Antiendothelial cell antibodies in systemic lupus erythematosus

Sera from patients with systemic lupus erythematosus have been reported to contain IgM and/or IgG binding to endothelial cells (EC), i.e. anti-EC antibodies (AECA). Similar autoantibodies have been claimed to occur in a number of conditions associated with vasculitis. The original cyto-enzyme-linked immunosorbent assay (ELISA) remains the most widely used method for the detection of AECAs, although numerous pitfalls have been identified since then. These difficulties may explain why a consensus on the prevalence of AECAs has not been reached thus far. It is therefore desirable to confirm a positive result in the cyto-ELISA using other methods, such as flow cytometry, immunoprecipitation or Western blot. Yet, these methods appear to be difficult to use on a routine basis. With regard to the AECA effects, their binding induces activation of ECs, as substantiated by up-regulation of adhesion molecules, and synthesis of cytokines and chemokines, followed by their secretion. Some of these autoantibodies encourage the local production of tissue factor, and thereby favour coagulation. Other AECAs trigger apoptosis of ECs, although the Fas receptor does not seem to be involved in this process. In fact, since the target antigens are not well defined, the current challenge is to identify EC target molecules, and thus to gain further insights into the pathogenesis of diseases with vasculitis.     

Character of anti-DNA antibodies in systemic lupus erythematosus

Anti-DNA antibodies in twenty-one systemic lupus erythematosus (SLE) sera were analysed by precipitation in gel, complement fixation, and the Farr globulin precipitation technique. Fifteen sera precipitated in agarose with both native and denatured DNA (Group 1) and six precipitated solely with denatured DNA (Group 2). Prior incubation of the sera with RNA or DNA digest abolished the precipitin reactions of all Group 2 sera, but had no appreciable effect on the precipitin patterns of the Group 1 sera. Molecular class of anti-DNA antibodies did not correlate with precipitation pattern. The ability of sucrose density gradient fractions of serum to fix complement with denatured DNA at 4°C did not correspond with the presence of precipitating antibodies against denatured DNA.The Farr globulin binding assay probably allowed detection of all anti-DNA antibodies, and each of the sera bound most of the [¹⁴C]DNA. No binding was observed when ¹⁴C-labelled nucleotides were substituted for the [¹⁴C]DNA. Both native and denatured unlabelled DNA were able to significantly inhibit binding by all sera tested (Groups 1 and 2), while RNA and DNA digest gave minimal inhibition. Three types of antigenic sites on the DNA molecule are postulated. It is suggested that all anti-DNA sera, regardless of their behaviour in precipitin or complement fixation tests, contain antibodies reactive with all three determinants on the DNA molecule.     

Lymphocytotoxic antibodies in patients with systemic lupus erythematosus

Lymphocytotoxic activity could be demonstrated in the sera of patients with systemic lupus erythematosus. The number of positive reactions varied with temperature of incubation. Lymphocytotoxicity was present in 88%, 49% and 11% of sera tested at 15°C, 22°C and 37°C respectively. At an incubation temperature of 22°C, the presence of the lymphocytotoxic antibody in the sera could be correlated with significantly higher titres of anti-nuclear factor, anti-single-stranded DNA and the histological appearance of active diffuse glomerulonephritis in renal biopsies.     

Heterogeneous neurocytotoxic antibodies in systemic lupus erythematosus.

Sera from eighteen patients with systemic lupus erythematosus (SLE) were tested for cytotoxic antibody to three neuronal and two glial continuous cell lines of human origin. Eighty per cent (fifteen out of eighteen) of the sera were cytotoxic to at least one of the cell lines, but only seven sera were active against all five lines. Three sera had anti-neuronal but not anti-glial reactivity. No sera were gliocytotoxic without neurocytotoxicity. Three SLE sera with relatively strong cytotoxicity to all five cell lines were abosrbed with each of the cell lines separately and the absorbed sera were then tested for residual cytotoxicity to each of the cell lines. The absorptions uncovered at least six different antibody specificities directed at antigens expressed on some but not all of the neuronal and glial cell lines. Each patient's serum had its own profile of antibody specificities reactive with membrane antigens on nervous tissue-derived cells.     

Placental pathology in systemic lupus erythematosus with antiphospholipid antibodies

Systemic lupus erythematosus (SLE) is associated with a poor pregnancy outcome. Antiphospholipid antibodies (APL), which include lupus anticoagulant (LAC) and anticardiolipin antibodies (aCL), are frequently found in patients with SLE, and their presence has been associated with fetal loss. To examine placental pathologic features of SLE patients with APL, we performed a pathologic study on 47 placental tissue samples from 47 pregnant SLE patients with APL (15 patients; four LAC single-positive patients, seven aCL single-positive patients, four LAC and aCL double-positive patients) and without APL (32 LAC and aCL double-negative patients). The incidence of extensive infarction, decidual vasculopathy, decidual thrombosis and perivillous fibrinoid change, which have been thought to be characteristic lesions of APL placenta, was significantly higher in the LAC and aCL double-positive patients than in the patients without APL. Conversely, the above-mentioned lesions between the LAC or aCL single-positive patients and the APL negative patients did not differ significantly. Among the 15 patients with APL, two of the three patients with both decidual vasculopathy and thrombosis had extensive infarction associated with fetal death. Moreover, the patients having fetal death showed LAC and aCL double-positivity. In conclusion, this study indicated that the LAC and aCL double-positivity is an important factor for extensive infarction resulting from decidual vasculopathy and decidual thrombosis in the SLE placenta. Moreover, it was indicated that LAC and aCL double-positivity is an important risk factor for fetal death in the SLE patient.     

Cross-reactive idiotypes in anti-DNA antibodies of systemic lupus erythematosus patients

Cross-reactive idiotypes associated with the combining site of anti-double-stranded DNA antibodies from systemic lupus erythematosus patients were demonstrated by the ability of isologous lupus sera to block functionally the binding of target anti-DNA antibodies to DNA in vitro. A framework idiotype, denoted AM Id, was identified using xenogeneic anti-idiotype antibodies rendered specific by affinity absorptions. The AM Id was found in 85% of patients with systemic lupus erythematosus (n = 63) and correlated positively with anti-DNA antibodies. Analysis of the distribution of the AM Id among individuals showed that, while present in anti-DNA antibodies to varying degrees in individual patients, it was also found in variable amounts on non-DNA-binding immunoglobulins. These results indicate that the AM Id and anti-DNA antibodies represent overlapping populations of immunoglobulins.     

抗核小体抗体与儿童系统型红斑狼疮的相关性

目的探讨抗核小体抗体（AnuA）在诊断儿童系统型红斑狼疮（SLE）中的敏感性和特异性，了解AnuA与儿童SLE临床特征、疾病活动性的相关性。方法用Hep-2细胞提取核小体。用酶联免疫吸附方法（ELISA）测定血清中的AnuA，分析AnuA和临床表现的相关性。结果52例SLE中18例AnuA阳性。27例疾病对照组中1例AnuA阳性，30例正常对照组AnuA均为阴性。AnuA在儿童SLE中的敏感性为35％，特异性为96％。AnuA阳性组SLE患儿100％有中枢神经系统损害，AnuA阴性组为47％（x^2=14．57，P〈0．05）。AnuA阳性组SLE患儿100％有肾脏损害，AnuA阴性组为5l％（x^2=13．31，P〈0．05）。AnuA阳性和AnuA阴性的SLE患儿SLEDAI评分高于10分者分别为100％和71％（x^2=6．56，P〈0．05）。结论AnuA对儿童SLE的诊断具有较高的特异性，有助于抗dsDNA抗体、抗心磷脂抗体阴性的儿童SLE的诊断。     

Complement activation by antibodies to Sm in systemic lupus erythematosus

The question of whether autoimmune reactions result from abnormality of the autoantigen or of the autoantibody is fundamental. When reaction of the thyroid stimulating autoantibodies (TSaab) of Graves' disease with their autoantigen is measured in the mouse bioassay which has a very sensitive dose-response curve this provides a favourable system for detecting any influence of allotypic variation in the autoantigen on the affinity of the corresponding autoantibodies. Seven high potency long acting thyroid stimulator (LATS) sera were tested for degree of neutralization by soluble extracts from nine thyroids, using the mouse bioassay to measure changes in LATS activity. The thyroid extracts differed in neutralizing potency and the LATS sera differed in susceptibility to neutralization, but these variations were consistent enough to enable ranking and there were no significant exceptions from especially strong or weak reactions between any individual thyroid extract and any individual LATS serum. Even autologous reactants had no greater or lesser affinity than homologous ones. Five LATS protector (LATSP) sera, tested against six thyroid extracts, including their own, again showed no evidence of allotypic variation in the autoantigen, nor did 55 LATSP sera tested with one of four thyroid extracts. Altogether we have looked at over 200 individual reactions between soluble thyroid antigen and thyroid stimulating autoantibody (LATS and LATSP). We have not found a single significant instance of any exceptionally strong or weak affinities, even with autologous antigen. The findings are in accord with Burnet's theory that autoimmune reactions are due to the emergence of forbidden clones of lymphocytes, reactive with normal self antigens.     

Opsonization by anti-dsDNA antibodies of apoptotic cells in systemic lupus erythematosus

In order to asses the role of the soluble mediators of serum from patients with SLE in the apoptotic cell clearance, we measured the in vitro phagocytosis of apoptotic Jurkat cells by normal healthy donor macrophages in the presence of SLE patients' sera. A significant increase of the phagocytic index (NHD = 1.0 +/- 0.3; SLE = 1.9 +/- 0.6; p < 0.01) was to be observed in the presence of serum from patients with SLE. The increased phagocytic index correlated to the anti-dsDNA antibodies titers. We conclude that anti-dsDNA antibodies present in sera of patients with SLE favor the apoptotic cell phagocytosis by opsonization of the target cells. This may represent a deviation of the clearance process towards inflammation and a new pathologic feature of these autoantibodies in SLE.     

The fine specificity of IgG antiguanosine antibodies in systemic lupus erythematosus

The antigen specificity, isotype, and subclass of antinuclear antibodies may be related to their pathogenicity in systemic lupus erythematosus (SLE). Our laboratory found that IgG antibodies that bound the nucleoside, guanosine, occurred frequently in SLE patients. In contrast, sera from healthy subjects contained IgM but not IgG antiguanosine antibodies. The present studies were designed to characterized the fine specificity of IgG antiguanosine antibodies in SLE and compare them with IgM antiguanosine antibodies in normal sera. Serum antinuclear antibodies from six healthy subjects and six SLE patients were isolated by affinity binding to guanosine and measured by an enzyme-linked immunosorbent assay (ELISA). IgM in normal sera, and both IgM and IgG in SLE sera bound guanosine. IgM antiguanosine antibodies in normal sera were polyspecific and bound other nucleosides and 1-methylguanosine but not denatured DNA (ssDNA). In contrast, IgG antiguanosine antibodies from the SLE patients bound guanosine and ssDNA but not other nucleosides or 1-methylguanosine. SLE IgM antiguanosine antibodies had the same fine specificity and bound guanosine and ssDNA but not any of the other nucleosides. These results suggest that SLE IgG and IgM antiguanosine antibodies have fine specificity in contrast to the polyspecific IgM antibodies in normal sera. In addition, subclass analysis indicated that all SLE patients had either IgG1 or IgG3 subclass of antiguanosine antibodies that bind complement. Characterizing the isotype, subclass, and fine antigen specificity of antiguanosine antibodies should assist in evaluating their potential pathogenicity in SLE.     

Antigranulocyte antibodies in patients with systemic lupus erythematosus (SLE)

Antigranulocyte antibodies were studied in patients with systemic lupus erythematosus. The frequency and type of the antibodies were identified with ELISA (Enzyme-Linked Immunosorbent Assay) and MGCT (microgranulocytotoxicity test). To check antibody specificity, a LCT (lymphocytotoxicity test) was used parallel with the above technique. The ELISA proved to be suitable for determining antigranulocyte antibodies. There was a correlation between the serum level of IgG-type antigranulocyte antibodies and granulocytopenia, but the IgM-type antigranulocyte antibodies failed to show a similar correlation. A good parallelism was found between MGCT--a test to be used to determine IgM-type antibodies--and the IgM-type antigranulocyte antibodies determined by ELISA. Of 25 SLE sera, 13 were found positive for antigranulocyte antibodies. LCT was used to examine the presence of HLA antibodies in these sera and 39% of the sera positive for antigranulocyte antibodies appeared to be granulocyte-specific while 61% reacted in the LCT, too.     

Relationship between anti-cardiolipin and anti-endothelial cell antibodies in systemic lupus erythematosus

Anti-endothelial cell antibodies (AECA) have been detected in 51 lupus sera by cell surface radioimmunoassay with a prevalence of 39.2% for IgG and 45.1% for IgM-AECA. No correlations were found between AECA and different clinical or laboratory parameters, including the presence of anti-cardiolipin antibodies and signs associated with the presence of anti-phospholipid antibodies. However, absorption with cardiolipin liposomes partially inhibited endothelial cell binding, and affinity purified anti-cardiolipin antibodies were able to react with intact human endothelial cells. The binding did not occur via Fc receptors since blocking of Fc receptors with rabbit IgG did not affect the endothelial cell reactivity. Taken together our findings support the hypothesis that antibodies directed against negatively charged phospholipids can be part of the anti-endothelial cell antibodies in certain lupus sera. The possible role of these cross-reacting antibodies in the pathogenesis of vascular thrombosis in lupus patients is discussed.     

Anti-DNA, antihistone, and antinucleosome antibodies in systemic lupus erythematosus and drug-induced lupus

Conclusion Anti-DNA antibodies play a crucial part in the pathogenesis of disease symptoms of SLE. Low avidity anti-DNA antibodies also occur in rheumatic diseases other than SLE. The Farr assay, which detects high avidity anti-DNA antibodies, is useful in helping to diagnose SLE. The optimal screening procedure is ELISA or Crithidia test, followed by confirmation of Farr assay. Use of a quantitative assay selective for high avidity anti-DNA antibodies is very valuable in the monitoring of individual SLE patients; measurements of anti-DNA antibodies should be performed every 4–6 wk. The results show a relation between low avidity anti-DNA antibodies and central nervous system involvement, and high avidity anti-DNA antibodies and nephritis. A significant rise in anti-DNA antibodies may correlate with a clinical relapse. All relapses are preceded by a prominent rise in anti-DNA antibodies as determined by Farr assay. A dramatic drop of anti-DNA antibody levels directly precedes the relapse; this phenomenon might be due to a concurrent immune deposit formation.