Auto-antibodies in Sjögren's syndrome. With special reference to liver-cell membrane antibody (LMA)

Granulomatous myopathy: Sarcoidosis and beyond

Non-necrotizing granulomatous inflammation is a rare but easily recognized histopathological finding in skeletal muscle biopsy. A limited number of diseases are known to be associated with non-necrotizing granulomatous myopathy. Once identified, a careful evaluation for evidence of extramuscular granulomatosis and other signs suggestive of sarcoidosis is warranted as about half of the patients have sarcoid myopathy. In addition, the presence of granulomatous myopathy should trigger a search for clinical and pathological clues of inclusion body myositis (IBM), which accounts for most of the remaining patients and can coexist with sarcoidosis. Recognizing the features of IBM in patients with granulomatous myopathy can potentially spare the patients from unnecessary exposure to immunosuppressive therapies. In patients whose granulomatous myopathy remain unexplained, further investigations should aim at identifying myasthenia gravis and other autoimmune disorders, especially those known to cause granulomatous inflammation in other organs. Laboratory investigations should include acetylcholine receptor, antimitochondrial, antineutrophil cytoplasmic, thyroglobulin, and thyroid peroxidase autoantibodies. In the appropriate clinical context, exposure to immune checkpoint inhibitors and chronic graft-vs-host disease can be causes of granulomatous myopathy. In cases of unexplained granulomatous myopathy, natural killer/T-cell lymphoma should be considered and careful histopathological examination for atypical cells and appropriate immunostaining is crucial. Identifying the etiology of granulomatous myopathy in each patient can guide appropriate treatment.

The spectrum of anti-chromatin/nucleosome autoantibodies: independent and interdependent biomarkers of disease

Autoantibodies directed to chromatin components date back to the discovery of the LE cell and the LE cell phenomenon circa 1950, and subsequent evidence that major components of that reaction were chromatin components and histones in particular. Over time, immunoassays ranging from ELISA and line immunoassays to more modern bead-based assays incorporated histone and DNA mixtures, purified histones, and purified nucleosomes leading to a more thorough understanding of the genesis and pathogenetic relationships of antibodies to chromatin components in systemic lupus erythematosus and other autoimmune conditions. More recently, interest has focussed on other components of chromatin such as high mobility group (HMG) proteins both as targets of B cell responses and pro-inflammatory mediators. This review will focus on immunoassays that utilize chromatin components, their clinical relationships, and newer evidence implicating HMG proteins and DNA neutrophil extracellular traps (NETs) as important players in systemic autoimmune rheumatic diseases.

A comprehensive review of autoantibodies in primary Sjögren's syndrome: clinical phenotypes and regulatory mechanisms

Sjögren's syndrome (SS) is a systemic autoimmune disease characterized by periepithelial lymphocytic infiltrates in affected tissues and the production of plethora of autoantibodies. Among them autoimmune responses against Ro/SSA and La/SSB are of major importance since their detection is routinely used for disease diagnosis and clinical characterization. Although the exact mechanisms underlying disease pathogenesis are not fully understood, the important role of salivary gland epithelial cells (SGEC) in the initiation and development of the local immune responses is well-established. SGECs are also capable to mediate the exposure of the Ro/SSA and La/SSB autoantigens to the immune system by elevated apoptosis and autoantigen release in apoptotic bodies and/or by the secretion of autoantigen-containing exosomes. The expression of these autoantigens in epithelial cells appears to be tightly regulated. Up-to-date, signaling of certain innate immunity receptors, such as TLR3, appear to be implicated in the regulation of Ro/SSA and La/SSB expression by SGECs, whereas the deregulated expression of certain miRNAs that are predicted to target them in SS patients suggests a regulatory feedback at the post-transcriptional level. In the periphery, the humoral autoimmune responses are further regulated by the development of an active network of idiotypic-antiidiotypic antibodies. The plethora of mechanisms suggests that autoimmune humoral responses in SS are tightly regulated. In this review, the major humoral autoimmune responses, recent advances on the role of epithelial cells in their development, as well as possible regulatory mechanisms will be discussed.

Subgroups of Sjögren syndrome patients according to serological profiles

Sjögren Syndrome (SS) is a systemic, autoimmune disorder characterized by lymphocytic infiltration of the exocrine glands. Different clinical associations have been described for each of the diverse autoantibodies found in SS patients. Antibodies directed against the Ro/La ribonucleoprotein complexes have been correlated with younger age, more severe dysfunction of the exocrine glands and a higher prevalence of extraglandular manifestations. Anti-nuclear antibodies and rheumatoid factors have been associated to extraglandular manifestations and an active immunological profile, while cryoglobulins are markers of more severe disease and correlate to lymphoma development and death. Antibodies to cyclic citrullinated peptides are scarce in SS and have been linked in some cases to the development of non-erosive arthritis. Furthermore, the presence of anti-mitochondrial antibodies and anti-smooth muscle antibodies in the sera of primary SS patients is considered indicative of primary biliary cirrhosis and autoimmune hepatitis, respectively. In addition, anti-centromere antibodies have been associated with a clinical phenotype intermediate between primary SS and systemic sclerosis, while antibodies against carbonic anhydrase have been related to renal tubular acidosis. Finally, an association of anti-muscarinic antibodies with cytopenias and a higher disease activity has also been described in primary SS. In conclusion, although not all of the above mentioned antibodies are useful for predicting distinct patient subgroups in SS, knowledge of the clinical associations of the different autoantibody specificities encountered in SS can advance our understanding of the disease and improve patient management.

Autoantibodies in Sjögren's syndrome: clinical presentation and regulatory mechanisms

Primary Sjögren's syndrome (pSS) is a systemic autoimmune disease mostly affecting the exocrine glands. A large number of autoantibodies have been detected in the serum of patients with pSS. Among them, anti-Ro/SSA and anti-La/SSB autoantibodies are the most common; they serve as disease markers and are involved in the pathogenesis of neonatal lupus syndrome (NLS). Other autoantibodies are associated with significant clinical phenotypes, such as cryoglobulins with development of non-Hodgkin's lymphoma, anti-centromere antibodies with Raynaud's phenomenon and anti-mitochondrial antibodies with liver pathology. As a result, pSS patients can be schematically categorized in subgroups according to their serological profile. Although the clinical utility of these autoantibodies is appreciated, little is known about the mechanisms related to their production and the regulation of the autoimmune response. In the present review, the clinical subsets of patients with pSS related to different autoantibodies as well as the regulating mechanisms of their production with special emphasis on idiotypic/anti-idiotypic network are discussed.

Hepatic manifestations of autoimmune rheumatic diseases

Hepatic manifestations in autoimmune disease include chronic active hepatitis, primary biliary cirrhosis, primary sclerosing cholangitis, and nodular regenerative hyperplasia. These diseases are rare and may occur concomitantly or serially. Clinicians must be aware of the possibility of liver disease so that it can be treated as soon as possible.

Autoantibodies to protein transport and messenger RNA processing pathways: endosomes, lysosomes, Golgi complex, proteasomes, assemblyosomes, exosomes, and GW bodies

Over 50 years ago the lupus erythematosus (LE) cell phenomenon was described and this was quickly followed by the introduction of the LE cell test and indirect immunofluorescence (IIF) to detect antinuclear antibodies (ANA) in clinical laboratories. Recently, attention has turned to the identification of the autoantigens that bind to cytoplasmic organelles such as the Golgi complex, endosomes and other "cytoplasmic somes". Three endosome autoantigens include early endosome antigen 1 (EEA1, 160 kDa), cytoplasmic linker protein-170 (CLIP-170, 170 kDa), and lysobisphosphatidic acid (LBPA). Antibodies to EEA1 were seen in a variety of conditions but approximately 40% of the patients had a neurological disease. Despite the prominence of lysosomes in cells and tissues, reports of autoantibodies are limited to the lysosomal antigen h-LAMP-2 and the cytoplasmic antineutrophil antibodies (cANCA). Autoantigens in the Golgi complex include giantin/macrogolgin, golgin-245, golgin 160, golgin-97, golgin 95/gm130, and golgin-67. More recently, there has been an interest in autoantibodies that bind components of the "SMN complex" or the "assemblyosome". Arginine/glycine (RG)-rich domains in components of the SMN complex interact with Sm, like-Sm (LSm), fibrillarin, RNA helicase A (Gu), and coilin proteins, all of which are antigen targets in a variety of diseases. More recently, components of a novel cytoplasmic structure named GW bodies (GWBs) have been identified as targets of human autoantibodies. Components of GWBs include GW182, a unique mRNA-binding protein, like Sm proteins (LSms), and decapping (hDcp1) and exonuclease (Xrn) enzymes. Current evidence suggests that GWBs are involved in the cytoplasmic processing of mRNAs. Autoantibodies to the "cytoplasmic somes" are relatively uncommon and serological tests to detect most of them are not widely available.

Current issues in Sjögren's syndrome

Sjögren's syndrome is a chronic autoimmune and rheumatic disorder with prominent sicca complaints from the mucous membranes because of lack of proper exocrine secretions. There is no straightforward and simple diagnostic test for Sjögren's syndrome, although several classification criteria have been designed including several oral diagnostic tests. A new set of classification criteria in a joint effort by research groups in Europe and USA has recently been presented. A large number of autoantibodies have been reported in Sjögren's syndrome where, in some cases, the antibodies are correlated with the extent and severity of disease. The finding of serum autoantibodies directed against the muscarinic M3 receptor is an important advance in understanding the pathogenesis of not only the impaired glandular function but also associated features of autonomic dysfunction in some patients. The treatment of primary Sjögren's syndrome is still mainly symptomatic.

Autoimmune liver disease in patients with primary Sjögren's syndrome

Forty-five patients with primary Sjögren's syndrome were studied for evidence of autoimmune liver disease. Twenty-nine patients had normal liver function tests, normal IgM and a normal test for antimitochondrial antibodies and smooth muscle antibodies. Among the remaining 16 patients, abnormal liver function tests were found in 12 (27% of all patients); eight of these patients had biochemical cholestasis. Elevated plasma IgM (> 2 g/l) was observed in nine patients, three with normal liver function tests, while antimitochondrial antibodies were positive in six patients, one with normal liver function tests, and smooth muscle antibodies were found in three. Based on these findings and percutaneous liver biopsy, a diagnosis of primary biliary cirrhosis was established in four patients and autoimmune chronic active hepatitis in two. The present study showed that abnormal liver function tests in patients with primary Sjögren's syndrome are frequent and may indicate associated autoimmune liver disease. These data further emphasize the systemic nature of autoimmune disorders.

Primary biliary cirrhosis. Sole presentation with rampant dental caries

A 55-year-old woman was referred by her general dental practitioner for management of rampant dental caries of recent onset. Examination revealed a very dry mouth, angular stomatitis, and multiple carious lesions. Labial salivary gland biopsy showed features consistent with Sjögren's syndrome. Hematologic investigations showed antimitochondrial antibodies at a titer of 1 in 320, highly suggestive of primary biliary cirrhosis that was confirmed by liver biopsy.

Liver membrane antibodies (LMA) recognize a 26-kD protein on the hepatocellular surface

Sera from 82 patients with chronic inflammatory liver diseases and from patients with systemic lupus erythematosus (SLE), rheumatoid arthritis (RA) and Hashimoto's thyroiditis were studied by immunoblotting against purified liver plasma membranes (LPM) and soluble liver protein (SLP) fractions from different species after previous separation by SDS-PAGE. Eighteen of 19 sera with LMA of IgG type in immunofluorescence assay and six LMA-negative sera (three sera from patients with RA) showed antibodies of the IgG or IgM classes against a protein with a molecular weight of 26 kD which was present in LPM and SLP fractions from rats, rabbits, pigs and humans. The reaction with 26-kD liver protein did not correlate with other known autoantibody-antigen systems. All sera were negative in the 26-kD region with liver mitochondria, liver microsomes and soluble proteins of kidney (with one exception), heart and gut from the rat. The 26-kD protein was purified by affinity chromatography on immobilized anti-26-kD protein antibodies from patients, eluted from the 26-kD band of immunoblots. Studies with purified 26-kD liver protein and with SLP as antigens after separation in two-dimensional electrophoresis confirmed that patient serum and experimental rabbit antiserum react with the same protein. Eluted patient antibodies and rabbit antisera showed a linear fluorescence pattern on isolated hepatocytes from rat and rabbit. The data indicate that one of the target antigens of LMA is a species-nonspecific 26-kD protein located on the hepatocellular surface.

Autoantibodies in chronic pancreatitis

In 60 consecutive patients clinically suspected of having chronic pancreatitis the serum concentration of the immunoglobulins (IgA, IgG, IgM), the IgG- and IgA-type non-organ-specific autoantibodies against nuclear material (ANA), smooth and striated muscle, mitochondria, basal membrane, and reticulin, and the IgG- and IgA-type pancreas-specific antibodies against islet cells, acinus cells, and ductal cells (DA) were estimated blindly. In 23 of the patients chronic pancreatitis was verified, whereas chronic pancreatitis was rejected in 37 patients (control group). IgG and IgA were found in significantly higher concentrations in the patients with chronic pancreatitis than in the control group but within the normal range. ANA and DA occurred very frequently in both groups but with no statistical difference. Other autoantibodies only occurred sporadically. The findings of this study do not support the view of an immunological pathogenesis in chronic pancreatitis.

Immunoglobulins, anti-IgG antibodies and antinuclear antibodies in paired serum and synovial fluid samples. A comparison between juvenile and adult rheumatoid arthritis

Paired samples of serum and synovial fluid (SF) from 13 patients with juvenile rheumatoid arthritis (JRA) and 10 patients with adult rheumatoid arthritis (RA) were examined regarding the level of immunoglobulins and the occurrence and titres of anti-IgG antibodies and antinuclear antibodies (ANA). The levels of immunoglobulins were lower in SF than in serum. In JRA the SF/serum ratio of IgG was equal to that of albumin, pointing to a local production of IgG. The SF/serum ratio of IgM was equal to that of alpha 2-macroglobulin. In JRA the SF/serum ratios of immunoglobulins tended to be lower than in RA, the difference being significant for IgM. IgD autoantibodies and IgA anti-IgG were not found in JRA. IgE autoantibodies occurred in some cases, but in RA in more than 60%. In JRA the SF titres of anti-IgG and ANA were most often lower than the serum titres. In RA the SF titres were often higher than the serum titres. In 9 of 10 paired SF samples from patients with RA the SF/serum ratios were mutually different with regard to one or several immunoglobulins. Evidence of synovial production of anti-IgG antibodies of classes other than IgG distinguished RA from JRA. Otherwise the differences were quantitative.

The clinical picture of benign lympho-epithelial lesion

The histopathological diagnosis 'benign lympho-epithelial lesion' characterizes the major salivary gland disease in Sjögren's syndrome. It is not known if all cases with microscopically diagnosed benign lympho-epithelial lesion are variants of Sjögren's syndrome. The present clinical investigation showed that in 19 patients with the microscopical diagnosis of lympho-epithelial lesion, 84% fulfilled all criteria of Sjögren's syndrome. The rheumatoid factor and/or antinuclear factor was found in 84% and M-component was present in 16%. Sialography revealed sialectasis in all parotid glands. Salivary gland enlargement was found in 79%, and keratoconjunctivitis sicca in 89% of the patients. Systemic disease was found in 32%. The disease in the 2 patients with M-component took a malignant course, culminating in immunoblastic sarcoma and myelomatosis. The clinical diagnosis 'autoimmune sialadenitis' is proposed for the oral and salivary gland component is Sjögren's syndrome.

Characterisation of Liver membrane autoantibodies determined by indirect immunofluorescence

Indirect immunofluorescence studies were performed using sera and IgG-Fab2 fragments from patients with chronic active hepatitis (CAH) who were positive for a liver membrane antibody (LMA). The specificity was investigated using hepatocytes from humans as well as rabbit, rat, guinea pig and monkey. Only sera also positive for smooth muscle antibody gave staining of lymphocytes and absorption with F-actin from rabbit muscle abolished this as well as all other smooth muscle staining without influencing LMA. It was concluded that LMA, routinely detected by indirect immunofluorescence using rabbit hepatocytes, represents specific binding to non-species-specific membrane antigens which are normal constituents of human hepatocytes. The antigen is separately located, and not cross-reactive with F-actin.

Localisation of immunoglobulin on the liver cell surface in primary biliary cirrhosis

Direct immunofluorescence studies were performed on isolated liver cells in order to detect surface localisation of IgG in acute and chronic hepatitis and primary biliary cirrhosis. Membrane-bound IgG was demonstrated in nine patients. Six of eight patients with primary biliary cirrhosis showed granular fluorescence on their liver cell surfaces suggesting that an antibody or immune complex-mediated cytotoxicity might be involved in the pathogenesis of this disease.