Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0024141 (systemic lupus erythematosus)
 44,322 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The relationship between fine specificity of linear epitopes and conformational determinants has been explored in a naturally arising human autoimmune response. In particular, the hypothesis tested is that the linear epitopes of the human Ro autoantigen are components of its conformational epitopes. Twenty groups among the 531 overlapping octapeptides 60 kDa Ro are variably bound by anti-Ro precipitin positive lupus sera whose reactivity was easily distinguished from sera of normal controls and of anti-Ro precipitin negative lupus patients. The specific activities of anti-peptide antibodies and of anti-native Ro autoantibodies are similarly increased after affinity enrichment using native human Ro as ligand. Moreover, affinity-enriched anti-native Ro autoantibodies bind virtually the same 20 groups of epitopes recognized by whole anti-Ro positive sera. Two peptides (residues 274-290 and 480-494) from the defined 60 kDa Ro octapeptide epitopes have been prepared and used as ligands for affinity purification of peptide specific autoantibodies. The binding of both whole IgG and affinity-enriched peptide specific autoantibodies is inhibited by native Ro autoantigen. Thus, none of the available data can be construed to support the existence of cryptic linear epitopes in this system. Indeed, the data are only consistent with the conclusion that all of the anti-Ro octapeptide autoantibodies are part of the population of anti-native Ro autoantibodies in this naturally arising autoimmune response.
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PMID:Human anti-Ro autoantibodies bind peptides accessible to the surface of the native Ro autoantigen. 753 72

Systemic lupus erythematosus is characterized by high titers of autoantibodies directed at multiple proteins of the U1/Sm small nuclear ribonucleoproteins (snRNPs). The origin of this type of autoimmunity, that is, whether it is initiated by foreign molecular mimics or by the self-snRNPs, is not known. In this study using normal mice, we investigated the presence of autoreactive B and T cells to the D protein of murine snRNPs. Although neither B nor T cell responses could be detected after immunization with native self-snRNPs, two synthetic self-peptides corresponding to amino acids 26-40 and 56-70 of the snRNP D protein elicited strong autoreactive T cell proliferation as well as a limited Ab response that bound the self-protein in immunoblots. T cells elicited by these peptides did not respond to stimulation with native snRNPs, suggesting that the peptides are cryptic and are not processed from the native protein for presentation by APCs. After priming with either of these cryptic self-peptides, exposure of the immune system to native murine snRNPs resulted in a diversified response with Abs that immunoprecipitated snRNPs and that produced an antinuclear immunofluorescence pattern on murine cell substrates. These studies demonstrate that autoreactive B and T cells specific for self-snRNPs are components of the normal repertoire of mouse lymphocytes; they have been neither deleted nor irreversibly anergized. Furthermore, we show that a diverse autoimmune response to lupus autoantigens, snRNPs, can originate from self-peptides without the influence of foreign Ags or molecular mimics.
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PMID:Self-peptides in the initiation of lupus autoimmunity. 753

Antinuclear antibodies (ANAs) reactive with a limited spectrum of nuclear antigens are characteristic of systemic lupus erythematosus (SLE) and other collagen vascular diseases, and are also associated with certain viral infections. The factors that initiate ANA production and determine ANA specificity are not well understood. In this study, high titer ANAs specific for the p53 tumor suppressor protein were induced in mice immunized with purified complexes of murine p53 and the Simian virus 40 large T antigen (SVT), but not in mice immunized with either protein separately. The autoantibodies to p53 in these mice were primarily of the IgG1 isotype, were not cross-reactive with SVT, and were produced at titers up to 1:25,000, without the appearance of other autoantibodies. The high levels of autoantibodies to p53 in mice immunized with p53/SVT complexes were transient, but low levels of the autoantibodies persisted. The latter may have been maintained by self antigen, since the anti-p53, but not the SVT, response in these mice could be boosted by immunizing with murine p53. Thus, once autoimmunity to p53 was established by immunizing with p53/SVT complexes, it could be maintained without a requirement for SVT. These data may be explained in at least two ways. First, altered antigen processing resulting from the formation of p53/SVT complexes might activate autoreactive T helper cells specific for cryptic epitopes of murine p53, driving anti-p53 autoantibody production. Alternatively, SVT-responsive T cells may provide intermolecular-intrastructural help to B cells specific for murine p53. In a second stage, these activated B cells might themselves process self p53, generating p53-responsive autoreactive T cells. The induction of autoantibodies during the course of an immune response directed against this naturally occurring complex of self and nonself antigens may be relevant to the generation of specific autoantibodies in viral infections, and may also have implications for understanding the pathogenesis of ANAs in SLE. In particular, our results imply that autoimmunity can be initiated by a "hit and run" mechanism in which the binding of a viral antigen to a self protein triggers an immune response that subsequently can be perpetuated by self antigen.
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PMID:Initiation of autoimmunity to the p53 tumor suppressor protein by complexes of p53 and SV40 large T antigen. 814 41

Autoantibodies detected by immunofluorescence, ELISA, and complement-fixation techniques have provided discriminatory markers for many human diseases. However, these commonly applied assays may fail to detect antibodies against antigenic sites which are either inaccessible or not displayed in recognizable cellular structures. Moreover, molecular identities of recognized antigen(s) are not determined with such methods. We have used Western blot analysis of cellular proteins derived from human renal microvascular endothelial cells (HRMEC) to identify autoantibodies in patients with pathological endothelial injury. Exploring the possibility that endothelial injury may expose cryptic endothelial antigens to immune recognition, we detected antibodies binding a number of distinct HRMEC proteins. Among these, antibodies recognizing specific HRMEC proteins of 43 kDa were commonly detected in plasmas from patients with thrombotic thrombocytopenic purpura (TTP) (13 of 14) and hemolytic uremic syndrome (HUS) (4 of 5) but were absent in 9 of 10 healthy subjects and 11 patients with a range of diseases not associated with endothelial injury or insult. Antibodies binding 43-kDa HRMEC antigens were detected in individual patients with systemic lupus erythematosus, anti-glomerular basement membrane nephropathy, and heparin-associated thrombocytopenia, as well as in one of three patients with immune thrombocytopenic purpura. Similar antibodies were detected in one hypercholesterolemic subject. Antibodies from four TTP patients were affinity purified and shown by two-dimensional analysis to recognize 43-kDa proteins having identical pl's (5.9, 6.0, and 6.1). Subcellular fractionation localized these antigens to cytosolic and nuclear compartments, sites presumably protected from immune recognition in the absence of endothelial injury.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:A western blot assay detects autoantibodies to cryptic endothelial antigens in thrombotic microangiopathies. 832 Mar 14

Some lupus anticoagulants (LA) have been shown to be directed against phospholipid-bound prothrombin. While developing an ELISA to detect anti-prothrombin autoantibodies in patient serum or plasma, no or very low signal was observed using human prothrombin immobilized on plain polystyrene plates. In contrast, the same LA-positive samples bound specifically to prothrombin coated on gamma-irradiated plates, depending on the radiation dose, in the absence of added calcium and phospholipid. Optimization of the assay required the addition of 0.1% Tween 20 to the buffers. Antibody specificity for immobilized prothrombin was ascertained by competition using liposome-bound prothrombin, since fluid-phase prothrombin competed poorly. Seventy-seven of 139 patients (55.4%) with LA related to a variety of underlying diseases possessed anti-prothrombin antibodies (27 IgG, 35 IgM and 15 both isotypes), either isolated or more often associated with anti-beta 2 glycoprotein I (beta 2GPI) antibodies. These included 67-71% of the patients with systemic lupus erythematosus and related disorders, primary antiphospholipid antibody syndrome or drug-induced LA (autoimmune groups), but only 19-20% of those with infection or malignancy (p < 0.001). As previously shown for anti-beta 2GPI antibodies, IgG2 was the predominant IgG subclass reactive with prothrombin. Thus, autoimmune patients with LA have a high incidence of antibodies to beta 2GPI and prothrombin, the binding of which could similarly require high antigen density and/or exposure of cryptic epitopes resulting from protein interaction with an irradiated (i.e. more anionic) polystyrene surface.
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PMID:Development of an ELISA for autoantibodies to prothrombin showing their prevalence in patients with lupus anticoagulants. 856 Apr 23

We conducted this study to investigate whether antioxidized low-density lipoprotein (a-oxLDL) is an antibody to cryptic and/or neo-antigen on beta2-glycoprotein I (GPI), which is introduced by binding to anionic phospholipid, similar to that of GPI-dependent anticardiolipin antibody (aCL) employing a-oxLDL ELISA. We found that no significant optical density differences existed among systemic lupus erythematosus patients, including cases with aCL and/or lupus anticoagulant positivity, before and after the addition of GPI. Our results suggest that a-oxLDL is not an antibody to denatured GPI, but rather to oxLDL.
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PMID:Negligible synergistic effect of beta2-glycoprotein I on the reactivity of antioxidized low-density lipoprotein antibody to oxidized low-density lipoprotein. 863 31

There is accumulating evidence that anti-phospholipid (aPL) antibodies in the sera of patients with autoimmune diseases bind to a complex of anionic phospholipids and plasma phospholipid-binding proteins, namely beta 2-glycoprotein I (beta 2-GPI) and prothrombin. It has been suggested that a conformational change in beta 2-GPI, induced by binding either to anionic phospholipids or to the oxygen molecules on the irradiated microtiter plate, reveals cryptic antigenic epitope(s) in the native protein. We used an enzyme-linked immunoassay for measuring antibodies against two phospholipid-binding proteins, i.e., beta 2-GPI and prothrombin, absorbed to an irradiated plate in an unselected series of 139 patients with systemic lupus erythematosus (SLE). Elevated levels of antibodies against beta 2-GPI were found in 49% of patients and antibodies against prothrombin in 34% of patients. Both antibodies were significantly associated with deep venous thrombosis in patients with SLE (P = 0.009 for both antibodies). Accordingly, testing of these antibodies seems to be clinically useful in evaluating the risk of thrombosis.
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PMID:Antibodies to phospholipid-binding plasma proteins and occurrence of thrombosis in patients with systemic lupus erythematosus. 867 35

Cardiolipin binding of IgG-class anticardiolipin antibody (aCL) depends on the existence of beta 2-glycoprotein I (beta 2-GPI). We developed an EIA system that enables detection of antibodies against beta 2-GPI, without the presence of cardiolipin. This system involves use of irradiated polystyrene plates, in which oxygen atoms are introduced onto the surfaces of the plates. beta 2-GPI bound to the surface of these plates is assumed to undergo a conformational change that exposes normally cryptic epitopes. Anti-beta 2-GPI antibody measured using this EIA system showed good correlation with aCL measured by conventional EIA methods and may prove useful in evaluating the risk of thrombosis and monitoring the clinical course in patients with SLE. Utilizing this EIA system and beta 2-GPI-deleted mutants, we found that the fourth domain of beta 2-GPI is involved in expression of one of the cryptic epitopes recognized by aCL. We also found that oxidized LDL are sequentially targeted by beta 2-GPI and aCL.
Lupus 1996 Oct
PMID:Anti-beta 2-glycoprotein I antibody: specificity and clinical significance. 890 64

The family of antiphospholipid antibodies includes antibodies binding to cardiolipin in serological test for syphilis, antibodies prolonging the clotting time in lupus anticoagulant test, antibodies reacting with plasma phospholipid-binding proteins, such as beta 2-glycoprotein I and prothrombin, and antibodies binding to oxidized low-density lipoprotein (LDL). Antiphospholipid antibodies are traditionally associated with arterial and venous thrombosis in patients with primary or secondary antiphospholipid syndrome. The recent studies, especially those on patients with myocardial infarction, extend the concept of antiphospholipid antibodies, and suggest that they play a role also in atherosclerosis. Based on the clinical studies and immunological findings, it seems that the differences in the specificity of antiphospholipid antibodies may reflect to their pathogenetic mechanisms and, finally, to their clinical consequences. The present review suggests that antibodies to oxidized LDL may not interfere directly with blood coagulation, but seem to have importance in the inflammation of the vessel wall in atherosclerosis and in vasculitis. Instead, antibodies to beta 2-glycoprotein I and to prothrombin show a closer association with thrombosis. It is possible that in the atherosclerotic plaque, the plasma proteins, such as beta 2-glycoprotein I or prothrombin, are bound to the endothelial surface and antibodies to cryptic epitopes revealed in these proteins are induced. These antibodies may contribute to the formation of atherosclerotic thrombosis by changing the balance of haemostasis toward hypercoagulative state.
Lupus 1996 Oct
PMID:Antiphospholipid antibodies and atherosclerosis. 890 78

Idiosyncratic adverse drug reactions have characteristics that suggest involvement of the immune system. In particular, drug-induced lupus which is an autoimmune syndrome, must be immune-mediated. A major working hypothesis for the first step in the mechanism of drug-induced autoimmunity is that the drug, or more commonly a reactive metabolite of the drug, must irreversibly bind to some structure. In view of the reactive nature of these metabolites, in most cases it is likely that the metabolite must be formed in the organ where toxicity occurs. The liver is the major site of drug metabolism and it is a common target for idiosyncratic drug reactions. In the case of immune reactions directly involving leukocytes, the enzyme system most likely responsible for the formation of reactive metabolites is the NADPH oxidase/myeloperoxidase system found in neutrophils and monocytes. In some cases, the reactive metabolite results in the production of antibodies or T-cells directed against the altered structure. However, in many other cases, the mechanism appears to be more complex than this. In some cases, true auto-antibodies are produced that do not require the presence of the drug, and furthermore, the antibodies produced often are the same as those induced by other stimuli, such as viruses. This suggests either molecular mimicry or a common alteration in the processing and presentation of antigens such that cryptic antigens are presented. Another possibility is that the reactive metabolite directly alters the class II MHC molecule leading to a graft-vs-host reaction.
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PMID:Current trends in drug-induced autoimmunity. 912 93


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