A novel trait of naturally occurring anti-DNA antibodies: dissociation from immune complexes in neutral 0.3-0.5 M NaCl

Hitchhiker antigens: Inconsistent ChIP results, questionable immunohistology data, and poor antibody performance may have a common factor

Questionable data and poor antibody performance may have a common factor: antigens “hitchhiking” on the very antibodies designed to target them. Here I focus on histone hitchhikers and their antibodies, given the impact of chromatin immunoprecipitation on our understanding of DNA regulation. Caused by a lack of stringency during antibody purification, hitchhikers will impede important advances in chromatin research and therapeutics derived from that research, if similar circumstances in the study of lupus decades ago are any guide. Evidence of this phenomenon is reviewed, purification modifications for antibody manufacturing are suggested, and a histone hitchhiker detection procedure is provided.

Amphiphysin I but not dynamin I nor synaptojanin mRNA expression increased after repeated methamphetamine administration in the rat cerebrum and cerebellum

Dopamine increases/decreases synaptic vesicle recycling and in schizophrenia the proteins/mRNA is decreased. We isolated cDNA clone, similar to amphiphysin 1 (vesicle protein) mRNA from the neocortex of rats injected repeatedly with methamphetamine using polymerase chain reaction (PCR) differential display. This clone is highly homologous to the 3' region of the human amphiphysin gene. PCR extension study using a primer specific for the rat amphiphysin 1 gene and a primer located within the clone revealed that it is the 3' UTR region of the rat amphiphysin 1 gene. Furthermore, in situ hybridization revealed that amphiphysin 1 mRNA is expressed in the cerebrum, medial thalamus, hippocampus and cerebellum. In the cerebellum, amphiphysin mRNA expression was confined to upper granule cell layer. Repeated methamphetamine administration increased amphiphysin I mRNA expression in both anterior part of the cerebrum, and the cerebellum. However, the repeated administration did not alter mRNA expression of the other vesicle proteins, synaptotagmin I, synapsin I, synaptojanin and dynamin I, we conclude that the repeated administration selectively increased amphiphysin 1 mRNA expression. Thus, amphiphysin 1 does not work as synaptic recycling, but it is suggested, as a part of pathogenesis of brain tissue injury (under Ca²⁺ and Mg²⁺ devoid environment) in repeated methamphetamine-injected states, the gene regulate actin-asssembly, learning, cell stress signaling and cell polarity.

Expression of Y7 Cross‐Reactive Idiotope on Human IgM Molecules

In this paper we report data regarding the IgM Y7 cross-reactive idiotope (CRIo) obtained by analysis of: 1) its V-gene subgroup dependance, 2) the frequency of its expression on human monoclonal IgMs and IgM molecules from normal and pathological sera. Furthermore, comparison of epitopic repertoire and nature of binding of human monoclonal IgMs expressing Y7 CRIo was performed to confirm the natural antibody properties of these molecules. IgM isolated from sera of patient DJ (IgM DJ) which expresses the Y7 idiotope has been classified to VH3/VL2 subgroup. From ten IgMs tested only IgM from patient RD (IgM RD) has been shown to express Y7 idiotope. Y7+ human IgMs bound to ssDNA, lactic acid bacteria, mouse laminin, porcine thyroglobulin and mouse IgG. Higher percentage of the expression of Y7 CRIo was detected in the sera of patients suffering from autoimmune diseases such as lupus, rheumatoid arthritis and psoriasis vulgaris as well as in patients suffering from chronic infections of the lower urinary tract. Antigen binding repertoire and properties of Y7+ monoclonal IgM, frequency of Y7 expression on monoclonal IgMs and its concentration in normal and pathological sera indicate the important biological role of this CRIo within the immune system.

Induction of anti-DNA antibodies by immunization with anti-DNA antibodies: mechanism and characterization

Two well-characterized IgG monoclonal antibodies, reactive with double-stranded (ds) DNA and nucleosomes, were administered to normal BALB/c mice to examine the reproducibility and the biology of a previously reported model of anti-DNA antibody induction by immunization with anti-DNA antibodies. The monoclonal antibodies were purified either with or without a high-salt wash to remove nucleosomal antigens bound to them during the cell culture. Both monoclonal antibodies, but not normal IgG, induced significant IgG anti-dsDNA antibody production from 1 week to 25 weeks after the last immunization. The antibodies produced in this manner possess different binding preferences to ds synthetic polynucleotides than the antibodies used for the immunization, and they did not react with nucleosomes. The monoclonal antibodies purified with the high-salt wash were more effective in anti-DNA antibody induction than those purified without the high-salt wash. Even when bound to these monoclonal antibodies, neither dsDNA, nucleosomes, or ds synthetic polynucleotides exert significant antigenicity. For example, anti-DNA antibodies produced by mice immunized with an immune complex formed by poly(dA-dT) and one of the monoclonal antibodies that has a high affinity to this polynucleotide did not show an increased affinity to poly(dA-dT). Together, these results suggest that anti-DNA antibody molecules or processed antibody peptides, and not DNA/nucleosomes carried by anti-DNA antibodies, play a role in this model of anti-DNA antibody production.

Enhancement of hydroxyl radical DNA cleavage by serum anti-dsDNA antibodies in SLE

Autoantibodies reactive with double-stranded (ds) DNA are a hallmark of systemic lupus erythematosus (SLE), but it is not fully elucidated how these antibodies contribute to the various pathological changes observed in lupus patients. In a previous study, we have found a significant enhancement effect of two murine monoclonal anti-dsDNA antibodies on DNA cleavage by the hydroxyl radical. We have extended this study and have found that purified polyclonal anti-dsDNA antibodies from sera of lupus patients and an MRL/lpr mouse, but not anti-ssDNA antibodies, also enhanced radical cleavage of DNA. The cleavage was inhibited by EDTA, DMSO and thiourea. The antibody preparations per se did not cleave DNA. These results suggest that such an enhancement effect on DNA cleavage is a feature of a significant part of anti-dsDNA antibody population and a possible clue in understanding the roles of anti-dsDNA antibodies in the pathophysiology of SLE under certain circumstances.

Enhancement of oxidative cleavage of DNA by the binding sites of two anti-double-stranded DNA antibodies

Nucleic acid specificity was tested for two monoclonal anti-double-stranded DNA autoantibodies, 2C10 and H241, derived from two lupus-prone MRL/Mp-lpr/lpr mice. Antibody 2C10 bound double-stranded oligonucleotides with a preference for dA-dT over dG-dC base pairs and did not bind single-stranded oligonucleotides. Distamycin A, an antibiotic that binds to the minor groove, inhibited 2C10 binding of double-stranded DNA, suggesting that this antibody interacts with dA-dT base pairs in the minor groove. Antibody H241 binding was previously shown to have a dG-dC preference and to involve both major and minor grooves. In attempted footprinting assays, both 2C10 and H241 markedly en- hanced rather than protected against cleavage of DNA by hydroxyl radical-generating systems. With 2C10, this enhancement effect was observed only when hydroxyl radical generation was associated with oxidation of Fe(II). In contrast, H241 enhancement occurred in the presence of H2O2 and ascorbate or UV light irradiation and did not depend on added metal ion. The enhancement sites were related to the antibody binding specificities. The oligonucleotide 5'-AAAATATATATTT-3' was a much more effective inhibitor of the 2C10 enhancement than of the H241 effect, whereas the oligonucleotide 5'-GGGGCGCGCGCCC-3' was a much more effective inhibitor of the H241 enhancement. In addition, the enhanced cleavage occurred preferentially at dA-dT-rich regions with 2C10 and at dG-dC-rich regions with H241. These findings raise the possibility that anti-DNA autoantibodies could enhance DNA damage in inflammatory lesions in which hydroxyl radicals are generated.

Heavy chain dominance in the binding of DNA by a lupus mouse monoclonal autoantibody

Antibodies H241 and 2C10 are lupus mouse IgG autoantibodies that bind native DNA. In previous experiments, oligonucleotide antigens affinity-labeled both H and L chains of H241 but only the H chain of antibody 2C10. Primary structures of the V regions of the 2C10 H and L chains and the H241 L chain, determined from cDNA, help to explain the previous affinity-labeling experiments. The 2C10 L chain CDRs had several Asp residues and a net negative charge of five, whereas the 2C10 H chain CDRs had four Arg residues and a net positive charge of five. The L chain CDRs of H241 had a net positive charge of one. [The H241 H chain cDNA sequence was published previously by Gangemi et al. (1993) J. Immun. 151, 4660-4671]. Plasmid vectors were used for bacterial expression of H and L chains of 2C10 alone and in combinations in single chain Fv (scFv) molecules. The H chain alone bound native DNA as well as or better than the H-plus-L chain scFv. The H chain alone also bound Z-DNA. Combination of the 2C10 H chain with the L chain of an anti-Z-DNA antibody maintained the selectivity for Z-DNA, whereas its combination with the 2C10 L chain (in the 2C10 Fab) yielded selective B-DNA binding. The results with 2C10 match other examples in which the H chain is sufficient for DNA binding but selectivity is modulated by the L chain. The H chain binding to autoantigen may reflect selective events in early stages of B cell development.

Novel monoclonal antibodies to double stranded DNA that require Ca2+ or Mg2+ for their binding

Murine monoclonal antibody (MoAb) 2B5 (IgG2aK) was obtained by its binding on a solid phase to double-stranded (ds) DNA from one of the mutant CBA/K1(CBA/K1Jms-1prcg/1prcg) mice which were recently found, in our institute, to develop lymphadenopathy associated with the production of anti-double-stranded (ds) antibodies. MoAb 2B5 was highly specific for dsDNA, as shown by enzyme-linked immunosorbent assay (ELISA). The dsDNA binding of 2B5 was decreased dose-dependently by the chelating agent EDTA, being lost completely with 2.5-5.0 mM EDTA, whereas dsDNA on the solid phase remained intact after incubation with EDTA. Addition of Ca2+ or Mg2+ to antibody in culture supernatant that had lost dsDNA binding activity by dialysis against Ca2+ and Mg(2+)-free buffer restored its binding with dsDNA to the original level, indicating that MoAb 2B5 requires Ca2+ or Mg2+ for its binding with dsDNA. It is unknown whether MoAb 2B5 recognizes new conformational epitopes created in the presence of Ca2+ or Mg2+, but this MoAb should be useful in studies on the modes of interaction of DNA with antibodies and DNA-binding proteins.

Transgenic mice expressing a B cell growth and differentiation factor gene (interleukin 5) develop eosinophilia and autoantibody production

Interleukin 5 (IL-5) has been suggested to be involved in the growth and differentiation of B cells and eosinophils. Especially, Ly-1+ B cells, which have been considered to produce autoantibodies, are selectively developed by this lymphokine in long-term bone marrow culture. To envisage the possible engagement of IL-5 in the development of these cells in vivo, transgenic mice carrying the mouse IL-5 gene ligated with a metallothionein promoter were generated. Transgenic mice carrying the IL-5 gene exhibited elevated levels of IL-5 in the serum and an increase in the levels of serum IgM and IgA. A massive eosinophilia in peripheral blood, bone marrow, and spleen, and an infiltration of muscle and liver with eosinophils, were observed. When cadmium-containing saline was injected intraperitoneally into transgenic mice, IL-5 production was augmented about five times within 24 h, and a distinctive Ly-1+ B cell population became apparent in the spleen after 5 d. IL-5 receptors were detected on those cells by monoclonal antibodies against IL-5 receptors. Another interesting finding in these transgenic mice was an increase in polyreactive anti-DNA antibodies of IgM class. It is suggested, therefore, that aberrant expression of the IL-5 gene may induce accumulation of Ly-1+ B cells and eosinophils. Furthermore, this IL-5 transgenic mouse can be a model mouse for eosinophilia, and we can determine the role of IL-5 in the differentiation of Ly-1+ B cells and eosinophils by using this mouse.