The influence of anti-fibronectin antibodies on interactions involving extracellular matrix components and cells: a possible pathogenic mechanism.

Antibodies, directed to the 30-kD collagen binding domain (CBD) of fibronectin (Fn), have been previously demonstrated in sera from patients with systemic lupus erythematosus (SLE), and we now investigate the possible pathogenic effects of these antibodies on collagen-Fn and cell-Fn interactions. The binding of type 1 collagen to Fn was demonstrated by ELISA, and could be specifically inhibited by the preincubation of solid-phase immobilized Fn with anti-Fn antibodies from SLE sera. By using indirect immunofluorescent staining, anti-Fn antibody containing SLE sera but not normal human serum (NHS) reduced the deposition of newly synthesized collagen and Fn on living human skin fibroblasts. We also found that sera from SLE patients containing anti-Fn antibodies significantly reduced thyroid cell attachment to Fn immobilized on plastic compared with NHS. These effects were shown to be due to the presence of anti-Fn antibodies in these sera, as SLE sera depleted of anti-Fn antibodies did not reduce the deposition of collagen or Fn on cultured fibroblasts, nor did they inhibit cell attachment.     

Autoantibodies to killer cell immunoglobulin-like receptor 3DL1 in patients with systemic lupus erythematosus

A genetic variant of the killer immunoglobulin-like receptor 3DL1 (KIR3DL1) has been found in patients with systemic lupus erythematosus (SLE). Herein, we investigated the presence of autoantibodies to KIR3DL1 in a cohort of patients with SLE. We tested sera from 28 patients with SLE, 11 patients with rheumatoid arthritis (RA) and 17 healthy control subjects for anti-KIR3DL1 activity by an enzyme-linked immunosorbent assay (ELISA) using recombinant KIR3DL1-enhanced green fluorescent protein (EGFP) and EGFP proteins. Anti-KIR3DL1 antibodies were detected in 22 (79%) of the 28 patients with SLE, whereas they were present in only three (27%) of the 11 patients with RA examined. Notably, 10 (91%) of the 11 samples from patients with SLE prior to therapy had anti-KIR3DL1 antibodies. None of the samples from healthy donors were positive for the antibodies. Here, we report the presence of anti-KIR3DL1 antibodies in the sera of patients with SLE for the first time. Anti-KIR3DL1 autoantibodies may be involved in the pathogenesis of autoimmune diseases.     

Measurement of anti-DNA antibodies by ELISA: a comparative study with Crithidia and a Farr assay

One hundred and twenty six sera from 116 patients with systemic lupus erythematosus (SLE) and from 51 control patients were assayed for the presence of anti-DNA antibodies, using a commercial enzyme linked immunosorbent assay (ELISA). Fifty three sera (42%) from SLE patients were positive and a further 13 sera (10%) fell in the 'equivocal' positive range. Three control sera were positive. In a standard 14C DNA Farr assay, 67 sera (53%) from SLE patients were positive. One control serum was weakly positive. There was a good linear correlation between absorption in the ELISA and the 14C DNA binding result (r = 0.73). Results in the ELISA and Farr assays were concordant in 96 of the 126 SLE sera, and 47 of 51 control sera. Sequential sera from a further 6 patients with fluctuating clinical activity of SLE showed similar patterns of change of anti-DNA antibodies in both assays. The ELISA was more sensitive than the Crithidia luciliae immunofluorescence assay which detected 44 positive sera (35%) in the SLE group. These results suggest that this ELISA assay may be a useful alternative to the Crithidia assay or an effective screen prior to testing in the more technically difficult and time consuming Farr assay for the measurement of anti-DNA antibodies.     

Human anti-fibronectin antibodies in systemic lupus erythematosus: occurrence and antigenic specificity.

Sera from patients with connective tissue diseases exhibit autoantibodies to a spectrum of extracellular matrix proteins. Antibodies binding to solid phase bovine fibronectin (Fn) were investigated by ELISA in patients with systemic lupus erythematosus (SLE). Sera showing binding of 2 s.d. above the mean of the normal human control were considered positive and 43/150 SLE sera (28.7%) demonstrated such binding. These antibodies were mainly IgG and IgA as determined by isotype-specific ELISA. Specificity studies on selected positive sera revealed that binding was inhibited by preincubation with soluble Fn, but not with thyroglobulin or type 1 collagen. The binding was demonstrated not to be related to interactions with rheumatoid factor, complement components or immune complexes. Additional studies to determine which Fn fragment is bound by naturally occurring anti-Fn antibodies demonstrated that the binding was predominantly to the 30-kD collagen binding domain (CBD) of Fn molecule. Inhibition studies using 120-kD, 40-kD and 30-kD Fn fragments confirmed that this binding site was the 30-kD CBD.     

Preparative isolation of p67, A, B, B' and D from nRNP/Sm and Sm antigens by reverse-phase chromatography. Use in a polypeptide-specific ELISA for independent quantitation of anti-nRNP and anti-Sm antibodies

The p67 (67 kDa) and A (33 kDa) polypeptides of nRNP/Sm antigen and the B, B' (28 and 29 kda) and D (16 kDa) polypeptides of 'free' Sm antigen were isolated and used in enzyme-linked immunoadsorbent assays (ELISA) for human autoantibodies. ELISA specificity was demonstrated using monoclonal antibodies. The ELISA using HPLC-purified polypeptides was found to be more sensitive than immunoblotting for detecting antibody. 86% of sera with precipitating anti-nRNP antibodies were positive in the ELISA, as were all sera with precipitating anti-Sm antibodies. Patients with rheumatoid arthritis (RA), Sj?grens syndrome (SS) and undifferentiated connective tissue disease (UCTD) had low levels of anti-p67 with a prevalence 11.6% and 18%, respectively, whilst patients with systemic lupus erythematosus (SLE) and mixed connective tissue disease (MCTD) had high levels and prevalence rates of 55.2% and 80%, respectively. Anti-B or anti-D antibodies were detected at high levels in SLE (prevalence 30%) but were found rarely in UCTD and MCTD (prevalence 7% and 10%) and not at all in RA or SS sera.     

Anti-H1 histone antibodies in systemic lupus erythematosus: epitope localization after immunoblotting of chymotrypsin-digested H1.

Using micro enzyme-linked immunosorbent assay (micro-ELISA) anti-H1 antibodies are most frequently seen in systemic lupus erythematosus (SLE) (61.4% of patients). Positive anti-H1 ELISA reactions are rare in rheumatoid arthritis (RA) (5.8% of cases), melanomas (16.7%), leukaemias (13.6%) and other cancers (5.6%). In SLE, the immunoglobulins (Ig) which constitute anti-H1 antibodies are, by order of importance, IgM, IgG and IgA. By means of immunoblotting using H1 solutions digested by alpha-1-chymotrypsin fixed on collagen membranes, we have shown that all the SLE sera containing anti-H1 antibodies recognize the sequential epitopes that are found on the carboxy terminal tail and, for 28% of anti-H1 sera, also the epitopes present on the aminoterminal half. The technique used did not make it possible to determine with certainty whether anti-H1 autoantibodies are also directed against the conformational epitopes of the globular part of the molecule.     

Reactive oxygen species modify human DNA, eliciting a more discriminating antigen for the diagnosis of systemic lupus erythematosus.

During the development of an ELISA to measure anti-DNA antibodies in systemic lupus erythematosus (SLE) sera, native dsDNA was found not to be the most appropriate antigen to use in ELISA assays for differentiating between SLE patients and those with rheumatoid arthritis (RA), a disease also associated with circulating serum anti-DNA antibodies. By modifying the ELISA technique to incorporate human DNA, denatured by reactive oxygen species, to detect anti-DNA antibodies in SLE sera, results consistently showed an increase in antibody binding when compared with the native antigen; no such trend was observed in the comparable group of RA patients. Using this assay serum anti-dsDNA antibody levels were measured in a group of 20 controls, 20 RA patients (10 seropositive and 10 seronegative) and 30 SLE patients (15 with clinically active disease, 15 with inactive disease). A comparison with the standard radioimmunoassay used to measure anti-DNA antibodies for the diagnosis of SLE showed that the ELISA assay using modified DNA performed better than the standard radioimmunoassay offering an improvement in both clinical specificity and sensitivity. The improved method particularly reduced the problem of false-negative results for SLE patients shown clinically to be either mildly active or inactive.     

Antibodies to Collagen: Comparative Epitope Mapping in Women with Silicon Breast Implants, Systemic Lupus Erythematosus and Rheumatoid Arthritis

Women with silicone breast implants have a significantly increased frequency of antibodies to collagen types I and II. To characterize the specificity of these antibodies; 70 women without a specific autoimmune disease, according to the criteria of the American College of Rheumatology, but who had silicone breast implants were studied for the presence of serum antibodies to native and denatured human types I and II collagen by ELISA. Positive sera were further studied by immunoblotting using peptides derived by cyanogen bromide digestion of the collagens. Samples of 82 women with systemic lupus erythematosus (SLE), 94 women with rheumatoid arthritis (RA), and 133 healthy controls were studied concurrently. There was a high frequency of autoantibodies to collagen in each of the study groups when compared to the healthy controls. However, and of particular interest, the epitope specificity of the autoantibodies differed markedly. Sera from women with silicone implants reacted strongly in an individual-specific manner with multiple peptides of type I collagen, whereas sera from women with SLE and RA reacted only weakly with a restricted range of peptides of type I collagen. Sera from women with RA reacted strongly with multiple peptides of type II, whereas sera from women with silicon implants or SLE reacted only weakly. The reactivity of women silicon implants suggests that silicone or its biodegradation products can act as adjuvants in situ to enhance the immunogenicity of type I collagen, or protein-silicone conjugates.     

Detection of autoantibodies against the globular domain of human C1q in the sera of systemic lupus erythematosus patients

The anti-C1q antibodies present in systemic lupus erythematosus (SLE) patients' sera are associated with renal involvement and the titer of these autoantibodies correlates with the clinical activity of the disease. It has previously been shown that anti-C1q antibodies bind neo-epitopes within the collagen region of human C1q. Evidence that these polyclonal autoantibodies recognize epitopes within the globular domain (gC1q) of the molecule has not been documented. In this study, we screened, using ELISA, a number of sera from SLE patients for the presence of anti-gC1q autoantibodies using recombinant globular head regions of individual A (ghA), B (ghB) and C (ghC) chains of human C1q. The recombinant proteins were used as test antigens to determine the levels of autoantibodies directed against ghA, ghB and ghC. SLE sera, containing high levels of anti-C1q antibodies, showed differentially increased binding towards ghA and ghB, which suggested that the gC1q domain can also be target of anti-C1q antibodies generated in SLE patients. Such antibodies can have severe pathophysiological consequences since these are likely to further impair the ability of C1q to clear immune complexes.     

Influenza vaccination of patients with systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA)

The role of influenza vaccination in patients suffering from autoimmune diseases, including systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA), has long been a subject of discussion. The risk of exacerbation of the main disease following vaccination is of particular concern, and needs to be carefully evaluated against the risk of disease flares as a result of infections. Our study included 69 SLE patients and 54 RA patients, all in stable condition. We split the groups into two subgroups each: patients in SLE1 (23 patients) and RA1 (23 patients) received the flu vaccine ("Vaxigrip", Aventis Pasteur) in November 2003. Patients in SLE2 (46 patients) and RA2 (31 patients) were not vaccinated. Throughout the following year, we studied parameters of disease activity and the occurrence of viral respiratory and bacterial infections in our patients. The vaccine was well tolerated in all cases. Vaccinated patients had significantly fewer occurrences of infections. Every viral and bacterial infection resulted in the worsening of the main disease. We believe that influenza vaccine is indicated for SLE and RA patients in stable condition. However, this decision must be made on a patient-by-patient basis. We plan to continue our study with the goal of formulating a better protocol for the clinical practice.     

Human Autoantibodies Against C1q: Lack of Cross-Reactivity with the Collectins Mannan-Binding Protein, Lung Surfactant Protein A and Bovine Conglutinin

The collectins, a group of humoral C-type lectins, have globular and collagen-like regions and share structural features with the complement protein C1q. The question was asked if autoantibodies to the collagen-like region of C1q (anti-C1qCLR) might cross-react with collectins, such as mannan-binding protein (MBP), lung surfactant protein A (SP-A) and bovine conglutinin (BK). Anti-C1qCLR antibodies of the systemic lupus erythematosus (SLE) type and anti-C1qCLR antibodies of the hypocomplementemic urticarial vasculitis syndrome (HUVS) type were investigated. Cross-absorption and elution experiments combined with antibody detection by enzyme-linked immunosorbent assay (ELISA) and immunoblot analysis gave no evidence of cross-reactive anti-C1qCLR antibodies. However, one serum with HUVS type anti-C1qCLR antibodies contained anti-MBP antibodies that were cross-reactive with SP-A. Judging from results of ELISA inhibition experiments and immunoblot analysis, four SLE sera contained antibodies to native BK, while two sera with HUVS type anti-C1qCLR antibodies contained antibodies to epitopes of denatured BK. This might imply that autoimmunity to collagen-like structures is not restricted to C1qCLR in HUVS and HUVS/SLE overlap syndromes.     

C3b binding immune complexes and immunoconglutinins in human sera. Detection by enzyme-linked immunosorbent assay (ELISA)

An enzyme-linked immunosorbent assay (ELISA) designed to measure autoantibodies against C3b (immunoconglutinins: IK) also detects immune complexes (IC). Solid phase C3b, in addition to binding IK of IgG, IgM and IgA classes, bound aggregated human IgG, IgA and aggregated immunologically purified anti-tetanus toxoid antibodies as well as model complexes of tetanus toxoid-human anti-toxoid. Significant C3b binding IgG, IgM and IgA activities were seen in the sera of 20 SLE patients but not in sera from healthy blood donors. Ultracentrifugation analysis of two SLE sera revealed C3b binding IgG and IgA activities in both light (7S) and heavy (11S) fractions. This indicates simultaneous presence of IK and IC in these sera. On the basis of the known relationship between IK and IC formation we suggest that the solid phase C3b ELISA may be of value in evaluating immune reactions in patients.     

A common anti-DNA idiotype and other autoantibodies in sera of offspring of mothers with systemic lupus erythematosus.

Since the immune response in fetuses of mothers with systemic lupus erythematosus (SLE) is unknown, we investigated sera from six mothers and their paired offspring by enzyme-linked immunosorbent assay (ELISA) for the presence of a common anti-DNA idiotype (16/6 Id) and, as control, for the presence of an unrelated public idiotype of antibody to hepatitis B surface antigen (HBsAg). In addition, maternal as well as fetal sera were evaluated for the presence of antibodies to ssDNA, dsDNA, poly(I), poly (dT), RNA, cardiolipin, total histones and the presence of lupus anticoagulant. Clinically active SLE mothers showed in general increased IgG and, to a lesser extent, IgM autoantibody activity. Circulating lupus anticoagulant was detectable in clinically active mothers only. All offspring of clinically active SLE mothers showed increased IgG autoantibodies to a variety of antigens, while IgM antibodies were detected in only one fetus. In contrast, fetuses of clinically inactive mothers showed only minor IgG activity. Common anti-DNA-idiotype (16/6 Id) activity also correlated with disease activity in both maternal and fetal compartments. One clinically active mother was 16/6-negative; her offspring was, however, positive, indicating de novo production of the idiotype by the fetus. In contrast, a control anti-HBsAg idiotype was not detected in either maternal or fetal sera. It therefore appears that offspring of clinically active SLE mothers serologically reflect maternal disease activity. Furthermore, autoantibodies and common idiotype of autoantibodies can be found within the fetal compartment even in the absence of such antibodies in the maternal serum. Discrepancies between mothers and offspring in IgM-autoantibody levels and the presence of new idiotypes in fetuses are indicative of fetal de novo autoantibody production.     

Antibodies to EYRKK vesicular stomatitis virus-related peptide account only for a minority of anti-Ro60kD antibodies.

Previous studies demonstrated a possible antigenic relation between the carboxyl terminal portion of anti-Ro60kD autoantigen and a nucleocapsid protein (N) of vesicular stomatitis virus (VSV). In order to investigate whether anti-Ro60kD autoantibodies react with the VSV homologous region of the Ro60kD protein we synthesized, according to Merrifield's method, the EYRKKMDI octapeptide (8p) sharing a common sequence with the N protein of VSV. Sera from 61 patients with autoimmune rheumatic diseases (34 systemic lupus erythematosus (SLE), 21 Sjörgren's syndrome (SS) and six rheumatoid arthritis (RA)) as well as 59 from normal blood donors were tested for the presence of anti-Ro60kD autoantibodies by ELISA and immunoblot (IB) and anti-8p antibodies by ELISA. Antibodies to 8p were found in 9/31 of anti-Ro60kD IB-positive sera, 5/30 of anti-Ro60kD-negative sera and 2/59 of normal control sera. The concordance between the anti-8p ELISA and the anti-Ro60kD IB was very poor (chi 2 = 0.71, P = 0.4) in contrast to the anti-Ro60kD ELISA and the anti-Ro IB (chi 2 = 27.6, P = 10(-7)). Subsequent affinity purification of the anti-8p antibodies from a strong positive anti-8p and anti-Ro60kD SLE serum yielded 95% depletion of the anti-8p activity and 37% reduction of the anti-Ro60kD activity. Inhibition assays with the affinity-purified anti-8p antibodies demonstrated that the octapeptide gave 94.5% inhibition of the anti-Ro60kD activity, while Ro60kD protein led to 42.3% inhibition of the anti-8p. Preincubation of the serum with the octapeptide produced 4% inhibition of anti-Ro60kD ELISA. These results indicate that the anti-8p antibodies account only for a minority of the anti-Ro60kD autoantibodies.     

Antimitochondrial (pyruvate dehydrogenase) antibodies in leprosy

Sera from 69 patients with leprosy but without liver involvement were assayed for the presence of mitochondrial pyruvate dehydrogenase (PDH)-specific autoantibodies by enzyme-linked immunoabsorbent assay (ELISA), immunoblotting using PDH as an antigen and by enzymatic inhibition test. Twenty-seven of the leprosy serum samples (39.1%) were found to react with PDH by ELISA. However, unlike sera from primary biliary cirrhosis (PBC) patients, none of these were able to inhibit the PDH enzymatic activity. By immunoblotting, it was found that only 2 of the 27 positive sera recognized the 74-kD protein of the PDH complex, which is recognized by sera of most PBC patients. The antimitochondrial antibodies in lepra most probably recognize different epitopes than those in PBC. These findings may indicate that anti-PDH autoantibodies in patients with leprosy may arise by polyclonal B cell stimulation and may represent natural anti-PDH autoantibodies.     

Immunoglobulin class and subclass restriction of autoimmune responses in secondary syphilis

The immunoglobulin (Ig) class and IgG subclasses of autoantibodies to commercial VDRL antigen, creatine kinase (CK), and fibronectin (Fn) in the sera of patients with various stages of syphilis were quantified using solid-phase radioimmunoassays (RIA) and ELISA. Sera from patients with active secondary syphilis, initially positive for anti-Fn and anti-CK autoantibodies by RIA, were re-evaluated by ELISA using monoclonal antibodies (MoAb) for detection of human Ig class and subclass responses. Results of these assays revealed that anti-Fn and anti-CK responses were not only IgG in nature, but dramatically skewed to IgG1 and IgG3 subclasses. While the restricted, co-expression of these isotypes seemingly paralleled anti-treponemal activity, inverse relationships actually existed between the subclass responses to Fn and those to Treponema pallidum. In contrast, anti-VDRL were predominantly IgM in 17 of 22 patients. Of those sera exhibiting detectable anti-VDRL IgG activity, responses appeared to be restricted to IgG1. These results suggest that different control mechanisms may be responsible for regulation of the various autoantibody responses expressed during syphilitic infection.     

Antihistones antibodies in systemic lupus erythematosus, comparison of three assays: Elisa, dot blot and immunoblot

AIMS: The purpose of our study is to determine and compare the sensitivity of an enzyme linked immunosorbent assay (ELISA), a dot blot assay and an immunoblot assay for the detection of the IgG class antihistones antibodies in a population of systemic lupus erythematosus. The correlation between antihistones antibodies and the main clinical features of SLE or between antihistones antibodies and the presence of anti-double-stranded-DNA antibodies were analysed. MATERIALS AND METHODS: Serum samples from 126 systemic lupus erythematosus patients, classified according to the criteria of the American College of Rheumatology, were analysed for the presence of antihistones antibodies using a dot blot assay and an ELISA. Antihistones subfractions antibodies were assessed using the immunoblot technique on 88 out of the 126 sera. Serum samples from 50 blood-donors were analyzed as negative controls. RESULTS: The sensitivity of antihistones antibodies assessed by dot blot assay and ELISA was 69% and 54% respectively, and was lower than that of anti-double-stranded-DNA antibodies (83%). The sensitivity of the immunoblot assay for the detection of antihistones antibodies was 72%. Incidence of autoantibodies against histones H1, H2 A, H2B, H3 and H4 was 60%, 53%, 48%, 36% and 29.5% respectively. We found a correlation between the presence of antihistones antibodies, detected by the dot blot assay and ELISA, and the presence of anti-double-stranded-DNA antibodies. Antihistones antibodies detected by ELISA were correlated with renal disease in systemic lupus erythematosus; they showed a specificity, a positive and a negative predictive value for renal disease in systemic lupus erythematosus higher than those of anti-double-stranded-DNA antibodies. CONCLUSIONS: The sensitivity of the dot blot assay for the detection of antihistones antibodies is better than that of ELISA, but the latter technique could detect some cases negative by ELISA. Antihistones antibodies detected by ELISA have an important predictive value in the renal complications in systemic lupus erythematosus, better than that of AdsDNA. Antibodies to histone H1 were the most frequent antihistones autoandibodies in systemic lupus erythematosus and they were highly correlated with anti-double-stranded-DNA antibodies and renal disease.     

Anti-SSB/La is one of the antineutrophil autoantibodies responsible for neutropenia and functional impairment of polymorphonuclear neutrophils in patients with systemic lupus erythematosus

Decreased number and impaired functions of polymorphonuclear neutrophils (PMN) due to the presence of anti-PMN autoantibodies in the serum render patients with systemic lupus erythematosus (SLE) susceptible to bacterial infections. However, the cognate antigens and pathological mechanisms of anti-PMN autoantibodies in SLE are rarely reported in the literature. In this study, we found approximately 20% of SLE sera contained anti-PMN autoantibodies detected by human PMN-coated cellular ELISA. A membrane protein with molecular weight of 50 kDa was identified as the cognate antigen of anti-PMN in Western blot after membrane-biotinylation and streptavidin column elution. The 50 kDa molecule was proved to be SSB/La after immunoscreening, molecular cloning and nucleotide sequencing of the gene from the human leucocyte cDNA library. Human anti-SSB/La autoantibodies purified from active SLE sera passing through the recombinant SSB/La conjugated Sepharose 4B affinity column could bind and penetrate into normal human PMN. Functional analysis revealed that the anti-SSB/La autoantibodies exerted a number of potent effects on human PMN, including suppressed phagocytosis, accelerated apoptosis and enhanced IL-8 production. These in vitro results suggest that anti-SSB/La is one of the anti-PMN autoantibodies capable of penetrating into PMN and responsible for neutropenia and functional impairment of PMN in patients with SLE.     

Autoantibodies directed against the amino-terminal domain I of human calpastatin (ACAST-DI Ab) in connective tissue diseases. High levels of ACAST-DI Ab are associated with vasculitis in lupus

To identify new autoantibody populations in patients with rheumatic diseases, a cDNA expression library was immunoscreened with a rheumatoid arthritis (RA) patient's serum which contains autoantibodies binding to uncharacterized polypeptides by Western-blotting. One clone encoding the amino-terminal region (Nt) [domain L and half of domain I] of human calpastatin was selected. Different fragments of the selected cDNA were prepared and the corresponding recombinant polypeptides were produced by in vitro translation and analysed by Western blotting. Most RA sera bound to recombinant amino-terminal region and domain I but not to domain L. This prompted us to use a recombinant polypeptide corresponding to the domain I of calpastatin as the antigen in a solid-phase ELISA to test sera from patients with various systemic rheumatic diseases and healthy controls.Anti-calpastatin domain I antibodies (ACAST-DI Ab), were detected by ELISA in RA, systemic lupus erythematosus (SLE), Sj?gren's syndrome and control sera at respective frequencies of 10, 9, 0 and 1%. These Ab did not have prognostic value in early RA; high levels were significantly associated with vasculitis in SLE. Antibodies reacting with the calpastatin amino-terminal region are produced during systemic rheumatic diseases and are predominantly directed against domain I. High levels of these Ab may constitute a marker of vasculitis in SLE.     

Antibodies from patients with rheumatoid arthritis and juvenile chronic arthritis analyzed with core histone synthetic peptides

Antihistone antibodies were detected in the sera of a randomly selected group of patients with rheumatoid arthritis (RA) and juvenile chronic arthritis (JCA) by an enzyme-linked immunosorbent assay (ELISA) with the five individual histones and by immunoblotting. In ELISA, the overall frequency of antihistone antibodies in RA and JCA was 51 and 44%, respectively. Antibodies present in these serum samples were further studied by ELISA by means of 17 core histone synthetic peptides. The fragment 1-21 of H3 was recognized by 60% of RA sera and by 62% of JCA sera. In addition, at least four terminal or internal peptides of H3 and H4 were recognized by more than a third of JCA sera, while only two of these peptides reacted with 20% of RA sera. Many of the sera that did not show any reactivity with the whole histone reacted with various histone peptides. This finding demonstrates the usefulness of synthetic peptides for identifying autoantibodies.