The detection of human antibodies against cytoskeletal components

Anti-tubulin-alpha-1c antibody as a marker of value in Behçet syndrome

Background

Behçet’s syndrome (BS) is a multi-systemic vasculitis characterized by recurrent oral ulcers, genital ulcers, ocular lesions, and other systemic manifestations. As there is no laboratory diagnostics of BS, the diagnosis is mainly clinical.

Objective

To investigate the utility of the autoantibody against tubulin-α-1c in diagnosis of BS and its clinical significance.

Methods

Sixty BS patients and sixty healthy controls were enrolled in this study. We assessed all patients by Behçet disease current activity form (BDCAF), routine laboratory investigations, and immunological markers (ANA, anti-DNA, ANCA). Anti-endothelial cell antibodies (AECA) and anti-tubulin-alpha-1c antibodies were performed for all participants.

Results

Regarding duration of illness, Birmingham Vasculitis Activity Score (BVAS), and BDCAF, the mean value was 4.77 ± 4.239, 19.80 ± 10.020, and 9.52 ± 5.476, respectively. On comparing laboratory investigations, there was only significant increase in anti-tubulin-alpha-1c antibody in BS patients compared to healthy controls. Regarding AECA, there was no any significant correlation except with CRP. Anti-tubulin-alpha-1c detected significant direct correlation with the presence of posterior uveitis, panuveitis, and venous thrombosis as well as BVAS, C4, and protein/creatinine ratio. Regarding diagnostic performance of both AECA and anti-tubulin-alpha-1c, the cutoff value of AECA for diagnosis was 27.250, with sensitivity and specificity of 93.3% and 96.7%, respectively. The cutoff value of the anti-tubulin-alpha-1c for diagnosis was 22.300, with sensitivity and specificity of 100% and 96.7% respectively.

Conclusion

Anti-tubulin-α-1c antibodies are of diagnostic value in BS and are indicative of activity with 100% sensitivity and 96.7% specificity.

Key Points • There is lack of specific laboratory, radiological, or histological diagnostics for Behcet syndrome. • We aimed to evaluate the significance of tubulin-α-1c autoantibody in diagnosis of Behcet syndrome. • There is elevation of tubulin-α-1c autoantibody with sensitivity and specificity of 100% and 96.7%, respectively.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10067-021-06025-7.

Anti-tubulin-α-1C autoantibody in systemic lupus erythematosus: a novel indicator of disease activity and vasculitis manifestations

A variety of autoantibodies has been involved in the pathogenesis of systemic lupus erythematosus (SLE), some of which are well known and applied as disease biomarkers. This study aimed to determine the prevalence of a novel autoantibody, anti-tubulin-α-1C, in patients with SLE and investigate its clinical significance. Anti-tubulin-α-1C autoantibody levels were determined by enzyme-linked immunosorbent assay (ELISA) in 128 SLE patients, 38 primary Sjögren's syndrome (pSS) patients, and 106 healthy controls (HCs).White blood cell (WBC) count, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), IgM, IgG, C3, C4, RF, ANA, dsDNA, Sm, AnuA, aCL, anti-SSA, and anti-SSB were measured by standard laboratory techniques. SLE Disease Activity Index (SLEDAI) was evaluated accordingly. Anti-tubulin-α-1C antibody levels were significantly increased in SLE patients. Elevated anti-tubulin-α-1C were correlated with higher levels of SLEDAI, increased titers of anti-Sm antibody, and decreased titers of anti-dsDNA antibody and significantly associated with cutaneous and mucosal vasculitis and milder renal involvement. Anti-tubulin-α-1C may become a novel biomarker indicative of active vasculitis in SLE and could be applied in future clinical practice.

Anti-vimentin Antibodies Present at the Time of Transplantation May Predict Early Development of Interstitial Fibrosis/Tubular Atrophy

BACKGROUND

Anti-vimentin (a cytoskeletal protein) autoantibodies in renal transplant recipients have been correlated with interstitial fibrosis/tubular atrophy (IFTA). In this study, we examine the association between pretransplantation anti-vimentin antibodies and the subsequent development of IFTA.

METHODS

Sera obtained before renal transplantation from 97 transplant recipients were analyzed for the presence of anti-vimentin antibodies via Luminex assays to determine the concentration of anti-vimentin antibodies. Results were correlated with findings of IFTA on biopsy as well as graft function and patient and graft survival.

RESULTS

In our patient population, 56 of 97 patients were diagnosed by biopsy with IFTA 2.9 (±2.1) years after renal transplantation. Patients with IFTA on biopsy had higher mean concentration of anti-vimentin antibodies when compared to patients without IFTA (32.2 μg/mL [3.97-269.12 μg/mL] vs 14.57 μg/mL [4.71-87.81 μg/mL]). The risk of developing IFTA with a concentration of anti-vimentin antibody >15 μg/mL before transplantation was 1.96 (95% CI = 1.38-2.79, P = .011). Patients with elevated anti-vimentin antibody concentrations (>15 μg/mL) at the time of transplantation also had a higher risk of developing IFTA (81.4% vs 41.2%; P < .05). In addition, graft function was worse at 1, 3, and 5 years posttransplantation in patients with elevated concentrations of pretransplantation anti-vimentin antibody. Although there were more graft losses in the IFTA groups (49.12% vs 25.64%, P = .021) and the IFTA patients loss their grafts earlier (4.3 years vs 3.6 years), there was no statistical difference in graft loss rates.

CONCLUSIONS

Pretransplantation anti-vimentin antibody concentrations >15 μg/mL may be a risk factor for IFTA.

Autoantibody signatures defined by serological proteome analysis in sera from patients with cholangiocarcinoma

BACKGROUND

The challenging diagnosis and poor prognosis of cholangiocarcinoma require the determination of biomarkers. Autoantibodies could be used in the clinic as diagnostic markers for the early detection of tumours. By proteomic approaches, several autoantibodies were proposed as potential markers. We tried in this study, to perform a serological proteome analysis, using various antigenic substrates, including tumours and human liver.

METHODS

Sera from patients (n = 13) and healthy donors (n = 10) were probed on immunoblots performed using 2-dimensionally separated proteins from cholangiocarcinoma cell lines (CCLP1 and CCSW1), from the liver of healthy subject and interestingly, from tumour and adjacent non-tumour liver tissues from five patients with cholangiocarcinoma and tested with their corresponding serum. Spots of interest were identified using mass spectrometry and classified according gene ontology analysis.

RESULTS

A comparison of the whole immunoblotting patterns given by cholangiocarcinoma sera against those obtained with normal control sera enabled the definition of 862 spots. Forty-five different proteins were further analysed, corresponding to (1) spots stained with more than four of 13 (30 %) sera tested with the CCLP1 or the CCSW1 cell line and with the normal liver, and (2) to spots immunoreactive with at least two of the five sera probed with their tumour and non-tumour counter-part of cholangiocarcinoma. Immunoreactive proteins with catalytic activity as molecular function were detected at rates of 93 and 64 % in liver from healthy subjects or cholangiocarcinoma non-tumour tissues respectively, compared to 43, 33, 33 % in tumour tissues, or CCSW1 and CCLP1 cell lines. A second pattern was represented by structural proteins with rates of 7 and 7 % in normal liver or non-tumour tissues compared to 14, 33 and 67 % in tumour tissue, CCSW1 or CCLP1 cell lines. Proteins with a binding function were detected at rates of 7 % in non-tumour tissue and 14 % in tumour tissue. Using the extracted tumour tissue, serotransferrin was targeted by all cholangiocarcinoma-related sera.

CONCLUSIONS

Immunological patterns depended on the type of antigen substrate used; i.e. tumour versus non tumour specimens. Nevertheless, a combination of multiple autoantibodies tested with the most appropriate substrate might be more sensitive and specific for the diagnosis of cholangiocarcinoma.

Autoantibodies in liver disease: important clues for the diagnosis, disease activity and prognosis

It has been well established that numerous kinds of autoantibodies have been detected in liver disease. Some kinds of autoantibodies may be helpful in the diagnosis of autoimmune liver diseases including autoimmune hepatitis, primary biliary cirrhosis or primary sclerosing cholangitis. However, these autoantibodies are present even in sera of patients with viral hepatitis, drug-induced hepatitis, alcoholic liver disease, non-alcoholic fatty liver disease and hepatocelluar carcinoma as well as in sera of patients with autoimmune liver diseases. Other kinds of autoantibodies are recognized as predictive hallmarks for disease activity or prognosis in liver diseases. On the other hand, treatment with interferon initiates the production of several types of autoantibodies in patients with chronic hepatitis C virus infection. Some of autoantibodies induced by interferon may postulate the treatment outcome in those patients. Recent studies also revealed the close correlation between oxidative stress and the production of autoantibodies in liver diseases. This article primarily reviews the recent advances of autoantibodies in the liver diseases and discusses the clinical significance of these autoantibodies.

Vimentin in cancer and its potential as a molecular target for cancer therapy

Vimentin, a major constituent of the intermediate filament family of proteins, is ubiquitously expressed in normal mesenchymal cells and is known to maintain cellular integrity and provide resistance against stress. Vimentin is overexpressed in various epithelial cancers, including prostate cancer, gastrointestinal tumors, tumors of the central nervous system, breast cancer, malignant melanoma, and lung cancer. Vimentin's overexpression in cancer correlates well with accelerated tumor growth, invasion, and poor prognosis; however, the role of vimentin in cancer progression remains obscure. In recent years, vimentin has been recognized as a marker for epithelial-mesenchymal transition (EMT). Although EMT is associated with several tumorigenic events, vimentin's role in the underlying events mediating these processes remains unknown. By virtue of its overexpression in cancer and its association with tumor growth and metastasis, vimentin serves as an attractive potential target for cancer therapy; however, more research would be crucial to evaluate its specific role in cancer. Our recent discovery of a vimentin-binding mini-peptide has generated further impetus for vimentin-targeted tumor-specific therapy. Furthermore, research directed toward elucidating the role of vimentin in various signaling pathways would reveal new approaches for the development of therapeutic agents. This review summarizes the expression and functions of vimentin in various types of cancer and suggests some directions toward future cancer therapy utilizing vimentin as a potential molecular target.

F-actin reactive smooth muscle antibody in subjects with normal liver function

AIMS

Smooth muscle antibody (SMA) with F-actin reactivity has been reported as a diagnostic marker of autoimmune hepatitis. We re-visited this relationship by randomly selecting SMA-positive sera to test for reactivity with F-actin by ELISA. We correlated such reactivity with liver function tests.

METHODS

Sera positive for SMA by indirect immunofluorescence were tested for reactivity by F-actin ELISA and the results correlated with liver function tests.

RESULTS

89 SMA-positive sera reacted with F-actin by ELISA. Of these, 35 (39%) had normal liver enzymes, while 54 (60%) had elevated liver enzymes. There was no difference between the groups with respect to age at presentation, female preponderance or presence of anti-nuclear antibody. In both groups, high titre SMA antibody predominantly with immunofluorescence staining of renal glomeruli and peritubular fibrils of renal tubules ('G/T' subset) correlated with makedly elevated F-actin values by ELISA. 'Actin cables' by immunofluorescence staining of Hep-2 cells were infrequently found in both groups.

CONCLUSIONS

This is the first report of SMA with F-actin reactivity in subjects with normal liver function.

Identification of tumor antigens that elicit a humoral immune response in breast cancer patients' sera by serological proteome analysis (SERPA)

BACKGROUND

In this study we applied a serological proteomics-based approach (SERPA) to identify tumor antigens that commonly induce a humoral immune response in patients with infiltrating ductal breast carcinomas.

METHODS

Sera obtained at the time of diagnosis from 40 patients with invasive breast cancer and 42 healthy controls were screened individually for the presence of IgG antibodies to MCF-7 cell line proteins. Immunoreactive proteins were isolated and subsequently identified by MALDI-TOF mass spectrometry.

RESULTS

We identified 26 proteins that reacted with antibodies in the sera from breast cancer patients. Among these antigens, a significantly higher frequency occurs against the molecular chaperone HSP60, the tumor suppressor prohibitin, beta-tubulin, the haptoglobin-related protein and peroxiredoxin-2. Immunoreactivity to hnRNPK, Mn-SOD and F1-ATPase was also clearly detected in the patients group, whereas scarcely in control sera. By contrast, two other antigens identified as cytokeratins 8 and 18, as well as, F1-actin were found to elicit humoral immune responses in both control and breast cancer patients' sera.

CONCLUSIONS

The immunoproteomic approach implemented here offers a powerful tool for determining novel tumor antigens that elicit a humoral immune response in patients with invasive breast cancer. These antigens and/or their related circulating antibodies may display clinical usefulness as potential diagnostic markers and provide a means for a better understanding of the molecular mechanisms underlying breast cancer development.

Cell surface expression of intermediate filament proteins vimentin and lamin B1 in human neutrophil spontaneous apoptosis

Neutrophils represent an important source of autoantigens for antineutrophil cytoplasmic antibody associated with vasculitis. To date, two cytoskeletal proteins, vinculin and vimentin, have been reported to be expressed on the cell surfaces of activated macrophages, platelets, and apoptotic T lymphocytes. However, such cell surface expression has never been studied in human neutrophils. As we recently demonstrated that different cytoskeletal proteins were cleaved in apoptotic neutrophils, we hypothesized that some of these were expressed on the cell surface of apoptotic neutrophils. Herein, we found that among vinculin, paxillin, gelsolin, vimentin, lamin B1, alpha-tubulin, and beta-tubulin, only the two intermediate filament (INFIL) proteins, vimentin and lamin B1, are expressed on the cell surface of 24-h aged neutrophils [spontaneous apoptosis (SA)]. By monitoring intracellular expression of vimentin and lamin B1 during SA, we found that these two proteins were cleaved and that such cleavage was reversed by the pan caspase inhibitor N-benzyloxy-carbonyl-V-A-D-O-methylfluoromethyl ketone (z-VAD-fmk). When neutrophil apoptosis was delayed or suppressed by lipopolysaccharide or the cytokines granulocyte-colony stimulating factor (G-CSF), granulocyte macrophage (GM)-CSF, or interleukin-4, the loss of intracellular expression of vimentin and lamin B1 was prevented. The INFIL proteins were absent from the cell surface when neutrophil apoptosis was delayed. Addition of z-VAD-fmk significantly decreased the cell surface expression of vimentin and lamin B1 during SA. This study provides the first evidence that apoptotic neutrophils express cytoskeletal proteins on their surface, opening the possibility that these cells may participate in the development of autoantibodies directed against cytoskeletal proteins, a condition frequently reported in several inflammatory diseases.

Anti-smooth muscle antibodies (ASMAs) and anti-cytoskeleton antibodies (ACTAs) in liver diseases: a comparison of classical indirect immunofluorescence with ELISA

In the diagnosis of autoimmune hepatitis type I (AIH-I), the routine assay of indirect immunofluorescence (IFL), used for the detection of anti-smooth muscle antibodies (ASMAs), has a low predictive value. On the other hand, the enzyme-linked immunosorbent assay (ELISA), which detects anti-cytoskeleton antibodies (ACTAs), presents contradictory results concerning their specific antigenic target. In this study, we first looked for the immunological properties (isotypes and antigenic targets) of autoantibodies in AIH-I and two other control liver diseases: primary biliary cirrhosis (PBC) and viral hepatitis (VH), using ELISA based on cytoskeleton proteins: F-actin, G-actin, myosin, tropomyosin, troponin, desmin, vimentin, keratin, and an extract of HEp-2 carcinoma cells. We also compared the diagnostic value of IFL and ELISA. In contrast to previous studies, we found that actin was not specific for AIH-I. No autoantigen and no antibody class or subclass discriminated AIH-I from the control diseases. IFL is more suitable for AIH-I diagnosis, as 97% of AIH-I sera but only 22% of PBC sera were ASMA-positive. Additionally, 96% of ASMA-positive, and all ASMA-negative sera from all three liver diseases were ACTA-positive. ASMA were mainly IgG, while >50% of ACTA also contained IgA and IgM. These data suggest that ACTAs recognize additional epitopes as compared to ASMAs, and they frequently occur in all liver diseases.

ANTIVIMENTIN ANTIBODIES ARE AN INDEPENDENT PREDICTOR OF TRANSPLANT-ASSOCIATED CORONARY ARTERY DISEASE AFTER CARDIAC TRANSPLANTATION1

BACKGROUND

Transplant-associated coronary artery disease (TxCAD) is the most serious long-term complication after cardiac transplantation. Anti-endothelial antibodies are associated with disease, and one of the major endothelial antigens recognized in the sera of patients has been shown to be the protein filament vimentin. In this study, we investigated whether antivimentin antibodies are associated with TxCAD and whether their presence can be used to identify patients at high risk of developing angiographically detectable TxCAD.

METHODS

Up to 5 years after transplantation, 880 sequential sera (7.07+/-1.8 samples/patient) were collected retrospectively from 109 patients; the majority were collected in the first 2 years. Sera were assessed for antivimentin antibodies using ELISA. TxCAD was assessed by annual angiography.

RESULTS

Mean titres of antivimentin antibodies, calculated up to 1, 2, and 5 years, were significantly higher in patients who developed TxCAD than those who remained disease free (P<0.0001, P<0.0038, and P<0.0001, respectively). A predictive test based on the first-year mean vimentin titre alone (> or = 120) produced a test with 63% sensitivity and 76% specificity. Inclusion of persistent rejection or high 1-year mean titre (> or = 270) as a risk factor produced a test with 66% sensitivity and 82% specificity. Multivariate analysis of time to occurrence of transplant vasculopathy showed that mean titre at 1 or 2 years was an independent predictor of time until disease in the presence of all other variables.

CONCLUSIONS

Antivimentin antibodies are an independent predictor of TxCAD and can be used to identify some of the patients who are at high risk of developing this complication.

Detection of anti-cytokeratin 8 antibody in the serum of patients with cryptogenic fibrosing alveolitis and pulmonary fibrosis associated with collagen vascular disorders

BACKGROUND

It has been suggested that the humoral immune system plays a role in the pathogenesis of cryptogenic fibrosing alveolitis (CFA). Although circulating autoantibodies to lung protein(s) have been suggested, none of the lung proteins have been characterised. The purpose of this study was to determine the antigen to which the serum from patients with pulmonary fibrosis reacted.

METHODS

The anti-A549 cell antibody was characterised in a patient with CFA using Western immunoblotting and immunohistochemical staining of A549 cells. As we identified that one of the antibodies against A549 cells was anti-cytokeratin 8, the expression of mRNA of cytokeratin 8 in A549 cells was evaluated. In addition, we attempted to establish an enzyme linked immunosorbent assay to measure the levels of anti-cytokeratin 8 antibody in the serum of patients with CFA and pulmonary fibrosis associated with collagen vascular disorders (PF-CVD).

RESULTS

Initially two anti-A549 cell antibodies were detected in the serum of patients with pulmonary fibrosis, one of which was characterised as anticytokeratin 8 antibody by Western immunoblotting. We were able to establish an ELISA to measure anti-cytokeratin 8 antibody and found significantly higher levels in patients with CFA and PF-CVD than in normal volunteers, patients with sarcoidosis, pneumonia, and pulmonary emphysema.

CONCLUSIONS

One of the anti-A549 cell antibodies in the serum of patients with CFA was against cytokeratin 8. The serum levels of anti-cytokeratin 8 antibody were increased in patients with CFA and PF-CVD. These results suggest that anticytokeratin 8 antibody may be involved in the process of lung injury in pulmonary fibrosis.

Molecular cloning and expression of 56-58 KD antigen associated with transplant coronary artery disease

High circulating levels of anti-endothelial antibodies have been reported in patients with accelerated transplant coronary artery disease (TxCAD); however, the nature or characteristics of the antigen to which these antibodies bind in vivo remain unclear. To identify the antigen, a human endothelial cell cDNA expression library was constructed in lambdaZAP and immuno-screened with serum containing a high titre of anti-endothelial antibodies. Nucleotide sequence of cloned cDNA inserts and GenBank database searches revealed a 94% identity in a 35 bp overlap to the human vimentin gene. The cloned antigen fusion protein co-migrated with human vimentin of molecular mass 56-58 KD in SDS-PAGE and exhibited immunoreactivity towards monoclonal and polyclonal anti-human vimentin antibodies. These results suggest that the 56-58 KD antigen associated with accelerated TxCAD is vimentin (or a vimentin-like protein), a cytoskeletal protein present in cells of the blood vessel walls.

Actin is a target antigen of anti-neutrophil cytoplasmic antibodies (ANCA) in autoimmune hepatitis type-1

BACKGROUND/AIM

Anti-neutrophil cytoplasmic antibodies (ANCA) are a group of autoantibodies first associated with Wegener's granulomatosis and microscopic polyangiitis. The significance of ANCA in autoimmune hepatitis remains uncertain; the nature of the antigen or antigens has not been defined yet. The purpose of this study was to identify the target antigen of ANCA in patients with autoimmune hepatitis.

METHODS/RESULTS

Sera from 32 type-1 autoimmune hepatitis patients were used in the present study. ANCA were detected in 24 of 32 sera (75%). A diffuse cytoplasmic staining pattern (C-ANCA) was detected in 14 patients; the P-ANCA pattern was observed in 10 patients. An extract of human neutrophils was prepared and subjected to SDS-PAGE and Western Blot analysis. A 43-kD dominant immunoreactive protein was found in 20 (63%) autoimmune hepatitis patients. Aminoacid sequence analysis of the 43 kD protein identified actin. Cytoplasmic or perinuclear staining pattern could be reduced after absorption of sera with actin and after removing anti-actin antibodies by affinity chromatography. This was observed for all C-ANCA and for 8 out of 10 P-ANCA. Moreover in double-staining indirect immunofluorescence, the same type of diffuse cytoplasmic staining was observed with autoimmune hepatitis-sera and anti-actin antibodies. In Western Blot analysis with actin, 17 (53%) patients gave a positive result, while 15 (47%) patients had a positive actin-ELISA.

CONCLUSION

This is the first report to identify the cytoskeletal protein actin as an ANCA antigen.

Enhancement in antigen binding by a combination of synergy and antibody capture

The effects of orientating pairs of synergistic monoclonal antibodies (mAb) on binding of human chorionic gonadotropin (hCG) was studied by radioimmunoassay (RIA), enzyme-linked immunosorbent assay (ELISA) and surface plasmon resonance (SPR). Antibody synergy towards hCG required two functionally intact antibodies located adjacent to each other and with different epitope specificities. We investigated whether immobilization procedures avoiding protein denaturation, increasing proper orientation and promoting higher molecular flexibility of the synergistic mAb resulted in significantly enhanced antigen, binding. Synergistic mAb pairs captured through their Fc-region by protein G or a polyclonal serum against the Fc-part of mouse IgG could be used at 10-fold lower coating concentrations to achieve maximal binding of the analyte as compared with the same mAb pairs coated directly onto polystyrene. The synergistic effect observed with protein A used as capture varied greatly with the subclasses of the two synergistic antibodies employed. Scatchard analysis revealed that the number of functionally synergistic antibody sites participating in the binding of hCG for one mAb pair was about 10 times higher for the protein G-captured as compared with the directly coated synergistic pair. Biotinylated synergistic mAb pairs, coated directly or captured by streptavidin, did not display any enhanced antigen binding when tested in SPR or ELISA. With SPR, synergy was only observed when the synergistic mAb had been captured through their Fc-region. Using protein G or a polyclonal rabbit anti-IgG1 serum as capture reagents in SPR, synergistic triple mAb combinations against hCG were demonstrated.

Autoantibodies against H- and M-subunits of neurofilaments are induced by PC12 cell grafts or lesions into different sites of rat brain

Since autoantibodies against neurofilaments (NF) were frequently found in neurodegenerative disorders, this work is an attempt to investigate whether the same phenomenon occurs after intracerebral grafting or lesioning. We have thus either grafted PC12 cells or injected culture medium alone into three sites of rat central nervous system (CNS): olfactory bulb (OB), olfactory anterior nucleus (OAN) and hippocampus (HC), all three sites being impaired in Alzheimer's disease. At day 15, rat sera were collected and tested against NF by western blotting. Sera from grafted rats recognized the H- and M-subunits of NF; we have then quantified the autoantibody response by using an ELISA technique. We show that, in all cases of grafts, the autoantibody response against NF significantly increased when compared to controls (normal rats without grafts or lesions) for total immunoglobulin (Ig) amount. In contrast, concerning the Ig isotypes, some differences appeared depending on the implantation site: for grafts into OB, the immune response was of both the IgG and IgM isotypes, into OAN it was mainly of the IgM isotype and into HC, the isotype of antibodies against NF was mostly IgG. In the case of lesions alone into OAN and HC, no significant enhancement of autoantibody response was observed; in contrast, lesions into OB induced an increase in autoantibody response against NF which significantly differed from controls for all Ig isotypes tested. These data point out the diversity of the autoantibody responses following lesions or grafts according to the rat brain areas.

A confocal microscopy study of anticytoskeletal antibody activity in patients with connective tissue disease

The significance of the presence of antibodies to cytoskeleton proteins in patients with connective tissue diseases is not clear, as there is a high level of these antibodies in healthy controls. In an attempt to improve the visualization of the immunofluorescence binding pattern of autoantibodies to cytoskeletal structures in cultured fibroblasts, we have used confocal microscopy. Of the 256 serum samples tested, 155 (61%) WERE reactive with cytoplasmic structures. These reactive samples could be divided into seven patterns of binding, as determined by double-blind examination of single-section confocal images. While confirming the results of previous immunofluorescence studies which have shown that autoantibodies that bind to filamentous structures in the cytoplasm of cultured cells are common in patients with connective tissue diseases, we were able to identify three patterns of cytoskeletal binding which may be useful as an adjunct to other tests for the diagnosis of some connective tissue diseases, in particular systemic sclerosis (scleroderma) and rheumatoid arthritis/Sjogren's syndrome. None of the seven patterns was exclusive to a particular disease. We conclude that confocal microscopy may be of limited use as an adjunct to other serological assays in the diagnosis of some forms of connective tissue disease.

Autoantibodies against vimentin in a murine model of myocarditis

The presence of autoantibodies in the sera of patients with myocarditis has suggested that autoimmunity is a sequela of myocarditis. In this study, we examined anti-vimentin antibodies in a murine model of myocarditis. Four-week-old male DBA/2 mice were inoculated intraperitoneally with 10 plaque-forming units of encephalomyocarditis (EMC) virus. The surviving mice were killed on Days 0 (n = 7), 2 (n = 6), 5 (n = 6), 7 (n = 6), 9 (n = 6), 14 (n = 5), 60 (n = 6) and 540 (n = 3) after virus inoculation. The presence of anti-vimentin autoantibodies in the sera of mice was determined by ELISA. The optical density (OD) of anti-vimentin IgG and IgM autoantibodies of day 0 mice was 0.03 +/- 0.03 and 0.12 +/- 0.08, respectively, when positive antibody was defined as over the mean value plus 2-standard deviations of the sera of day 0 mice, anti-vimentin IgG antibodies were negative before day 5 but positive in all mice on day 9. Both IgG and IgM OD of the sera from day 9 mice (IgG; 0.26 +/- 0.12, IgM; 0.30 +/- 0.08) were significantly higher than those of the sera from day 0 mice (p < 0.005) and decreased thereafter on day 14. In the chronic stage, five of six mice were positive on day 60 and two of three mice were positive on day 540. Although further studies are needed to elucidate the pathogenetic role of anti-vimentin antibodies, these antibodies may be a parameter of the interstitial injury.

Anti-neutrophil antibodies in chronic hepatitis and the effect of alpha-interferon therapy

In 34 patients with non-A non-B, 28 with type B and 11 with autoimmune chronic hepatitis, anti-neutrophil antibodies were investigated using indirect immunofluorescence and anti-myeloperoxidase antibodies by enzyme-linked immunosorbent assay. Granulocyte-specific antinuclear antibodies, were detected in 14 patients with advanced stages of non-A, non-B hepatitis (41%). Their presence correlated with histological features of disease activity but not with response to interferon therapy. Within 24 h after the first dose of interferon, 9 of these became negative and 3 more became negative after 1, 3 and 5 months. Myeloperoxidase-positive perinuclear neutrophil cytoplasmic antibodies were detected in a single patient and increased reaching a peak level after 8 weeks of interferon, decreasing thereafter. In type B, all were negative before and during the 6 months of therapy. In 6 patients with autoimmune hepatitis (55%), myeloperoxidase-negative perinuclear neutrophil cytoplasmic antibodies were detected in high titers. The association of granulocyte-specific anti-nuclear antibodies with non-A, non-B hepatitis support the hypothesis that hepatitis C virus infection might trigger humoral autoimmune response. In chronic autoimmune hepatitis, perinuclear neutrophil cytoplasmic antibodies appear as another marker of autoimmunity.

Antiperinuclear factor, a marker autoantibody for rheumatoid arthritis: colocalisation of the perinuclear factor and profilaggrin

The antiperinuclear factor, an autoantibody specific for rheumatoid arthritis, was found in 51/63 (81%) patients with rheumatoid arthritis by indirect immunofluorescence on human buccal mucosa cells. The sensitivity of the antiperinuclear factor test was increased by pretreating the buccal mucosa cells with 0.5% Triton-X100. The specificity of the test for rheumatoid arthritis as compared with control serum samples was maintained. The localisation of the perinuclear factor in the keratohyalin granules of the buccal mucosa cells was verified by immunoelectron microscopy. The perinuclear factor was found to be an insoluble protein whose antigenicity was sensitive to various fixation procedures. In serum samples from patients with rheumatoid arthritis there was a positive correlation between the presence of antiperinuclear factor and the presence of the so called antikeratin antibodies as detected by immunofluorescence on unfixed rat oesophagus cryostat sections. No relation was found between the presence of the perinuclear factor and either the rheumatoid factor, Epstein-Barr virus components, or any cytokeratin. By double immunofluorescence an exact colocalisation of the perinuclear factor and profilaggrin was found. Although the precise biochemical identity of the perinuclear factor remains unclear, our results suggest that it is a protein only present in the fully differentiated squamous epithelial cell layer.

Production of antikeratin autoantibodies by hybrid spleen cells of naive mice

The mechanism of the occurrence of natural antikeratin antibodies in human sera was studied using hybrid spleen cells obtained from experimentally naive or from immunized mice. Antikeratin antibodies were detected by enzyme-linked immunosorbent assay (ELISA) in 5.9-9.5% of the culture supernatants of fused spleen cells taken from naive mice. When mice were immunized with keratins, the number of supernatants containing antikeratin antibodies was increased to eight out of 51 (15.7%). When immunized with non-keratin materials such as activated human T cells, adult T-cell leukaemia cell lysates, and human T-cell lymphotropic virus type-I (HTLV-I), 16.7-20.8% of the supernatants were found to contain antikeratin antibodies by ELISA. The antikeratin antibodies in the supernatants showed cytoplasmic staining of keratinocytes in human as well as mouse skin by indirect immunofluorescence. The antibodies reacted with extracted human epidermal keratins by dot-blot and Western blot analysis. Most antikeratin antibodies in the supernatants did not show cross-reactivity with exogenous antigens used for immunization and vimentin-type intermediate-sized filaments. These findings demonstrate that B cells producing antikeratin antibodies are common in naive mice, and produce various types of antikeratin antibodies following specific activation with epidermal keratins and non-specific immunological stimuli.

Pancreatic cytokeratin: an antigen of pancreatic exocrine cell autoantibodies in type 1 (insulin-dependent) diabetes mellitus

Autoantibodies reacting with human pancreatic exocrine cells were investigated by immunofluorescent techniques in 107 patients with Type 1 (insulin-dependent) diabetes mellitus, 20 first-degree relatives of the Type 1 diabetic patients, 347 patients with Type 2 (non-insulin-dependent) diabetes, 34 with alcoholic pancreatitis, 26 with rheumatoid arthritis and 107 normal control subjects. Both immunoblotting analysis and double-immunostaining methods were used to characterize the antigens targeted by the pancreatic exocrine cell autoantibodies. Sera positive for human pancreatic exocrine cell cytoplasm, producing a "fine fibrillar" pattern, were found in 21% (23/107) of the Type 1 diabetic patients. The autoantibodies were present in 39% (15/38) of Type 1 diabetic patients diagnosed within 3 months, and the prevalence decreased with duration of diabetes. The antibodies were of the IgM class in 87% (13/15) of recent-onset Type 1 diabetes cases, but IgG-autoantibodies became more prevalent with increasing duration of diabetes. Three out of 347 (0.9%) Type 2 diabetic patients and 4 of 20 (20%) first-degree relatives of Type 1 diabetic patients had autoantibodies targeted against pancreatic exocrine cells. None of the patients with alcoholic pancreatitis or rheumatoid arthritis and none of the control subjects had these antibodies. Immunoblotting analysis and double-immunostaining demonstrated that the autoantibodies reacted with 40 kilodalton cytokeratin in pancreatic exocrine cell cytoplasm. The antibody was absorbed by the Triton X-100-insoluble fraction of pancreatic extract. These results indicate the presence of distinct autoantibodies to pancreatic exocrine cells in Type 1 diabetes. This suggests the provocative concept that the cytoskeletal system of pancreatic exocrine cells is involved in the pathogenetic process of Type 1 diabetes.

Desmin antibodies in acute infectious myopericarditis

The role of autoantibodies against cardiac tissue in the pathogenesis of acute myopericarditis is poorly understood--partly because the specificity of the antibodies is unknown. We assayed antibodies against desmin, a cytoskeletal muscle protein, in 18 patients with acute infectious myopericarditis (AIM), in 24 patients with acute uncomplicated infections, in ten patients with acute myocardial infarction, and in 68 blood donors by an immunoenzymatic assay using purified desmin from Purkinje fibers of cow heart. In addition, anti-heart antibodies were assayed by indirect immunofluorescence. Anti-heart antibodies were detected in all groups by indirect immunofluorescence. On the other hand, anti-desmin antibody levels exceeding the mean + 2 SD of the blood donors could demonstrated in seven (39%) AIM patients but in only one patient in the other groups. The analysis of serial samples indicated that the antibody level was highest in the acute phase of AIM and declined during the recovery.

Specificity of human anti-neurofilament autoantibodies

The specificities and isotypes of human antibodies that react with neurofilament (NF) proteins were examined by Western blot analysis. Two-thirds of the subjects tested had antibodies to the 200 kDa high molecular weight neurofilament protein (NF-H), and fewer had antibodies to the low and middle molecular weight neurofilament proteins (NF-L and NF-M respectively). Human autoantibodies bound to both native and dephosphorylated NF-H, but some antibodies bound to dephosphorylated NF-H only, indicating the presence of at least two target epitopes. They also recognized a fusion protein containing a segment of the NF-H protein produced by a cDNA clone in Escherichia coli, indicating that they bind to unmodified peptide epitopes. The anti-NF-H antibodies were mostly IgG, but were frequently complexed to IgA or IgM antibodies, possibly with rheumatoid factor or anti-idiotypic activity. These characteristics of anti-NF-H antibodies are most consistent with a secondary immune response that is antigen driven and T-cell dependent.

Anti-neural antibodies in leprosy sera: further characterization of the antigens

Sera or plasmas from 129 leprosy patients were tested by immunoblotting for antibodies that bound to proteins in a Triton-insoluble fraction enriched in neural intermediate filaments (IF fraction) from human or bovine spinal cord. Sixty samples (47%) showed positive staining of proteins at 35 kDa, 42 kDa or both. The presence of these antibodies appeared to be evenly distributed across the spectrum of disease. The frequency of these antibodies in samples from 12 healthy Ethiopians was similar to that in the leprosy group. Similar antibodies were found in only three of 28 samples from U.S. patients with neurologic diseases and in seven of 35 normal U.S. sera. Sera from U.S. tuberculosis patients stained multiple bands in the 50-30 kDa region of the blots; 11 of 16 stained bands corresponding to the 35 kDa or 42 kDa bands along with a number of other bands in this region. The 35 kDa and 42 kDa antigens do not appear to be breakdown products of neural filaments or glial fibrillary acidic protein, since antibodies to these proteins do not react with the 35 kDa or 42 kDa antigen. Further, the staining pattern with the leprosy sera is unchanged following Ca2+-mediated proteolysis of the IF-enriched fraction. The two antigens differ from one another in isoelectric point: the pI of the 35 kDa antigen is 5.9, and the pI of the 42 kDa antigen is 4.8. Staining of the immunoblots with antibodies against a number of known neural antigens failed to identify the 35 kDa and 42 kDa antigens. The 42 kDa antigen appears to be a component of axolemma, since 42 kDa-positive leprosy sera stained a protein with identical migration in preparations of bovine peripheral nervous system and human central nervous system axolemma. In some sera, antibodies reacting with the 35 kDa antigen were adsorbed by D-O bovine serum albumin, a synthetic analogue of the terminal disaccharide portion of the phenolic glycolipid 1 of Mycobacterium leprae. Antibodies to the 42 kDa antigen were not removed by this treatment.

Quantitation of autoantibodies to cytokeratins in sera from patients with squamous cell carcinoma of the oesophagus

Sera drawn from healthy individuals, patients with squamous cell carcinoma (SCC) of the oesophagus and patients with mild active oesophagitis were examined for autoantibodies to cytoskeletal proteins extracted from the normal oesophageal keratinocyte or from 2 carcinoma cell lines, each of the latter have a simple cytoskeleton. Using a radioimmunoassay with normal oesophageal cytokeratins as bound antigen, 86 normal, 76 SCC and 14 oesophagitis sera were compared. No significant difference in autoantibody titre was found. When the bound antigen was changed to one containing predominantly simple epithelial cytokeratins a significant increase (32% P less than 0.001) was noted in the SCC category only. Western blots using simple epithelial cell extracts as antigen revealed autoantibodies to cytokeratins 8, 18 and 19 as well as to one other unidentified protein in most SCC sera, and in some normal sera. Antibodies to cytokeratin 18 predominated. Normal and SCC sera were applied using indirect immunofluorescent techniques to normal oesophageal keratinocytes, SNO oesophageal SCC cells and HeLa cells grown in vitro. Autoantibodies to oesophageal cytokeratins were, with few exceptions, barely detectable. Strong reactions were noted against SNO and HeLa cytoskeletal components, but also against nuclear membrane and nucleolar determinants. These experiments suggest that raised levels of autoantibodies to certain cytoskeletal and nuclear determinants may be a feature of oesophageal cancer.

Evaluation of an enzyme-linked immunosorbent assay to actin in cultured fibroblasts

The amount of actin in cultured human skin fibroblasts was determined by an enzyme-linked immunosorbent assay. Absorbance values (OD), resulting from specific binding of an antiactin monoclonal antibody to intracellular actin, were converted to cell concentrations (pg/cell) from an actin standard curve. Actin concentration for cultured human skin fibroblasts by this technique was estimated to be 55.5 picograms/cell and constituted approximately 3.9% of the total cellular protein. This assay procedure offers the following advantages: (1) It is time efficient, can be completed in 2-3 hours; (2) cells are unaltered except for membrane permeabilization; (3) the sensitivity is equal to or greater than previous procedures involving gel electrophoresis; and (4) the assay is easy and inexpensive to perform.

Immunoprecipitation of human adrenal microsomal antigen

Human adrenal microsomes have been labelled with 125I and immunoprecipitated with sera from patients with Addison's disease. The immunoprecipitates were then analysed by SDS-PAGE and autoradiography. 13 of the 23 sera from the Addison patients studied contained antibodies which reacted with a 55 kDa adrenal microsomal protein. The same 13 sera were also positive for adrenal antibodies as judged by immunofluorescence. The 55 kDa protein was not immunoprecipitated from placenta or thyroid microsomes by Addison sera. Furthermore, patients with Graves' disease or rheumatoid arthritis did not immunoprecipitate the 55 kDa protein from adrenal microsomes. Our studies suggest therefore that Addison sera contain antibodies to a 55 kDa adrenal specific protein which may well be the antigen observed on immunofluorescence.

Expression of cytoskeleton components in various Epstein-Barr virus infected cell lines

It has been shown that viruses can induce alterations in the content and distribution of cytoskeleton structures, particularly actin microfilaments and microtubules. An immunomorphologic study of the cytoskeleton components of various EBV-infected cell lines with expression of different functions of EBV genome has been performed using antibodies to each of its three major components. Intermediate filaments and microtubules were similarly represented in all examined lymphoblastoid cell lines. The distribution of actin microfilaments, on the contrary, differed significantly from cell line to cell line. It is concluded that the morphologic expression of actin might depend on the expression of EBV genome. Furthermore, some of these cell lines might represent a useful substrate for the identification of anticytoskeleton antibodies, mainly anti-actin antibodies, in human sera.

Autoantibodies in infectious mononucleosis have specificity for the glycine-alanine repeating region of the Epstein-Barr virus nuclear antigen

Viruses have been postulated to be involved in the induction of autoantibodies by: autoimmunization with tissue proteins released by virally induced tissue damage; immunization with virally encoded antigens bearing molecular similarities to normal tissue proteins; or nonspecific (polyclonal) B cell stimulation by the infection. Infectious mononucleosis (IM) is an experiment of nature that provides the opportunity for examining these possibilities. We show here that IgM antibodies produced in this disease react with at least nine normal tissue proteins, in addition to the virally encoded Epstein-Barr nuclear antigen (EBNA-1). The antibodies are generated to configurations in the glycine-alanine repeat region of EBNA-1 and are crossreactive with the normal tissue proteins through similar configurations, as demonstrated by the effectiveness of a synthetic glycine-alanine peptide in inhibiting the reactions. The antibodies are absent in preillness sera and gradually disappear over a period of months after illness, being replaced by IgG anti-EBNA-1 antibodies that do not crossreact with the normal tissue proteins but that are still inhibited by the glycine-alanine peptide. These findings are most easily explained by either a molecular mimicry model of IgM autoantibody production or by the polyclonal activation of a germline gene for a crossreactive antibody. It also indicates a selection of highly specific, non-crossreactive anti-EBNA-1 antibodies during IgM to IgG isotype switching.

Microtubules and intermediate filaments of herpes simplex virus infected cells

The fate of microtubules and of vimentin or keratin containing intermediate filaments during infection with fusion or rounding producing strains of herpes simplex virus (HSV) was investigated. Microtubules polymerize early after fusion of cells. However, they do not reconstitute 6-7 hours post infection (p.i.) after release of a colcemid block. Keratin and vimentin are maintained around the original nucleus still inside of recruited cells in the polykaryocyte. Cells of fibroblastic and epithelial origin fuse. Inside of polykaryocytes keratin or vimentin containing fibers seem to polymerize. Keratin is to be found in invaginations in the nuclei surrounded by the inner layer of the nuclear membrane. Anti-keratin antibodies specifically label HSV envelopes located in the cytoplasm or outside of the cell. Controls of the procedure allowed to exclude labelling of HSV envelopes via gpE, which represents HSV induced Fc receptors. Late stages of infected cells contain thickened and condensed keratin fibers. Conversely, vimentin fibers late after infection appear to be evenly distributed and to be thin. Microtubules decay late after infection with rounding producing strains of HSV, whereas keratin and vimentin fibers are still present late after infection.

Phagocytosis of keratin filament aggregates following opsonization with IgG-anti-keratin filament autoantibodies

IgG-anti-keratin intermediate filament autoantibodies occur in low titers in all normal human sera. These same antibodies are present in high titers in the sera of patients who have diseases in which cells containing keratin intermediate filaments (KIF) have been damaged, such as systemic lupus erythematosus, graft-versus-host disease, and cutaneous tumors. Since some human autoantibodies are thought to function in part as opsonins promoting the removal of insoluble cellular proteins after tissue injury, we investigated the influence of IgG-anti-KIF autoantibodies on the phagocytosis of insoluble KIF aggregates by human monocytes and polymorphonuclear neutrophils (PMN). Keratin intermediate filaments assembled in vitro were reconstituted into dense spherical KIF aggregates 0.3-2.5 microns in diameter by dialysis against phosphate-buffered saline. Immunoelectron microscopy revealed that, as expected, human IgG-anti-KIF autoantibodies bound to the KIF aggregates. Human monocytes or PMN were incubated either with nonopsonized KIF aggregates or with KIF aggregates that had been reacted with IgG-anti-KIF autoantibodies. The uptake of KIF aggregates was visualized by indirect immunofluorescence, immunoperoxidase staining, and immunoelectron microscopy. Monocytes rapidly and efficiently bound and phagocytosed KIF aggregates that had been coated with IgG-anti-KIF autoantibodies. Nonopsonized KIF aggregates, in contrast, were taken up much less efficiently. Differences were most marked at 4 degrees C for 60 min with phagocytosis of opsonized KIF aggregates by 23 +/- 8% of monocytes in contrast to phagocytosis by only 0.2 +/- 3% monocytes when nonopsonized KIF aggregates were used. Similar results occurred at 37 degrees C for 5 min with phagocytosis by 38 +/- 28% vs 1.8 +/- 0.4% of monocytes of opsonized and nonopsonized KIF aggregates, respectively. A high percentage of PMN also phagocytosed opsonized KIF aggregates, whereas nonopsonized KIF aggregates were ingested less avidly. These data indicate that the opsonization of extracellular KIF aggregates by IgG-anti-KIF autoantibodies plays an important role in promoting the phagocytosis of KIF aggregates. The subsequent phagocytosis represents a rapid and very effective mechanism for the removal of insoluble KIF following keratinocyte cell death.

Antibodies to neurofilament protein in retinitis pigmentosa

Antibodies reactive with heterologous neural tissue were detected by indirect immunofluorescence microscopy in the sera of 17 of 34 patients with retinitis pigmentosa, one of 30 normal control sera, and a variable percentage of sera derived from subjects with diverse ocular and neurological diseases. These antibodies were also found both in disease-free first degree relatives and in spouses of patients with retinitis pigmentosa. Analytical sodium dodecyl sulfate-polyacrylamide gel electrophoresis of human spinal cord components followed by immunoblots with sera under study revealed that the serum antibody was specific for the high molecular weight protein subunit of neurofilaments. No correlation was found between the presence of these antibodies and other immunological and clinical parameters in retinitis pigmentosa. These findings suggest that release of piled-up neurofilaments from damaged neurones in retinitis pigmentosa triggers B lymphocytes autoreactive to neurofilament antigens.

Epstein-Barr virus-transformed lymphocytes from patients with bullous diseases produce autoantibodies to cytokeratins

Human cell lines obtained after Epstein-Barr virus transformation of lymphocytes from seven patients with bullous diseases (Bullous pemphigoid, Pemphigus) and five controls were screened for the production of autoantibodies against skin antigens. In five out of seven patients, the culture supernatants tested by indirect immunofluorescence on frozen sections of normal human skin and rabbit lip showed the production of autoantibodies with different specificities: basal epidermal cells, whole epidermis, Merkel cells, fibroblasts endothelial cells, etc. All autoantibodies were of IgM class and reacted with intracellular structures. Some of them were further tested by immunoblotting against epidermal keratins and were found to react with the main human epidermal keratins (56 to 67 kDa). In contrast, even when patients had circulating autoantibodies, no supernatant showed any reactivity against the antigens usually involved in these diseases, i.e., the dermoepidermal junction or the intercellular spaces of epidermis. Supernatants from controls did not show any reactivity by immunofluorescence. The results demonstrated that human lymphoid cell lines obtained from patients with bullous diseases elicited the production of anti-intermediate filament autoantibodies known to occur spontaneously in normal patients. It is suggested that this phenomenon may be linked to the blistering conditions that provoke tissue destruction.

Autoantibodies to intermediate filaments in experimental infections with Trypanosoma brucei gambiense

Sera from rats with chronic Trypanosoma brucei gambiense infection were tested for autoantibodies by an indirect immunofluorescence assay. All the sera contained IgM autoantibodies which reacted with blood vessel walls. On cultured vascular smooth muscle cells positive sera reacted with cytoplasmic filaments which were rearranged into perinuclear coils of filaments in colcemid-pretreated smooth muscle cells. These observations strongly suggest that the cytoplasmic autoantigens are intermediate filaments (I.F.). It is probable that the anti-intermediate filament autoantibodies result from polyclonal lymphocyte activation, since in rats experimentally infected with T.b. gambiense the appearance of these autoantibodies occurs already 1 week post-infection.

Solid-phase preparation of vimentin-type intermediate filaments for immunoassays

A simple method is described for the preparation of vimentin-type intermediate filaments for solid-phase immunoassays. Bovine aortic endothelial cells were grown to confluency in multiwells, and extracted with Triton X-100 and a high-salt buffer. Residual protein in the wells consisted of 53% vimentin as judged by SDS electrophoresis, and the recovery of vimentin was 41%. Methanol-fixed and dried filaments can be used directly for immunological assays.

Immunofluorescent detection of anti-cytoskeleton antibodies using vinblastine-treated mononuclear cells

A reliable and reproducible immunofluorescence method is described for the detection of anti-cytoskeleton antibodies in human sera, based on the use of vinblastine-treated peripheral blood mononuclear cells as substrate. Three immunofluorescence patterns associated with antibodies to microfilaments, intermediate filaments and microtubules are readily identified.

Circulating autoantibodies to the 200,000-dalton protein of neurofilaments in the serum of healthy individuals

There is substantial evidence that human serum contains antibodies to many autoantigens. For example, all healthy people have autoantibodies (immunoglobulin M) to some undefined brain antigens. In this study immunoblots and immunohistochemical staining were used to detect antibodies to neural tissues in serum samples from 200 healthy people and 200 patients with various neurological diseases. Ninety-nine percent of the 400 subjects had serum immunoglobulin M and 95 percent had immunoglobulin G that bound to a 200-kilodalton protein in homogenates of neural tissues. In most cases there were no antibodies to anything else in the homogenates. The 200-kilodalton protein was the heaviest of the neurofilament triplet proteins. These observations do not support a role for antibodies to the 200-kilodalton protein of neurofilaments in the pathogenesis of neurological diseases.

Immunoprecipitation of TSH-TSH receptor complexes

The ability of Graves' sera to interact with the TSH receptor crosslinked to a 125I-labelled photoactive derivative of TSH has been investigated. Crosslinked complexes were prepared using non-purified detergent solubilized human thyroid and guinea pig fat TSH receptors. Affinity purified porcine TSH receptor preparations wee also used. After crosslinking, the crosslinked TSH-TSH receptor complexes were separated from aggregates and free TSH on Sephacryl S-300, incubated with test sera followed by immunoprecipitation using anti-IgG or Protein A. Using non-purified human TSH receptors crosslinked to TSH, a mean +/- SD of 12.1 +/- 4.9% of the crosslinked complex was immunoprecipitated with Graves' sera (n = 7) compared with 10.3 +/- 2.6% with Hashimoto sera (n = 6; P greater than 0.14) and 3.8 +/- 1.0% with normal sera (n = 6; P less than 0.004). These values were markedly reduced when TSH receptor preparations free of other thyroid autoantigens (guinea pig fat TSH receptors) were used. Under these conditions immunoprecipitation with Graves' sera (n = 24) was 1.6 +/- 1.3% compared with 0.8 +/- 0.6% for Hashimoto sera (n = 13) and 0.8 +/- 0.4% for normal sera (n = 12; P less than 0.003). In addition complexes formed between TSH and affinity purified porcine TSH receptors gave low immunoprecipitation values for Graves' (1.44 +/- 0.73%; n = 20) and Hashimoto sera (1.7 +/- 0.94; n = 11) which were not significantly different (P greater than 0.4). Overall, therefore, the effects of Graves' and Hashimoto sera were similar and the amounts of material immunoprecipitated were markedly reduced when TSH receptor preparations containing reduced amounts of other autoantigens were used. Consequently the Graves' sera did not appear to interact specifically with crosslinked TSH-TSH receptor complexes. However the Graves' sera studied did contain TSH receptor antibodies which could inhibit the binding of labelled TSH to TSH receptors in the preparations used and our results suggest that the binding of TSH and these antibodies to the receptor is mutually exclusive. There is considerable evidence that serum from patients with Graves' disease contains antibodies to the TSH receptor (Rees Smith, 1981). Several studies have suggested that binding of the receptor antibody and TSH to the TSH receptor is mutually exclusive (Manley et al., 1977; Petersen et al., 1977; Rickards et al., 1981) but recently the formation of termolecular complexes consisting of detergent solubilized receptors, labelled TSH and Graves' IgG has been reported (Konishi et al., 1982; De Bruin et al., 1984).(ABSTRACT TRUNCATED AT 400 WORDS)