Study of anti-DNA antibodies prepared by DNA cellulose or Cibacron blue chromatography

Induction of ssDNA-binding autoantibody secreting B cell immunity during murine malaria infection is a critical part of the protective immune responses

Although it has been hypothesized that autoimmune-like phenomena may play a critical role in the protective immune responses to both human and animal malaria, there are still no evidence-based data to support this view. In this study we demonstrate that the majority of anti-single stranded (ss) DNA autoantibody secreting B cells were confined to B220(+)CD21(+)CD23(-) cells and that these cells expanded significantly in the spleen of C57BL/6 mice infected with Plasmodium yoelii 17X non-lethal (PyNL). To determine the role of ssDNA-binding autoantibody secreting B cell responses in murine malaria, we conjugated generation 6 (poly) amidoamine dendrimer nanoparticles with ssDNA to deplete ssDNA-binding autoreactive B cells in vivo. Our data revealed that 55.5% of mice died after DNA-coated nanoparticle-mediated in vivo depletion of ssDNA-specific autoreactive B cells and subsequent challenge using PyNL. Adoptive transfer of B cells with ssDNA specificity to mice, followed by PyNL infection, caused a later appearance and inhibition of parasitemia. The possible mechanism by which the ssDNA-binding autoantibody secreting B cells is involved in the protection against murine malaria has also been demonstrated.

Cross-reaction of anti-DNA autoantibodies with membrane proteins of human glomerular mesangial cells in sera from patients with lupus nephritis

Anti-DNA autoantibodies were thought to play a major role in the pathogenesis of lupus nephritis (LN). A recent study revealed that affinity-purified anti-DNA antibodies had a cross-reaction with human glomerular mesangial cells (HMC). However, whether the cross-reaction was antigen-antibody-mediated was unclear. The aim of the current study was to investigate the binding of anti-DNA antibodies to HMC membrane proteins and to characterize the target antigens. Affinity-purified IgG anti-DNA antibodies were purified by DNA-cellulose chromatography in sera from nine patients with biopsy-proven active lupus nephritis. In vitro cultured primary HMCs were disrupted by sonication and HMC membranes were obtained by differential centrifugation. The membranes of human umbilical vein endothelial cells (HUVEC), human proximal renal tubular epithelial cell line (HK2) and peripheral mononuclear cells (PMC) were obtained as controls. Binding of anti-DNA antibodies to the membrane proteins was investigated by Western blot analysis using soluble membrane proteins as antigens. Both HMC membrane and affinity-purified anti-DNA antibodies were treated with DNase I to exclude DNA bridging. All nine affinity-purified anti-DNA antibodies could blot the HMC membrane proteins, and there were at least three bands at 74 kDa, 63 kDa and 42 kDa that could be blotted. Among the nine IgG preparations, all nine (100%) could blot the 74 kDa band; eight (88.9%) could recognize 63 kDa and 42 kDa protein bands separately. After DNase treatment, the same bands could still be blotted by most affinity-purified anti-DNA antibodies. Affinity-purified anti-DNA antibodies could also blot similar bands on membrane proteins of other cells, but some bands were different. In conclusion, anti-DNA autoantibodies could cross-react directly with cell membrane proteins of human glomerular mesangial cells and might play an important role in the pathogenetic mechanism in lupus nephritis.

Non-DNA-Binding Antibodies in Patients with Lupus Nephritis Could Recognize Membrane Proteins of Glomerular Mesangial Cells

Lupus nephritis (LN) is a prototypic autoimmune disease, however, the precise immuno-pathogenesis of LN remains to be elucidated. In our previous studies, autoantibodies against mesangial cells had been identified in sera from patients with lupus nephritis and could bind the membrane proteins of human mesangial cells (HMC) directly through antigen-antibody interaction without DNA bridge. The current study is to investigate whether the autoantibodies were associated with anti-DNA antibodies and their target antigens distribution in different cell types. Sera from nine patients with renal biopsy proven lupus nephritis with positive anti-dsDNA antibodies and four healthy subjects were collected. IgG was isolated by Protein G affinity chromatography and then non-DNA-binding IgG fractions were obtained after deletion of anti-DNA antibodies using a DNA-cellulose affinity column. Membrane proteins, obtained from HMC, human umbilical vein endothelial cells (HUVEC), peripheral mononuclear cells by sonication and sequential centrifugation, were solubilized and applied in Western-blot analysis to characterize the target antigens. In results, the non-DNA-binding IgG fractions from sera of patients with lupus nephritis could blot the protein(s) of HMC membrane at 74, 63, and 42 kD. However, only a similar 74-kD protein could be blotted on membrane of HUVEC, and the target antigens on membranes of mononuclear cells were heterogeneous. In conclusion, our preliminary study had demonstrated that non-DNA binding autoantibodies against mesangial cells could be found in sera from patients with lupus nephritis. Although the target antigens might not be cell specific, the roles of these autoantibodies in the pathogenesis of lupus nephritis need further investigation.

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

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

Affinity purification of DNA-binding proteins

The focus of this review is on DNA affinity chromatography, which is the most powerful tool for purification of DNA binding proteins. The use of nonspecific-, sequence specific- and single stranded-DNA affinity columns in purification of various DNA binding proteins is discussed. The purification strategies for transcription factors, restriction enzymes, telomerases, DNA and RNA polymerase and DNA binding antibodies are described. Different applications of DNA affinity chromatography are presented.

Crossreactivity of human anti-dsDNA antibodies to phosphorylcholine: clues to their origin

The presence of anti-double stranded DNA (dsDNA) antibodies is a serological diagnostic feature of systemic lupus erythematosus (SLE), an autoimmune rheumatic disorder. Studies by several investigators have suggested that a response to a microbial antigen can lead to the induction of SLE-like autoimmunity, in both humans and mice, since anti-dsDNA antibodies have been shown to crossreact with foreign antigens. In particular, anti-DNA antibodies have been shown to crossreact with phosphorylcholine (PC), a dominant epitope on pneumococcal cell wall polysaccharide. We have investigated the binding characteristics of human polyclonal anti-DNA antibodies from the sera of SLE patients. In this study we show that the DNA binding of polyclonal serum derived antibodies can be partially inhibited by phosphorylcholine (PC). The binding of affinity-purified anti-DNA antibodies from the sera of patients with SLE was also found to be inhibited by PC. We further demonstrated that the serum IgG1 (T dependent) anti-DNA response was more likely to crossreact with PC than the IgG2 (T independent) response to DNA. The studies suggest there may be a T dependent and T independent response to DNA with the T dependent response displaying more crossreactivity with microbial antigen.

Isolation of anti-nucleosome antibodies from the plasma of lupus nephritis patients

Anti-nucleosome antibodies, which recognise conformational epitopes consisting of histone and DNA in chromatin, have been described in autoimmune diseases. In this study, an attempt was made to isolate anti-nucleosome antibodies from the anti-DNA-depleted plasma IgG of two lupus patients either with or without nephritis by nucleohistone affinity chromatography. The purified nucleohistone-binding antibodies bound to nucleohistone in a specific manner and contained enriched anti-histone antibodies. However, adsorption of the purified antibodies with histone revealed that the nephritis patient-derived antibodies contained nucleohistone-specific antibodies. Although such purified antibodies may not recognise native structures of nucleosomes, this chromatography may provide a method to isolate and determine the fine specificity of anti-nucleosome antibodies in various autoimmune diseases.

V gene sequences of lupus-derived human IgM anti-ssDNA antibody: implication for the importance of the location of DNA-binding amino acids

Binding and structural characteristics of human IgMk anti-ssDNA antibody 7B3 were determined. 7B3 was derived from Epstein-Barr virus-transformed peripheral blood B cells of a lupus nephritis patient. Purified 7B3 bound ssDNA from various species, but not dsDNA or structurally unrelated antigens. The relative avidity of 7B3 was high in comparison with IgM anti-DNA antibodies previously described by other investigators. Sequence analysis showed that 7B3 used VH26/D35/JH3 and Humkv328h5/JK1 germline genes, and had a few mutations in the complementarity determining regions (CDRs). No arginine was expressed in the heavy-chain CDR3. However, the putative DNA contact sites, based on the previous crystallographic and computer modeling studies, were occupied by mutated or germline-derived basic and polar amino acids. These results suggest that a minimally mutated IgM anti-ssDNA antibody with a paucity of arginines could display monospecificity and high avidity if DNA-binding amino acids are enriched at the critical DNA contact sites.

Identification of endothelial cell membrane proteins that bind anti-DNA antibodies from patients with systemic lupus erythematosus by direct or indirect mechanisms

A subgroup of murine monoclonal anti-DNA antibodies bind to vascular endothelial cells either directly as a result of cross-reactivity, or indirectly through immunoglobulin-bound DNA and DNA-binding proteins on the endothelial cell membrane. To determine whether these mechanisms apply in human systemic lupus erythematosus (SLE), and to identify endothelial cell membrane protein(s) that bind human anti-DNA antibodies, we examined, by Western blotting, the binding of human polyclonal anti-DNA antibodies (PoAb) isolated from eight patients with SLE to human umbilical vein endothelial cell membrane proteins. PoAbs bind to endothelial membrane proteins with Mr 84,000 and 46,000, which correspond to the DNA-binding proteins previously reported. Such binding is diminished after removal of DNA by DNase treatment. In addition, PoAbs bind to membrane proteins with Mr 180, 000, 110,000, 68,000, 44,000, and 35,000-30,000. Such binding is unaffected by alterations in DNA concentration. Anti-dsDNA and anti-ssDNA PoAbs from individual patients exhibit identical binding patterns, as are PoAbs isolated during active disease or remission. The results show that human anti-DNA antibodies can bind to endothelial cells both indirectly via immunoglobulin-bound DNA, and directly due to cross-reactivity. These mechanisms of cellular binding by anti-DNA antibodies may depict patho-genetic steps in human SLE.

Increased release of von Willebrand factor antigen from endothelial cells by anti-DNA autoantibodies

OBJECTIVE

To determine whether antibodies to double stranded DNA (anti-dsDNA) have a pathogenic role in systemic lupus erythematosus (SLE).

METHODS

IgG was purified from 17 patients with SLE (median anti-dsDNA titre 1212 IU/ml) and nine healthy controls (median titre 40 IU/ml). Anti-dsDNA depleted polyclonal IgG (median anti-dsDNA titre 17 IU/ml) was also prepared from sera of the 17 patients by affinity chromatography on a DNA cellulose column. Binding to antiendothelial cell antibodies (AECA) and expression of von Willebrand factor (VWF) antigen by cultured human umbilical vein endothelial cells (HUVECs) were studied by flow cytometry.

RESULTS

The percentage of HUVECs binding to AECA or expressing VWF was greater for cells incubated with IgG from patients with SLE than for cells incubated with control IgG, though values did not reach statistical significance; nevertheless, HUVECs incubated with IgG from patients expressed a greater mean fluorescence intensity with AECA (p = 0.0001) and greater VWF expression (p = 0.019). Both the fluorescence intensity and percentage of HUVECs binding to AECA or expressing VWF were significantly greater in HUVEC incubated with IgG containing anti-dsDNA than in those incubated with anti-dsDNA depleted IgG. The concentration of VWF in the supernatant was significantly increased in HUVECs incubated with IgG containing anti-dsDNA compared with control IgG or anti-dsDNA depleted IgG. Pretreatment of HUVECs with native DNA before incubation with IgG from lupus patients did not increase binding to AECA, or expression or release of VWF.

CONCLUSIONS

Our study provides in vitro evidence that antibodies to DNA have a pathogenic role in the induction of inflammatory injury of the vascular endothelium in SLE.

Endothelial cell binding by human polyclonal anti-DNA antibodies: relationship to disease activity and endothelial functional alterations

Polyclonal anti-dsDNA and anti-ssDNA antibodies (PoAb) that showed significant binding to human umbilical vein endothelial cells (HUVEC) were isolated from eight patients with systemic lupus erythematosus (SLE). Anti-dsDNA PoAbs from five patients and anti-ssDNA PoAbs from seven patients demonstrated enhanced binding to HUVEC during active disease, compared with PoAbs obtained from corresponding patients during remission. Reduction of the DNA content in the PoAb preparations by DNase treatment was associated with enhanced binding to HUVEC in 20 of 32 PoAbs tested, which included 75% 'active disease' PoAbs, and with reduced binding to HUVEC in three of 32 PoAbs tested, all obtained during remission. Such altered endothelial cell binding was reversed with DNA reconstitution. Binding of the remaining nine PoAbs to HUVEC was not altered by variations in their DNA content. Induced plasma membrane expression of E-selectin, but reduced expression of vascular cell adhesion molecule-1 (VCAM-1) by HUVEC, was observed following incubation of HUVEC with 'active disease' PoAbs from three and two of the eight patients, respectively. PoAbs and serum samples from two of the eight patients during active disease induced von Willebrand factor release from HUVEC, which was not observed during remission. We conclude that anti-DNA antibodies from selected patients with SLE can bind to endothelial cells. Correlation between cellular binding and disease activity suggests that such binding of anti-DNA antibodies to endothelial cells could be of pathogenic significance. Preliminary data also suggest that the expression of adhesion molecules and haemostatic factor(s) by endothelial cells may be modified following their binding by anti-DNA antibodies.

Heparan sulphate-ELISA gives false positive results for anti-DNA-DNA/histone immune complexes in sera of patients with SLE

Heparan sulphate-reactive antibodies in lupus sera have been suggested to be anti-DNA-DNA/histone immune complexes and to be associated with lupus nephritis. In this study, 23 anti-DNA-positive lupus sera including 13 active nephritis sera were tested for the presence of circulating anti-DNA-DNA/histone immune complexes by solid phase heparan sulphate-ELISA. Because of high background binding to protamine chloride-linked heparan sulphate plates, poly-L-lysine (PLL) was used as a linker and the remaining active sites of PLL were blocked with poly-L-glutamic acid. The ELISA was capable of detecting small amounts of anti-DNA IgG-DNA/histone immune complexes formed in vitro. However, only three active nephritis sera of the 23 sera tested showed significant binding to heparan sulphate plates. This binding was found to be non-specific, the result of high background binding of IgG to PLL. Anti-heparan sulphate ELISA using positively charged linkers detects non-specific binding when lupus sera are tested. Specific assays need to be developed for DNA/histone-related immune complexes present in lupus sera.

Anti-interleukin-6 and soluble interleukin-6 receptor in systemic lupus erythematosus

IL-6, soluble IL-6 receptor and IgG with anti-IL-6 activity were measured in the plasma of 14 lupus patients and 10 normal subjects. The capacity of peripheral blood mononuclear cells to spontaneously produce IL-6 in vitro was also measured. Our results indicate that IL-6 plasma levels in patient plasma as measured by ELISA were not different from normal but that supernatant levels were significantly lower than normal (P < 0.05). In vitro IgG production was comparable for all lupus patients' cells irrespective of the in vitro IL-6 levels. Plasma soluble IL-6 receptor levels directly correlated with IL-6 production capacity of SLE cells and the ratio of soluble receptor to anti-IL-6 directly correlated with IL-6 production in patients but not in normals. Inhibition assays demonstrated competition between anti-IL-6 and soluble receptors for IL-6 and the inhibition by plasma of IL-6 binding to monoclonal anti-IL-6. We believe the interaction of anti-IL-6 and IL-6 receptor with IL-6 may contribute to the homeostasis in IL-6 activity in vivo and skewing of the soluble receptor/anti-IL-6 ration may contribute to the lupus disease process.

Cationic and high affinity serum IgG anti-dsDNA antibodies in active lupus nephritis

To investigate differences between cationic anti-dsDNA antibodies during active and inactive nephritis, low- and high-affinity IgG anti-dsDNA antibodies were prepared from sera of a lupus patient and compared for their binding affinity, spectrotype, and idiotype expression. The ratio of high-affinity to low-affinity anti-DNA antibodies and the relative avidity of the high-affinity anti-DNA antibodies decreased when active nephritis became inactive. Isoelectric focusing showed that cationic anti-dsDNA populations were present predominantly in the high-affinity fraction during active nephritis and in the low-affinity fraction during inactive nephritis. Idiotypic analysis by ELISA and Western blotting showed that the high-affinity cationic anti-DNA antibodies during active nephritis were idiotypically different from their low-affinity counterparts during inactive nephritis. The differences in binding affinity and idiotypy of the cationic anti-dsDNA antibodies suggest that certain serum IgG anti-dsDNA antibodies with both cationic charge and high affinity may be associated with active nephritis.

In vitro modulation of anti-DNA secreting peripheral blood mononuclear cells of lupus patients by anti-idiotypic antibody of pooled human intravenous immune globulin

Anti-idiotypic antibody and its F(ab')2 fragments prepared from pooled normal human IgG had a partial inhibitory effect on the spontaneous in vitro secretion of anti-DNA antibodies from blood mononuclear cells of lupus patients. The inhibitory effect was specific for anti-DNA secretion as the anti-idiotype failed to inhibit the spontaneous secretion of anti-tetanus toxoid in the same culture supernatants. Non-anti-DNA IgG or its F(ab')2 fragments from pooled normal human IgG had less inhibitory effect on anti-DNA secretion than the purified anti-Id. In vitro polyclonal IgG secretion by lupus blood mononuclear cells was equally inhibited by both the anti-idiotype and the non-anti-DNA IgG of pooled normal human IgG. There was no correlation between the in vitro suppression of anti-DNA and that of total IgG or of anti-tetanus toxoid antibody. Pooled normal human IgG could have a potential beneficial effect in the therapy of systemic lupus erythematosus by inhibiting anti-DNA production via an anti-idiotypic mechanism.

Lupus-derived human monoclonal IgM anti-DNA antibody displays monospecificity, high affinity and private idiotype specificity

A human monoclonal IgM k anti-DNA antibody, designated 2F7, was prepared by somatic hybridization of peripheral blood lymphocytes from a lupus patient with a human-mouse heterohybridoma cell line, K6H6/B5. 2F7 was tested for its antigen binding and idiotypic specificity by direct binding and inhibition enzyme-linked immunosorbent assays. 2F7 had a high binding activity to single-stranded DNA (ssDNA) but not to double-stranded DNA. It cross-reacted with single-stranded homopolymers with pyrimidine bases and double-stranded polynucleotides containing those homopolymers, suggesting that 2F7 recognizes a conformational determinant made up of both deoxyribose-phosphate backbone and specific nucleotide base. 2F7 did not cross-react with eight structurally unrelated self-antigens. Dissociation constant (Kd) of 2F7 for sonicated ssDNA was approximately 4.5 x 10(-9) M, indicating its relatively high affinity. Idiotypic characterization with rabbit anti-idiotype raised against 2F7 suggested that 2F7 expressed an idiotype at or near its antigen-binding sites that was not detected in sera from 20 unrelated lupus patients, 10 lupus family members and 10 normal individuals. These results suggest that certain IgM class anti-DNA antibodies in human systemic lupus erythematosus may arise by antigen stimulation and not simply by polyclonal B-cell activation.

Idiotypic mimicry of a cell surface DNA receptor: evidence for anti-DNA antibodies being a subset of anti-anti-DNA receptor antibodies

Anti-idiotypic anti-DNA antibodies (anti-anti-DNA) have previously been described in both patients with systemic lupus erythematosus and healthy individuals. Jerne's hypothesis predicts that such antibodies would bear a paratope reactive with non-sequence specific DNA binding proteins. Here we have explored the notion of a molecular mimicry between anti-anti-DNA antibodies and antibodies to a previously described 28-29 kD cell surface DNA binding molecule. It was shown that affinity purified anti-anti-DNA antibodies inhibit the binding of DNA to cells and that MoAb to the 28-29 kD receptor react with anti-DNA antibodies. These findings indicate that a subset of anti-anti-DNA antibodies are idiotypically related to antibodies reactive with a cell surface DNA binding molecule. It is hypothesized that anti-DNA antibodies may arise when a convergence of genetic and environmental influences favours an unrestrained anti-idiotypic response to cell surface DNA binding molecule(s).

Induction of anti-DNA IgG and IgE antibodies in BALB/c mice

Immunization of BALB/c mice with denatured DNA (dnDNA)-methylated bovine serum albumin (MBSA) complex along with aluminium hydroxide gel as adjuvant, resulted in the induction of anti-DNA antibodies of both IgG and IgE isotypes demonstrable by avidin-biotin micro enzyme-linked immunosorbent assay (ELISA) and solid phase radioimmunoassay (SPRIA), respectively. In contrast to the high levels of IgG2a and IgG2b anti-DNA antibodies observed in SLE-prone autoimmune mice, more than 90% of the anti-DNA antibodies of IgG isotype were found to be of IgG1 subclass. Specificity of both IgG and IgE antibodies which recognized activated DNA, dnDNA and double-stranded DNA but not RNA was established by competitive ELISA and SPRIA inhibition assays. These antibodies cross-reacted with cibacron blue and chondroitin sulfate but not with various other proteoglycans, nucleosides and nucleotides. Passive cutaneous anaphylaxis reaction in rats showed that these antibodies are capable of inducing in vivo degranulation of mast cells in a dose-dependent manner. These studies lend support to the concept that IgE antibodies directed against DNA may mediate mast cell degranulation and thus contribute to immediate-type hypersensitivity phenomena including hives seen in patients with systemic lupus erythematosus and to the localization of IgE-nucleic acid complexes.

The atherogenic effect of lupus sera: systemic lupus erythematosus-derived immune complexes stimulate the accumulation of cholesterol in cultured smooth muscle cells from human aorta

The influence of systemic lupus erythematosus (SLE) patients' sera on lipid accumulation in the cultured smooth muscle cells (SMC) from unaffected human aortic intima was examined. It was demonstrated that the cholesterol uptake in the SMC cultured in the presence of SLE sera is 1.5- to 6-fold higher than in the cells cultured with normal human sera (NHS) obtained from healthy donors. Incubation of the SMC with circulating immune complexes (CIC) isolated from lupus sera by precipitation with 2.5% polyethylene glycol 6000 (PEG) caused a 3- to 4-fold rise in the intracellular cholesterol level. The atherogenic effect of lupus sera, as well as isolated CIC, strongly correlated (r = 0.98) with the low density lipoprotein (LDL) content in the PEG-precipitated CIC. The cholesterol level in cultured SMC also increased 2- to 3-fold when growth medium was supplemented with LDL, DNA, and anti-DNA autoantibodies (IgG) affinity isolated from lupus sera. Using immunofluorescent staining, it was shown that the addition of a DNA-anti-DNA IgG mixture to the growth medium, together with NHS, stimulated LDL incorporation in the SMC. The results of double-label staining suggest the formation of LDL-DNA-IgG complexes which seem to be entrapped in cells more actively than free LDL. The composition of PEG-precipitated CIC was studied by electrophoresis and immunoblotting. Significant amounts of apolipoprotein B, as well as low molecular weight DNA and immunoglobulins, were found in SLE-derived CIC. The data obtained suggest that the atherogenic effect of human lupus sera in vitro is generally due to the appearance of LDL-containing immune complexes. Different mechanisms possibly involved in the lupus atherogenesis are discussed.

Expression of inactive stage anti-dsDNA idiotypes on anti-ssDNA antibodies in a lupus patient during active stage of lupus cerebritis

The possibility that idiotypes (Ids) defined on anti-double stranded DNA (dsDNA) antibodies during active and inactive stages of lupus (1/84 Id and 4/90 Id, respectively) were expressed on anti-DNA antibodies during a subsequent active period (9/90) of the disease was investigated in a lupus patient with lupus cerebritis. Using rabbit (R)-anti-Ids specific to 1/84 Id and 4/90 Id in inhibition assays, the 4/90 Id was shown to be expressed on the framework regions of anti-single stranded DNA (ssDNA) but poorly on co-existing anti-dsDNA antibodies of active (9/90) stage. The 1/84 Id was poorly expressed on both types of 9/90 anti-DNA antibodies. While the 9/90 anti-ssDNA significantly bound to immobilized ssDNA and several single-stranded polynucleotides, only ssDNA inhibited the binding of the anti-ssDNA to ssDNA, suggesting its monospecificity toward ssDNA. Western blot analysis following isoelectric focusing showed that a spectrotype pattern of 4/90 Id-positive 9/90 anti-ssDNA IgG was similar to that of the 4/90 anti-dsDNA, suggesting that they are of related clonal origin. The present study suggests the idiotypic heterogeneity of anti-DNA antibodies and the shift of antigen specificity within an idiotypically related anti-DNA population during exacerbation of the disease.

Shift of private and not of cross-reactive anti-DNA idiotypes in systemic lupus erythematosus

The shift of private idiotype (Id) and cross-reactive Id (CRI) on anti-DNA antibodies in a lupus patient KE was investigated during a 7-year period. Anti-private Id and anti-CRI activities were separated by affinity chromatography from rabbit (R)-anti-Ids raised against KE anti-DNA antibodies during active (1/84) and inactive (4/90) stages of the disease. Anti-CRI isolated from the 84 R-anti-Id appeared to recognize binding site-related Ids that are shared with KE non-anti-DNA antibodies, unrelated lupus patients' sera, and certain normal sera. Id expression on serial serum samples of KE using these fractionated R-anti-Ids as probes showed that the 1/84 private Id expression declined while the 4/90 private Id expression gradually increased. Expression of the CRI showed a relatively stable pattern. These results suggest that anti-DNA populations detected by anti-private Id can shift, while populations expressing CRI may stay stable.

Idiotypic and immunochemical differences of anti-DNA antibodies of a lupus patient during active and inactive disease

IgG anti-DNA antibodies of a lupus patient during active and inactive stages of her disease were studied. There were no significant differences in the amounts, in double-stranded DNA-binding activity, or in complement-fixing ability between purified IgG anti-DNA antibodies of both stages. However, their idiotype (Id) expressions were different as revealed by binding to rabbit anti-Ids raised against each of the anti-DNA antibodies. Moreover, the active stage anti-DNA antibodies had higher activity and less cross-reactivity with polynucleotides. Dominant anti-DNA populations during the active and inactive stages of systemic lupus erythematosus are clonally and qualitatively different.

Detection and purification of antiidiotypic antibody against anti-DNA in intravenous immune globulin

Pooled normal human IgG for therapeutic use, following depletion of anti-DNA, anti-Fc, and anti-F(ab')2 of normal IgG, expressed antiidiotypic activity against anti-DNA derived from lupus sera. The antiidiotype enriched by elution from anti-DNA affinity columns bound directly to anti-DNA IgG and inhibited the binding of lupus sera to DNA but did not bind to normal IgG or inhibit the binding of anti-tetanus toxoid to tetanus toxoid. Antiidiotypes in pooled normal sera may have a role in the clinical improvement seen in patients with autoimmune diseases receiving intravenous immune globulin.

LDL-mediated interaction of DNA and DNA-anti-DNA immune complexes with cell surface

The effect of low-density lipoprotein (LDL) on the binding of DNA and DNA-anti-DNA immune complexes to cultured human skin fibroblasts was examined. Using radioisotope analysis, ELISA and indirect immunofluorescent staining, a correlation between plasma membrane-bound DNA or DNA-anti-DNA immune complexes and cell-associated LDL was established. It was demonstrated that cytotoxicity and internalization of DNA-anti-DNA immune complexes may be LDL mediated. The data obtained suggest that the binding of the major part of DNA and immune complexes bound to surface of normal skin fibroblasts is due to the formation of a DNA-LDL-LDL receptor linkage. A possible role of LDL-containing immune complexes in the pathogenesis of systemic lupus erythematosus is discussed.

Polyanions inhibit binding of human autoantibodies to certain cellular proteins

The effect of polyanions on the reactivity of human autoantibodies with cellular proteins was studied. The results of immunoblotting revealed that dextran sulfate (DS), heparin, single-stranded (ss) DNA, and polyinosinic acid (poly I) inhibit interaction between immunoglobulins (Ig) from human autoimmune sera and many polypeptides with various molecular mass. These proteins were suggested to belong to a new subclass of autoantigens, the immunoreactivity of which is sensitive to the presence of polyanions. For some of these antigens, molecular mass, intracellular localization and frequency of appearance of positive sera were determined.

Immunoregulation of anti-islet cell antibody in insulin-dependent diabetes: failure to detect anti-idiotypic antibody following seroconversion

A search was made for the presence of spontaneous auto-anti-idiotype in sera of three insulin-dependent diabetics when they converted from islet cell antibody positive to islet cell antibody negative states. Rabbit anti-idiotype specific for islet cell antibody was used as the positive control. Using an enzyme-linked immunoabsorbent assay, binding of the rabbit anti-idiotype to idiotype-coated plates could not be inhibited by islet cell antibody negative sera. Using this same assay, there was no significant difference in the binding of islet cell antibody positive or negative sera to either idiotype-coated or normal IgG-coated plates. Binding of islet cell antibody to pancreatic sections could not be inhibited by islet cell antibody negative sera in an immunofluorescent assay. Network regulation by auto-anti-idiotype does not seem to play a role in the decline or absence of islet cell antibody in the early phases of insulin-dependent diabetes mellitus.

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.

Characterization of two anti-DNA antibodies bearing distinct idiotypes. Correlation with clinical manifestations

Spontaneous idiotype shift of anti-DNA antibodies in systemic lupus erythematosus was shown to be associated with changes in the clinical manifestations of the disease. Characterization of two anti-DNA antibody preparations from the same lupus patient showed that lupus nephritis was associated with antibodies showing higher specific antigen-binding activity and avidity to DNA and presenting more cationic quality upon isoelectric focusing and Western blot analysis than the ones found in patients without renal involvement. Lupus cerebritis was associated with anti-DNA antibodies with different idiotypic characteristics not shared by anti-DNA antibodies present in lupus nephritis. Lupus cerebritis anti-DNA antibodies had less specific antigen-binding activity and avidity to DNA and did not show cationic quality. Idiotypic and immunochemical changes of anti-DNA antibodies in lupus may be associated with various clinical manifestations.

Antibodies raised against denatured DNA bind to double-stranded DNA

Antibodies raised against denatured DNA complexed with methylated bovine serum albumin have been reported to react with ssDNA but not with dsDNA. Using a highly sensitive avidin-biotin microELISA, we report that such antibodies also bind to dsDNA. Antibodies which reacted with ssDNA and dsDNA were found to be of IgG type. The antibodies did not react with tRNA and rRNA. The binding of antibodies to dsDNA was partially inhibited by individual deoxyribonucleotides. ssDNA as well as dsDNA inhibited the binding of antibodies to dsDNA. The binding of these antibodies to supercoiled and relaxed forms of pBR322 DNA was demonstrated by gel retardation assay. The cross-reaction with ssDNA was observed even after affinity purification on native DNA-cellulose. The antibodies were also shown to bind to poly(dA-dT).poly(dA-dT).

Antiidiotypic antibodies against anti-DNA antibodies in sera of families of lupus patients

We searched for antiidiotypes directed against anti-DNA in sera of healthy family members of lupus patients. Controls were healthy individuals without a personal or family history of lupus. No significant differences were noted between the family members' and the control group's sera with respect to binding to DNA or to non-anti-DNA F(ab')2 fragments. Family members' sera had higher binding to anti-DNA F(ab')2 and to normal IgG F(ab')2 fragments (P less than 0.01). Sera of the family members had significantly higher binding to anti-DNA F(ab')2 than to normal IgG F(ab')2 fragments (P less than 0.0036). Inhibition experiments have shown that the antiidiotype is directed against the framework determinants and not against the antigen binding sites of the idiotype. The antiidiotypic antibodies were directed against cross-reactive anti-DNA idiotypes and were not restricted to the idiotypes of the lupus proband. Age, sex, and blood relationship to the lupus patient did not influence the presence of antiidiotypes in the family members. The possible role of environmental factors in the induction of antiidiotypes and the role of the latter in regulating anti-DNA antibodies are discussed.

Private idiotypes on human polyclonal IgG anti-DNA antibodies are not expressed on coexisting IgM anti-DNA antibodies in systemic lupus erythematosus

Sharing of private idiotypes (Id) on human polyclonal IgG anti-double-stranded DNA (dsDNA) with coexisting IgM anti-dsDNA was investigated using rabbit (R) anti-Id raised against IgG anti-dsDNA. The R-anti-Id showed specificity to private Id in or near the antigen-binding sites. The R-anti-Id poorly bound to the immobilized enriched IgM anti-dsDNA preparation but significantly bound to IgG anti-dsDNA preparation by a direct-binding ELISA (0.020 OD vs 0.295 OD, respectively). The R-anti-Id poorly inhibited the binding of IgM anti-dsDNA to immobilized dsDNA but significantly inhibited the binding of IgG anti-dsDNA to dsDNA (6% vs 55% inhibition, respectively). This was confirmed by poor inhibition of binding of the R-anti-Id to immobilized IgG anti-dsDNA by the enriched IgM anti-dsDNA preparation (maximum of 26% inhibition at 50 micrograms/ml). Nonsharing of private Id between IgG and coexisting IgM anti-dsDNA may represent the idiotypic diversity of human anti-DNA antibodies secondary to the frequent occurrence of somatic mutation on anti-DNA antibody during class switching.

The use of dye-ligand affinity chromatography for the purification of non-enzymatic human plasma proteins

Literature data are analysed in this review on the use of immobilized triazine dyes for the characterization, isolation and purification of non-enzymatic human plasma proteins in both conventional and high-pressure liquid chromatography systems. Attention is focused on the mode of interaction between the dyes and these proteins, as well as on the advantages over previously reported techniques. Future developments are discussed.