Characterization of human smooth muscle autoantibodies reacting with cytoplasmic intermediate filaments

Polyreactive antibodies in adaptive immune responses to viruses

B cells express immunoglobulins on their surface where they serve as antigen receptors. When secreted as antibodies, the same molecules are key elements of the humoral immune response against pathogens such as viruses. Although most antibodies are restricted to binding a specific antigen, some are polyreactive and have the ability to bind to several different ligands, usually with low affinity. Highly polyreactive antibodies are removed from the repertoire during B-cell development by physiologic tolerance mechanisms including deletion and receptor editing. However, a low level of antibody polyreactivity is tolerated and can confer additional binding properties to pathogen-specific antibodies. For example, high-affinity human antibodies to HIV are frequently polyreactive. Here we review the evidence suggesting that in the case of some pathogens like HIV, polyreactivity may confer a selective advantage to pathogen-specific antibodies.

Immunological and virological study of sudden deafness

Thirty-three patients with sudden deafness and 11 controls were selected from the patients admitted to the Department of Otolaryngology, Tokai University Hospital from November 1990 to October 1991. Viral titers were measured for mumps, adenovirus, rubella, measles, herpes simplex virus (HSV), varicella zoster virus (VZV), rhinosyncytial virus, cytomegalo-virus (CMV), and mycoplasma pneumoniae in 33 sudden deafness patients and 11 controls at a 2-week interval. In 20 of 33 sudden deafness patients and 5 of 11 controls, autoantibodies of rheumatoid factor (RF), anti-mitochondrial antibody (AMA), anti-nuclear antibody (ANA), anti-parietal cell antibody (APA), anti-smooth muscle antibody (ASA), and anti-type II collagen antibody were studied. Viral titer study did not reveal any significant change either in the patients or in the controls, whereas autoantibody study revealed a relatively high incidence for ASA in the patients as compared with the controls. The relatively high incidence for ASA suggests that immune-mediated processes may be involved in the etiology of sudden deafness.

Antibodies to cytoskeletal proteins in patients with Crohn's disease

The immunologic basis of inflammatory bowel disease has been the focus of interest of a series of studies on Crohn's disease and the process of immune sensitization at the gastrointestinal mucosal level is functionally poorly understood. To date only few contradictory reports concerning the incidence of autoantibodies in patients with this disease exist. The aim of this study was to investigate the sera drawn from 60 patients suffering from biopsy-proven Crohn's disease to evaluate the prevalence of autoantibodies against nuclear antigens and cytoskeletal proteins. Using standard methods, no anti-nuclear antibodies or antibodies to extractable nuclear antigens could be detected. All sera were also negative for antibodies to double-stranded DNA, anti-mitochondrial antibodies, and antibodies to gastric parietal cells. Using sensitive enzyme-linke immunosorbent assays with purified antigens and Western blotting with cytoskeletal proteins of human intestinal cells, the following antibodies could be demonstrated: cytokeratin 18 autoantibodies (IgG 20.0%; IgM 6.7%; IgA 13.3%), actin antibodies (IgG 36.7%; IgM 48.3%, IgA 26.7%), desmin antibodies (IgG 6.7%; IgM 15.08%; IgA 5.0%), vimentin antibodies (IgG 3.3%; IgM 16.7%; IgA 10.0%) and tropomyosin antibodies (IgG 3.3%; IgM 3.3%, IgA 5.0%). Statistically significant correlations could be found for levels of cytokeratin 18 antibodies (IgM-type) and the BEST index of activity, and for levels of desmin antibodies (IgM-type) and the van HEES index of activity. Highest levels could be measured for actin antibodies (IgG-type) in patients with isolated disease manifestation in the colon. The mechanism of induction of autoantibodies against cytoskeletal components in Crohn's disease still remains obscure. Unmasking of hidden antigens after cell injury during the inflammatory process of disease might lead to sensitization and antibody production. The pattern of antibodies in patients with Crohn's disease seems to be different compared with that of connective tissue diseases.

Sera with high levels of anti-smooth muscle and anti-mitochondrial antibodies frequently bind to cytoskeleton proteins

Using ELISA methods, 54 sera from chronic active hepatitis (CAH) patients displaying high levels of anti-smooth muscle antibodies (SMA) and 18 sera from primary biliary cirrhosis (PBC) patients with high levels of anti-M2 antibodies were examined for the presence of high antibody levels against actin, tubulin, myosin, tropomyosin, troponin, vimentin and desmin. Our results showed that: (i) in CAH with high SMA activity, increased antibody levels were found in 51.9% of sera for actin, 31.5% for myosin, 35.2% for tubulin, 34.0% for tropomyosin, 11.3% for troponin, 22.6% for vimentin and 43.4% for desmin, compared with natural antibody levels in 21 normal sera; (ii) Similar high levels of these antibodies were found in the case of PBC; (iii) in most cases, sera simultaneously bound to several antigens of the panel; and (iv) approximately 26% of the CAH sera were found to be negative with the seven antigens examined while 22% were reacted with a cytoskeleton protein (CP) other than actin. These results indicate that current opinion associating SMA with anti-actin activity in CAH is confirmed for only 50% of cases and that although a good correlation between SMA and anti-CP antibodies can be obtained, there is still a significant percentage of SMA for which the putative antigen recognized needs to be determined.

Antibody to intermediate filaments of the cytoskeleton in patients with Behçet's disease

Antibodies to 10-nm intermediate filaments (anti-IF) were determined in the sera of 30 patients with Behçet's disease (BD), in addition to C-reactive protein and C9, and an attempt has been made to determine whether the presence of anti-IF indicate disease activity. The vimentin type of anti-IF was found to be positive in 14 out of 30 patients with BD (47%), whereas it was positive in 35% of the patients with rheumatoid arthritis (20 cases), 16% of the patients with systemic lupus erythematosus (19 cases) and in only 9% of the normal controls. The anti-IF were predominantly IgG class and the titers in BD were significantly higher than those in normal controls. Out of the 14 patients with anti-IF, 10 showed significantly increased levels of serum C9 and 8 showed increased levels of CRP activity. Only one patient showed increased C9, but was negative for anti-IF and CRP. The presence of anti-IF in the patients' sera was found to be a more sensitive indicator, though not specific, for the clinical assessment of disease activity.

Virus-related pathology: is the continued presence of the virus necessary?

This chapter examines the effect of viruses in inducing modifications in chromosomes, immune system interactions, and cell metabolism to support such a hypothesis that virus may no longer be present when the pathology appears. When vaccines were available to protect the population against the major epidemics, then chronic, recurrent, or persistent infections came into focus. Viruses are everywhere and all organisms are permanently exposed to them. The result of this contact depends on the particular moment a t which a given cell is exposed to the virus. Rubella, for example, provokes a very benign disease in adults, but can induce abnormalities in the differentiating fetus. Although interferon is active against virus aggression, excess interferon has a toxic effect and can block differentiation. The capacity of several viruses to act as cellular mutagens by modifying chromosomes is well established, whatever the molecular mechanism may be. Mutations at the cellular level were carefully analyzed for their tumorigenic potential.

Anticytoskeletal autoantibodies in the connective tissue diseases

The sera of 103 patients with connective tissue diseases were studied for the presence of anticytoskeletal antibodies by using an indirect immunofluorescence method. PTK2 cells fixed with paraformaldehyde and digitonin were used as substrate. Antibodies to intermediate filaments were detected in sera of 85.7% of polymyositis/dermatomyositis (PM/DM), 62.8% of systemic sclerosis, 54.5% of rheumatoid arthritis, and 37.5% of systemic lupus erythematosus patients, and in 42.5% of normal sera. High titers of these antibodies, which were IgM, were present in 30% of patients' and 5% of normal sera. Antibodies to microfilaments were present in 11.6% of patients' sera and absent in all control sera. These antibodies were IgM or IgG. The switch from an IgM to an IgG antibody was observed in 1 patient. An IgG antibody to the spindle poles and midbody of mitotic cells was present in the serum of 1 patient with the CREST syndrome (calcinosis, Raynaud's phenomenon, esophageal dysmotility, sclerodactyly, telangiectasias). Antibodies to intermediate filaments and to microfilaments occur commonly in the connective tissue diseases, particularly in PM/DM, and are not detected with substrates or fixation methods used in routine antinuclear antibody testing.

Antigenic mimicry of mammalian intermediate filaments by mycoplasmas

A murine monoclonal antibody raised against Mycoplasma hyorhinis specifically reacted by indirect immunofluorescence with mammalian intermediate filaments. The antibody recognized a related epitope on a 74,000-molecular-weight protein of M. hyorhinis and on components of similar size from other pathogenic mycoplasmas. This defines a shared antigenic structure of interest in autoantibody development during mycoplasmal diseases.

Incidence of anti-intermediate filament antibody in serum samples of students with suspected glandular fever

Serum samples from 40 students with suspected infectious mononucleosis were tested for the presence of antibodies to intermediate filaments (AIFA) of the cytoskeleton. Twenty had antibodies to the Epstein-Barr virus capsid antigen before their illness, and during it their sera remained negative by the Paul-Bunnell test. The other 20 patients did not have antibodies to the Epstein-Barr virus capsid antigen before their illness and seroconverted during the illness. These patients (true infectious mononucleosis group) developed positive Paul-Bunnell tests. Sera from normal subjects (blood donors) were also tested for AIFA. AIFA was present in titres greater than 1/10 in 80% of the infectious mononucleosis group (mean titre 1/40-1/80), 10% of the Paul-Bunnell negative glandular fever group, and 8.5% of the normal blood donors.

The detection of smooth muscle antibodies reacting with intermediate filaments of desmin type

Some human smooth muscle antibodies (SMA) react with cytoskeletal intermediate filament (IMF) antigens. The smooth muscle tissue contains two types of IMF: vimentin and desmin filaments. In this study, SMA of anti-IMF type in 52 patients' sera have been classified into anti-vimentin filament and anti-desmin filament types according to their immunofluorescence staining patterns on rat testis. This classification is based on the fact that the arterial walls of testis contains both vimentin and desmin whereas the myoid cell layer surrounding the seminiferous tubuli contains only desmin. Four out of the 52 sera gave the anti-desmin staining pattern and 40 sera showed the anti-vimentin type of staining. Thirty-two sera were further classified by using cultured human rhabdomyosarcoma (RD) cells as targets. Nine sera reacted with the intermediate filaments of the RD cells. Among these were 3 out of the 4 sera that gave the anti-desmin filament staining pattern. The anti-desmin specificity of SMA was confirmed in 1 serum by the immunoblotting technique. These results indicate that while human anti-desmin filament antibodies exist, most human SMA of anti-IMF type react with vimentin filaments.

Three monoclonal antibodies against measles virus F protein cross-react with cellular stress proteins

In a group of 11 monoclonal antibodies specifically reacting with the measles virus fusion protein, three antibodies also immunoprecipitated other proteins, in particular a 79,000-molecular-weight protein from virus-infected cells. The cross-reacting 79,000-molecular-weight protein was shown to be a virus-induced host stress protein. This protein could be induced by (i) different paramyxoviruses, (ii) heat shock of uninfected HeLa cells, and (iii) 2-deoxyglucose, tunicamycin, or L-canavanine treatment of different mammalian cell lines. Immunofluorescence of stressed HeLa cells localized the cross-reacting host protein(s) mainly in the cytoplasm. The significance of these results in relation to autoimmunity is discussed.

Anti-actin antibodies of IgM and IgG class in chronic liver diseases detected by fluorometric immunoassay

Using a sensitive fluoroimmunoassay, anti-actin antibodies (AA) of the IgM and IgG classes were measured in 240 patients with various chronic liver diseases and in 211 patients with non-hepatic autoimmune muscle, heart, malignant and inflammatory bowel diseases. Thirty-two out of 40 patients (80%) with autoimmune chronic active hepatitis (CAH) had AA only of the IgG class (geom. mean X = 1.78, SEM +/- 0.07) and only three patients (8%) had both IgG and IgM AA, the latter in lower titres. In patients with primary biliary cirrhosis (PBC) and AMA-positive cholestatic CAH, AA of both IgM and IgG classes were equally represented (60% IgG and 64% IgM AA in PBC, 73% IgG and 51% IgM AA in cholestatic CAH) but the titres were very low (geom. mean IgG AA in PBC 1.035, SEM +/- 0.03, in cholestatic CAH 1.18, SEM +/- 0.02). In contrast to autoimmune (lupoid) CAH, AA were rare in HBsAg positive CAH (9/43, 21%) and only present in low titres. However, in six out of 21 patients with anti-HBs and anti-HBc-positive chronic active hepatitis, high AA of IgG class were found, suggesting the autoimmune type of liver disease. In NANB virus-induced chronic liver disease after blood transfusion, AA were only occasionally found (IgG antibodies 1/19, IgM antibodies 3/19) and none were found in the eight patients with sporadic NANB hepatitis. They were also rare in 30 patients with alcoholic liver disease (3/30, 10%).(ABSTRACT TRUNCATED AT 250 WORDS)

Human upper epidermal cytoplasmic antibodies are directed against keratin intermediate filament proteins

Upper cytoplasmic (U-Cyt) antibodies are directed against cytoplasmic antigens found in keratinocytes in the upper layers of the epidermis. Until now, they have been defined by indirect immunofluorescence and are known to occur in the sera of patients with cutaneous diseases such as bullous dermatoses, basal cell carcinomas, and melanomas. An increased incidence of U-Cyt antibodies has also been reported in the sera of patients with noncutaneous diseases, such as pulmonary neoplasms. They have been found in addition in the sera of some normal individuals. In this study we have identified keratin intermediate filaments (KIF) as antigens U-Cyt antibodies are directed against. KIF proteins were prepared, separated by polyacrylamide gel electrophoresis, transblotted to nitro-cellulose strips, and used as substrates for antibody binding. Sera containing U-Cyt antibodies by indirect immunofluorescence also had antibodies that were directed against high molecular weight (65,000, 63,000, 61,500) KIF proteins. When KIF proteins were separated according to their charge and their molecular weight by two-dimensional gel electrophoresis and transblotted, the anti-KIF protein antibodies bound to virtually all charge isomers of the KIF proteins at the respective molecular weight. The antibody titers measured using the transblotting technique were 10 to 160 times higher than those found by indirect immunofluorescence. To determine whether U-Cyt antibodies were directed against KIF, a series of absorption and elution experiments were performed. Absorption of test sera with purified KIF removed both U-Cyt antibodies and anti-KIF protein antibodies. Absorption with another type of intermediate filament derived from fibroblasts, vimentin, did not remove U-Cyt or anti-KIF protein antibodies. Absorbed U-Cyt and anti-KIF protein antibodies were both eluted from the same KIF preparation and shown to bind to U-Cyt antigens by indirect immunofluorescence and KIF proteins by transblotting. Absorption of a serum containing U-Cyt antibodies, anti-nuclear antibodies, and anti-basement membrane zone antibodies with purified KIF resulted in the removal of the U-Cyt antibodies but not the other types of antibody. In addition, all test sera, even those that lacked U-Cyt antibodies, were found to have low-titer antibodies against KIF proteins by the transblotting technique. These data indicate that KIF proteins bear antigens to which U-Cyt antibodies are directed and that low titer antibodies against KIF proteins may be much more common than previously appreciated.

Cytoskeleton antibodies in chronic active hepatitis, primary biliary cirrhosis, and alcoholic liver disease

Antibodies to cytoplasmic microfilaments, intermediate filaments (vimentin filaments), and microtubules which comprise the cytoskeleton of the cell were assayed in sera from 23 patients with HBsAg-negative chronic active hepatitis and 1 with HBsAg-positive chronic active hepatitis, 15 patients with primary biliary cirrhosis, 20 patients with alcoholic liver disease, and 32 healthy controls. The cytoskeleton antibodies were assayed by indirect immunofluorescence technique using vinblastine-treated cultured human embryonic fibroblasts as substrates. There was a significantly increased incidence of cytoskeleton antibodies in patients with liver disease as compared to the control group. Antibodies to microfilaments were found frequently in sera from patients with chronic active hepatitis (67%) and primary biliary cirrhosis (53%) but were rare in sera from patients with alcoholic liver disease (25%) and in control sera (3%). On the other hand, antibodies to microtubules were found in 50% of sera from patients with alcoholic liver disease but in only 7 to 13% of sera from other groups. Intermediate filament antibodies of IgG or IgA class were found only in patient sera whereas intermediate filament antibodies of IgM class were found in the majority of sera in all groups including control sera. The highest titers of intermediate filament antibodies were seen in primary biliary cirrhosis and chronic active hepatitis. The production of cytoskeleton antibodies may be due to the reorganization or destruction of cytoskeletal structures in the liver.

Molecular mimicry in virus infection: crossreaction of measles virus phosphoprotein or of herpes simplex virus protein with human intermediate filaments

Using monoclonal antibodies, we demonstrate that the phosphoprotein of measles virus and a protein of herpes simplex virus type 1 crossreact with an intermediate filament protein of human cells. This intermediate filament protein, probably vimentin, has a molecular weight of 52,000, whereas the molecular weights of the measles viral phosphoprotein and the herpes virus protein are 70,000 and 146,000, respectively. Crossreactivity was shown by immunofluorescent staining of infected and uninfected cells and by immunoblotting. The monoclonal antibody against measles virus phosphoprotein did not react with herpes simplex virus protein and vice versa, indicating that these monoclonal antibodies recognize different antigenic determinants on the intermediate filament molecule. The significance of these results in explaining the appearance of autoantibodies during virus infections in humans is discussed.

Immunoglobulin M autoantibody to vimentin intermediate filaments

Serum from a patient with the CREST Syndrome and systemic lupus erythematosus contained an IgM antibody that reacted at dilutions up to 1:800 with a fibrous cytoplasmic network in several epithelioid and fibroblastic cell lines. The antibody was shown by immunofluorescence microscopy to label a specific subset of cytoskeletal polymers, the intermediate filaments. The reactive antigen from this biochemically heterogeneous group of filaments was established as the 58,000-mol wt protein, vimentin: (a) the patient's serum reacts with a range of cell lines that contain intermediate filaments composed of vimentin, but not with cells whose intermediate filaments are composed of different protein subunits; (b) in PTK2 epithelioid cells the serum reacts with the class of filaments that coils around the nucleus after colchicine treatment (vimentin) and not with the filaments that remain dispersed after colchicine (prekeratin); and (c) the component of reactive cells that combines with the serum is shown by immunoelectrophoresis to be a 58,000-mol wt protein antigen. A similar antibody that binds intermediate filaments of PTK2 cells was encountered at lower titer in some sera from other patients with connective tissue diseases and in control sera. Previous routine antinuclear antibody assays using mouse liver or commercially prepared HEp-2 cells have failed to reveal anticytoskeletal antibodies in patient sera, perhaps due to inadequate presentation or preservation of cytoplasmic antigens.

Antibody to intermediate filaments of the cytoskeleton

IgM antibodies against cultures of intermediate filaments (IMF) of the cytoskeleton were demonstrated by immunofluorescence in the sera of 94 (80%) of 118 patients with seropositive rheumatoid arthritis. These antibodies reacted with IMF in cultures of both human fetal fibroblasts and laryngeal carcinoma (HEp2) cells. Of 10 patients from whom paired synovial fluids were also available 8 had anti-IMF antibodies in both serum and fluid. In seronegative RA the incidence of anti-IMF was 40%, in ankylosing spondylitis 25%, in osteoarthrosis 16%, and in normal subjects 14%. Only a minority of RA sera positive for anti-IMF antibodies were also positive for smooth muscle antibody. Absorption experiments suggest that in RA anti-IMF is directed at the intermediate filament protein, vimentin.

Antibody-independent binding of Clq and activation of serum complement by human skin in vitro

By exposing frozen sections of human skin to fresh normal human serum, binding and activation of complement was observed. Attached complement components Clq, C4, and C3 were detected by immunofluorescence microscopy using anticomplement conjugates. Isolated Clq bound to the same structures as serum Clq, C4, and C3 and binding of C4 and C3 was dependent on binding of Clq. The complement components bound to capillary endothelial cells and to fibrillar structures in the dermis and reacted with the epidermis. Complement binding dermal fibrillar structures in adult skin were scant but abundant in fetal skin. They had similar distribution as "microfibrils" demonstrable by human autoantibodies. Antibody independence of the Clq binding was shown using isolated Clq and by the observed constant and reproducible binding of complement of normal sera lacking antibodies to the described target structures. The observations suggest that antibody independent binding of complement should be considered as a possible mechanism leading to dermal complement deposition in vivo.

Cytoplasmic intermediate filaments in cultured glial cells

Monolayer cultures of rat glial cells derived from 12 to 14 day fetal spinal cords and rat C6 glioma cells were examined for immunofluorescent reactivity with human or rabbit autoantibodies to intermediate filaments and with rabbit antibody to GFAP. The embryonic glial cells and C6 glima cells reacted identically with both. Protoplasmic astrocytes gave immunofluorescent staining of an intricate network of cytoplasmic filaments while fibrous astrocytes and C6 glioma cells gave diffuse cytoplasmic staining of the cell body and cell processes. Cells, pretreated with colchicine or vinblastine, showed staining of thick coils of peri-nuclear, circum-nuclear, or juxtanuclear filaments. The observations suggest that intermediate filaments in glial cells contain unique antigenic determinants as well as antigenic determinants shared with intermediate filaments in other cell types,

Glial fibrillary acidic protein and intermediate filaments in human glioma cells

Cultured human glioma cells were studied by double indirect immunofluorescence technique using antisera against intermediate filaments and glial fibrillary acidic protein. With both antisera cytoplasmic fibrillar fluorescence was seen. Perinuclear bundles of intermediate-sized filaments, induced by vinblastine treatment, were strongly stained with both antisera. The degree of codistribution of the two types of antigenic determinants varied considerably from cell to cell. The results suggest that two types of filament-related antigenic determinants can be present in the same cell, and also that glial fibrillary acidic protein-related filaments may possess functional similarities to the intermediate filaments found in other cells. Glial fibrillary acidic protein remains as a useful and specific antigenic marker for the study of glial cells in vitro.