Clinical and serologic associations of the antiribosomal P protein antibody

Women in rheumatology: major contributions and key discoveries of the twentieth century

In the twentieth century, rheumatology saw an exponential growth. Discoveries in the pathophysiology of rheumatic diseases, progress in research methodology and novel treatments cardinally changed the natural course of rheumatic diseases and revolutionized patient management. Although underrepresented in this field, women have made considerable input in advancing our specialty towards the new era. In this article we acknowledge key scientific discoveries and major contributions made by 18 brilliant women scientists that shaped the field of rheumatology in the twentieth century. We hope that the achievements of these remarkable women will inspire young rheumatologists and researchers.

Mood Disorder in Systemic Lupus Erythematosus Induced by Antiribosomal P Protein Antibodies Associated with Decreased Serum and Brain Tryptophan

Antiribosomal P protein (anti-P) autoantibodies commonly develop in patients with systemic lupus erythematosus. We have previously established hybridoma clones producing anti-P mAbs. In this study, we explored the pathogenesis of behavioral disorders induced by anti-P Abs using these mAbs. New Zealand Black × New Zealand White F1, New Zealand White, C57BL/6, and BALB/c mice were treated with 1 mg of anti-P Abs once every 2 wk. The behavioral disorder was evaluated by the tail suspension test, forced swim test, and open field test. Following administration of anti-P Abs, New Zealand Black × New Zealand White F1 and C57BL/6 mice developed depressive behavior and showed increased anxiety with elevated serum TNF-α and IL-6 levels. Anti-P Abs were not deposited in the affected brain tissue; instead, this mood disorder was associated with lower serum and brain tryptophan concentrations. Tryptophan supplementation recovered serum tryptophan levels and prevented the behavioral disorder. TNF-α and IL-6 were essential for the decreased serum tryptophan and disease development, which were ameliorated by treatment with anti-TNF-α neutralizing Abs or dexamethasone. Peritoneal macrophages from C57BL/6 mice produced TNF-α, IL-6, and IDO-1 via interaction with anti-P Abs through activating FcγRs, which were required for disease development. IVIg, which has an immunosuppressive effect partly through the regulation of FcγR expression, also prevented the decrease in serum tryptophan and disease development. Furthermore, serum tryptophan concentrations were decreased in the sera of systemic lupus erythematosus patients with anti-P Abs, and lower tryptophan levels correlated with disease activity. Our study revealed some of the molecular mechanisms of mood disorder induced by anti-P Abs.

Case Report: Psychopathological Syndromes in the Course of Lupus Erythematosus and the Co-occurrence of Lupus Erythematous With Mental Disorders

Background: Systemic lupus erythematosus (SLE) is an autoimmune disease that leads to a chronic inflammatory process in tissues and organs. The neuropsychiatric systemic lupus erythematosus (NPSLE) is a set of neuropsychiatric symptoms that derive from the central and peripheral nervous system and are observed in the course of SLE. Case Report and Final Diagnostic and Therapeutic Results: A diagnostic and therapeutic process in a patient with the signs and symptoms of SLE and bipolar disorder (BD) has been described. Bipolar disorder has been diagnosed as a primary disorder while SLE as a comorbid disease. Discussion: Common immunological mechanisms in BD and SLE are the reason for difficulties in diagnosing BD with co-occurring SLE. It should be determined whether BD is a primary disorder or a secondary component of a clinical picture of SLE (NPSLE) or whether mood and/or psychotic disorders are the result of steroid therapy in the course of SLE (steroid-induced mood and psychotic disorders, SIMPD). Conclusion and the Patient's Perspective: The presented case report is a unique description of a patient with a primary diagnosis of BD with comorbid SLE.

The immunologic etiology of psychiatric manifestations in systemic lupus erythematosus: A narrative review on the role of the blood brain barrier, antibodies, cytokines and chemokines

INTRODUCTION

The aim of this narrative review is to provide an overview of the literature on the possible immunologic pathophysiology of psychiatric manifestations of neuropsychiatric systemic lupus erythematosus (NPSLE).

METHODS

A systematic search on PubMed was conducted. English studies with full text availability that investigated the correlation between blood-brain barrier (BBB) dysfunction, intrathecal synthesis of antibodies, antibodies, cytokines, chemokines, metalloproteinases, complement and psychiatric NPSLE manifestations in adults were included.

RESULTS

Both transient BBB-dysfunction with consequent access of antibodies to the cerebrospinal fluid (CSF) and intrathecal synthesis of antibodies could occur in psychiatric NPSLE. Anti-phospholipid antibodies, anti-NMDA antibodies and anti-ribosomal protein p antibodies seem to mediate concentration dependent neuronal dysfunction. Interferon-α may induce microglial engulfment of neurons, direct neuronal damage and production of cytokines and chemokines in psychiatric NPSLE. Several cytokines, chemokines and matrix metalloproteinase-9 may contribute to the pathophysiology of psychiatric NPSLE by attracting and activating Th1-cells and B-cells.

DISCUSSION

This potential pathophysiology may help understand NPSLE and may have implications for the diagnostic management and therapy of psychiatric NPSLE. However, the presented pathophysiological model is based on correlations between potential immunologic etiologies and psychiatric NPSLE that remain questionable. More research on this topic is necessary to further elucidate the pathophysiology of NPSLE.

A review and meta-analysis of anti-ribosomal P autoantibodies in systemic lupus erythematosus

The discovery of autoantibodies to ribosomal proteins (anti-RibP) dates back more than fifty years when antibodies to ribosomes were identified in systemic lupus erythematosus (SLE) sera. Over the years, anti-RibP autoantibodies have been the subject of extensive study and became known as a highly specific biomarker for the diagnosis of SLE and were associated with neuropsychiatric SLE (NPSLE), lupus nephritis (LN) and hepatitis (LH). As demonstrated by studies on cultured human cells and of murine models, there is evidence to suggest that anti-RibP may have a pathogenic role in LN and NPSLE. Despite a wealth of evidence, in comparison to other SLE autoantibodies such as anti-Sm and anti-dsDNA, anti-RibP has not been included in classification criteria for SLE. A significant challenge is the variability of assays used to detect anti-RibP, including the antigens and diagnostic platforms employed. This may account for the marked variation in frequencies (10-47%) in SLE and its association with clinical and demographic features reported in SLE cohorts. We performed a systematic literature review and meta-analysis to help clarify its prevalence, various clinical and serological associations in SLE based on the different RibP antigens and assay platforms used.

Autoantibodies Associated With Connective Tissue Diseases: What Meaning for Clinicians?

Connective tissue diseases (CTDs) such as systemic lupus erythematosus, systemic sclerosis, myositis, Sjögren's syndrome, and rheumatoid arthritis are systemic diseases which are often associated with a challenge in diagnosis. Autoantibodies (AAbs) can be detected in these diseases and help clinicians in their diagnosis. Actually, pathophysiology of these diseases is associated with the presence of antinuclear antibodies. In the last decades, many new antibodies were discovered, but their implication in pathogenesis of CTDs remains unclear. Furthermore, the classification of these AAbs is nowadays misused, as their targets can be localized outside of the nuclear compartment. Interestingly, in most cases, each antibody is associated with a specific phenotype in CTDs and therefore help in better defining either the disease subtypes or diseases activity and outcome. Because of recent progresses in their detection and in the comprehension of their pathogenesis implication in CTD-associated antibodies, clinicians should pay attention to the presence of these different AAbs to improve patient's management. In this review, we propose to focus on the different phenotypes and features associated with each autoantibody used in clinical practice in those CTDs.

Ribosomal P antibody: 30 years on the road

The identity of the protein antigens targeted by anti-cytoplasmic antibodies in lupus was discovered 30 years ago. These antigens are three acidic ribosomal phosphoproteins, P0, P1, and P2. Precise identification of the shared epitope on these three proteins enabled sensitive and specific immunoassays to be developed. Anti-P antibodies are highly specific for systemic lupus erythematosus (SLE) and occur in 15%–35% of patients, depending on ethnicity as well as the age of onset. Increased frequencies of detection of anti-P have been reported in childhood SLE as well as in neuropsychiatric, renal, and hepatic disease. While longitudinal studies by the Systemic Lupus International Collaborating Clinics (SLICC) consortium supported the association of anti-P with neuropsychiatric lupus, the predictive value of antibody determination remains controversial. This is likely explained by the heterogeneity of neuropsychiatric lupus as well as by the different methodologies used for assay. A number of experimental studies have suggested a direct pathogenic role for anti-P antibodies in brain disease. Findings include cross reactivity between anti-P and a neuronal surface antigen, which was detected in areas of the brain involved in memory, cognition, and emotion. Direct injection of anti-P antibodies into the brains of rodents was also associated with abnormal electrical activity and behavioral disturbances. Taken together, research over the last 30 years has established anti-P antibodies as a useful diagnostic marker of SLE and at least a subset of patients with neuropsychiatric disease. Further research is required to fine tune the association of anti-P with clinical manifestations and establish beyond high probability a pathophysiologic role for the antibodies.

Anti-ribosomal P-protein and its role in psychiatric manifestations of systemic lupus erythematosus: myth or reality?

Systemic lupus erythematosus (SLE) is an autoimmune disease that may involve the central nervous system (CNS) resulting in neuropsychiatric manifestations. The associated psychiatric disorders include depression, psychosis, mood disorders, anxiety, cognitive dysfunction, and delirium/encephalopathy. Several autoantibodies may play a role in the pathogenesis of psychiatric complications of SLE, particularly antibodies against ribosomal P-proteins (anti-P) and possibly antibodies against endothelial cells (AECA). The reported prevalence of anti-P is highly variable in SLE patients and is dependent on different ethnic backgrounds, sensitivity and specificity of the assays employed for autoantibody detection, and the time at which sera were analysed in relation to the clinical event. Controversial data exist on the association of anti-P with psychiatric manifestations of SLE. These autoantibodies have been suggested to be specific markers of the psychiatric manifestations of SLE, particularly of the psychosis and depression, and the antibody level varied with the clinical activity of the disease. Some studies have confirmed the hypothesis of an association of anti-P antibodies with psychiatric manifestations of neuropsychiatric SLE (NPSLE) while others have disputed this relationship. This review summarizes the recent studies about relationship between anti-P antibodies and psychiatric manifestation of SLE.

Review: Neuropsychiatric involvement in pediatric systemic lupus erythematosus

Neuropsychiatric (NP) manifestations are found in approximately 25% of children and adolescents with pediatric SLE (pSLE). In 70% of those, NP involvement will occur within the first year from the time of diagnosis. Headaches (66%), psychosis (36%), cognitive dysfunction (27%) and cerebrovascular disease (24%) are the most common presentations. The support of a psychiatrist is often required. Anti-phospholipid antibodies are associated with distinct NP disease entities and may be implicated in the pathogenesis of several manifestations of NP-pSLE including chorea, cerebrovascular disease and seizures. The role of novel auto-antibodies and imaging modalities is currently explored. The treatment of NP-pSLE is not based on prospective studies; however, an immunosuppressive combination therapy consisting of high doses of prednisone and a second line agent such as cyclophosphamide or azathioprine is commonly suggested for children with NP-pSLE. The role of novel therapies is currently studied. The outcome of children with NP-pSLE is relatively good. The overall survival is 95—97%, 20% of children experience a disease flare during childhood and 25% have evidence of permanent neuropsychiatric damage. Lupus (2007) 16, 564—571.

The association of serum anti-ribosomal P antibody with clinical and serological disorders in systemic lupus erythematosus: a systematic review and meta-analysis

Objective

Anti-ribosomal P (anti-P) antibody is a serological specific marker of systemic lupus erythematosus (SLE). The aim of this study is to investigate the association of this antibody with clinical and serological disorders in SLE.

Methods

All relevant literature was retrieved from PubMed, EMBASE, Web of Science and CNKI databases. The qualities of these studies were evaluated using a modified version of the Newcastle–Ottawa scale. The associations of anti-P antibody with clinical and serological disorders were determined by the pooled odds ratio (OR) and the confidence interval (CI) calculated using meta-analysis with the Mantel–Haenszel method.

Results

Sixteen cohort studies with 2355 patients were included in this study. Malar rash, oral ulcer and photosensitivity were strongly associated with serum anti-P antibody, with OR (95% CI) values of 2.05 (1.42–2.92), 1.49 (1.05–2.13) and 1.44 (1.08–1.91), respectively. Arthritis and renal involvement were not associated with anti-P antibody, whereas a high heterogeneity was observed due to ethnicity and publication bias, respectively. Neuropsychiatric SLE (NPSLE), hepatic involvement, anti-dsDNA, anti-Sm and anti-cardiolipin antibodies (aCL) were observed more frequently in anti-P positive patients than in negative patients. Studies on hepatic involvement showed a low precision with substantially broad CI (2.56–11.2). A high heterogeneity presented among studies on NPSLE, anti-Sm and aCL.

Conclusions

Anti-P antibody is significantly associated with malar rash, oral ulcer, photosensitivity and serum anti-dsDNA antibody, and potentially associated with NPSLE, hepatic damage, serum anti-Sm and aCL.

Anti-ribosomal P protein: a novel antibody in autoimmune hepatitis

BACKGROUND

Autoantibodies to ribosomal P proteins (anti-rib P) are specific serological markers for systemic lupus erythematosus (SLE) and are associated with liver involvement in this disease. The similarity in autoimmune background between autoimmune hepatitis (AIH) and SLE-associated hepatitis raises the possibility that anti-rib P antibodies might also have relevance in AIH.

AIMS

To evaluate the frequency and clinical significance of anti-rib P antibodies in a large AIH cohort.

METHODS

Sera obtained at diagnosis of 96 AIH patients and of 82 healthy controls were tested for IgG anti-ribosomal P protein by ELISA. All of the sera were also screened for other lupus-specific autoantibodies, three patients with the presence of anti-dsDNA (n = 1) and anti-Sm (n = 2) were excluded.

RESULTS

Moderate to high titres (>40 U) of anti-rib P antibody were found in 9.7% (9/93) of the AIH patients and none of the controls (P = 0.003). At presentation, AIH patients with and without anti-rib P antibodies had similar demographic/clinical features, including the frequency of cirrhosis (44.4 vs. 28.5%, P = 0.44), hepatic laboratorial findings (P > 0.05). Importantly, at the final observation (follow-up period 10.2 ± 4.9 years), the AIH patients with anti-rib P had a significantly higher frequency of cirrhosis compared with the negative group (100 vs. 60%, P = 0.04).

CONCLUSION

The novel demonstration of anti-rib P in AIH patients without clinical or laboratory evidence of SLE suggests a common underlying mechanism targeting the liver in these two diseases. In addition, this antibody appears to predict the patients with worse AIH prognoses.

Brain-reactive antibodies and disease

Autoimmune diseases currently affect 5-7% of the world's population; in most diseases there are circulating autoantibodies. Brain-reactive antibodies are present in approximately 2-3% of the general population but do not usually contribute to brain pathology. These antibodies penetrate brain tissue only early in development or under pathologic conditions. This restriction on their pathogenicity and the lack of correlation between serum titers and brain pathology have, no doubt, contributed to a delayed appreciation of the contribution of autoantibodies in diseases of the central nervous system. Nonetheless, it is increasingly clear that antibodies can cause damage in the brain and likely initiate or aggravate multiple neurologic conditions; brain-reactive antibodies contribute to symptomatology in autoimmune disease, infectious disease, and malignancy.

Comparative study of immunofluorescent antinuclear antibody test and line immunoassay detecting 15 specific autoantibodies in patients with systemic rheumatic disease

Based on the currently proposed algorithms, antibodies specificities (sp-ANAs) are identified mainly in samples positive for fluorescent antinuclear antibodies (FANA) screening tests. The purpose of the present study was to compare diagnostic performances of FANA and line immune assay (LIA) detecting 15 sp-ANAs in patients with systemic rheumatic diseases (SRD). In 948 sera from the patients with SRD (n = 590) and non-SRD (n = 358), we evaluated the fluorescent patterns and intensities in the FANA test, and compared the FANA results with sp-ANAs against nRNP, Sm, SS-A, Ro52, SS-B, Scl-70, PM/Scl, Jo-1, CENP B, PCNA, dsDNA, nucleosome, histone, ribosomal-P, and M2. The sensitivity and specificity was 75.9% and 52.5% of FANA test and 62.0% and 84.4% of sp-ANAs test for SRD detection. The overall agreement between FANA and sp-ANAs results was 69.2% (Kappa coefficient; 0.404). According to the clinical diagnosis, the levels of agreement varied from 33.3% to 83.1%. The positive predictive values of each FANA pattern for the detection of sp-ANAs were less than 50% except for the discrete speckled pattern (91.7%). The 1:100 intensity of FANA as well as the monoreactivity of LIA, anti-SSA(-)/anti-Ro52(+), or FANA(-)/sp-ANAs(+) was associated with non-SRD. Antibodies against ribosomal-P or PCNA were specific for systemic lupus eryhthematosus. This study highlights the need for careful interpretation of FANA test results to assess sp-ANAs and the application of sp-ANAs tests including less-common autoantibodies. In patients with clinical suspicion of SRD, screening with both FANA and sp-ANAs tests could improve diagnostic efficiency.

A 17-Year-Old Female with Systemic Lupus Presents with Complex Movement Disorder: Possible Relationship with Antiribosomal P Antibodies

Complex movement disorder is a relatively rare presentation of neurolupus. Antiphospholipid antibodies are associated with movement disorders likely via aberrant neuronal stimulation. Antiribosomal P antibodies have been previously associated with neuropsychiatric disorders but their correlation with movement disorder was not previously established. Our case report involves a 17-year-old Caucasian female patient positive for only antiribosomal P antibody and lupus anticoagulant who presented with a sudden onset of complex movement disorder. After complete cessation of physical signs with olanzapine, anticardiolipin and anti-β2 glycoprotein I antibodies became positive which indicates a likely discordance between movement disorder and antiphospholipid antibodies. This also indicates a potential causal role of antiribosomal P antibodies in inducing movement disorder.

Autoantibodies in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a multifactorial disorder with multigenic inheritance and various environmental factors implicated in its aetiopathogenesis. Despite the multiple mechanisms involved in the aetiology of SLE being elusive, recent studies have made progress in our understanding of the pathogenic mechanisms via abnormal regulation of cell-mediated and humoral immunity that lead to tissue damage. The heterogeneity of the clinical manifestations probably reflects the complexity of the disease pathogenesis itself. The immune system in SLE is characterised by a complex interplay between overactive B cells, abnormally activated T cells and antigen-presenting cells. This interplay leads to the production of an array of inflammatory cytokines, apoptotic cells, diverse autoantibodies and immune complexes that in turn activate effector cells and the complement system, leading to tissue injury and damage which are the hallmarks of the clinical manifestations. SLE patients have dysregulation of inflammatory cytokines, chemokines and immune response-related genes, as well as of the genes involved in apoptosis, signal transduction and the cell cycle.

Evaluation of anti-ribosomal P protein immunoassay in Japanese patients with connective tissue diseases: comparison with an indirect immunofluorescence assay

OBJECTIVES

To investigate the prevalence of anti-ribosomal P protein (anti-P) antibodies in Japanese patients with connective tissue diseases (CTDs) using enzyme-linked immunosorbent assays (ELISAs) and western blotting (WB) and to evaluate the indirect immunofluorescence (IIF) staining patterns of anti-P-positive sera.

METHODS

Anti-P antibodies were measured by two different commercially available ELISA kits and WB in 239 outpatients, 99 with systemic sclerosis (SSc), 73 with systemic lupus erythematosus (SLE), 45 with dermatomyositis (DM), and 22 with Sjögren's syndrome (SjS). Sera positive for anti-P antibodies by WB were analysed by IIF.

RESULTS

The frequency of positive WB findings in SLE (18/73, 25%) was higher than in other diseases. ELISA kits A and B for anti-P antibodies showed 21% and 43% sensitivity, and 93% and 88% specificity, respectively, for diagnosing SLE, based on the manufacturer's cut-off values. Receiver operating characteristic (ROC) curve analysis, based on positive WB findings, determined a new cut-off threshold but revealed that both ELISA kits still had good diagnostic characteristics. In IIF assays on anti-P antibody positive sera, typical anti-P antibody cytoplasmic staining patterns (n=8) were seen less frequently than other staining patterns (n=17).

CONCLUSIONS

Routine screening for anti-P antibodies by IIF has low sensitivity. ELISAs using cut-off values established by individual facilities are suitable for detecting anti-P antibodies and provide a tool with good diagnostic characteristics, on a parity with WB.

Anti-proteasome activator 28alpha is a novel anti-cytoplasmic antibody in patients with systemic lupus erythematosus and Sjögren's syndrome

We evaluated the extent to which anti-proteasome activator (PA) 28alpha antibodies act as anti-cytoplasmic antibodies in systemic lupus erythematosus (SLE) and Sjögren's syndrome (SS). Sera from 46 SLE patients without SS, 11 SLE patients with SS, and 45 primary SS patients were tested. Using anti-PA28alpha and anti-PA28gamma (Ki) antibodies purified from nitrocellulose membranes onto which recombinant PA28alpha and Ki had been transferred, the cellular distributions of the targeted antigens were analyzed immunohistochemically. In addition, the incidence of anti-PA28alpha antibodies was compared with those of other anti-cytoplasmic antibodies. Immunofluorescent staining showed that purified anti-PA28alpha antibodies reacted with the cytoplasm of HEp-2 cells, whereas purified anti-Ki antibodies reacted with nucleoplasm. Among the 15 SLE patients without SS, the six SLE patients with SS, and the 30 primary SS patients who were anti-cytoplasmic-antibody positive, anti-SS-A/Ro antibodies were the most frequently detected (53, 67, and 70%, respectively); anti-PA28alpha antibodies were, respectively, detected in 33, 50, and 40% of those patient groups, incidences that were higher than those of anti-ribosomal P, anti-smooth muscle and anti-mitochondrial M2 antibodies. These results show that anti-PA28alpha antibodies are major anti-cytoplasmic antibodies in patients with SLE and SS, and the distinct cellular distributions of PA28alpha and Ki suggest these proteins are associated with different cellular functions.

Clinical and diagnostic value of ribosomal P autoantibodies in systemic lupus erythematosus

OBJECTIVE

To analyse prospectively the diagnostic sensitivity and specificity as well as the clinical relevance of ribosomal P (anti-P) autoantibodies in a large cohort of SLE patients.

METHODS

The anti-P autoantibodies were evaluated in the serum of 200 Tunisian SLE patients at disease onset and 130 various control subjects by a sensitive immunodot assay. A complete laboratory evaluation and clinical examination were performed in each SLE patient. During the follow-up, the patients were regularly monitored for clinical parameters. Global SLE activity was measured by the ECLAM.

RESULTS

The sensitivity and specificity of anti-P testing for SLE were 23.5 and 98.4%, respectively. The anti-P-positive samples 14/47 (29.8%), 27/47 (57.4%) and 5/47 (10.6%) were negative for anti-dsDNA, anti-Sm or both antibodies, respectively. The anti-P-positive patients showed more active disease activity and a much higher prevalence of arthritis. An association between IgG aCLs and anti-P antibodies was also found. However, anti-P antibodies were not associated with neuropsychiatric manifestations or lupus nephritis.

CONCLUSION

This study does not seem to confirm the described association of anti-P antibodies with neuropsychiatric manifestations of SLE. However, it supports the anti-P antibody association with arthritis and disease activity as well as the presence of aCL. Based on our study and other related studies, we propose that, akin to anti-Sm and anti-dsDNA, anti-P antibodies detected by one agreed method may be considered for inclusion as a criterion for the classification of SLE.

Autoantibodies involved in neuropsychiatric manifestations associated with systemic lupus erythematosus

In the course of Systemic Lupus Erythematosus (SLE), a variety of neuropsychiatric disturbances is reported with a prevalence ranging from 17% to 75%. The diagnosis of these syndromes is difficult and requires a careful psychiatric evaluation. Distinct autoantibodies detectable in serum or cerebrospinal fluid of patients with SLE are associated with the presence of neuropsychiatric disorders. These autoantibodies may have a pathogenic relevance in neuropsychiatric SLE or they may be merely an epiphenomenon. This review describes the various autoantibodies reported to be associated with neuropsychiatric manifestations in SLE and discusses their possible role.

Limited reliability of the indirect immunofluorescence technique for the detection of anti-Rib-P antibodies

Introduction

Autoantibodies to the ribosomal P proteins represent a highly specific marker for the diagnosis of systemic lupus erythematosus, where they have been associated with certain clinical manifestations. Historically, autoantibodies against ribosomal P proteins have been detected by indirect immunofluorescence, immunodiffusion, immunoblot, and other immunoassays. More recently, enzyme-linked immunosorbent assays and line and addressable laser bead immunoassays have become more widely used. The primary goal of this study was to determine the sensitivity of indirect immunofluorescence using conventional HEp-2 substrates in the detection of sera with ribosomal P antibodies as detected by other immunoassays.

Methods

Anti-ribosomal P-positive sera (n = 345) as detected by an addressable laser bead immunoassay were collected between 2003 and 2007 and analysed by indirect immunofluorescence. Furthermore, 51 anti-ribosomal P-positive samples from an unselected systemic lupus erythematosus cohort (n = 100) and the Centers for Disease Control and Prevention (CDC) anti-nuclear antibody (ANA) reference sera were tested for anti-ribosomal P reactivity.

Results

In the cohort of 345 anti-ribosomal P-positive samples identified by addressable laser bead immunoassay, a low sensitivity (<30%) of indirect immunofluorescence on HEp-2 cell substrates was observed. Although the degree of sensitivity varied among different manufacturers, all immunofluorescence substrates exhibited limited sensitivity and false-negative results were not restricted to samples with low anti-ribosomal P titers. Even the anti-ribosomal P reactivity of CDC ANA reference serum number 12 was not clearly predictable by indirect immunofluorescence. Comparison of five different methods for the detection of anti-ribosomal P found moderate qualitative agreements.

Conclusions

Based on our data, we conclude that indirect immunofluorescence on HEp-2 cells is not a reliable screening test for the prediction of ribosomal P antibodies. As this method is widely used as a first-line screening test for anti-nuclear and other autoantibodies, special considerations for the detection of ribosomal P antibodies are needed. As with many other autoantibodies, further effort is required for the standardisation of ribosomal P immunoassays.

Prevalence of depressive and anxiety disorders in systemic lupus erythematosus and their association with anti-ribosomal P antibodies

OBJECTIVE

To estimate the prevalence of psychiatric disorders in patients with systemic lupus erythematosus (SLE) and explore their association with anti-ribosomal P (anti-P) antibodies.

METHODS

Seventy-one consecutive female SLE patients without neurological manifestations were evaluated for psychiatric disorders using the Structured Clinical Interview for DSM-IV (SCID). Anti-P antibodies were measured by enzyme-linked immunosorbent assay (ELISA)/immunoblot analysis.

RESULTS

The mean age of subjects was 34.8 years (SD: 10.1 years), and the mean duration of SLE was 9.8 years (SD: 6.5 years). The 30-day prevalences of psychiatric disorders were: mood disorders 26.8%, anxiety disorders 46.5%, adjustment disorders 8.4%, alcohol abuse 1.4%, and somatoform disorder 1.4%. The lifetime prevalences of psychiatric disorders were: mood disorders 69%, anxiety disorders 52.1%, alcohol abuse 1.4%, and somatoform disorder 1.4%. Subjects with and without psychiatric manifestations did not differ regarding SLE clinical and laboratorial parameters including presence or absence of anti-P antibodies (23.1% vs. 20%, respectively, p=1.0), disease activity, as measured by the Systemic Lupus Erythematosus Disease activity Index (4.08+/-5.7 vs. 4.95+/-6.3 respectively, p=0.60) and cumulated damage, as measured by the Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index (0.7+/-2.3 vs. 0.3+/-0.7 respectively, p=0.33).

CONCLUSIONS

Mood and anxiety disorders are the most frequently observed psychiatric disorders in female SLE patients without concomitant neurological manifestations. These mild/moderate forms of psychiatric disorders are not associated with anti-P antibodies in SLE patients. Our findings reinforce the importance of systematic psychiatric evaluation for these patients in order to provide adequate and comprehensive care.

Lymphocytotoxic antibodies in systemic lupus erythematosus are associated with disease activity irrespective of the presence of neuropsychiatric manifestations

OBJECTIVES

To evaluate the association of the presence of lymphocytotoxic, anti-beta2-glycoprotein I (anti-beta2-GPI) and anti-ribosomal P (anti-P) antibodies in patients with systemic lupus erythematosus (SLE), presenting or not neuropsychiatric (NP) manifestations, stratified according to the activity of the disease.

METHODS

A total of 138 patients with SLE (59 with active NPSLE, 49 with active non-NPSLE, and 30 with inactive disease) and 57 healthy controls were studied. Disease activity was assessed by the SLE Disease Activity Index (SLEDAI). The presence of lymphocytotoxic antibodies was assessed using a complement-dependent lymphocytotoxicity assay. The presence of anti-beta2-GPI and anti-P antibodies was detected by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Lymphocytotoxic antibodies were detected primarily in patients with active disease, that is in 35 out of 59 (59.3%) NPSLE and 23 out of 49 (46.9%) non-NPSLE patients, whereas only four out of 30 (13.3%) inactive SLE patients and none of the healthy controls exhibited the autoantibody. The frequency of lymphocytotoxic antibodies in active SLE patients, considered as a whole or stratified into NPSLE or non-NPSLE, was significantly increased in relation to inactive SLE patients (p<0.001 for each comparison). No significant difference was observed when comparing active NPSLE with non-NPSLE patients. No associations were observed between the presence of anti-beta2-GPI or anti-P antibodies and the activity of SLE or the presence of lymphocytotoxic antibodies.

CONCLUSIONS

Lymphocytotoxic antibodies occurred more frequently in patients with active SLE than in patients with inactive disease, irrespective of the presence of NP manifestations, a finding that is similar to classical biomarkers of lupus activity (anti-dsDNA and complement). These results indicate that the assessment of the presence of lymphocytotoxic antibodies may be an additional useful tool for the evaluation of SLE activity.

Autoantibodies Involved in Neuropsychiatric SLE and Antiphospholipid Syndrome

OBJECTIVE

We sought (1) to identify and (2) to define the association of all reported antibodies (Abs) with neuropsychiatric lupus (NPSLE), (3) to search for possible mechanisms that are involved in NPSLE, and (4) to determine whether we can recognize a panel of Abs associated with specific neuropsychiatric (NP) manifestations.

METHODS

A MEDLINE search (1975 to 2005) was performed utilizing the following terms: neuropsychiatric lupus, antiphospholipid syndrome, or central nervous system systemic lupus erythematosus matched with the term antibodies.

RESULTS

Twenty Abs (11 brain-specific and 9 systemic) were described in NPSLE patients. These include Abs that target brain-specific antigens (neuronal, ganglioside, synaptosomes, glia, methyl-d-aspartate receptors, lymphocytotoxic) and systemic antigens (nuclear, cytoplasmic, phospholipid, endothelial cells). Cognitive impairment, psychosis, and depression were associated with many Abs. Elevated titers of anticardiolipin Abs (aCL) were reported most often and found in patients with cognitive impairment, psychosis, depression, seizures, chorea, and migraine. No specificity was encountered among brain-specific or systemic Abs for any single NP manifestation. No studies evaluated a specific NP manifestation with the full panel of 20 Abs. A panel of brain-specific and systemic Abs may be helpful in establishing the diagnosis of NPSLE. Postulated mechanisms in experimental models included vascular occlusion and injury by pathogenic Abs in a disrupted blood brain barrier.

CONCLUSIONS

NPSLE is associated with brain-specific and systemic Abs. Cognitive impairment, psychosis, and depression were associated with many Abs, including aCL Abs. Possible mechanisms include vascular occlusion and injury by pathogenic Abs in a disrupted blood brain barrier.

Clinical and biological aspects of anti-P-ribosomal protein autoantibodies

Among the many clinical manifestations of systemic lupus erythematosus (SLE), central nervous system (CNS) involvement is of a prognostic importance. In this respect, anti-ribosomal P protein antibodies were shown by many to occur in association with SLE neuropsychiatric manifestations, mainly psychosis. The prevalence of anti-P antibodies was strongly related to disease activity wherein disease remission was associated with the disappearance of these antibodies. In addition to its association with CNS involvement, the occurrence of liver and kidney disease in SLE patients with anti-P antibodies was widely reported. Anti-P antibodies are able to bind T cells, monocytes, neurons and hepatocytes thereby enhancing the production of pro-inflammatory cytokines and both CNS and liver damage. Similar to the ability of anti-dsDNA antibodies, anti-P antibodies were shown to penetrate into living cells, leading to cell dysfunctions such as cell apoptosis. These biological aspects may play an important role in the pathogenesis of SLE.

Anti-endothelial antibodies and neuropsychiatric systemic lupus erythematosus

The pathogenesis of neuropsychiatric systemic lupus erythematosus (NPSLE) has been attributed to autoantibody-mediated neural dysfunction, vasculopathy, and coagulopathy. Several autoantibodies specificities have been reported in serum and cerebrospinal fluid of NPSLE patients (i.e., antineuronal, antiribosomal P proteins, antiglial fibrillary acidic proteins, antiphospholipid, and anti-endothelial antibodies). We have recently demonstrated an association between serum anti-endothelial antibodies and psychosis or depression in patients with SLE. Subsequently, by screening a cDNA library from human umbilical artery endothelial cells with serum from a SLE patient with psychosis, one positive strongly reactive clone was identified encoding the C-terminal region (C-ter) of Nedd5, an intracytoplasmatic protein of the septin family. Anti-Nedd5 antibodies have been found significantly associated with psychiatric manifestations in SLE patients, strengthening the view of a possible implication of autoantibodies in the development of psychiatric disorders.

Autoantibodies to intracellular autoantigens and their B-cell epitopes: molecular probes to study the autoimmune response

A common laboratory finding in systemic autoimmune diseases is the presence of autoantibodies against intracellular autoantigens. Although their pathogenesis is not fully understood, autoantibodies are important tools for establishing diagnosis, classification, and prognosis of autoimmune diseases. Autoantibodies mainly target multicomponent complexes containing both protein antigens and (ribo)-nucleic acid(s), such as the spliceosome or Ro/La RNPs. In this review, we address the main characteristics and the clinical value of the main autoantibody types with respect to their disease association, and we describe the corresponding autoantigens, their biologic function, and their B-cell antigenic determinants (epitopes). The structural characteristics and clinical associations of these epitopes, and their utility as tools to investigate the autoimmune response, are discussed in detail. New insights into the pathogenetic role of epitopes in systemic autoimmunity are also examined. In this regard, using the defined structures of the B-cell antigenic epitopes, complementary epitopes can be designed according to the "molecular recognition" theory. These complementary epitopes can be used as probes to study pathogenetic and immunoregulatory aspects of the anti-idiotypic response. The origin of humoral autoimmunity and the spreading of the epitopes in systemic lupus erythematosus are also discussed. Finally, the ability of post-translational modifications to induce autoreactive immune attack via the generation of neo-epitopes is summarized.

International multicenter evaluation of autoantibodies to ribosomal P proteins

Autoantibodies to the ribosomal phosphoproteins (Rib-P) are a serological feature of patients with systemic lupus erythematosus (SLE). The reported prevalence of anti-Rib-P antibodies in SLE ranges from 10 to 40%, being higher in Asian patients. The variation in the observed frequency may be related to a number of factors but is dependent in large part on the test system used to detect the autoantibodies. An association of anti-Rib-P with central nervous system involvement and neuropsychiatric manifestations of SLE has been controversial. In the present international multicenter study, we evaluated the clinical accuracy of a new sensitive Rib-P-specific enzyme-linked immunosorbent assay based on recombinant Rib-P polypeptides. The results showed that 21.3% of 947 SLE patients, but only 0.7% of 1,113 control patients, had a positive test result (P < 0.0001). The sensitivity, specificity, positive and negative predictive values, and diagnostic efficiency were determined to be 21.3%, 99.3%, 95.6%, 62.2%, and 65.3%, respectively. When evaluated in the context of participating centers, the prevalence of anti-Rib-P antibodies was found in descending frequency, as follows: China (35%) > Poland (34%) > Japan (28%) > United States (26%) > Germany (Freiburg; 23.3%) > Denmark (20.5%) > Germany (Berlin; 19%) > Mexico (15.7%) > Israel (11.7%) > Brazil (10%) > Canada (8%). The substantial data from this study indicate that the prevalence of anti-Rib-P antibodies may not be restricted to the genetic background of the patients or to the detection system but may depend on regional practice differences and patient selection. We confirm previously reported associations of antiribosomal antibodies with clinical symptoms and serological findings. Remarkably, we found a lower occurrence of serositis in Rib-P-positive lupus patients.

Diseases of white matter and schizophrenia-like psychosis

OBJECTIVE

To analyse the available data regarding the presentation of psychosis in diseases of central nervous system (CNS) white matter.

METHOD

The available neurological and psychiatric literature on developmental, neoplastic, infective, immunological and other white matter diseases was reviewed.

RESULTS

A number of diseases of the white matter can present as schizophrenia-like psychoses, including leukodystrophies, neoplasms, velocardiofacial syndrome, callosal anomalies and inflammatory diseases.

CONCLUSIONS

Production of psychotic symptoms may result from functional asynchrony of interdependent regions, due to alterations in critical circuits as a result of pathology. The nature, location and timing of white matter pathology seem to be the key factors in the development of psychosis, especially during the critical adolescent period of association area myelination. Diseases that disrupt the normal formation of myelin appear to cause psychosis at higher rates than those that disrupt mature myelinated structures. Diffuse rather than discrete lesions, in particular those affecting frontotemporal zones, are also more strongly associated with schizophrenia-like psychosis. These illnesses point to the central role that white matter plays in maintaining CNS connectivity and to how pathology of the white matter may contribute to the neurobiology of psychosis.

Major immunoreactive domains of human ribosomal P proteins lie N-terminal to a homologous C-22 sequence: application to a novel ELISA for systemic lupus erythematosus

The aim of this study was to identify immunoreactive domains on human ribosomal P0, P1 and P2 proteins, other than the C-22 peptide, to develop a novel ELISA using a combination of these proteins and to compare this ELISA with one using the C-22 peptide. Human recombinant P0, P1, P2 and mutant P0 lacking the homologous C-22 peptide (N-P0) were produced in bacteria and tested by ELISA and immunoblotting using sera from 48 patients with systemic lupus erythematosus (SLE), 48 with an unrelated inflammatory disorder (Crohn's disease) and 47 healthy controls. ELISA with P0, P1 and P2, premixed at equimolar concentrations, gave higher OD readings than each protein tested individually. Eighteen SLE sera tested positive by ELISA with premixed P0, P1, P2 but only 3 tested positive with the C-22 peptide. Twenty-two SLE sera reacted positively, as determined by immunoblotting, with 5 different P protein combinations: P1P2, P0P1P2, P1, P0P1, P0 and P1. Only sera reactive with all three P proteins reacted with the C-22 peptide, with absent or minimal reactivity with N-P0. Native antigens yielded sensitivity (6/48, 13%) similar to the C-22 peptide assay. An ELISA with premixed P1 and P2 gave higher OD values than the arithmetic means with P1 or P2. Fifteen SLE patients had antibodies to double stranded (ds)-DNA, of which 6 also had antibodies to P0P1P2 by ELISA but 12 reactive with P0P1P2 did not have discernable ds-DNA antibodies. Ribosomal P autoantibodies react mainly with epitopes N-terminal to a homologous C-22 peptide. An ELISA with premixed P0, P1 and P2 has 5-fold greater sensitivity (38%) for SLE than an assay with the conventional C-22 peptide (7%). The combined sensitivity for SLE for antibodies to P0P1P2 and ds-DNA is 56%, higher than C-22 and ds-DNA, 38%. Only one of the SLE patients had neuropsychiatric lupus.

Comparison of Different Test Systems for Simultaneous Autoantibody Detection in Connective Tissue Diseases

The serological diagnosis of connective tissue diseases (CTDs) is based on the analysis of circulating autoantibodies to cytoplasmic and nuclear proteins (extractable nuclear antigens [ENAs]). The determination of autoantibody specificities supports the clinical diagnosis of the type of CTD and also often the prognosis of the disease. The former indirect immunofluorescence (IIF) technique still provides a useful screening method that currently is supplemented by a range of different techniques allowing the exact determination of single autoantibody specificities. These ENA profiling techniques include ELISA, immunoblotting, line-blot assays, and flow cytometric bead-based multiplex assays. The novel line immunoassay (LIA) from Mikrogen has been introduced in a recent study as a suitable technique for the simultaneous detection of autoantibodies in a routine clinical laboratory, providing comparable results as ELISA and ELiA (both from Pharmacia Diagnostics) (see Damoiseaux et al., this volume). In this study, LIAs from three different manufacturers were performed in 30 serum samples from patients with dermatological manifestations and 27 samples from SLE patients with renal involvement. The line assays from Mikrogen (recomLine ANA/ENA), Innogenetics (Inno-Lia ANA Update), and Imtec (ANA-LIA) were compared for antigen composition, handling, and statistical analysis including sensitivity and concordance. Autoantibody frequencies detected by the Mikrogen, Innogenetics, and Imtec line assays were 14.0%, 19.3%, and 15.8% for RNP; 14.0%, 22.8%, and 14.0% for Sm; 26.3%, 31.6%, and 40.3% for SSA; 3.5%, 12.3%, and 14.0% for SSB; and 3.5%, 14.0%, and 10.5% for histones. Our studies show that the line assay format is an easy-to-use, sensitive, and specific method for ENA antibody detection in human sera.

ANTI-RIBOSOMAL P ANTIBODIES ARE ASSOCIATED WITH NEPHRITIS, VASCULAR THROMBOSIS AND LYMPHOCYTOPENIA IN PATIENTS WITH SYSTEMIC LUPUS ERYTHEMATOSUS

In the present study, anti-ribosomal P antibody in sera of patients with systemic lupus erythematosus was assayed using an enzyme-linked immunosorbent assay, and its association with clinical symptoms of the patients was analyzed. The presence of anti-ribosomal P antibody was associated with increased frequency of lupus nephritis in the presence of anti-DNA antibody, and was associated with increased frequency of vascular thrombosis in the presence of anti-beta2 glycoprotein I antibody and/or lupus anticoagulant. The level of anti-ribosomal P antibody correlated inversely with the peripheral lymphocyte counts.

Update on the immunology, diagnosis and management of systemic lupus erythematosus

Lupus occurs with a prevalence of 2-9 in 10,000 people, targeting female and indigenous populations in particular. Lupus and related systemic autoimmune syndromes (scleroderma, Sjögren's syndrome, rheumatoid arthritis and polymyositis) result from a similar set of genetically and environmentally modulated immune disturbances, and the diagnostic and management approach to these conditions is broadly comparable. Evanescent, vague symptoms, restrictive diagnostic criteria and low diagnostic suspicion might have resulted in the under-diagnosis of these problems in the past, imposing considerable burdens on sufferers and the community. Serological screening should be employed cautiously and wisely, given the rapidly occurring changes in methodology, which have lowered their specificity. Close liaison with the immunology laboratories performing these tests is therefore advisable. Clinicians should emphasize the improving prognosis of lupus and related conditions as a result of earlier disease detection, improved educational support systems and refined medical therapies.

Autoantibody profile in systemic lupus erythematosus with psychiatric manifestations: a role for anti-endothelial-cell antibodies

This study was performed to determine the correlation between psychiatric manifestations and several autoantibodies that might participate in the pathogenesis of psychiatric disorders in the course of systemic lupus erythematosus (SLE). Fifty-one unselected outpatients with SLE were enrolled. Psychiatric evaluation was performed according to the Diagnostic and Statistical Manual of Mental Disorders, 4th edition. The prevalence of antibodies against endothelial cells (AECA), cardiolipin, β2 glycoprotein I, Ro, Ro52, La, glial fibrillary acidic protein, ribosomal P protein, dsDNA, and nucleosomes was assessed by experimental and commercial enzyme-linked immunosorbent assays. According to the cutoff value, AECA were present in 11 of 17 (64.7%) SLE patients with psychosis and mood disorders and in 10 of 34 (29.4%) patients without psychiatric manifestations other than anxiety (P = 0.03). Moreover, the AECA binding index was significantly higher in the first group (P = 0.03). Conversely, no significant correlation was found between the presence of the other autoantibodies studied and psychiatric involvement. The results of this study suggest a relationship between AECA and psychosis and mood disorders in SLE, supporting the hypothesis of a biological origin of these disturbances.

Ribosomal P antibodies and CNS lupus

Within two years of the recognition of autoantibodies to ribosomal P proteins in patients with systemic lupus erythematosus (SLE) an association with anti-P autoantibodies with psychosis was noted. While there has been some controversy about this association, ample evidence suggests a meaningful relationship between anti-P antibodies and central nervous system (CNS) disease. This evidence consists of 1) seven independent studies showing a strong relationship between anti-P antibodies and CNS disease; 2) longitudinal studies showing fluctuations of anti-P antibodies with episodes of psychosis; 3) correlation of anti-P antibodies with general disease activity; and 4) acid eluates form lupus renal tissue were found to contain anti-P antibodies enriched 30-fold with respect to their specific activity in serum heralding a direct role of anti-P antibodies in disease expression. Finally, there is evidence that the P protein resides on normal cells in an immunologically accessible way and evidence exists that anti-P antibodies are able to bind and penerate cells in culture, and once inside cells can affect a profound inhibition of protein synthesis in living cells. Taken together, these observations provide evidence linking anti-P antibodies to various forms of CNS disease. While this is true, there are other autoantibodies in SLE patients such as anti-dsDNA and antiglial fibrillary protein which may also play a role in the CNS disease of SLE patients. Continued study will inform us of the relative contribution of these autoantibodies to CNS disease in SLE patients.

Presence of autoantibodies against HeLa small nuclear ribonucleoproteins in chagasic and non-chagasic cardiac patients

We detected anti-human small nuclear ribonucleoprotein (snRNP) autoantibodies in chagasic patients by different immunological methods using HeLa snRNPs. ELISA with Trypanosoma cruzi total lysate antigen or HeLa human U small nuclear ribonucleoproteins (UsnRNPs) followed by incubation with sera from chronic chagasic and non-chagasic cardiac patients was used to screen and compare serum reactivity. Western blot analysis using a T. cruzi total cell extract was also performed in order to select some sera for Western blot and immunoprecipitation assays with HeLa nuclear extract. ELISA showed that 73 and 95% of chronic chagasic sera reacted with HeLa UsnRNPs and T. cruzi antigens, respectively. The Western blot assay demonstrated that non-chagasic cardiac sera reacted with high molecular weight proteins present in T. cruzi total extract, probably explaining the 31% reactivity found by ELISA. However, these sera reacted weakly with HeLa UsnRNPs, in contrast to the chagasic sera, which showed autoantibodies with human Sm (from Stefanie Smith, the first patient in whom this activity was identified) proteins (B/B', D1, D2, D3, E, F, and G UsnRNP). Immunoprecipitation reactions using HeLa nuclear extracts confirmed the reactivity of chagasic sera and human UsnRNA/RNPs, while the other sera reacted weakly only with U1snRNP. These findings agree with previously reported data, thus supporting the idea of the presence of autoimmune antibodies in chagasic patients. Interestingly, non-chagasic cardiac sera also showed reactivity with T. cruzi antigen and HeLa UsnRNPs, which suggests that individuals with heart disease of unknown etiology may develop autoimmune antibodies at any time. The detection of UsnRNP autoantibodies in chagasic patients might contribute to our understanding of how they develop upon initial T. cruzi infection.

Central nervous system involvement in connective tissue diseases

Neuropsychiatric manifestations are relatively common and serious complications in systemic lupus erythematosus (CNS lupus). Overall, in patients with CNS lupus, CSF IgM, IgA, IgG indexes (indicators of intrathecal Ig synthesis) as well as CSF IL-6 activities were significantly elevated. Of note, especially in patients lupus psychosis, but not in those with focal CNS lesions, anti-ribosomal P antibody (anti-P) in the sera as well as anti-neuronal antibody (anti-N) in the CSF was significantly elevated in relation to their CNS disease activities. These data indicate that the immune system activation within the CNS, possibly resulting in the elevation of CSF anti-N, plays an important role in the pathogenesis of CNS lupus, including lupus psychosis. CNS involvement in Behçet's disease, usually called neuro-Behçet's syndrome (NB), includes acute type and chronic progressive type. Acute NB is characterized by acute meningoencephalitis with focal lesions, presenting high intensity areas in T2-weightened images or Flare images on MRI scans, whereas chronic progressive NB is characterized by intractable slowly progressive dementia, ataxia and dysarthria with persistent elevation of CSF IL-6 activity. Chronic progressive NB is resistant to conventional treatment with steroid, cyclophosphamide, or azathioprine, but responds to low dose methotrexate. As for ANCA-related vasculitis, pachymeningitis has been found to be associated with P-ANCA as well as C-ANCA.

Autoantibody-mediated inhibition of pancreatic cancer cell growth in an athymic (nude) mouse model

INTRODUCTION

Antiribosomal P autoantibodies are detectable in 12-16% of patients with systemic lupus erythematosus.

AIM

To assess whether antiribosomal P autoantibodies could be useful as a novel form of immunotherapy for pancreatic cancer.

METHODOLOGY

Three pancreatic cancer cell lines were incubated with antiribosomal P or normal human immunoglobulin. Viability was assayed with MTT, and apoptosis was detected by TUNEL. MIA PaCa-2 cells were injected into athymic mice. Animals were treated with intraperitoneal antibody or control immunoglobulin. Serum antibody levels were measured by ELISA. Tumor nodule size was measured weekly. Binding of the antibody to tumors was demonstrated with fluorescent microscopy.

RESULTS

Antiribosomal P antibody inhibited pancreatic cancer cell proliferation up to 54.6% (p < 0.01) and was associated with a threefold increase in the rate of apoptosis (p < 0.05). Tumor volume after 4 weeks of treatment was 23.2 mm3, versus 141.5 mm3 for the control group (p < 0.05). Apoptosis rate within the nodules was increased twofold, to 11.4%, in comparison with control (p < 0.05).

CONCLUSION

Antiribosomal P autoantibody at levels similar to those that can exist in SLE inhibits the growth of pancreatic cancer cells, in vitro and in vivo. The mechanism involves surface binding and apoptosis.

Anti-ribosomal antibodies from lupus patients bind DNA

Antibodies specific for ribosomal P proteins (anti-P) are a hallmark of systemic lupus as anti-DNA antibodies are. It has been reported that anti-P antibodies are more frequently detected in anti-dsDNA positive sera. The aim of the present study was to verify the binding ability of anti-P antibodies towards polynucleotides and nucleosomes. We purified anti-P antibodies from 8 SLE patients' sera and we analysed them by ELISA on plates coated with DNA or nucleosomes. We performed also inhibition experiments in order to verify the specificity of the binding. All the purified anti-P antibodies bound DNA, but some anti-DNA binding activity remained among the non-anti-P antibodies in the flow through. Only half of the purified antibodies bound to nucleosomes, and anti-nucleosomal activity was demonstrated also in non anti-P antibody fraction. The inhibition experiments performed on two anti-P antibodies pointed out that only the homologous antigen inhibited the binding to either P peptide or DNA coated onto the solid phase. These results show that sera in which the two specificities coexist contain antibodies endowed with a double binding ability for DNA and the P peptide.

Antiribosomal P protein antibodies in Chilean SLE patients: no association with renal disease

The objective of this work was to determine the frequency and clinical associations of anti-ribosomal P protein antibodies (Anti-P) in a cohort of Chilean patients with systemic lupus erythematosus (SLE). Between 1996 and 1998, 141 consecutive patients with SLE were examined prospectively according with a standard protocol. Disease activity was measured by MEX-SLEDAI in 138 patients. Anti-P positivity was determined by double immune diffusion or Western blot and ELISA. Anti-P was found in 21 (15%) patients. In the Anti-P positive patients recent onset SLE (disease duration of 1 year or less) was more frequent (P = 0.018). Anti-P was found in 23% of 83 patients with active SLE vs 4% of the 55 patients with inactive SLE (Yates corrected P = 0.00479). An association with anti-dsDNA antibodies by Farr assay was observed. Anti-P positive patients had a median Farr of 65 IU/ml (1.4-1240) and Anti-P negative of 12 IU/ml (1.4-992; P-value = 0.0084). During the study only two patients had lupus psychosis and they were Anti-P positive. No association was found with liver disease (six patients, two with Anti-P antibodies) or active glomerulonephritis (22 patients four with Anti-P). Our data shows that the presence of Anti-P antibodies supports the clinical diagnosis of lupus psychosis.

Diagnostic tests for antiribosomal p protein antibodies: a comparative evaluation of immunoblotting and ELISA assays

We compared the clinical sensitivity and specificity of three different methods for the detection of serum antiribosomal P protein (anti-P) antibodies in systemic lupus erythematosus (SLE). Sera from 60 unselected SLE patients, 100 healthy subjects and 100 patients with other rheumatic inflammatory diseases were screened for anti-P antibodies by immunoblotting (IB) on P proteins from Raji cells and by two ELISA assays, one using the C-terminal 22 aminoacid long synthetic peptide (C-22) of P proteins, the other using a multiple antigen peptide (MAP) carrying four copies of the C-terminal 13 aminoacid long P peptide.Anti-P antibodies were found in 20% lupus sera by IB, 16.7% by MAP ELISA and 11.7% by C-22 ELISA. The specificity for SLE diagnosis of the three tests in healthy subjects and other rheumatic diseases was: 100% by IB, 100% (vs healthy subjects) and 97% (vs rheumatic diseases) by C-22 ELISA, 100% by MAP ELISA. The agreement between methods was good; differences in concordance rates were restricted to weak positivities. We observed a high concordance in the results of IB and ELISA methods for anti-P antibody detection. IB on P proteins extracted from human lymphoid cells is more sensitive than both ELISAs; IB and MAP ELISA perform better than the C-22 ELISA in determining weakly positive sera.