by 20 weeks. Together these data suggest that events involved in the mechanism(s) whereby p62-73 immunization delayed nephritis occurred early after immunization, and involved modulation of APCs, B and T cell populations.

Anti-idiotypic antibody specific to GAD65 autoantibody prevents type 1 diabetes in the NOD mouse

Overt autoantibodies to the smaller isoform of glutamate decarboxylase (GAD65Ab) are a characteristic in patients with Type 1 diabetes (T1D). Anti-idiotypic antibodies (anti-Id) directed to GAD65Ab effectively prevent the binding of GAD65 to GAD65Ab in healthy individuals. Levels of GAD65Ab-specific anti-Id are significantly lower in patients with T1D, leading to overt GAD65Ab in these patients. To determine the possible protective role of GAD65Ab-specific anti-Id in T1D pathogenesis, we developed the monoclonal anti-Id MAb 8E6G4 specifically targeting human monoclonal GAD65Ab b96.11. MAb 8E6G4 was demonstrated as a specific anti-Id directed to the antigen binding site of b96.11. MAb 8E6G4 recognized human antibodies in sera from healthy individuals, T2D patients, and T1D patients as established by ELISA. We confirmed these MAb 8E6G4-bound human antibodies to contain GAD65Ab by testing the eluted antibodies for binding to GAD65 in radioligand binding assays. These findings confirm that GAD65Ab are present in sera of individuals, who test GAD65Ab-negative in conventional detection assays. To test our hypothesis that GAD65Ab-specific anti-Id have an immune modulatory role in T1D, we injected young Non Obese Diabetic (NOD) mice with MAb 8E6G4. The animals were carefully monitored for development of T1D for 40 weeks. Infiltration of pancreatic islets by mononuclear cells (insulitis) was determined to establish the extent of an autoimmune attack on the pancreatic islets. Administration of MAb 8E6G4 significantly reduced the cumulative incidence rate of T1D and delayed the time of onset. Insulitis was significantly less severe in animals that received MAb 8E6G4 as compared to control animals. These results support our hypothesis that anti-Id specific to GAD65Ab have a protective role in T1D.

Protective role of anti-idiotypic antibodies in autoimmunity--lessons for type 1 diabetes

Circulating autoantibodies to beta cell antigens are present in the majority of patients with Type 1 diabetes. These autoantibodies can be detected before and at time of clinical diagnosis of disease. Although the role of autoantibodies in the pathogenesis of the disease is debated, their presence indicates a dysregulation of the humoral immune response. Mechanisms regulating autoantibodies in Type 1 diabetes are not well understood. In contrast, in other autoimmune diseases there is acceptance that autoantibodies are regulated not only by antigen but also by other antibodies that bind to the antigen-binding site of these autoantibodies (anti-idiotypic antibodies). The proposed purpose of this network is to maintain an equilibrium between autoantibodies and their anti-idiotypic antibodies, preventing autoimmunity, while allowing a robust response to exogenous antigen. Anti-idiotypic antibodies regulate both autoantibody binding and their levels by a) neutralizing autoantibodies, and b) inhibiting the secretion of autoantibodies. Because it has been proposed that the B lymphocytes that produce autoantibodies function as autoantigen presenting cells, inhibiting their binding to autoantigen by anti-idiotypic antibodies may prevent development of autoimmune disease. This hypothesis is supported by the presence of anti-idiotypic antibodies in healthy individuals and in patients in remission from autoimmune diseases, and by the lack of anti-idiotypic antibodies during active disease. We recently reported the presence of autoantibodies to glutamate decarboxylase in the majority of healthy individuals, where their binding to autoantigen is prevented by anti-idiotypic antibodies. These anti-idiotypic antibodies are absent at clinical diagnosis of Type 1 diabetes, revealing the presence of autoantibodies. Type 1 diabetes (T1D) is an autoimmune disease characterized by the dysfunction and destruction of insulin-producing beta cells by autoreactive T cells. Although much progress has been made towards understanding the respective roles of effector and regulatory T cells in this beta cell destruction, the development of autoantibodies to beta cell proteins is widely considered simply a by-product of the autoimmune destruction of the beta cells, rather than having an active role in the pathogenesis. This view is starting to change based on increasing recognition that autoantibodies can have defined roles in other autoimmune diseases, and the emergence of new data on their role in T1D. This exploration of the role of autoantibodies in autoimmune disease has been spurred, in part, by increasing recognition that development of autoimmune diseases is influenced by regulatory antibodies (anti-idiotypic antibodies) directed against the unique binding site of autoantibodies. This review provides an overview of the development and function of these anti-idiotypic antibodies, and present evidence supporting their role in the development of autoimmune diseases. Finally, we conclude this review with a model of the events that may cause loss of anti-idiotypic antibodies and the implications for the development of T1D.

Modulation of diabetes in NOD mice by GAD65-specific monoclonal antibodies is epitope specific and accompanied by anti-idiotypic antibodies

Type 1 diabetes is caused by the autoimmune destruction of pancreatic beta cells. Here we show that administration of a human monoclonal antibody (b96.11) specific to the 65-kDa isoform of glutamate decarboxylase (GAD65) to prediabetic non-obese diabetic (NOD) mice significantly delays the onset of autoimmune diabetes. We found this effect to be epitope-specific, as only b96.11 showed this therapeutic property, while a GAD65-specific human monoclonal control antibody (b78) derived from the same patient, but specific to a different determinant of GAD65, had no significant effect on the progression of disease. Administration of b96.11 or b78 to NOD mice was accompanied by the generation of anti-idiotypic antibodies. Importantly, the induced anti-idiotypic antibodies were specific for the immunizing antibody and blocked the binding of GAD65 by the respective antibody. These findings suggest a potential role for the internal image of the GAD65 determinant recognized by b96.11 in the anti-idiotypic antibody, supporting an immunomodulatory role for GAD65-specific autoantibodies, as originally postulated by Jerne.

The role of VH determinants in systemic lupus erythematosus

The V-regions of anti-DNA antibodies contain determinants which can drive the autoimmune in SLE. Most of the evidence comes from murine studies where VH-derived epitopes accelerate the disease process in lupus prone-mice and can elicit mild inflammatory changes reminiscent of lupus in healthy animals. T helper cells reactive with VH peptides arise spontaneously during the disease and are thought to assist production of both anti-peptide antibodies and the generation of autoantibodies that deposit in the glomeruli. In mice stimulatory epitopes may be unique to autoantibodies. As tolerogens VH peptides may delay or diminish the autoimmune response by altering the production of cytokines. An artificial VH peptide, (pCONCENSUS) has been derived and this inhibits responses to VH and other autoantigens but leaves the murine immune system intact and able to generate reponses to external antigens. Limited number of studies of V-region determinants of human anti-DNA MAbs indicate prior sensitization of lupus T cells to VH determinants and that V-region reactive T cells are not deleted in periphery of healthy individuals.

Intravenous immunoglobulins induce the in vitro differentiation of human B lymphocytes and the secretion of IgG

The therapeutic effects of intravenous immunoglobulins (IVIGs) in several autoimmune diseases are characterized by a decrease in pathologic autoantibody levels. Although little direct evidence has been reported in humans, the large repertoire of natural immunoglobulin G (IgG) antibodies in IVIGs is expected to be involved in the regulation of autoreactive B lymphocytes. In normal adult mice, IVIGs have been reported to modulate immature B cells as well as peripheral B lymphocytes through V-region connections. Studies with human serum also indicated that anti-idiotypic antibodies, present in IVIG preparations, could recognize both natural and pathologic autoantibodies. We have used an in vitro culture system to characterize the direct effect of IVIGs on human B lymphocytes. This in vitro culture system involves CD40 activation of B lymphocytes by its ligand CD154 in the presence of cytokines. In this system, addition of IVIGs decreased by 50% to 80% the expansion of B lymphocytes. This reduced expansion was due to a decrease in the proliferation rate. In addition, a portion of B lymphocytes was differentiated into IgG-secreting cells in the presence of IVIGs and the secreted IgGs were reactive with antigens such as nucleoprotamine, dsDNA, tetanus toxin, and human IgG F(ab')(2) fragments. These observations indicate that IVIGs can have direct effects on B lymphocytes and suggest that such IVIG regulation of B lymphocytes could be involved in the therapeutic effects of IVIGs in autoimmune diseases.

Cationic myeloma M-components frequently show cross-reacting anti-DNA, Anti-F(ab')2 and anti-nucleosome specificities

134 cationic human IgG myeloma proteins were studied for expression of anti-DNA Idiotypic markers. 64 were studied for 16/6, F4, 3I, and 8.12, and 70 for expression of F4 and 3I. 31.3% showed at least one anti-DNA Id marker and many cationic myelomas were also positive for anti-DNA ELISA reactivity as well as anti-F(ab')2. Five M-components showed anti-nucleosome reactivity and one without detectable anti-DNA Id markers showed very strong anti-nucleosome antibody which was also inhibited by DNA and Sm antigens. Anti-idiotypic antisera produced either against Id(+) anti-DNA reactive M components or F(ab')2 fragments of affinity purified SLE IgG anti-DNA showed preferential cross-reactive idiotype reactivity between Id(+) anti-DNA reactive M components. Our findings indicate that human IgG monoclonal proteins positive for several common anti-DNA Ids and possessing anti-DNA ELISA reactivity, can serve as models for SLE Id marker antigens and as a source to prepare anti-Ids from IVIG.

Autoantibodies as chameleons

Autoantibody determinations are frequently used by rheumatologists to establish the diagnosis or assess follow up clinical status in patients with connective tissue diseases. Such autoantibodies are often presumed to have harmful effects, particularly since some such as anti-native DNA or anti-Ro have frequently been related to tissue damage or to functional impairments. However, there are many other autoantibodies which react with antigenic components of normal autologous tissues which have not been demonstrated to have self-damaging or harmful effects. Some of these autoantibodies may actually represent natural built-in mechanisms of feed-back inhibition, serving to modulate normal physiologic function. Autoantibodies may be compared to chameleons since their function or quality is often judged by the company they keep or by their anatomical localization. Since many autoantibodies to intra-cellular products seem to react with active sites of important biologic molecules, they may provide us with a much sharper image of a number of natural cellular functions.

Characterization and V(H) sequences of human monoclonal anti-F(ab')(2) autoantibodies from normals and Sjögren's syndrome patients

To investigate the genetic background of anti-F(ab')(2) autoantibodies and the mechanism behind their production we have analyzed 10 human monoclonal antibodies directed against IgG F(ab')(2) and IgG Fab. They were all derived from peripheral blood by the EBV/hybridoma technique. Eight were from three healthy individuals and two from two patients with primary Sjögren's syndrome (pSS). They react with epitopes on distinct regions of IgG, including epitopes present on or near the hinge of IgG, epitopes on the Fd gamma, and an antigenic determinant(s) present on lambda light chains. These determinants are either exposed on the intact IgG molecule or revealed following pepsin or papain digestion. The V(H) germline gene repertoire used is diverse and with considerable overlap with that used by rheumatoid factors (RF). The two IgG antibodies from normals are extensively mutated (13 and 24 mutations/V(H)), but with a replacement to silent mutation ratio in the CDR(H)1 + 2 of only 3.7. The IgM antibodies from normals are also heavily mutated (mean 10 mutations/V(H)). This suggests that anti-F(ab')(2) from normals are generated by an antigen-driven somatic hypermutation mechanism. In contrast, the two IgM antibodies from pSS are virtually unmutated in both V(H) and V(L). Together with published data of pSS RF and anti-Ro 52-kDa sequences (1-3), this suggests that there is an expanded population of naïve B cells with autoantibody specificities in the peripheral blood of pSS patients.

Antiidiotype antibody against platelet anti-GPIIIa contributes to the regulation of thrombocytopenia in HIV-1-ITP patients

Patients with human immunodeficiency virus 1-associated immunological thrombocytopenia (HIV-1-ITP) have markedly elevated platelet-bound immunoglobulin (Ig)G, IgM, and C3C4, as well as serum circulating immune complexes (CICs) composed of the same. Affinity purification of IgGs from their CICs with fixed platelets reveals high-affinity antibody (Ab) against platelet glycoprotein (GP)IIIa 49-66, which correlates inversely with their platelet count. However, sera from these patients have little to no anti-GPIIIa activity. To investigate this, we assayed serum, purified serum IgG, and CIC-Ig from these patients. This revealed approximately 150-fold greater Ab activity in purified serum IgG, and approximately 4,000-fold greater reactivity in CIC-IgG. This was shown to be associated with the presence of antiidiotype Ab2 (both IgG and IgM) sequestered in the CIC-IgG. The IgM antiidiotype was predominantly blocking Ab, as demonstrated by specificity for F(ab')(2) fragments of anti-GPIIIa 49-66 of HIV-1-ITP patients and inhibition of reactivity with peptide GPIIIa 49-66, not with a control peptide. The IgM antiidiotype was not polyreactive. Similar measurements were made in nonthrombocytopenic HIV-1-infected patients. Their serum reactivity was not measurable, but serum Ig and CIC-IgG against platelet GPIIIa 49-66 was present, although considerably lower than that found in HIV-1-ITP patients (26- and 35-fold lower, respectively). In addition, their IgM antiidiotype reactivity was 12-fold greater than that found in HIV-1-ITP patients. The IgM antiidiotype Ab titer of both cohorts correlated with in vivo platelet count (r = 0.7, P = 0. 0001, n = 32). To test the in vivo effectiveness of the IgM antiidiotype, thrombocytopenia was induced in mice with 25 microgram of affinity-purified anti-GPIIIa 49-66 (mouse GPIIIa has 83% homology with human GPIIIa and Fc receptors for human IgG1). Maximum effect was obtained at 4-6 h after intraperitoneal injection into Balb/c mice with a platelet count of approximately 30% baseline value. Preincubation of the anti-GPIIIa Ab with control IgM at molar ratios of IgM/IgG of 1:7 before intraperitoneal injection had no effect on the in vivo platelet count, whereas preincubation with patient IgM antiidiotype improved the platelet count to 50-80% of normal. Thrombocytopenia could be reversed after addition of IgM antiidiotype 4 h after induction of thrombocytopenia. Thus, CICs of HIV-1-infected patients contain IgM antiidiotype Ab against anti-GPIIIa, which appears to regulate their serum reactivity in vitro and their level of thrombocytopenia in vivo.

Urinary loss of immunoglobulin G anti-F(ab)2 and anti-DNA antibody in systemic lupus erythematosus nephritis

The objective of this study was to determine whether the low levels of serum immunoglobulin G (IgG) anti-F(ab)2 seen in some patients with active systemic lupus erythematosus (SLE) were directly related to the deposition of antibody with this specificity in the kidney or alternatively to the urinary loss of IgG anti-F(ab)2. Serum Levels of IgG anti-F(ab)2, anti-tetanus toxoid, and anti-ds DNA antibody were measured in parallel with urinary excretion of these same 3 antibodies in 28 patients with SLE nephritis and in 28 control patients with other forms of chronic kidney disease. Low levels of both serum IgG anti-F(ab)2 or anti-tetanus antibody appeared to correlate with increased levels of urinary loss of these same antibodies in some patients with SLE and in control subjects with kidney disease. However, urinary loss could not account for low serum levels of either IgG antibody in many subjects. Quantitative 24-hour urinary losses of IgG anti-F(ab)2 and anti-DNA were much higher in patients with SLE than in control subjects with kidney disease (P < .05), whereas amounts of IgG urinary loss of anti-tetanus were similar in patients with SLE and in control subjects. In nearly 1 third of SLE nephritis patients, 13% to 53% of total excreted urinary IgG showed anti-DNA enzyme-linked-immunosorbent assay reactivity. Urinary IgG in many patients with SLE showed both anti-DNA and anti-F(ab)2 reactivity, but dual anti-DNA/F(ab)2 specificity was more pronounced in affinity-isolated serum IgG anti-DNA or anti-F(ab)2 than in excreted urinary IgG molecules. The affinity of urinary IgG for either DNA or F(ab)2 was much lower than the same antibody activities measured either in serum or in kidney biopsy eluates. When the relative affinity of anti-DNA antibody in serum, urine, and kidney biopsy eluate was measured in parallel, the highest affinity antibody was found in kidney biopsy eluates, followed by serum antibody with urine antibody affinity showing the lowest values. These findings suggest a relative concentration of the highest affinity, doubly reactive IgG anti-DNA/F(ab)2 in SLE kidney tissues during SLE nephritis and implicate this process as an important factor in ongoing tissue damage.

Anti-idiotypic antibodies prevent the serologic detection of antiribosomal P autoantibodies in healthy adults

A subset of SLE patients has serologically detectable autoantibodies to the ribosomal P proteins (anti-P). We reported the discovery of covert anti-P antibodies and their masking IgG-inhibitory antibodies in the sera of healthy adults. The aim of this study was to determine if these IgG-inhibitory antibodies are anti-idiotypic antibodies (anti-Ids). IgG and IgG-depleted fractions of plasma from two healthy adults were assayed for inhibition of anti-P F(ab')2 binding to the ribosomal P proteins in immunoblot. Anti-P antibody activity was completely inhibited by plasma IgG, whereas there was no inhibition by IgG-depleted plasma. IgG-inhibitory antibodies recognized a cross-reactive epitope among anti-P from different SLE patients. Plasma IgG from one healthy adult was depleted of pepsin agglutinators and generic anti-F(ab')2 antibodies by adsorption with an affinity column prepared with normal IgG F(ab')2. Unretained IgG bound exclusively to anti-P F(ab')2 in ELISA. Using four affinity columns, we isolated IgG anti-Ids to anti-P antibodies from four healthy adults. These purified anti-Ids bound to anti-P F(ab')2 from a healthy adult and SLE patients. They did not bind to F(ab')2 fragments prepared from normal IgG or anti-dsDNA. Ribosomal antigens blocked this anti-Id-Id interaction. Purified anti-Ids inhibited the binding of anti-P F(ab')2 from patients to ribosomal P proteins. SLE patients without overt anti-P antibodies also possessed IgG anti-Ids to anti-P antibodies. We conclude that IgG-inhibitory antibodies are anti-Ids to anti-P antibodies, and are directed to public idiotopes on anti-P antibodies. These anti-Ids may be part of an Id network that regulates anti-P antibody expression, and perhaps pathogenicity.

Naturally occurring anti-idiotypic antibodies reactive with anti-DNA antibodies in systemic lupus erythematosus

The levels of 'putative' anti-idiotypic antibodies reactive with F(ab')2 fragments of affinity purified DNA binding antibodies from five SLE patients were measured in the serum of active and inactive systemic lupus erythematosus (SLE) patients, their relatives, spouses and healthy non-related individuals. Serum anti-idiotypic antibodies of the IgG isotype could be detected in the serum of 8/15 inactive SLE patients, 3/19 active SLE patients, 17/27 SLE relatives, 1/4 SLE spouses and 6/32 healthy non-related individuals. When the serum immunoglobulins from the individuals in each group were separated into IgG and IgM antibody fractions and analysed, a significant increase in levels of IgG anti-idiotypic reactivity were found in healthy individuals (16/32), whilst no significant increase in IgG anti-idiotypic antibodies were detected in SLE patients, SLE relatives and SLE spouses. Comparatively few individuals tested showed detectable levels of IgM anti-idiotypic antibodies. These results demonstrate that anti-idiotypic antibodies reactive with anti-DNA antibodies are detectable in the serum of SLE patients, SLE relatives, SLE spouses and healthy individuals, and are predominantly of the IgG isotype. The increased frequency of IgG anti-idiotypic antibodies after separation from serum IgM antibodies infers that anti-idiotypic activity of some IgG immunoglobulins in the sera of healthy individuals may be masked by the presence of IgM antibodies in the serum.

Anti-F(ab')2 antibody in HIV type 1 infection: relationship to hypergammaglobulinemia and to antibody specific to the V3 loop region of glycoprotein 120

As HIV infection and autoimmune disease share certain similarities, it has been suggested that HIV may disrupt control of humoral immunity by the antiidiotype network, and that this may be evident as increased IgG antibody to F(ab')2. When anti-F(ab')2 was quantified by ELISA in sera of randomly chosen HIV-infected versus uninfected donors, some HIV-infected sera did contain increased anti-F(ab')2, resulting in a median amount twofold higher than in uninfected sera. Moreover, when data were grouped by blood CD4 lymphocyte count, anti-F(ab')2 in HIV+ groups appeared to rise as CD4 lymphocytes declined. However, increased anti-F(ab')2 mirrored the elevation in serum IgG closely, and normalization of anti-F(ab')2 to serum IgG concentration equalized the groups so that no relationship to CD4 lymphocytes remained. Hypergammaglobulinemia is therefore strongly implicated as a cause of variation in anti-F(ab')2. After dissociation of immune complexes, anti-F(ab')2 activity per microgram of monomeric IgG was slightly increased over normal only in the HIV-infected group with fewest CD4 lymphocytes, without statistical significance. In contrast, the proportion of IgG antibody to the V3-neutralizing determinant in HIV-1 decreased significantly as disease advanced. The same was true for 12 HIV+ individuals studied longitudinally for 500-1300 days. The data suggest that measuring serum anti-F(ab')2 is misleading when immune complexes are present: apparent increases as disease progresses are due to increased IgG and, possibly, to related technical artifacts. During HIV infection, the proportion of antiidiotypic IgG in fact remains unaltered or falls, making this an unlikely cause of suppressed humoral immunity to HIV-1.

Relationship between progression of disease and immunoglobulin A-anti-Fab-/F(ab')2 autoantibodies in patients with head and neck cancer

Patients with malignant tumors of the head and neck often have immune defects. Higher serum immunoglobulin (Ig)A levels were reported in this group of patients. We investigated whether IgA-anti-Fab- or IgA-anti-F(ab')2 autoantibodies, which have been shown to correlate with severe dysfunction of the immune system, also appear in patients with head and neck cancer. Sera of 110 patients with squamous cell carcinoma (SCCHN), eight patients with adenoid cystic carcinoma, and 57 healthy control subjects were tested by enzyme-linked immunosorbent assay for IgA-anti-Fab autoantibody activity. Patients with head and neck cancer showed a higher IgA-anti-Fab activity (optical density (OD) = 399; n = 118) than did healthy control subjects (OD = 84; n = 57; p < 0.0001). An association between stage of disease and IgA-anti-Fab activity could be established in patients with SCCHN. Patients with stage IV disease had a significantly higher IgA-anti-Fab activity (OD = 538; n = 51) than had patients with stage I disease (OD = 283; n = 18; p < 0.05). Patients with stage II (OD = 293; n = 13) or stage III (OD = 379; n = 28) disease had intermediate activity. Also a higher IgA-anti-Fab activity than in healthy control subjects could be shown in the eight patients with adenoid cystic carcinoma (OD = 314; n = 8; p < 0.01). The highest IgA-anti-Fab activity was observed in eight patients with SCCHN who died within 6 months after testing (OD = 1004; n = 8), suggesting an association between autoimmunity and final desintegration of physiologic body functions. The occurrence of IgA-anti-Fab/IgA-anti-F(ab')2 autoantibodies might be interpreted as an aspect of immune deficiency in patients with malignant tumors of the head and neck.

Affinity columns containing anti-DNA Id+ human myeloma proteins adsorb human epibodies from intravenous gamma globulin

OBJECTIVE

To study eluates of intravenous gamma globulin (IVGG) prepared from affinity columns of human cationic IgG myeloma proteins bearing anti-DNA idiotype (Id) markers 16/6, F4, 3I, and 8.12 for possible anti-Id (combining site) blocking activity.

METHODS

Anti-DNA idiotypic antibody activity was studied in 3 preparations of IVGG containing high, medium, and low levels of IgG anti-F(ab')2, and in 4 other commercial IVGG preparations. Affinity-purified IgG anti-DNA (APAD) from systemic lupus erythematosus (SLE) patients was biotinylated, and binding to DNA coated on enzyme-linked immunosorbent assay plates was used to measure anti-DNA antibody activity. IVGG was adsorbed to Sepharose 4B affinity columns linked to a panel of cationic human IgG myeloma proteins positive for anti-DNA Id markers 16/6, F4, 3I, and 8.12. Material adsorbing to such columns was eluted at low pH (2.5) and after neutralization, tested for its ability to inhibit biotinylated APAD reacting with DNA.

RESULTS

Only 0.05-0.9% of IVGGs bound firmly to Id affinity columns. These IVGGs were then eluted, using pH 2.5 glycine-saline and eluates neutralized to pH 7.4. Column flowthrough and eluate fractions were compared for their ability to block SLE APAD reacting with DNA. Significant inhibition of SLE APAD combining sites was observed with eluates from anti-DNA Id affinity columns; however, no correlation between IVGG anti-F(ab')2 activity and true anti-Id blocking of APAD was apparent. No residual anti-Id activity remained in column flowthrough fractions. No anti-Id blocking activity was recorded for IVGG eluates from human cationic myeloma columns devoid of the 4 anti-DNA Id markers. DNase treatment of IVGG or Id column eluates did not affect anti-Id blocking activity. Thus, all detectable anti-DNA idiotypic antibody capable of blocking SLE anti-DNA combining sites bound to Id+ affinity columns. Column eluates also showed some relative concentration of IgG anti-DNA activity, which was of lower affinity for DNA than antibodies also present in eluates which blocked anti-DNA combining sites.

CONCLUSION

The presence of both anti-DNA and antiidiotypic (anti-combining site) activity in human anti-DNA Id column eluates indicates that epibodies from IVGG are relatively concentrated when this strategy is used. This approach may lead to a new strategy for treatment of SLE nephritis.

The antigen-binding domain of a human IgG-anti-F(ab')2 autoantibody

Recent studies revealed an immunoregulatory role of natural IgG-anti-F(ab')2 antibodies in both healthy individuals and patients with certain diseases. The implication of anti-F(ab')2 antibodies in the pathogenesis of diseases prompted us to study the gene segment structure of their antigen-binding domains and their binding characteristics. cDNA was prepared from the lymphocytes of a patient with a high IgG-anti-F(ab')2 serum titer. Variable heavy and light gene segments were amplified by PCR and inserted into a phagemid surface expression vector. Single-chain antibodies displayed on the phage surface were screened for binding to F(ab')2 fragments. The subsequent analysis of 95 single clones demonstrated that they all bound specifically to F(ab')2. Sequence analyses of 12 clones showed that 11 were identical and 1 contained a silent point mutation in the heavy chain and three amino acid exchanges in the light chain. The heavy chains belonged to the V(H)3 and the light chains to the V(kappa)2 gene family. The 11 identical light-chain genes were completely homologous to a germ-line sequence (DPK-15). Binding assays showed that the single-chain antibodies bind to F(ab')2, but not to Fab, Fc, or intact IgG. This binding pattern was confirmed by surface plasmon resonance studies, which revealed a relatively high affinity (Ka = 2.8 x 10(7) M(-1)). The strong binding capacity was further demonstrated by competitive inhibition of the serum anti-IgG antibody's interaction with antigen. The present study defines for the first time to our knowledge the gene segment structure of the antigen-binding domain of two human IgG-anti-F(ab')2 autoantibody clones and describes the binding kinetics of the purified monomeric fragments.

Cross-reactivity of human IgG anti-F(ab')2 antibody with DNA and other nuclear antigens

OBJECTIVE

To characterize immunologic specificity and possible antiidiotype activity of IgG anti-F(ab')2 in normal subjects as well as in patients with active and inactive systemic lupus erythematosus (SLE).

METHODS

IgG anti-F(ab')2 and anti-double-stranded DNA (anti-dsDNA) were affinity isolated from immunoadsorption columns of F(ab')2 and dsDNA linked to Sepharose 4B. Affinity-purified IgG anti-F(ab')2 (APAF) and affinity-isolated IgG anti-dsDNA (APAD) were tested by enzyme-linked immunosorbent assay (ELISA) for other cross-reacting specificities including anti-Sm, anti-Sm/RNP, and anti- Crithidia binding. Anti-DNA specificity of APAF and APAD was assayed by S1 nuclease treatment of heat-denatured DNA. Rabbit antiidiotypic antisera were prepared by immunization with APAF and APAD from normal subjects and SLE patients and absorption with insolubilized human Cohn fraction II (Fr II). VL and VH regions of 5 monoclonal IgM antibodies with anti-F(ab')2/anti-DNA specificity generated by Epstein-Barr virus B cell stimulation were sequenced by polymerase chain reaction and characterized for VH and VL subgroup. APAF and APAD were also examined by high-resolution electron microscopy for possible ring forms indicative of antiidiotypic V-region interactions.

RESULTS

APAF from normal subjects, representing 0.08-0.18% of serum IgG, showed striking relative concentrations of both anti-F(ab')2 and anti-DNA, as well as anti-Sm and anti-Sm/RNP ELISA reactivity. Both APAF and APAD reacting with F(ab')2 or dsDNA on the ELISA plate could be cross-inhibited by F(ab')2 or DNA in solution. Anti-DNA reactivity in normal APAF and APAD was much more sensitive to S1 nuclease treatment than similar fractions from SLE patients. Neither APAF nor APAD from controls produced positive antinuclear immunofluorescence or positive Crithidia staining, whereas these were strongly positive using SLE APAF and APAD. Absorbed rabbit antisera against normal or SLE APAF and APAD showed strong ELISA reactivity against both APAF and APAD, but no residual reactivity with normal Fr II. VL and VH sequencing of monoclonal human IgM antibodies showing both anti-F(ab')2 and anti-DNA reactivity showed relative VH3, V kappa 1 or VH1, V kappa 3 restriction. No evidence of ring forms or V-region "kissing" dimers was obtained when normal or SLE APAD or APAF was examined by high-resolution electron microscopy.

CONCLUSION

IgG anti-F(ab')2 in both normal subjects and SLE patients represents a polyreactive Ig subfraction with concomitant anti-DNA, anti-Sm, and anti-Sm/RNP specificities. Anti-DNA reactivity in SLE is qualitatively different from that in normal APAD and APAF since normal APAD and APAF anti-DNA is much more sensitive to S1 nuclease digestion of denatured dsDNA. APAF and APAD share distinct V-region antigens which may be related to prominent VH3 or VH1 antigenic components. No evidence for in vivo complexing of anti-DNA and anti-F(ab')2 as ring forms or antiidiotype-IgG complexes was observed during ultrastructural studies. In both normal individuals and SLE patients, APAF may represent a small polyreactive IgG subfraction which also contains antinuclear and anti-DNA specificities.

Anti-IgG autoantibodies and possible immune regulatory mechanisms in patients with pulmonary tuberculosis

SETTING

Anti-Ig antibodies are known to have important clinical and biological implications.

OBJECTIVES

To determine naturally occurring anti-F(ab')2 gamma and anti-Fc gamma antibodies in patients with pulmonary tuberculosis (PTB) in relation to various clinical manifestations and human leukocyte antigen (HLA).

DESIGN

Antibodies to F(ab')2 and Fc portions of IgG were detected in the sera of normal healthy individuals (n = 41), patients with pulmonary tuberculosis (n = 50) and their household family contacts (n = 20) using an enzyme immuno assay (EIA) system.

RESULTS

As compared to controls (0.110 +/- 0.01 optical density [OD]), the levels of anti-F(ab')2 gamma were significantly increased in PTB patients (0.998 +/- 0.08 OD, P < 0.0001) and in their contacts (0.486 +/- 0.04 OD, P < 0.001) suggesting that the occurrence of these autoantibodies is related to infection/exposure to Mycobacterium tuberculosis. Anti-F(ab')2 gamma antibodies were significantly increased in both sputum positive and negative patients (P < 0.0001) and no deviation was observed between these two groups. The levels of these antibodies were positively correlated with disease severity assessed by chest X-ray. The drug failure patients had higher activity of anti-F(ab')2 gamma than drug responders and no impact of anti-tuberculosis chemotherapy was observed. A statistically significant increase of anti-F(ab')2 gamma levels (1.25 +/- 0.21 OD) was observed in HLA-DR2 positive patients as compared to the DR2 negative groups (1.02 +/- 0.09 OD), P < 0.01. No deviation was observed in the levels of anti-Fc gamma levels between controls and any group of PTB patients.

CONCLUSION

The present data suggests that the elevated levels of anti-F(ab')2 gamma antibodies in PTB patients represent an anti-idiotypic antibody response to anti-M. tuberculosis antibody caused by an immune imbalance following M. tuberculosis infection.

Immunologic markers for differentiation of autoimmune responses

Several approaches have been directed at identifying accurate parameters for the measurement of disease activity in autoimmune disorders, both in humans and in experimental animal models. A great deal of previous effort has focused on determining what constitutes antigenic epitopes on various autologous proteins or tissue components, which then can generate an immune response in the host. Much of this work has been clouded by the fact that normal subjects (both animal and human) seem to mount an immune response to myriad autologous proteins, characterized by the formation of antibodies known as natural autoantibodies. During the course of certain autoimmune diseases such as systemic lupus erythematosus (SLE) or Wegener's granulomatosis (WG), patients produce what appear to be autoantibodies reacting with autologous components such as DNA and Sm antigen (SLE) or proteinase-3 (WG). Low levels of these same autoantibodies are present in IgG derived from normal subjects. Recently, we have found that IgG anti-F(ab')2 from normal subjects, affinity-purified from immunoabsorbent columns of human F(ab_)2 Sepharose, exhibits not only anti-F(ab')2 but also anti-dsDNA and anti-Sm activity. These antibodies constitute an average of 0.02% of normal serum IgG. Similar findings have also been observed in SLE patients with active disease. Our findings suggest that perturbation of the idiotypic network may represent an important fundamental aspect of many autoimmune disorders.

Some autoantibodies to Ro/SS-A and La/SS-B are antiidiotypes to anti-double-stranded DNA

OBJECTIVE

To determine the relationship of anti-Ro/SS-A and anti-La/SS-B antibodies to anti-double- stranded DNA (anti-dsDNA) in sera from patients with systemic lupus erythematosus.

METHODS

Sera with anti-Ro/SS-A alone (n = 5) or those with anti-Ro/SS-A and anti-La/SS-B (n = 7) were absorbed with purified Ro/SS-A and La/SS-B, respectively. The absorbed sera were then tested for reactivity with MOLT-4 extract by Western blot and dsDNA by enzyme-linked immunosorbent assay (ELISA). With selected sera, anti-dsDNA was isolated on DNA cellulose columns and anti-Ro/SS-A and anti-La/SS-B were isolated on antigen-affinity columns. Reactivity between anti-dsDNA and autologous anti-Ro/SS-A or anti-La/SS-B, as well as inhibition by cognate antigens, was studied.

RESULTS

After absorption, all sera showed reactivity with small nuclear RNP A and D bands in Western blots, and some showed reactivity with dsDNA by ELISA. Anti-dsDNA populations (n = 4) were purified on dsDNA cellulose columns. Anti-Ro/SS-A (n = 1) and anti-La/SS-B (n = 3) were affinity purified from the same sera as the anti-dsDNA. In all cases, anti-dsDNA bound autologous anti-Ro/SS-A and anti-La/SS-B much more strongly than it bound normal pooled IgG. Moreover, dsDNA, but not RNA, blocked these interactions. In addition, Ro/SS-A blocked anti-Ro/SS-A and La/SS-B blocked anti-La/SS-B in these same interactions.

CONCLUSION

In sera with anti-Ro/SS-A and anti- La/SS-B, there are subpopulations of these antibodies that bind and mask anti-dsDNA. We hypothesize that these anti-Ro/SS-A and anti-La/SS-B antibodies are antiidiotypes to idiotypes on anti-dsDNA and that they both mask and down-regulate these anti-dsDNA antibodies.

Does AIDS emerge from a disequilibrium between two complementary groups of molecules that mimic MHC?

There is increasing evidence that a disturbance of self-nonself-recognition plays an important role in the immunopathogenesis of AIDS. Here, Caner Susal, Volker Daniel and Gerhard Opelz speculate that the immune system is balanced between two groups of molecules that mimic major histocompatibility complex (MHC) proteins; AIDS is suggested to emerge as a consequence of human immunodeficiency virus (HIV) disturbing this balance in favor of anti-MHC class II responses.

Molecular localization of human IgG anti-F(ab')2 reactivity with variable- and constant-region lambda light-chain epitopes

Human IgG antibodies reacting with antigenic determinants on F(ab')2 fragments represent generic antiidiotypic antibodies present in the serum of normal individuals. Additionally, the titers of these antibodies in the sera of patients with systemic lupus erythematosus (SLE) are inversely related to disease activity. Because these autoantibodies recognize predominantly light chain-related epitopes, especially lambda type, we synthesized constant (C)lambda- and variable (V)lambda-related overlapping 7-mer peptides on polypropylene pins to determine anti-F(ab')2-reactive epitopes on human lambda light chains. ELISA reactivity of affinity-purified anti-F(ab')2 antibodies obtained from normal individuals and from patients with SLE, as well as murine anti-human light-chain monoclonal antibodies specific for C lambda and V lambda subgroup-related determinants, was tested using the overlapping 7-mers of human lambda light-chain sequence. The patterns of reactivity against C lambda-related peptides were similar in both normal and SLE-derived anti-F(ab')2 antibodies. However, reactivity profiles against V lambda-related peptides were distinctively different between the normal and the SLE-associated anti-F(ab')2 autoantibodies. A decrease in reactivity among the SLE IgG anti-F(ab')2 antibodies was noted for particular amino acid V lambda complementarity-determining region (CDR) residues, including glycine at positions 27 and 54, alanine at 16 and 37, and tyrosine at 28 and 91. This different pattern of reactivity from normal may indicate that in SLE there is a failure of antiidiotypic control mechanisms, as reflected by a defect in production of antibody to immunodominant V lambda CDR residues.

Pathogenic anti-DNA idiotype-reactive IgG in intravenous immunoglobulin preparations

This study was addressed to explore the reactivity of natural anti-idiotypes from commercial lots of immunoglobulins to several idiotypes (Ids), usually expressed by anti-DNA molecules in lupus nephritis. Eleven intravenous immunoglobulin (IVIG) preparations and nine (three polyvalent and six hyper-immune) intramuscular IgG were investigated for specific content of anti-DNA, anti-F(ab')2 and antibodies reacting with several anti-DNA IgG Ids. Two samples (nos 6 and 11) showed high reactivity with allogeneic F(ab')2 and with F(ab')2 of myeloma proteins bearing the anti-DNA Id 3I+ and the 8.12+. Since both 3I and 8.12 Id markers are known to characterize pathogenic anti-DNA IgG in systemic lupus erythematosus (SLE), anti-Id antibodies to these markers were obtained by absorbing the IVIG samples nos 6 and 11 to Sepharose columns coupled with pooled F(ab')2 fragments of 3I(+)-F4(+)-8.12(+)-myeloma proteins. Inhibition experiments showed that anti-8.12 Id-eluted IgG induced a selective suppression of the DNA-reactive antibodies derived from patients with active lupus nephritis to their substrate, suggesting the involvement of 8.12+ molecules in the SLE glomerular damage. Since 8.12+ anti-DNA are nephritogenic antibodies, the occurrence of anti-8.12+ Id in commercial IVIG may be of potential therapeutic relevance in modulating the pathogenic SLE Id network. Previous variable results of IVIG treatment in SLE, such as resolution of proteinuria or worsening nephritis, could be related to variable enrichment of different lots of IVIG in suppressive anti-pathogenic Id antibodies.

Suppression of anti-erythrocyte autoantibody-producing B cells by a physiological IgG-anti-F(ab')2 antibody and escape from suppression by tumour transformation; a model relevant for the pathogenesis of autoimmune haemolytic anaemia

We showed previously that broadly reactive IgG anti-immunoglobulin autoantibodies produced by rats during the immune response suppress the B cell response. We report here on the effect of a similar human antibody on self-reactive human B cells. IgG anti-F(ab')2 was added to cultures of anti-erythrocyte autoantibody-producing B cells derived from healthy donors. A dose-dependent suppression of the antibody response was obtained (maximum at 1.3 ng IgG/10(6) cells). This effect was competitively inhibited by F(ab')2 gamma. Autoimmune haemolytic anaemia can be caused by chronic monoclonal B cell proliferation. To reproduce this condition in vitro we immortalized B cells with Epstein-Barr virus (EBV) and raised a B cell population with anti-erythrocyte autoantibody activity. These cells were electrically fused with CB-F7 tumour cells and an IgG1 cold-reactive anti-erythrocyte autoantibody-producing B cell line was established. Surprisingly, the tumour cells were not suppressed by IgG anti-F(ab')2. It is known that anti-immunoglobulins selectively suppress antigen-receptor (AgR)-occupied B cells by a Fc gamma-receptor (Fc gamma R)-mediated mechanism. To occupy their AgR, we preincubated the tumour cells with anti-AgR antibody. In spite of this, their susceptibility to suppression was not restored. As shown by rabbit IgG-sensitized ox erythrocyte (EA)-rosetting, this refractoriness was not due to a loss of Fc gamma R. Our experiments delineate a mechanism of peripheral B cell suppression to autoantigens, and show a way of escape from control relevant for the pathogenesis of autoimmune haemolytic anaemia.

Differences in anti-Fab antibodies in adult and late onset rheumatoid arthritis

In the present study the ratio of antigen-bound anti-IgG-Fab antibodies (hidden aFab) to free aFab was found to be significantly increased in patients with adult onset rheumatoid arthritis (AORA) as compared to late onset rheumatoid arthritis (LORA). The overall amount of aFab was similar in both groups. The difference was only seen in seropositive patients. Within the seropositive AORA group, the aFab ratio was correlated with the duration and the stage of disease but not with the patients' age at investigation. This might reflect a higher affinity of anti-Fab antibodies and/or a greater diversity of the idiotypic repertoire in adult onset disease resulting in the formation of immune complexes, the stability of which might be enhanced further by the presence of rheumatoid factors. Although a pathophysiological involvement of aFab cannot be concluded from our observations, it is conceivable that different immunoregulatory mechanisms could be operative in RA with onset at different ages.

Molecular mimicry between HIV-1 and antigen receptor molecules: a clue to the pathogenesis of AIDS

There is increasing evidence that autoimmune phenomena play an important role in the immunopathogenesis of AIDS. We found a high degree of sequence homology between HIV-1 and antigen receptor molecules, immunoglobulins and T cell receptors. Based on recent findings that the appearance of anti-Fab autoantibodies and attachment of gp120/immunoglobulin/complement complexes on CD4+ T cells are associated with the decrease of CD4+ T cells in HIV-infected patients, we hypothesize herein that cross-reactive anti-F (ab')2 autoantibodies and circulating gp120 molecules are responsible for a destabilization of the immune network and the elimination of CD4+ T cells.

Human anti-F(ab')2 antibodies show preferential reactivity for F(ab')2 molecules bearing lambda light chains

In order to evaluate binding specificities of anti-F(ab')2 antibodies from patients with systemic lupus erythematosus (SLE) and from normal healthy controls, F(ab')2 fragments were prepared from 24 IgG myelomas with defined isoelectric points, DNA-associated idiotypes, and kappa/lambda light chain types. Using ELISA and hemagglutination assays, anti-F(ab')2 antibodies from 12 healthy controls and 29 SLE patients were observed to exhibit preferential binding (lambda > kappa) to myeloma F(ab')2 fragments composed of lambda light chains (P < 0.0001). No correlation of anti-F(ab')2 binding and presence of cationic, neutral, or anionic isoelectric points or for DNA-associated idiotypes on monoclonal F(ab')2 was detected. Anti-F(ab')2 antibodies, often elevated in SLE during remission, show preferential specificity for F(ab')2 fragments bearing lambda light chains.

Molecular heterogeneity of auto-anti-idiotypic antibodies in MLR-lpr/lpr mice

The VH and V kappa gene families expressed by 20 monoclonal auto-anti-idiotypes (Ab2) derived from unmanipulated MLR-lpr/lpr mice were determined by Northern blotting. Complete variable region sequences of six Ab2, along with three additional V kappa-JH Ab2 sequences, were obtained. These auto-anti-idiotypes arose spontaneously in the animals, and they bound specifically to an idiotypic determinant (Id/r) on mAb 28/12, a monoclonal IgG2b MLR-lpr/lpr anti-small nuclear ribonucleoprotein antibody. The 16 Ab2 heavy chains belonged to 7 different VH gene families, and the 10 Ab2 light chains were derived from 8 V kappa families. The light chains of two Ab2 were approximately 99% identical; the remaining variable region sequences were highly heterogeneous. There was no correlation between primary amino acid sequence of either heavy or light chain and idiotypic properties of the auto-anti-idiotypes. Six Ab2 used VH or V kappa genes that are identical to known germ-line genes. A high proportion of the spontaneous auto-anti-idiotypes was shown to have autoantibody activity (anti-DNA, anti-ribonucleoprotein), or specific binding reactions with lipopolysaccharide of Salmonella RE, or both properties. The structural diversity of spontaneous MLR-lpr/lpr auto-anti-idiotypes differs sharply from the structural homogeneity reported for Ab2 induced in normal animals against syngeneic Ab1. Our results suggest that auto-anti-idiotypes might arise independently of an immunogenic stimulus from an Ab1.

Relationship between naturally occurring human antibodies to casein and autologous antiidiotypic antibodies: implications for the network theory

Previous studies on human autologous antiidiotypes have been based largely upon analyses of autoimmune disease. We have previously described polyclonal, naturally occurring human autoantibodies directed against antibodies with specificity toward bovine casein in the sera of IgA-deficient humans. In order to define this system more exactly we have not produced two murine monoclonal antibodies directed against bovine milk kappa-casein to use as clonal tools to identify specific antiidiotypes in these human sera. Kappa-casein is an important part of the casein micelle in milk and cheese; in addition to being an important immunogen for man, kappa-casein is known to have conserved amino acid sequence and two antigenic epitopes. Data presented here show that the serum of up to 74% of IgA-deficient and 10% of normal humans have specific autologous antiidiotypes in their serum which bind to monoclonal antibodies directed to bovine kappa-casein. These human antibodies [intact or F(ab)'2] can be blocked from binding to the monoclonal anti-kappa-caseins by pure bovine kappa-casein or the kappa-casein peptide fragment. In contrast to previous studies in autoimmune disease, serum levels of the autoantiidiotypes were directly proportional to the level of IgG antibody to bovine kappa-casein. These observations suggest that continual exposure to a ubiquitous dietary antigen may produce an antigen driven system in which stimulation of both Ab1 and Ab2 occurs in concert.

Human autoantibodies to lamin B receptor are also anti-idiotypic to certain anti-lamin B antibodies

Autoantibodies reactive with nuclear envelope proteins are mainly detected in human sera from patients with liver diseases. Some of these antibodies are directed to lamin B, lamins A and C, or to the lamin B receptor (LBR). We show here that the latter one are anti-idiotypic to certain anti-lamin B antibodies. Using an enzyme-linked immunosorbent assay specific for lamins we found that serum M containing anti-LBR antibodies inhibited the binding to lamins of anti-lamin B autoantibodies from three of five sera tested. Similar results were obtained using patient's M purified IgG. The binding of monoclonal IgM, lambda anti-lamin B antibodies produced by a lymphoblastoid cell line derived from the patient's blood lymphocytes was also inhibited. Absorption of serum M with nuclei abolished the inhibitory activity. No inhibition was recorded with normal sera or sera containing other antinuclear specificities. Anti-LBR antibodies did not alter the binding to lamins of sera containing anti-lamins A and C antibodies. Altogether these findings demonstrate that anti-LBR antibodies are also combining site related anti-idiotypic antibodies (Ab2) to certain anti-lamin B antibodies, provide further evidence for discrete specificities among anti-lamin B antibodies and suggest that the occurrence of autoantibodies to nuclear envelope antigens may be under idiotypic regulation.

Parallelism of serum anti-F(ab')2 and anti-cationic IgG reactivities in patients with systemic lupus erythematosus

Cationic anti-DNA antibodies may be related to glomerular injury in murine lupus nephritis or in patients with systemic lupus erythematosus (SLE). Therefore, anti-cationic antibodies in SLE could include antibodies with regulatory function on such pathogenic cationic molecules. Since anti-F(ab')2 antibodies may be involved in the idiotype control of anti-DNA antibodies in some patients with inactive SLE, the present study was aimed to determine if SLE patients with significant serum levels of anti-F(ab')2 produce antibodies reacting with cationic IgG molecules. Three SLE sera with high titers of anti-F(ab')2 antibodies were individually adsorbed by sequential affinity chromatography on three Sepharose columns coupling normal IgG from Cohn Fraction II, pooled cationic IgG myeloma paraproteins displaying idiotypic anti-DNA markers (F4 and 8.12), and F(ab')2 fragment from allogeneic IgG, respectively. Eluates obtained from cationic IgG adsorption showed predominant anti-F(ab')2 reactivity. A similar profile was also detected in a serum from a normal control donor with high levels of anti-F(ab')2. Biotinylation of anti-cationic eluates showed that such antibodies were significantly more reactive with cationic than anionic or neutral IgG, confirming their apparent affinity for positively charged antigens on IgG molecules. Since anti-cationic absorptions were able to remove the anti-F(ab')2 activities in the SLE sera studied, it is possible that anti-cationic antibodies could function as immunoregulatory antibodies in the idiotypic control of some SLE autoreactive phenomena, including glomerular anti-DNA deposition.

Monoclonal antibodies against human anti-F(ab')2 antibodies react with light chain epitopes

Anti-F(ab')2 antibodies affinity isolated from sera of patients with rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), or normal SLE relatives were used to produce monoclonal antibodies (mAbs) in Balb/c and NZB mice. Four of five mAbs showed only primary light chain specificity. Only one mAb produced in an NZB mouse against anti-F(ab')2 from a single SLE patient showed anti-mu-chain specificity. Parallel identical control immunizations with IgG or a single human IgG kappa myeloma produced mAbs with a predominant gamma-chain/Fc fragment specificity. Anti-light chain specificity of mAbs was demonstrated to involve epitopes requiring tertiary structure of the entire light chain instead of antigens confined to Ckappa/lambda or Vkappa/lambda fragments. Anti-kappa specificity of three mAbs was extremely similar but not identical to that defined by anti-Km1 allotyping systems. No evidence was obtained with any of the mAbs produced for antigens unique to SLE or RA anti-F(ab')2 antibodies. The light chain antigenic prominence of many anti-F(ab')2 antibodies may reflect structural features shared by this group of immunoglobulins somehow important for their biologic function.

Autoimmunity in periodontal disease

Periodontal disease in characterized by the loss of the normal supporting tissues of the teeth and a humoral and cellular immune response to bacterial antigen of dental plaque which accumulates at the dento-gingival junction. This review considers the evidence for the existence of an autoimmune component of the host immune response, the possible origin of such a response and the way in which such a host response may contribute to the changes observed in the periodontium in the disease.

Specificity of autoantibodies to histone H1 in SLE: relationship to DNA-binding domains

Autoantibodies in the sera of patients with systemic lupus erythematosus were examined with respect to their specificity for proteolytic fragments of histone H1 that retain, or do not retain, DNA-binding domains. 16 of 31 sera contained IgG and IgM antibodies to histone H1. IgM antibodies to H1 in 8 sera (50%) were directed at 18 kD and 20 kD alpha-chymotrypic H1 fragments that bore binding sites for DNA, as identified by staining immunoblots containing the fragments with ssDNA plus 6/0, a mouse monoclonal antibody against ssDNA, IgM with this type of histone H1 specificity did not react with comparably-sized V8 protease fragments of H1. IgM antibodies to H1 in the other patients were directed against entirely different epitopes which were preserved in V8 protease digests of H1. In serial studies of three patients during different phase of their SLE, the level of antibodies against the 18 kD and 20 kD histone H1 fragments varied in parallel with the level of anti-ssDNA antibodies in one and varied inversely in the other two. The data suggest that a significant proportion of autoantibodies to histone H1 are directed at a limited number of epitopes localized to H1 fragments containing DNA-binding sites.

Induction and immunochemical properties of a novel anti-antibody

This paper describes results which characterize an induced antibody in normal outbred rabbits which we have, for convenience, called parareactant (PR). PR resulting from autoimmunization of rabbits with either keyhole limpet hemocyanin-anti-tetanus toxoid F(ab')2 or with tetanus toxoid-anti-tetanus toxoid F(ab')2 complexes was studied. PR activity was directed solely to autologous, homologous or heterologous F(ab')2 fragments regardless of their specificity. PR failed to react with intact antibodies or with antigen-antibody complexes consisting of homologous antibody bound to specific antigen. Radioimmunoassay and ELISA inhibition assays showed that reactivity between PR and autologous anti-tetanus toxoid F(ab')2 or homologous anti-bovine serum albumin F(ab')2 fragments was specifically inhibited with antigen. Anti-allotypic antibodies specific for a2 and b6 markers strongly inhibited binding of 125I-anti-micrococcal carbohydrate F(ab')2 (a2, b6) with PR (a3, b4, b5). PR specificity thus appears to be directed against non-idiotypic determinants present in Fv regions. Affinity immunoblotting was used to analyze clonality of PR in the sera collected from individual rabbits during the course of an active immune response. PR-positive sera displayed clonally restricted spectrotype patterns. PR molecules were predominantly IgG with isoelectric points of 5.9-6.8. These results strongly suggest that these PR molecules are coded by a small number of V region genes.

Regulation of retinal autoimmunity via the idiotypic network

The immune response to self antigens is regulated through an interplay of idiotypes and anti-idiotypes expressed on antibodies and lymphoid cells. The equilibrium of the different components of the immune system has been modulated in various autoimmune diseases by manipulation of the idiotypic network. Experimental autoimmune uveoretinitis (EAU) was induced in rats with one foot pad injection of S-antigen (S-Ag) in complete Freund's adjuvant (CFA). 1. Injection of rats with the mouse anti-S-Ag monoclonal antibody (mAb) S2D2 either simultaneously with or before S-Ag challenge, led to an anti-idiotypic (anti-Id) response and to inhibition of EAU. 2. Suppression of the disease could be passively transferred using lymph node and/or spleen cells from donors immunized with S2D2 to naive recipients, prior to immunization with bovine S-Ag in CFA. In contrast, one injection of IgG from S2D2-immunized rats did not prevent EAU. 3. Preimmunization against a purified rat polyclonal anti-Id-S2D2 antibody (internal image of the epitope recognized by mAb S2D2) before S-Ag challenge also allowed to inhibit EAU. As S2D2 was the best of several anti-S-Ag mAbs tested for disease inhibition, the epitope recognized by S2D2 should be of particular interest in the regulation of the immune response. This epitope has been localized to the N-terminal region of S-Ag, in the amino acid sequence 40-50. The S2D2 epitope is distant from all presently known uveitogenic sites. Manipulation of the idiotypic network for selected epitopes of the autoantigen may provide a valuable approach to therapy of autoimmune disease.

Experimental autoimmune uveoretinitis: idiotypic regulation and disease suppression

Experimental autoimmune uveoretinitis (EAU), a mostly T-cell dependent disease, was induced in laboratory animals by a single immunization with retinal extract or purified S-antigen in complete Freund's adjuvant. It can be prevented or suppressed by injections of either the autoantigen or monoclonal antibodies against the autoantigen. The suppression of EAU by these antibodies was associated with an anti-idiotypic antibody response. The inhibition of the pathogenic immune response by the antigen or the antibodies could be explained, according to Jerne's hypothesis of immunoregulation, by a disturbance of the network of idiotype and anti-idiotype interactions.

Distribution of anti-F(ab')2 antibodies and the 16/6 idiotype in systemic lupus erythematosus (SLE) probands and kindreds

Levels of serum anti-F(ab')2 antibodies and expression of the 16/6 anti-DNA idiotype were studied in 103 sera from first-degree relatives of 17 systemic lupus erythematosus (SLE) kindreds. Among healthy SLE relatives, 35.9% showed anti-F(ab')2 elevations and 24%, Id 16/6 expression. Forty-three and two-tenths percent of healthy SLE relatives with elevated anti-F(ab')2 also showed expression of 16/6; when Id 16/6 was positive, 16 of 25 relatives (64%) showed parallel elevations of anti-F(ab')2. However, within individual families, distribution patterns of elevated anti-F(ab')2 and Id 16/6 often did not coincide. Affinity-isolated anti-F(ab')2 from four members of a single SLE kindred showed relative enrichment for Id 16/6 in only two of the four individuals studied. Moreover, none of the isolated anti-F(ab')2 antibodies within this kindred or another kindred showing 16/6 Id expression reacted directly with 16/6 Id. Our studies suggest that whereas both anti-F(ab')2 and Id 16/6 are increased within SLE kindreds, expression of the two does not always coincide. Furthermore, anti-F(ab')2 antibodies do not show direct reactivity with Id 16/6. A number of anti-DNA idiotypic markers may play a role in idiotypic networks among such SLE kindreds.

Studies of anti-F(ab')2 antibodies and VH region distribution among SLE kindreds

Genomic DNA samples from kindreds of patients with systemic lupus erythematosus were examined for VH region genotypes using probes representing JH and representative members of the human VH gene families (VHI-VHVI) in parallel with distribution of high levels of anti-F(ab')2 (generic anti-idiotype) in some non-affected SLE family members. Identical VH region genotypes were present in an SLE female proband and one unaffected normal male sibling. Three normal unaffected family members with elevated anti-F(ab')2 showed AB, AD, and AC (non-identical)VH genotypes. VH region genotype pattern distributions do not appear to directly correlate with production of high levels of anti-F(ab')2 in SLE families.

Lack of correlation between HLA types and anti-idiotypic production in family members of a lupus patient

Correlations of anti-single-stranded (ss) DNA, anti-F(ab')2, and anti-idiotypes to HLA types of 16 healthy family members of a lupus patient were studied. High levels of anti-ss DNA (63%) and anti-F(ab')2 (69%) were detected. Of the 12 family members who expressed HLA-DR2 antigen, 8 had anti-ss DNA and anti-F(ab')2 antibodies. One out of 3 family members who shared the same HLA phenotypes, A1B8DR2, of the proband had high levels of anti-idiotype directed against the proband's F(ab')2 anti-DNA. Though a high prevalence of A1B8DR2, of anti-ss DNA, and of anti-F(ab')2 in healthy family members of a lupus patient was found, anti-idiotypes against anti-DNA were not dependent on HLA-A, B, Dr.