Antibodies targeting extractable nuclear antigens: historical development and current knowledge

The Potential Utility of Salivary and Tear Proteomics to Discriminate Sjögren's Disease from Non-Sjögren's Sicca

Sjögren's Disease (SjD) is an autoimmune disorder associated with decreased saliva and/or tear secretions, resulting in patients reporting dryness in the mouth and eyes. Serum autoantibodies directed against the Ro60/SS-A and La/SS-B autoantigens are a distinctive feature of the disease. Analysis of the saliva and tear proteomes represents one promising alternative method of both classifying and monitoring the condition, and research into salivary and tear proteomics in patients with SjD, with and without sicca, has shown its efficacy and practicality in both clinical and research settings. Studies analyzing the saliva proteomics of SjD patients have generally shown an overexpression of proteins involved in T-cell activation, the immune response, β-2 microglobulin, and the recruitment of pro-inflammatory agents. These studies also show a decrease in or downregulation of proteins involved in salivary secretion. Studies analyzing the tear proteomics of patients with SjD have generally indicated an upregulation of proteins involved with TNF-α signaling, B-cell survival, and the recruitment of pro-inflammatory agents. Studies also note the differential expression of tear protein folding as a hallmark of ocular involvement in this condition. These findings help to elucidate the biochemical relationship between the proteomes of saliva/tear fluids and the general pathophysiology of the gland involved with the pathogenesis of this condition, giving further credence to the potential role of salivary and tear proteomics in the future of diagnosis and treatment for patients with SjD.

Evaluation of a novel latex enhanced turbidimetric immunoassay for detecting autoantibody against extractable nuclear antigens

Detection of autoantibody against extractable nuclear antigens (ENAs) plays a critical role in the diagnosis and management of autoimmune diseases.In this study, we assessed the performance of LETIA in detecting anti-ENAs. Total 606 serum samples from the Second Hospital of Shanxi Medical University were collected. Anti-SSA, anti-SSB, anti-Sm, anti-U1-snRNP, and anti-Sm/RNP were parallelly detected by LETIA and line immunoblot (LIA). Besides, this study assessed LETIA for its repeatability in detecting anti-ENAs autoantibodies, and consistency with LIA. A receiver operating characteristic (ROC) curves was drawn to assess the accuracy of LETIA. The LETIA and LIA showed high coincidence rate in detecting anti-SSA, anti-SSB, anti-Sm, anti-U1-snRNP, and anti-Sm/RNP autoantibodies, with the results being 87.22%, 96.61%, 97.03%, 88.28%, and 92.06%, respectively. Almost perfect consistency (kappa > 0.8) were found in the detection of anti-SSB and anti-Sm by LETIA and LIA. While in the detection of anti-SSA, anti-U1-snRNP, and anti-Sm/RNP, moderate consistency (0.6 ⩽ kappa ⩽ 0.8) were shown. The AUCs of anti-SSA, anti-SSB, anti-Sm, anti-U1-snRNP, and anti-Sm/RNP detected by LETIA were 0.972 (95% confidence interval (CI): 0.941–1.000, p < 0.001), 0.986 (95% CI: 0.967–1.000, p < 0.001), 0.912 (95% CI: 0.763–1.000, p < 0.001), 0.829 (95% CI: 0.731–0.928, p < 0.001), and 0.828 (95% CI: 0.715–0.941, p < 0.001), respectively. LETIA and LIA showed considerable consistency in detecting anti-ENAs. Moreover, with the pronounced advantages of automatic and rapid detection, and high universality, LETIA can meet the requirements for quantitative detection of anti-ENAs.

Laboratory Investigations for Diagnosis of Autoimmune and Inflammatory Periocular Disease: Part II

PURPOSE

To review the important laboratory serological investigations routinely performed for the diagnosis of autoimmune and inflammatory diseases of the orbit and ocular adnexa.

METHODS

Review of the literature as well as personal clinical experience of the authors. Due to the extensive nature of the topic, the review has been split into 2 parts. Part I covers thyroid eye disease, IgG4-related disease, and myasthenia gravis. In part II of the review, sarcoidosis, vasculitis, Sjögren syndrome, and giant cell arteritis will be discussed.

RESULTS

Several relatively specific serologic tests are available for the diagnosis of a variety of inflammatory and serologic diseases of the orbit.

CONCLUSION

In cases of limited orbital or sino-orbital disease, serologic testing may be negative in a significant number of patients. Specifically, the clinician should be wary of ruling out limited orbital sarcoid or sinoorbital granulomatosis with polyangiitis based on serologic testing alone. Part I of this review has covered serologic testing for thyroid eye disease, IgG4-related disease, and myasthenia gravis. In part II, the authors discuss serologic testing for sarcoidosis, vasculitis, Sjögren syndrome (SS), and giant cell arteritis (GCA).

Update on the role of plasmacytoid dendritic cells in inflammatory/autoimmune skin diseases

Plasmacytoid dendritic cells (pDCs) represent a specialized dendritic cell population that exhibit plasma cell morphology, express CD4, CD123, blood-derived dendritic cell antigen-2 (BDCA-2) and Toll-like receptor (TLR)7 and TLR9 within endosomal compartments. When activated, pDCs are capable of producing large quantities of type I IFNs (mainly IFN-α/β), which provide antiviral resistance and link the innate and adaptive immunity. While generally lacking from normal skin, pDCs infiltrate the skin and appear to be involved in the pathogenesis of several inflammatory, infectious (especially viral) and neoplastic entities. In recent years, pDC role in inflammatory/autoimmune skin conditions has been extensively studied. Unlike type I IFN-mediated protective immunity that pDCs provide at the level of the skin by regulated sensing of microbial or self-nucleic acids upon skin damage, excessive sensing may elicit IFN-driven inflammatory/autoimmune diseases. In this review, focus will be on the role of pDCs in cutaneous inflammatory/autoimmune dermatoses.

Immunoglobulin-like transcripts 6 (ILT6) polymorphism influences the anti-Ro60/52 autoantibody status in south Indian SLE patients

Introduction

Systemic lupus erythematosus (SLE) is a multisystem autoimmune disorder with complex etiology. Loss of immune tolerance against self-antigens results in activation of the immune system to produce autoantibodies, which in turn contribute to the clinical manifestations of the disease. Immune cells harbor a plethora of regulatory receptors. Immunoglobulin-like transcripts (ILTs) exhibit both immune activation and inhibitory properties. Genetic defects in genes encoding these receptors may predispose to development of autoimmune diseases secondary to loss of their function. The aim of our study was to analyze the presence or absence of the 6.7 kb segment in the ILT6 gene and its association with susceptibility to SLE and its different manifestations.

Method

A total of 188 SLE patients and 192 age-, sex similar-, ethnicity-matched controls were recruited. They were genotyped to test the presence or absence of the 6.7 kb segment of the ILT6 gene by polymerase chain reaction.

Results

The mutant allele lacking the 6.7 kb gene segment had an equal frequency in patients as well as controls (20% and 18%, respectively). The mutant allele was not associated with SLE or its clinical manifestations. However, the mutant allele was associated with the presence of anti-Ro60 ( p = 0.0005, OR 3.5, 95% CI 1.8–7.1) and anti-Ro52 ( p = 0.0027, OR 2.99, 95% CI 1.5–6.06) autoantibodies.

Conclusion

ILT6 deletion polymorphism does not appear to be a lupus susceptibility gene in South Indian Tamils, but may behave as a genetic modifier of autoantibody phenotype by influencing the production of anti-Ro60 and anti-Ro52 autoantibodies and thus indirectly contribute to autoimmune responses in SLE.

Current concepts and future directions for the assessment of autoantibodies to cellular antigens referred to as anti-nuclear antibodies

The detection of autoantibodies that target intracellular antigens, commonly termed anti-nuclear antibodies (ANA), is a serological hallmark in the diagnosis of systemic autoimmune rheumatic diseases (SARD). Different methods are available for detection of ANA and all bearing their own advantages and limitations. Most laboratories use the indirect immunofluorescence (IIF) assay based on HEp-2 cell substrates. Due to the subjectivity of this diagnostic platform, automated digital reading systems have been developed during the last decade. In addition, solid phase immunoassays using well characterized antigens have gained widespread adoption in high throughput laboratories due to their ease of use and open automation. Despite all the advances in the field of ANA detection and its contribution to the diagnosis of SARD, significant challenges persist. This review provides a comprehensive overview of the current status on ANA testing including automated IIF reading systems and solid phase assays and suggests an approach to interpretation of results and discusses meeting the problems of assay standardization and other persistent challenges.

Clinical and pathological roles of Ro/SSA autoantibody system

Anti-Ro/SSA antibodies are among the most frequently detected autoantibodies against extractable nuclear antigens and have been associated with systemic lupus erythematosus (SLE) and Sjögren's syndrome (SS). Although the presence of these autoantibodies is one of the criteria for the diagnosis and classification of SS, they are also sometimes seen in other systemic autoimmune diseases. In the last few decades, the knowledge of the prevalence of anti-Ro/SSA antibodies in various autoimmune diseases and symptoms has been expanded, and the clinical importance of these antibodies is increasing. Nonetheless, the pathological role of the antibodies is still poorly understood. In this paper, we summarize the milestones of the anti-Ro/SSA autoantibody system and provide new insights into the association between the autoantibodies and the pathogenesis of autoimmune diseases.

Pathogenesis of cutaneous lupus erythematosus: common and different features in distinct subsets

The term 'cutaneous lupus erythematosus' (CLE) comprises several related autoimmune skin disorders, defined as 'specific' skin manifestations of lupus erythematosus (LE). The spectrum of clinical presentation of CLE is wide, reaching from mild erythema to disseminated scarring skin lesions. There is increasing knowledge concerning the pathogenesis of LE skin lesions and it has been shown that a complex network of cutaneous cytokines, chemokines and adhesion molecules orchestrate and promote tissue injury observed in LE skin lesions. However, a complete understanding of the diverse pathophysiological mechanisms in the different CLE subsets does not exist. Here we review the main pathological features described in CLE patients against the background of the clinical diversity of different CLE subtypes.

Identification of type I interferon-associated inflammation in the pathogenesis of cutaneous lupus erythematosus opens up options for novel therapeutic approaches

Cutaneous lupus erythematosus (CLE) is one of the most common dermatological autoimmune disorders worldwide. Recently, several studies provided evidence for a pathogenic role of type I interferons (IFNs) in this disease. Plasmacytoid dendritic cells are major type I IFN producers in CLE skin lesions. Type I IFNs are able to induce the expression of several proinflammatory chemokines, including CXCL9 and 10, and enhance the cytotoxic capacity of infiltrating cells. Additionally, adhesion molecules and chemokine receptors, such as intercellular adhesion molecule-1, cutaneous lymphocyte antigen, E-selectin, CCR4 and CXCR3, are involved in the recruitment of potentially autoreactive lymphocytes into the skin. Here, we review the role of type I IFNs, adhesion molecules and chemokine receptors in CLE and discuss options for novel therapeutic approaches.

High serum levels of antibodies against the recombinant 70 kDa ribonucleoprotein are useful for diagnosing mixed connective tissue disease

BACKGROUND

Anti-Sm antibodies and anti-RNP antibodies are considered to be diagnostic markers of systemic lupus erythematosus (SLE) and mixed connective tissue disease (MCTD). However, cross-reactivity between the antibodies diminishes their discriminating specificity between these diagnoses.

OBJECTIVE

We examined whether we could achieve better differentiation between these two disease entities using recombinant antigens to RNP70 and SmD and quantitative immunoassays.

PATIENTS/METHODS

Sera from 51 patients with SLE and 10 patients with MCTD and from a control group of 59 patients were used in a cross-sectional setting. Semiquantitative ELISAs for the detection of antibodies to RNP-70, RNP-A, RNP-C, SmBB' and SmD were used and the results were compared to conventional ELISA tests using U(1)-snRNP and a mixture of SmBB' and SmD as antigenic substrates.

RESULTS

Sera from MCTD patients showed higher levels of anti-RNP-70 antibodies than sera from SLE patients. Levels of anti-SmBB' or anti-SmD antibodies were not significantly different between SLE and MCTD sera. However, the presence of antibodies directed against SmD was more frequent in SLE.

CONCLUSIONS

Our results suggest that the use of RNP-70 and SmD antigens may increase the practical value of immunoassays used to confirm a diagnosis of SLE or MCTD in patients with connective tissue disease.

Immunopathology of vesicular cutaneous lupus erythematosus in the rough collie and Shetland sheepdog: a canine homologue of subacute cutaneous lupus erythematosus in humans

Clinical and histological features of an erosive disease in the rough collie and Shetland sheepdog are most consistent with a vesicular variant of cutaneous lupus erythematosus (VCLE). This paper reports the immunopathological findings of canine VCLE using samples from 17 affected dogs. Lesional skin sections were stained with monoclonal antibodies specific for CD3 (11 dogs) or a panel of monoclonal antibodies specific for leukocyte antigens (two dogs). Apoptotic cells were detected using the TUNEL method in 12 cases. Direct (14 dogs) and indirect immunofluorescence tests (five dogs) were also performed. Circulating antibodies to extractable nuclear antigens (ENA) were surveyed in 11 dogs by immunoblotting and ELISA. The predominant cells at the dermal-epidermal interface were identified as CD3(+) T lymphocytes expressing CD4 or CD8 and CD1(+) dendritic antigen presenting cells. In 7/12 dogs (58%), apoptosis of basal keratinocyte nuclei was present. Up-regulation of MHCII and ICAM-1 was observed on basal keratinocytes from the two dogs examined. Direct immunofluorescence revealed deposition of immunoglobulins bound to the cytoplasm of keratinocytes (6/14 dogs; 43%), to the dermal-epidermal junction (7/14 dogs; 50%), or to superficial dermal venules (13/14 dogs; 93%). Circulating IgG auto-antibodies targeting one or more ENA were detected in nine (82%) and eight (73%) of 11 dogs by immunoblotting and ELISA, respectively. These auto-antibodies recognized Ro/SSA and/or La/SSB in four (36%) and six (55%) of 11 dogs respectively by these two methods. Altogether, results of these studies provide evidence supporting the hypothesis that canine VCLE is an immunological homologue of subacute cutaneous lupus erythematosus in humans.

Lymphocytopenia in lupus erythematosus: close in vivo association to autoantibodies targeting nuclear antigens

BACKGROUND

Leukopenia and lymphopenia are typical features of lupus erythematosus (LE) and correlate with elevated disease activity and higher grades of systemic involvement. Antilymphocyte antibodies are regarded as the most likely rationale for the decreased cell numbers; however, their relevance has not been confirmed so far.

OBJECTIVES

Previous investigations at our department have shown a significant correlation between diminished lymphocyte numbers and the presence of antinuclear antibodies (ANA). We wanted to achieve a better understanding of this phenomenon.

METHODS

We performed a detailed analysis of autoantibodies and peripheral leucocyte subsets in 82 patients with different subtypes of LE. Leucocyte subsets were measured using flow cytometry (FACScan; Becton Dickinson, Franklin Lakes, NJ, USA.); autoantibodies were detected by indirect immunofluorescence and by enzyme-linked immunosorbent assay.

RESULTS

A significant association (P < 0.05) between specific antibodies targeting nuclear antigens (SSA/Ro-52, SSB/La, snRNPs) and lymphocytopenia was found.

CONCLUSIONS

We suppose that some of these autoantibodies might have an antilymphocyte effect. Apoptosis induction by specific antinuclear antibodies has already been described earlier, but to the best of our knowledge this is the first study presenting a strong indication of a possible interaction between these antibodies and lymphocyte subsets in vivo.