anti-dsDNA Activity Research Articles

Iron Status Alters Murine Systemic Lupus Erythematosus

The effect of Fe status on murine systemic lupus erythematosus was investigated. Weanling female MRL/MPJ-lpr/lpr mice (systemic lupus erythematosus strain) were fed diets with the following levels (mg Fe/kg diet): 3 (severely deficient), 10 (moderately deficient), 35 (control) and 250 (supplemented). A fifth group was pair fed the control diet in the amounts consumed by the severely deficient group. C3H/Hej mice fed the same diets were used as nonlupus controls. Anemia was more severe in severely deficient mice than in all other MRL groups and C3H severely deficient mice. Incidence of skin lesions was highest in MRL severely and moderately deficient mice compared with pair-fed, control and supplemented mice. By 22 wk of age, mortality was higher in supplemented and severely deficient mice than in moderately deficient, pair-fed and control MRL mice. Anti-dsDNA activity in serum was not altered by Fe. In a second experiment, kidney function was examined in mice fed severely deficient, control, supplemented and pair-fed diets. Urine protein concentration was highest in supplemented mice at 14 wk of age. Serum urea nitrogen was significantly higher in MRL severely deficient mice than in pair-fed and control mice at 18 wk of age. Glomerular filtration rate, measured by creatinine clearance, was significantly lower in MRL severely deficient mice than in pair-fed and Fe supplemented mice at 16 wk of age and pair-fed and control mice at 18 wk of age. Renal histopathology was more severe in Fe supplemented mice than in pair-fed and control mice, and more severe in severely deficient and pair-fed mice than in control mice. Fluorescent staining of kidneys with anti-Ig G and anti-C3 fluorescein-conjugated antibodies was most intense in severely deficient mice, and the concentration of circulating immune complexes in serum was significantly higher in severely deficient mice than in all other groups. These data demonstrate that systemic lupus erythematosus in MRL/MPJ-lpr/lpr mice is altered by dietary iron.

Detection of serum anti-B/B' UsnRNP antibodies in patients with connective tissue diseases by immunoblotting

To investigate the reliability of the immunoblot method in the detection of serum immunoreactivity towards the B/B' polypeptides of U small nuclear ribonucleoproteins (UsnRNP) and to assess the significance of these antibodies in connective tissue disease (CTD) patients. We tested the sera of 348 patients with CTD (101 SLE, 51 systemic sclerosis, 53 primary Sjögren's syndrome, 27 poly/dermatomyositis, 15 rheumatoid arthritis and 101 overlap CTD), of 31 matched healthy subjects and 13 patients with primary Epstein-Barr virus (EBV) infection with high titre of IgG anti-EBV antibodies. IgG anti-UsnRNP antibodies were determined by immunoblotting on nuclear extract from Raji cells (an EBV-immortalised human B lymphoid cell line) and Jurkat cells (a human T lymphoid cell line). Anti-dsDNA antibodies were detected by indirect immunofluorescence on Crithidia luciliae and anti-ENA by counterimmunoelectrophoresis. Anti-dsDNA activity and avidity were measured in SLE sera by ELISA with Scatchard analysis. Results were statistically analysed by chi-square and Mann-Whitney tests. A high frequency of anti-B/B' antibodies was found in the sera of CTD patients, confined to SLE (54.4%) and overlap CTD with SLE features (55,2%). Anti-B/B' immune reactivity was closely associated with other anti-UsnRNP specificities, gel precipitating anti-nRNP and anti-P antibodies. Nine out of 15 (60%) anti-B/B' positive/anti-ENA negative lupus sera on Raji blots were confirmed to be positive also on Jurkat blots. The sera from patients with EBV infection provided, on Raji blots, completely different band patterns from those obtained with auto-immune sera. CONCLUSIONS. The Sm B/B' proteins are the predominant or, at least, the most frequently targeted antigens of the UsnRNP auto-immune response in SLE and "lupus-like" overlap CTD. Moreover, anti-B/B' is diagnostically specific for CTD with SLE features. Immunoblotting on human B lymphoid cells is a reliable method, in terms of sensitivity and specificity, for the detection of anti-Sm B/B' antibodies.

Estudo longitudinal do anticorpo antilipoproteína lipase e sua relação com atividade de doença nos indivíduos com lúpus eritematoso sistêmico sem anticorpos anti-dsDNA

INTRODUÇÃO: O Lúpus Eritematoso Sistêmico (LES) se caracteriza por períodos de exacerbação e remissão clínica que frequentemente são acompanhados por alterações nos níveis séricos de anticorpos específicos, como o anti-dsDNA, que está presente em 40% dos casos, associado principalmente à atividade renal. Recentemente houve a descrição de duas subpopulações de anticorpos antilipoproteína lipase (anti-LPL) no LES: uma com e a outra sem atividade anti-dsDNA. A possível relação desse último grupo de anticorpos com a atividade inflamatória de doença ainda não foi analisada no LES. OBJETIVOS: Avaliar longitudinalmente a associação dos níveis séricos dos anticorpos anti-LPL com atividade do LES em pacientes com anti-dsDNA persistentemente negativo. PACIENTES E MÉTODOS: Cinco pacientes com LES com anti-dsDNA persistentemente negativo mensurado por ELISA e por imunofluorescência indireta em crithidia luciliae e altos títulos de anti-LPL por ELISA (> 5 desvios-padrão (DP) da média de 20 controles normais) foram selecionados e acompanhados longitudinalmente durante um período mínimo de dois anos. RESULTADOS: Caso 1: Homem, 24 anos com LES desde 2001 apresentou hemorragia alveolar, proteinúria, hipertensão arterial sistêmica, eritema malar, aftas, artrite, FAN+, com SLEDAI (systemic lupus erythematosus disease activity index) = 16 e anti-LPL = 144UA. Tratado com pulso de metilprednisolona e prednisona com melhora clínica e SLEDAI = 0 e redução do anti-LPL (109UA). Nova atividade com acometimento renal em abril de 2002, SLEDAI = 10 e aumento de anti-LPL (150UA). Iniciada pulsoterapia de ciclofosfamida e metilprednisolona com boa resposta, SLEDAI = 0 e diminuição de anti-LPL (77UA) até a sua total negativação acompanhando a remissão do quadro no ano de 2003. Caso 2: Mulher, 32 anos, com LES desde 1997. Em setembro de 2001 iniciou vasculite cutânea, febre e rash, SLEDAI = 10, anti-LPL = 80UA. Em janeiro de 2002, teve atividade renal e HAS, SLEDAI = 8 e anti-LPL = 25UA, mas com a introdução de CE e ciclofosfamida evoluiu com melhora importante. Em 2003, assintomática, apresentava SLEDAI = 2 e anti-LPL = 12UA. Caso 3: Homem, 39 anos, com LES desde 1997. Estável em uso de cloroquina, sem atividade durante 3 anos, SLEDAI = 0 em todas as ocasiões e sem variação dos títulos de anti-LPL no período do estudo: 85UA (2001),100UA (2002) e 86UA (2003). Caso 4: Mulher, 58 anos com LES desde 1996. Remissão do LES desde agosto de 2001 e com SLEDAI = 0 no período do estudo. Títulos de anti-LPL sem flutuações significativas: 71UA (2001), 42UA (2002) e 61UA (2003). Caso 5: Mulher, 55 anos com LES desde 1989. Estável desde 2000 em uso de cloroquina, SLEDAI = 0, e títulos de anti-LPL também sem variações: 71UA (1999), 92UA (2001), 71UA (2002) e 90UA (2003). CONCLUSÃO: A avaliação longitudinal dos pacientes selecionados mostrou-se estar associada à flutuação dos títulos de anti-LPL com o SLEDAI, sugerindo ser essa variação um novo marcador de atividade do LES, na ausência de anticorpos anti-dsDNA.

Catalytic Anti-dsDNA Activity from SLE Sera is Associated with Remission Phases of the Disease

Catalytic Anti-dsDNA Activity from SLE Sera is Associated with Remission Phases of the Disease

Characterization of Anti-Phosphatidylcholine Polyreactive Natural Autoantibodies from Normal Human Subjects

In 1990 our group reported a patient with autoimmune hemolytic anemia and high titers of IgM anticardiolipin antibodies that cross-reacted with phosphatidylcholine (PTC). These autoantibodies also recognized bromelain-treated erythrocytes (BrE) and in vitro aged erythrocytes. The epitope exposed with this treatment is PTC. To detect and characterize antiphosphatidylcholine antibodies (anti-PTC) in a normal human population, we studied by ELISA the presence of serum anti-PTC (IgG and IgM) in clinically healthy human subjects. The most representative samples were also studied for IgG or IgM activity against BrE by flow cytometry, rheumatoid factor activity, anti-dsDNA, anti-ssDNA by ELISA and by indirect immunofluorecence (IIF) using HEp-2 line and a healthy human fibroblast strain as substratum. Eighty five percent of sera had IgM anti-PTC and none had IgG. IgM antibodies against BrE were inhibited by PTC micelles (mPTC). Anti-PTC were also inhibited by phosphorylcholine and phosphatidic acid. Aggregated gammaglobulin (AGG) reactivity was inhibited by dsDNA and mPTC. The IgM anti-dsDNA activity was inhibited by soluble dsDNA, AGG and mPTC. All sera gave intermediate filaments pattern by IIF and reacted against purified vimentin by dot blot and Western blot.Our study shows hemolytic IgM anti-PTC present in normal human serum. The main epitope recognized by these autoantibodies is phosphorylcholine. The physicochemical characteristics, crossreactivity with self-antigens and functional properties are typical features of natural autoantibodies.

Interaction of dual-specific autoantibodies with dsDNA and a synthetic dimer peptide simulating the hinge region of IgG2a molecules

Anti-dsDNA autoantibodies and immune complex formation are major factors in SLE pathogenesis. Understanding stable immune complex formation is critical in deciphering mechanisms of autoimmune pathogenesis. Previous studies identified a subpopulation of murine lupus monoclonal autoantibodies that exhibited dual specificity (anti-DNA and anti-IgG2a hinge) and formed stable immune complexes [J. Mol. Rec. 10(1997)225]. Two monoclonal autoantibodies, BV 17–45 and BV 16–13, were extensively studied because of their dual specificity. To quantitatively assess the role of each specificity in the formation of stable immune complexes, studies were performed to determine binding affinities for various sized dsDNA fragments (21, 43, 84, and 114 bp) and the covalent dimer of a nine amino acid hinge peptide. Results characterizing BV 17–45 showed that the affinity for dsDNA directly correlated with increased dsDNA size. Results with BV 16–13 revealed a generally lower affinity for the various dsDNA fragments. Binding inhibition studies, using a covalently linked dimer of a nine amino acid synthetic hinge peptide as an inhibitor of the antibody–43 bp dsDNA interaction, yielded relative affinities for the anti-hinge activity. Binding affinities for the synthetic hinge specificity were lower than affinities measured for the anti-dsDNA activity. Collectively, the binding and inhibition studies provided insight into the correlation between dual specificity and avid immune complex formation. A model was proposed based on the concept that large dsDNA fragments caused localization of the dual-specific antibodies through the anti-dsDNA activity, thereby facilitating subsequent binding and cross-linkage via the anti-hinge specificity. These synergistic interactions resulted in the formation of avid immune complexes.

Monoclonal anti-double-stranded DNA autoantibody stimulates the expression and release of IL-1beta, IL-6, IL-8, IL-10 and TNF-alpha from normal human mononuclear cells involving in the lupus pathogenesis.

In our previous reports, we found polyclonal anti-double-stranded DNA antibodies (anti-dsDNA) purified from patients with active systemic lupus erythematosus (SLE) exerted inhibitory effect on [3H]thymidine incorporation of human mononuclear cells (MNC). However, the other immunological effects of anti-dsDNA on the functions of MNC have not yet been reported. In this study, two monoclonal antibodies, 12B3 and 9D7, with different anti-dsDNA activity were evaluated for their effects on the expression and release of different cytokines from human MNC. We confirmed absence of endotoxin in the two monoclonal antibody preparations and the used medium as detected by Limulus amoebocyte lysate test. The mRNA expression and release of different cytokines including interleukin (IL)-1beta, IL-2, IL-4, IL-6, IL-8, IL-10, tumour necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) were measured. We found the two monoclonal anti-dsDNA not only dose-responsively suppressed the phytohaemagglutinin (PHA)-induced thymidine uptake of human MNC but stimulated the mRNA expression of IL-1beta, IL-6 and IL-8 in normal human MNC detected by reverse transcription-polymerase chain reaction (RT-PCR). Enzyme-linked immunosorbent assay (ELISA) measurement of cytokines in MNC culture supernatants revealed that anti-dsDNA enhanced IL-1beta, IL-8, TNF-alpha and IL-10 release from resting MNC. These effects of anti-dsDNA antibodies were not affected by polymyxin B, a potent binder and neutralizer of lipopolysaccharide (LPS). These in vitro studies suggest that anti-dsDNA possess a dual effect on normal human MNC: (a) to enhance the release of proinflammatory cytokines (IL-1beta, IL-8 and TNF-alpha) from MNC to augment inflammatory reaction; and (b) to polarize the immune reaction towards the T helper 2 (Th2) (increased IL-10 production) pathway. This unique effect of anti-dsDNA may play a role in lupus pathogenesis by augmenting inflammatory reactions and autoantibody production which are commonly found in patients with active SLE.

Interplay of four Idiotypes and Interaction with Autoantibodies in Lupus Patients, their Relatives and their Spouses

Our aim was to investigate links between systemic lupus erythematosus (SLE)-associated autoantibodies, idiotypes (Id) and genetic predisposition to their development. We studied four public Ids (16/6, WRI 176β, RT72 and RT84), identified the Km and Gm phenotypes and sought six selected autoantibodies in 32 SLE patients, 174 of their relatives and 15 spouses. Though anti-double-stranded DNA antibody was uncommon in the relatives (9%), the range of antinuclear reactivities was as broad in the relatives as in the probands. Antibodies to the synthetic peptide U1-RNP-A 35–38 were found in 56% of the patients, 28% of their relatives and 20% of the spouses, whereas antibodies to the Golgi apparatus was present in 7% of the patients, 26% of their relatives and 33% of the spouses. However, most of these family members were unaffected. RT84 Id was positively associated with antibodies to Sm-D peptide 1–20 and to Ro/SSA 60 kD peptide 304–324, but negatively associated with anti-dsDNA activity. The median of age was significantly lower in the RT84 Id-positive than in the RT84 Id-negative individuals. These data suggest that genetic as well as environmental factors are involved in the aetiology of SLE. In addition, RT84-carrying immunoglobulins (Ab2) might be directed to one of many cross-reactive Ids of dsDNA-binding antibodies (Ab1), perhaps down-regulating their production.

Enhanced membrane binding of autoantibodies to cultured keratinocytes of systemic lupus erythematosus patients after ultraviolet B/ultraviolet A irradiation.

Although sunlight is known to induce skin lesions in patients with systemic lupus erythematosus (SLE) and to exacerbate systemic manifestations, the underlying mechanisms remain obscure. We report experiments that show enhanced binding of IgG autoantibodies to the cell surface membrane of ultraviolet-B (UVB) irradiated (200-1,600 J/m2) cultured SLE keratinocytes in 10 out of 12 such cell strains. The autoantibody probes showing increased binding were directed against the soluble intracellular antigens, Sm, RNP, SSA/Ro, SSB/La, whereas serum with anti-dsDNA activity did not demonstrate such binding. Control keratinocytes from several sources shared low level binding of autoantibodies after ultraviolet light exposure. In addition, 4/6 UVB-sensitive SLE strains showed increased autoantibody binding to the surface of SLE keratinocytes after UVA exposure (50-150 kJ/m2), but of lower magnitude. When UVB-sensitive nonirradiated SLE strains were exposed to autologous serum, 3/8 sera demonstrated a striking increase in IgG binding, which increased further after UVB exposure. Enhanced expression of saline-soluble intracellular antigens on the cell surface membrane of patient, but not control, keratinocytes may, in part, explain the photosensitivity of patients with SLE.

Anti‐DNA Antibodies Induced by BK Virus Inoculations

The ability of BK virus to induce anti-DNA antibodies in rabbits, and the ability of these antibodies to bind natural eukaryotic DNA and synthetic polynucleotides have been analysed. The specificity of the binding was assayed by inhibition of anti-dsDNA and -ssDNA ELISA tests with dsDNA, ssDNA, and synthetic single-stranded as well as double-stranded polynucleotides. The anti-dsDNA activity of two rabbit antisera was effectively inhibited by dsDNA and ssDNA and poly(dAdT)-poly(dAdT). The other nucleotide antigens produced relatively less inhibition. The anti-ssDNA binding was most efficiently inhibited by the homologous antigen, whereas inhibition by dsDNA only reached approximately 70% of the maximum as defined by ssDNA as inhibitor. This indicates the existence of a selective anti-ssDNA antibody population and a population recognizing both ssDNA and dsDNA within the sera. Cross-reaction of the induced anti-DNA antibodies with phospholipid antigens, such as cardiolipin, phosphatidylic acid, and bacterial cell surface, could not be demonstrated. We conclude that antibodies resulting from inoculation with BK virus specifically bind to dsDNA and ssDNA and possess a high affinity for the synthetic duplex poly(dAdT). In this way, they have some similarities with anti-DNA antibodies encountered in SLE (systemic lupus erythematosus) in both man and mouse.

Circulating antibodies to prothymosin α in systemic lupus erythematosus

Autoantibodies to prothymosin α, an immunoactive protein that exists in a large variety of mammalian tissues, were found to be present in patients with systemic lupus erythematosus (SLE) by a new, sensitive, and specific anti-prothymosin α ELISA. The antigen was prothymosin α, purified by high-pressure liquid chromatography from goat spleen extracts. Sera from 44 SLE patients and 276 healthy individuals were screened for the presence of anti-prothymosin α activity; 18% of SLE sera were found to be positive, compared with 1.8% of control sera. This anti-prothymosin α activity appears to be idiotypically distinct from either anti-thymosin α 1 activity or anti-dsDNA activity, as demonstrated by inhibition experiments. Significant positive correlation exists between anti-prothymosin α and anti-dsDNA activities of SLE sera ( r = +0.596, n = 36, P < 0.001), while no correlation was observed with the clinical activity ( χ 2 = 1.239, 0.1 < P < 0.5) or with complement levels C 3 and C 4.

Complement fixation by anti-dsDNA antibodies in SLE: measurement by radioimmunoassay and relationship with disease activity.

We have developed a sensitive, solid phase radioimmunoassay (RIA) to quantify the amount of complement (C') fixation by anti-double-stranded DNA (anti-dsDNA) antibodies and have studied sera from 48 patients with systemic lupus erythematosus (SLE). 46% of the patients were positive in this assay. There was no correlation with serum C' levels, and only weak correlation with anti-dsDNA activity as measured by a solid phase RIA. An association was shown between positive values for C' fixation by anti-dsDNA antibodies and the presence of active lupus (p less than 0.01); there was a similar association with the presence of active renal disease in those patients with raised DNA binding (p less than 0.01). Our results suggest that quantitative measurement of C' fixation by anti-dsDNA antibodies may provide information about the pathogenicity of such antibodies in patients with SLE and be a better guide to potential end organ damage than the conventional measurement of DNA binding.

Detection of masked anti-DNA antibodies in lupus sera by a monoclonal anti-idiotype.

We report here the use of a monoclonal anti-idiotype 3I to human anti-DNA antibodies to detect in serum idiotype-positive antigen-binding antibodies lacking DNA-binding activity as measured by conventional antigen binding assays. We studied paired serum samples from 13 patients with systemic lupus obtained at two times in the course of their disease: in each patient, one serum sample has anti-DNA activity and the second serum sample has no anti-dsDNA activity detectable by Millipore filter, ELISA, or Crithidia assay. Reactivity with 3I as detected with a radioimmunoassay (RIA) was present in all 13 sera with anti-dsDNA activity. Six patients showed a decrease in 3I reactivity to normal levels in the second serum sample, in which anti-dsDNA antibodies were not detectable by conventional antigen-binding assays. The other seven patients' second serum sample continued to show elevated 3I reactivity by RIA even though no anti-dsDNA activity was apparent. When the 3I-reactive antibodies from these latter patients' sera were eluted from a 3I affinity column, they revealed DNA-binding activity. Furthermore, dsDNA binding by these sera was apparent when they were displayed on Western blots of isoelectric focusing gels run in 8 M urea and incubated with radiolabeled dsDNA. These results indicate that the 3I anti-idiotype can detect anti-DNA antibodies in some sera of SLE patients that lack anti-DNA activity by ordinary assays. These antibodies may be inhibited in binding dsDNA by excess antigen or autologous anti-idiotype, and their DNA binding activity can be unmasked by procedures promoting immune complex dissociation.