Autoantibodies of various specificities encoded by genes from the VH J558 family bind to foreign antigens and share idiotopes of antibodies specific for self and foreign antigens.

We examined the binding to foreign antigens and the expression of crossreactive idiotypes by a panel of 20 murine monoclonal autoantibodies encoded by V genes from the VH J558 family. 9 of 20 antibodies bound to foreign antigens such as bacterial polysaccharides, poly(Glu50, Tyr50), poly(Glu54,Lys37,Phe9), arsonate, and lysozyme, known to interact with antibodies encoded by genes from the VH J558 family. A high proportion of our panel of autoantibodies expressed crossreactive idiotypes originally borne by monoclonal rheumatoid factors, anti-Sm, and anti-DNA antibodies, all encoded by V genes from the VH J558 family. Some of these VH J558+ autoantibodies shared crossreactive idiotypes with VH J558+ antibodies directed against foreign antigens such as influenza virus hemagglutinin, poly(Glu60,Ala30,Tyr10), arsonate, and dextran. The implications of these findings are discussed with respect to the process of activation of self-reactive clones.

Specificities and V genes encoding monoclonal autoantibodies from viable motheaten mice.

Several hundred hybridomas were obtained from 1-2-mo-old viable motheaten (mev) mice. Among the Ig-secreting hybridomas tested, greater than 50% (17/33) exhibited reactivity for autoantigens, supporting the idea that the Ly-1 B cells that predominate in mev mice contain frequent precursors of autoantibody-forming cells. Certain of the specificities of these autoantibodies correlated with the documented pathophysiology of mev mice (antithymocyte, -erythrocyte, -skin, -kidney, and -IgG); others were specific for autoantigens not previously observed in motheaten mice but though to be involved in other autoimmune diseases (e.g., intrinsic factor, transferrin, myelin basic protein, and thyroglobulin). About 2 of 3 (11/17) of the self-reactive antibodies exhibited multispecific binding activity for various autoantigens. Analysis by Northern blotting of the V gene families used in mev autoantibodies showed a random usage of VH families and a biased usage of four Vk gene families. Of 16 autoantibodies tested, 12 used a Vk gene from the Vk1, 4, 10, or 19 families. These patterns of Vk gene usage differ from nonautoimmune control animals. Overall, an immunoregulatory defect operating at a more generalized level than the VH or Vk loci, and due to a single gene mutation, appears to be responsible for the multiple immune abnormalities of mev mice.

High frequency of autoantibodies bearing cross-reactive idiotopes among hybridomas using VH7183 genes prepared from normal and autoimmune murine strains.

Hybridomas obtained by in vitro stimulation with lipopolysaccharides (LPS) of BALB/c, MRL/lpr, and NZB splenocytes were selected for expression of VH7183 by hybridization using slot blotting. Northern blot analysis showed that the majority of hybrids produce a full length message complementary to the VH7183 probe. The frequency of VH7183 hybridomas was significantly higher in NZB mice as compared with BALB/c mice. Using multiple binding assays, 60% of the total antibodies encoded by VH7183 were specific for self-epitopes. Finally, the vast majority express cross-reactive idiotypes borne by autoantibodies of various specificities.

Shared idiotypes and restricted immunoglobulin variable region heavy chain genes characterize murine autoantibodies of various specificities.

The study of the Ig variable region heavy chain (VH) genes used to encode antibodies specific for self-epitopes from murine hybridomas showed that three VH families are primarily utilized: VH J558, the largest family, and VH QPC52 and VH 7183, the families most proximal to the Ig joining region heavy chain genes. These monoclonal autoantibodies express cross-reactive idiotopes shared by rheumatoid factors and antibodies specific for Sm. The expression of these idiotypes is independent of major histocompatibility complex and Ig constant region heavy chain haplotypes, self-antigen specificity, and even the VH gene family utilized. Though the experiments described here are limited to murine autoantibodies, similarities exist between murine and human autoimmune diseases. Studies that aim to investigate the relationship between VH gene expression and the presence of cross-reactive idiotypes among human autoantibodies should enable us to better understand the mechanisms of autoimmunity and self-tolerance.

Syngeneic anti-idiotype monoclonal antibodies to murine anticarcinoembryonic antigen monoclonal antibodies.

BALB/c mice were immunized with either NP-3 or NP-4, two anticarcinoembryonic antigen murine monoclonal antibodies. Each animal produced anti-idiotype antibodies to the corresponding immunogen and no cross-reactivity between anti-NP-3 sera and anti-NP-4 sera was detected. Hybridomas were produced from these animals and two IgG1 anti-idiotype monoclonal antibodies were obtained: CM1 specific for NP-3 and CM11 specific for NP-4. CM1 and CM11 recognized determinants located within the antibody-combining site, since each anti-idiotype antibody inhibited the binding between the corresponding idiotype and carcinoembryonic antigens. Using an immunoblotting technique, neither CM1 nor CM11 reacted with isolated heavy or light chains of NP-3 or NP-4, whereas binding was observed with the intact molecule. This observation indicates that CM1 and CM11 are directed against conformational idiotypes resulting from the association of the variable regions of the heavy and light chains. Taken together, these results suggest that CM1 and CM11 might bear internal images of carcinoembryonic antigen epitopes, and that they are potential candidates as idiotype vaccines against colorectal tumors.

Human immune response to anti-carcinoembryonic antigen murine monoclonal antibodies.

We previously demonstrated that patients with carcinoembryonic antigen [CEA]-producing neoplastic tumors, treated with murine monoclonal antibody to CEA, produced antibodies directed against the constant regions [human anti-mouse antibody (HAMA)] and the idiotypes [anti-Id] of these murine immunoglobulins. In this study, we describe a method for analyzing the presence of such antibodies in the sera of these patients. The HAMAs were measured by enzyme immunoassay and removed by immunoadsorption on Affi-Gel mouse IgG. The unabsorbed fraction contained the anti-Id antibodies; their presence was demonstrated by binding to the CEA monoclonal antibody (Ab1). The specificity of the binding was assessed by preincubating the sera with Ab1 and measuring the residual nonspecific binding. When specific binding was detected, the anti-Id antibodies were isolated by adsorption and elution on Affi-Gel Ab1. The anti-Id antibodies were fixed on enzyme immunoassay plates and incubated with a panel of mouse anti-human immunoglobulin to determine their isotypes. In a first series of 24 patients, HAMAs were found in 20 cases and anti-Id antibodies in 19 cases. The isolation of a specific IgG to Ab1 was achieved in 2 cases. In an ongoing series, the HAMA and anti-Id antibodies were detected in all five patients given injections of another monoclonal antibody to CEA. In two patients an IgG1 kappa anti-Id was isolated from the serum. The potential therapeutic effect of these antibodies is under investigation.

An immuno-electron microscopical analysis of transcribing multinucleosomal templates: what happens to the histones?

Immuno-electron microscopy was used to visualize the structure of reconstituted chromatin after in vitro transcription by purified T7 RNA polymerase. T7 RNA polymerase disrupts the nucleosomal structure in the transcribed region. This disruption is not influenced by the template, linear or supercoiled, and the presence or absence of nucleosomal positioning sequences in the transcribed region. In this study, we used monoclonal autoantibodies reacting with the nucleosome core particles and epitopes within several regions of the four different core histones. Some of the residues recognized by the autoantibodies are accessible on the surface of the nucleosomes and some are more internal and therefore less exposed at the surface. We show that the loss of the nucleosomal configuration during transcription is due to the loss of histone/DNA binding and that at least part of the histones are transferred to the nascent RNA chains. Consequently, after in vitro transcription by T7 RNA polymerase, the nucleosomal template does not conserve its original configuration, and no interaction of antigen/antibodies is observed anymore in the region that has been transcribed. Therefore, we conclude that in our in vitro transcription assay, nucleosomes are detached from the template, and not simply unfolded with histones remaining attached to the DNA.

Specificities and genetic characteristics of nucleosome-reactive antibodies from autoimmune mice.

Antinuclear antibodies are present in the serum of individuals with systemic autoimmune diseases such as SLE. Most autoantibodies characterized to date are directed against isolated nuclear molecules such as DNA or histones. We have obtained from spontaneously autoimmune mice six IgG mAb that recognize conformational nucleosome epitopes, but do not react with individual histones or DNA. For three of these mAb, the epitope is at least partially present in the H2A-H2B-DNA nucleosome subparticle, although their binding characteristics differ from those of conventional anti-H2A-H2B-DNA antibodies. All six mAb use VH or Vkappa genes which are recurrently utilized in anti-DNA and other antinuclear antibodies. The V regions of the nucleosome-reactive mAb also contain charged (mostly cationic) residues at sites that are likely to be critical for interaction with nucleosomal antigens. These results suggest that the usage of certain V gene segments in conjunction with suitable V(D)J rearrangements may confer reactivity to nucleosomal antigens. B cells producing such autoantibodies are probably expanded early during the autoimmune process. Somatic mutations in the V regions of nucleosome-reactive mAb may modulate their specificities and result in the acquisition of binding patterns restricted to individual chromatin components such as DNA.

Monoclonal anti-histone H1 autoantibodies from MRL lpr/lpr mice.

Hybridomas producing anti-histone monoclonal antibodies were generated from a 2-month old MRL lpr/lpr mouse. Five IgM antibodies showed binding to histone H3 and three of these IgM antibodies also bound histone H1. Two IgG2a antibodies (MRA3 and MRA12) were specific for histone H1 and their binding was further characterized. Both reacted strongly with mouse and calf thymus histones H1, but showed limited (if any) binding to H1 from non-mammalian species such as duck, trout, or sea urchin sperm. Histone H1 is composed of three domains: N (N-terminal), G (globular) and C (C-terminal). The binding of MRA3 and MRA12 antibodies to the N, G and C domains of the histone H1 molecule was also investigated, using purified H1 fragments. Significant binding was observed only with the GC fragment but not with isolated NG, G or C fragments. Moreover, the integrity of most, if not all, of the G domain (residues 33-122) was necessary for antibody binding, since cleavage of the H1 molecule either at residue 72 or 106 abolished the binding to MRA3 and MRA12. Taken together, these results could indicate that MRA3 and MRA12 antibodies recognize a conformational determinant of the H1 molecule.

Biased usage of certain Vk gene families by autoantibodies and their polymorphism in autoimmune mice.

Of 79 hybridomas derived from stimulated or unstimulated autoimmune disease prone mouse strains, secreting autoantibodies of various specificities more than 65% use V genes from five Vk families, namely, Vk1, Vk4, Vk8, Vk10 and Vk19. Restriction fragment length polymorphism (RFLP) analysis of genomic DNAs from autoimmune prone mouse strains, tight skin, NZB and SJL show marked differences in the polymorphism of the Vk1, Vk10 and Vk19 gene families.

Induction of anti-polycation antibodies in H-2s mice by immunization with nuclear antigens.

Following administration of certain chemicals (heavy metals or lupus-inducing drugs), H-2s mice produce autoantibodies reacting with various nuclear antigens such as fibrillarin in the nucleolus and histones in chromatin. In the present study, we have immunized A.SW (H-2s) mice and their congenic counterparts A.BY (H-2b) mice with bovine thymus nuclei in Freund's adjuvant. As was previously observed with lupus-prone mice, such active immunization did not elicit antinuclear antibodies in any of the experimental groups. Surprisingly, the A.SW immunized with nuclei in adjuvant developed high titers of IgG antibodies that reacted exclusively with synthetic polycations. We obtained several monoclonal IgG antibodies from these mice and verified that these polycation-reactive antibodies were not directed against a specific nuclear antigen. The genetic analysis of the monoclonal antibodies further confirmed their clonal diversity. The mechanisms leading to the appearance of antibodies reactive with highly basic molecules in A.SW mice may be related to their predisposition to produce autoantibodies to cationic nuclear antigens (fibrillarin, histones) during chemically-induced autoimmunity.

Structure and binding properties of monoclonal antibodies to core histones from autoimmune mice.

Histones are frequent targets of self-reactive antibodies during autoimmune syndromes. We report the specificities and V region genes of three IgG anti-histone MAbs obtained from autoimmune mice. Each of the MAbs, named LG2-1, LG2-2 and BWA3, is directed against a different determinant located in the basic amino-terminal domain of core histones. LG2-1 reacts with a peptide from histone H3 (residues 30-45), LG2-2 recognizes the amino-terminus of H2B (residues 1-13) and BWA3 binds an epitope corresponding to a region of high sequence similarity between H2A and H4 (residues 1-20 and 1-29, respectively). The analysis of their V region sequences indicates that the H chain CDRs of these MAbs are remarkable for the presence of negatively charged amino acid residues that may play a role in the binding to cationic histones. The H chain importance in conferring reactivity to histones is corroborated by the observation that each of the VH gene segments of these MAbs is very similar to VH genes of previously described murine anti-histone antibodies.

Murine mercury-induced autoimmunity: a model of chemically related autoimmunity in humans.

Human exposure to certain compounds or therapeutic drugs can result in the development of an autoimmune syndrome. Mercury (Hg) induced autoimmunity is one of the few animal models in which administration of a chemical induces a specific loss of tolerance to self-antigens. After receiving subtoxic doses of Hg or other heavy metals, susceptible mouse strains rapidly develop highly specific antibodies to nucleolar antigens. In addition, these animals display a general activation of the immune system, especially pronounced for the Th2 subset and a transient glomerulonephritis with immunoglobulin deposits. Like many human autoimmune diseases, this syndrome is associated with the expression of susceptible major histocompatibility complex (MHC) class II genes. In this article, we review the essential features of this model, and we discuss the putative mechanisms by which Hg creates such a severe immune dysfunction.

Establishment of human cell lines producing anti-D monoclonal antibodies: identification of Rhesus D antigen.

Two cell lines producing monoclonal antibodies have been established from peripheral blood of a negative Rhesus blood donor which has been immunized with positive Rhesus red blood cells. Two monoclonal antibodies Co II 8.8 and Co II 7.12 have been selected. Both are IgG1 antibodies, but recognize different epitopes on the Rhesus D antigen, apparently associated with different subunits of the D antigen. Thus the Co II 8.8, like the positive serum, immunoprecipitates an antigen of a relative molecular weight of 33 kDa, while the Co II 7.12 recognizes an antigen of Mr 42 kDa.

Characterization of variable-region genes and shared crossreactive idiotypes of antibodies specific for antigens of various influenza viruses.

Several syngeneic monoclonal anti-idiotypic antibodies were obtained against PY206, a monoclonal antibody specific for X-31 (H3N2) influenza virus hemagglutinin. This idiotype was found in the sera of BALB/c mice immunized with various influenza viruses. Adsorption experiments indicated that the PY206 Id was borne by antibodies specific for viral hemagglutinin (HA) and/or neuraminidase (NA). This idiotype was identified on other monoclonal antibodies specific for various influenza HAs (H3 and H1). Study of the variable-region (V) genes of these monoclonal antibodies showed that its expression is independent of variable kappa (VK)21 light-chains and that the heavy-chains of the strongly idiotype-positive hybridomas derive from either the variable heavy (VH) J558 or VH 7183 family. Finally, Western blot analysis demonstrated that PY206 idiotypic determinants are located exclusively on the heavy chain.

Cytokine regulation of a rodent model of mercuric chloride-induced autoimmunity.

Experimental models of chemically induced autoimmunity have contributed to our understanding of the development of autoimmune diseases in humans. Heavy metals such as mercury induce a dramatic activation of the immune system and autoantibody production in genetically susceptible rats and mice. This autoimmune syndrome is dependent on T cells, which are important for B-cell activation and cytokine secretion. Several studies have focused on the roles of T-helper (Th)1 and Th2 cells and their respective cytokines in the pathogenesis of mercury-induced disease. This article reviews recent studies that have examined the patterns of cytokine gene expression and where investigators have manipulated the Th1 and Th2 responses that occur during mercury-induced autoimmunity. Finally, we will discuss some biochemical/molecular mechanisms by which heavy metals may induce cytokine gene expression.

Epitope recognition in histone H1 by SLE autoantibodies in the presence of a DNA-ligand.

To investigate the specificity of anti H1 antibodies peptides from the N- and C-domain of H1 and the synthetic oligonucleotide (AT)6 were complexed. Circular dichroism (CD) spectroscopy indicated that the free peptides H1(1-16), H1(204-218) and C(121-210) in low salt buffer assume a random structure but become helical when bound to the oligonucleotide. The structured and unstructured H1 fragments were then analyzed by enzyme linked immunosorbent assay (ELISA) with anti-H1 antibodies in sera from patients with systemic lupus erythematosis (SLE) and with the monoclonal anti-H1 antibody MRA-12 derived from MLR lpr/lpr autoimmune mice. Binding of these antibodies to H1(204-218) and C was inhibited to a level of 50% when these H1 peptides were complexed with (AT)6. When the same antibody was tested with H1 fragment GC(34-210), attachment to oligonucleotide (AT)6 did not influence antibody binding. Competition studies with liquid phase GC and C antigen against solid phase GC and C indicated that liquid phase GC was more efficient in displacing antibody binding reactivity than liquid phase C. The displacement effect of both liquid phase antigens was greatest against solid phase C. We conclude that anti-H1 autoantibodies are directed against an epitope located near the junction of the G- and C-domain which is exposed and not masked when H1 is bound to DNA.

Antibodies to histones in systemic lupus erythematosus and drug-induced lupus syndromes.

Antihistone antibodies are some of the most frequent autoantibodies in rheumatic diseases and can represent useful diagnostic markers in some autoimmune syndromes. Histone epitopes are often located in accessible regions of chromatin or are conformational determinants resulting from the association of several components. These observations and studies with murine models of lupus strongly support the view that histones play a direct stimulatory role in triggering autoantibody production.

Anti-double stranded DNA, anti-histone, and anti-nucleosome IgG reactivities in children with systemic lupus erythematosus.

In this study we evaluated the presence of anti-nucleosome reactivity in children with systemic lupus erythematosus (SLE), and assessed its clinical correlations in comparison with anti-dsDNA and anti-histone IgG levels. Reactivities to nuclear substrates were determined by enzymatic immunoassays in 80 sera from 22 children with SLE, and solid phase adsorption experiments were performed. In children with active SLE, the anti-dsDNA, anti-histone, and anti-nucleosome IgG levels were elevated, and were significantly correlated with disease severity; during remission anti-histone (but not anti-dsDNA and anti-nucleosome) antibodies, although reduced, were still significantly elevated. The results of adsorption studies showed that anti-dsDNA antibodies contributed to anti-nucleosome reactivity, while anti-histone antibodies did not. The recognition of the H3H4-DNA nucleosome subparticle, rather than H2AH2B-DNA, may be related to the nucleosome reactivity. In children with SLE anti-nucleosome reactivity is present; it is in part due to anti-dsDNA antibodies and in part to antibodies recognizing conformational epitopes that may be related to the H3H4-DNA nucleosome subparticle. Its clinical significance for diagnosis is not greater than that of the anti-dsDNA antibodies.

Rat monoclonal antibodies to murine IgM determinants: application to antibody purification.

Two monoclonal rat antibodies (RAM11 and RAM12) were raised against mouse IgM antibodies. These 2 antibodies were isotype-specific since they bound murine IgM but not IgG or IgA antibodies; moreover, sera from mouse strains possessing different allotypic determinants inhibited the binding of RAM11 and RAM12. Both antibodies can be readily purified from culture supernatants on protein G-agarose (but not on protein A-agarose). After coupling to Sepharose 4B, RAM11 provided a useful affinity chromatography support for the purification of murine IgM antibodies from biological fluids.