Penetrating anti-DNA monoclonal antibodies induce activation of human peripheral blood mononuclear cells

Anti-β2 -glycoprotein I antibody with DNA binding activity enters living monocytes via cell surface DNA and induces tissue factor expression

Autoantibodies characteristic for anti‐phospholipid syndrome (APS) and systemic lupus erythematosus (SLE) are anti‐β₂‐glycoprotein I (β₂GPI) antibodies and anti‐DNA antibodies, respectively, and almost half of APS cases occur in SLE. Anti‐β₂GPI antibodies are recognized to play a pivotal role in inducing a prothrombotic state, but the precise mechanism has not been fully elucidated. In a widely accepted view, binding of anti‐β₂GPI antibodies to cell surface β₂GPI in monocytes and endothelial cells triggers the Toll‐like receptor 4‐myeloid differentiation primary response 88 (TLR)‐4‐MyD88) signaling pathway which leads to activation of p38 mitogen‐activated protein kinase (MAPK), mitogen‐activated protein kinase kinase 1/extracellular signal‐regulated kinases (MEK‐1/ERK) and/or nuclear factor kappa B (NF‐κB) and expression of tissue factor (TF). However, resting cells do not express substantial amounts of TLR‐4. Previously, we generated a mouse monoclonal anti‐β₂GPI antibody WB‐6 and showed that it induced a prothrombotic state – including TF expression on circulating monocytes – in normal mice. In the current study, we aimed to clarify the mechanism of interaction between WB‐6 and resting monocytes, and found that WB‐6 exhibits binding activity to DNA and enters living monocytes or a monocytic cell line and, to a lesser extent, vascular endothelial cells. Treatment of the cells with DNase I reduced the internalization, suggesting the involvement of cell surface DNA in this phenomenon. Monocytes harboring internalized WB‐6 expressed TF and tumor necrosis factor (TNF)‐α which, in turn, stimulated endothelial cells to express intercellular adhesion molecule 1 (ICAM‐I) and vascular cell adhesion molecule 1 (VCAM‐I). These results suggest the possibility that a subset of anti‐β₂GPI antibodies with dual reactivity to DNA possesses ability to stimulate DNA sensors in the cytoplasm, in addition to the cell surface receptor‐mediated pathways, leading to produce proinflammatory and prothrombotic states.

Peptide Sharing Between Viruses and DLX Proteins: A Potential Cross-Reactivity Pathway to Neuropsychiatric Disorders

The present study seeks to determine potential associations between viral infections and neuropsychiatric diseases. To address this issue, we investigated the peptide commonalities between viruses that have been related to psychiatric and neurological disorders—such as rubella, human immunodeficiency virus, and herpesviruses—and human distal-less homeobox (DLX) proteins expressed in developing brain—namely, DLX1, DLX2, DLX5, and DLX6. Peptide matching analyses revealed a high degree of pentapeptide sharing. From an immunological perspective, this overlap is relevant because pentapeptides are endowed with immunogenicity and antigenicity—that is, they are immune determinants. Moreover, infection-induced immune cross-reactions might have functional, spatial, and temporal implications related to the functions and expression patterns of DLX1 and DLX5 in the fetal and adult human brain. In sum, our data support the hypothesis that viral infections may be linked to neuropsychiatric diseases through autoimmune cross-reactions caused by molecular mimicry between viral proteins and brain-specific DLX self-antigens.

TRIM21 and the Function of Antibodies inside Cells

Therapeutic antibodies targeting disease-associated antigens are key tools in the treatment of cancer and autoimmunity. So far, therapeutic antibodies have targeted antigens that are, or are presumed to be, extracellular. A largely overlooked property of antibodies is their functional activity inside cells. The diverse literature dealing with intracellular antibodies emerged historically from studies of the properties of some autoantibodies. The identification of tripartite motif (TRIM) 21 as an intracellular Fc receptor linking cytosolic antibody recognition to the ubiquitin proteasome system brings this research into sharper focus. We review critically the research related to intracellular antibodies, link this to the TRIM21 effector mechanism, and highlight how this work is exposing the previously restricted intracellular space to the potential of therapeutic antibodies.

Increased frequency of GM-CSF secreting PBMC in patients with active systemic lupus erythematosus can be reduced by immunoadsorption

An objective was to determine the frequency of GM-CSF secreting peripheral blood mononuclear cells (PBMC) in patients with active systemic lupus erythematosus (SLE) and their relation to other cytokine secreting PBMC, activation markers on lymphocytes/monocytes, clinical manifestations and anti- dsDNA antibodies.A second objectivewas to further investigatethe influence of immunoadsorption(IA) therapy on these parameters.The number of GM-CSF, interleukin-1b (IL-1b), IL-6, interferon-g (INF-g) or tumour necrosis factor-a (TNF-a) secreting PBMC was assessed by ELISPOT assay in 10 patients with active SLE. Further, the expression of activation markers on lymphocytes and monocytes was determined by flow cytometry. Three courses of IA were performed in the patients. Seventeen healthy, age- and sex-matched volunteers served as controls. GM-CSF secreting PBMC were significantly increased whereas INF-g secreting cells were decreased in SLE patients. The expression of CD71 (transferrin receptor) on CD4 + T-cells and of the costimulatorymolecule CD86 on B-lymphocyteswas significantly increased in SLE patients. GM-CSF secreting PBMC and CD4 + /CD71 + T-cells correlated with anti-dsDNA antibody titres and decreased towards levels of controls during IA. Disease activity and anti-dsDNA autoantibody titres were significantly reduced after the treatment. Our results demonstrate significant alterations of cellular and humoral immunity in SLE patients. The impaired immunity can be modulated by IA. Thus IA may prove an immunomodulatory therapeutic option in addition to the mere depletion of anti-dsDNA autoantibodies.

Immunological evidence and regulatory potential for cell-penetrating antibodies in intravenous immunoglobulin

Anti-DNA cell-penetrating autoantibodies have been extensively studied in autoimmune but not in normal sera. We investigated herein the presence and properties of cell-penetrating antibodies (CPAbs) in intravenous immunoglobulin (IVIg), a blood product of pooled normal human IgG. IVIg cell penetration was observed into various cell lines, as well as cells from several organs of mice injected intravenously with IVIg therapeutic dose. In all cell types examined in vitro and in vivo, intracellular IgG localized in the cytoplasm, in contrast to the nuclear accumulation of disease-related CPAbs. IVIg was found to rapidly enter cells via an energy-independent mode. The CPAb-fraction was isolated and found to be polyreactive to nuclear and cytoplasmic components; although it corresponded to ~2% of IVIg, it accounted for its inhibitory effect on splenocyte activation. Investigation of IVIg cell penetration capacity provides insight into its mechanisms of action and may account for some of its beneficial effects in numerous diseases.

Immunophenotypic characterization of lymphoid cell infiltrates in vitiligo

The pathogenesis of vitiligo is still controversial. The purpose of this study was to gain insight into the nature of lymphoid cells infiltrating depigmented areas of skin in vitiligo. Immunochemical procedures were carried out in biopsies from 20 patients with active lesions to search for cells expressing CD1a, CD2, CD3, CD4, CD5, CD8, CD20, CD25, CD30, CD56, CD68 and CD79a. Results indicate that early lesions are infiltrated mainly by dendritic cells, whereas older lesions display significantly lower proportions of these cells and increased percentages of mature T cells. This finding might suggest that the autoimmune reactivity towards melanocyte antigens might be T cell-dependent and antigen-driven. It is possible that a non-immune offence of melanocytes is responsible for the exposure of intracellular antigens, while autoreactivity might be a secondary, self-perpetuating mechanism.

A Novel Method for Real-Time, Continuous, Fluorescence-Based Analysis of Anti-DNA Abzyme Activity in Systemic Lupus

Systemic Lupus Erythematosus (SLE) is an autoimmune disease characterized by the production of antibodies against a variety of self-antigens including nucleic acids. These antibodies are cytotoxic, catalytic (hydrolyzing DNA, RNA, and protein), and nephritogenic. Current methods for investigating catalytic activities of natural abzymes produced by individuals suffering from autoimmunity are mostly discontinuous and often employ hazardous reagents. Here we demonstrate the utility of dual-labeled, fluorogenic DNA hydrolysis probes in highly specific, sensitive, continuous, fluorescence-based measurement of DNA hydrolytic activity of anti-ssDNA abzymes purified from the serum of patients suffering from SLE. An assay for the presence and levels of antibodies exhibiting hydrolytic activity could facilitate disease diagnosis, prediction of flares, monitoring of disease state, and response to therapy. The assay may allow indirect identification of additional targets of anti-DNA antibodies and the discovery of molecules that inhibit their activity. Combined, these approaches may provide new insights into molecular mechanisms of lupus pathogenesis.

Engineering the first chimeric antibody in targeting intracellular PRL-3 oncoprotein for cancer therapy in mice

Antibodies are considered as ‘magic bullets’ because of their high specificity. It is believed that antibodies are too large to routinely enter the cytosol, thus antibody therapeutic approach has been limited to extracellular or secreted proteins expressed by cancer cells. However, many oncogenic proteins are localized within the cell. To explore the possibility of antibody therapies against intracellular targets, we generated a chimeric antibody targeting the intracellular PRL-3 oncoprotein to assess its antitumor activities in mice. Remarkably, we observed that the PRL-3 chimeric antibody could efficiently and specifically reduce the formation of PRL-3 expressing metastatic tumors. We further found that natural killer (NK) cells were important in mediating the therapeutic effect, which was only observed in a nude mouse model (T-cell deficient), but not in a Severe Combined Immunodeficiency’ (scid) mouse model (B- and T-cell deficient), indicating the anticancer effect also depends on host B-cell activity. Our study involving 377 nude and scid mice suggests that antibodies targeting intracellular proteins can be developed to treat cancer.

Pathogenic and Epiphenomenal Anti-DNA Antibodies in SLE

The discoveries of natural and the development of manufactured highly efficient catalytic antibodies (abzymes) opens the door to many practical applications. One of the most fascinating is the use of such antibodies in human therapy and prevention (vaccination), of cancer, AIDS, autoimmune diseases. A special entity of naturally occurring DNA hydrolytic anti-DNA antibodies is emerging within past decades linked to autoimmune and lymphoproliferative disorders, such as systemic lupus erythematosus (SLE), multiple sclerosis (MS), Sjogren Syndrome (SS), B - Chronic lymphocytic leucosis (B-CLL), and Multiple Myeloma (MM). The origin of the antibodies is unknown. The underlying mechanisms of these activities are suggested to be penetration into the living cells and translocation in the nucleus, with recognition of the specific binding sites at particular (ss or ds) DNA. There are controversies in the literature whether hydrolysis is a sequence-specific event. The interplay between anti-DNA antibodies and DNA is not yet elucidated. This molecular “twist” also suggests that anti-DNA antibodies with DNA hydrolytic capacity could be the organism's immune response to a microbial attack, with microbial DNA, or specific genes within microbial DNA sequence, as a target for neutralization. The catalytic antibody-based approach can become a key tool in selective chemotherapeutic strategies.

Highly specific novel method for isolation and purification of lupus anti-DNA antibody via oligo-(dT) magnetic beads

A novel method for isolation and purification of anti-ssDNA antibodies from human sera is developed. The process involves: antibody purification based on their affinity for single-stranded sequence of thymidines and removal of remaining components via protein G coated magnetic beads, with high affinity for only IgG subclass. The high degree of purity and molecular weights of healthy versus lupus anti-ssDNA antibodies were confirmed by SDS-PAGE and silver staining. Western blot confirmed IgG isotype. This novel technique allows for diagnostic purposes, structural and functional analysis of anti-DNA antibodies, and studies of their role in autoimmune diseases.

Autoantibodies from Sjögren's syndrome trigger apoptosis in salivary gland cell line

The presence of serum autoantibodies has been associated with Sjögren's syndrome (SS), an autoimmune rheumatic disease that targets salivary and lachrymal glands. The association of apoptosis with autoantibodies production seems to play a role in the pathogenesis of glandular damage. The best-defined antibodies in SS are those reacting with the ribonucleoprotein antigens SS-A (Ro) and SS-B (La). Anti-Ro antibodies are found in about 70-90%, and anti-La in approximately the same frequency, of patients with primary SS. The objective of this work was to explore whether anti-Ro and anti-La autoantibodies purified from Sjögren IgG fractions are able to trigger apoptotic process in the human salivary gland cell line A-253. Anti-Ro and anti-La autoantibodies were purified on protein G Sepharose affinity column and used for the A-253 cell treatment. Apoptosis induced by autoantibodies was revealed by FACS analysis, and the active caspase-3 and the cleaved caspase-3 substrate poly (ADP-ribose) polymerase (PARP) was demonstrated by colorimetric assay and Western blot. This report shows that anti-Ro and anti-La autoantibodies, but not healthy IgG, activate the caspase-3 and determine the cleavage of PARP in A-253 cells. Apoptosis triggered by Sjögren autoantibodies could be responsible for the impairment of the secretory function in the salivary glands.

Fcgamma receptors mediate internalization of anti-Ro and anti-La autoantibodies from Sjögren's syndrome and apoptosis in human salivary gland cell line A-253

BACKGROUND

The presence of serum anti-Ro and anti-La autoantibodies directed against the ribonucleoproteins Ro and La has been associated with Sjögren's syndrome (SS), an autoimmune rheumatic disease that targets salivary and lachrymal glands. There is increasing evidence of the direct involvement of autoantibodies in the pathogenesis of tissue injury and correlation of their presence with clinical manifestations in SS. The focus of this work was to explore the cellular apoptotic pathway triggered by binding and penetration of anti-Ro and anti-La autoantibodies in human salivary gland cell line A-253 and to identify the membrane receptors through which anti-Ro and anti-La could exert their effect.

METHODS

Anti-Ro and anti-La autoantibodies were purified from IgG fractions, obtained from eleven healthy volunteers and patients with primary Sjögren's syndrome, using Sepharose 4B-Ro and Sepharose 4B-La affinity columns. Flow cytometry, RT-PCR, western blot and confocal microscopy analysis were used to visualize the FCgammaRI, FCgammaRII and FCgammaRIII receptors on the A-253 cell membrane. DNA laddering and western blot analysis of caspases activation were studied to evaluate in A-253 cells treated with anti-Ro and anti-La autoantibodies.

RESULTS

The results yeilded the evidence of the presence of members of the Fcgamma receptors (FcgammaRs) family on the cell membrane of the human salivary gland cell line A-253. Furthermore, we demonstrated that, in the A-253 cell line, anti-Ro and anti-La autoantibodies can access the cells probably through Fcgamma receptors, and trigger apoptotis.

CONCLUSIONS

We conclude that anti-Ro and anti-La autoantibodies have pathogenic effects that could depend on binding to Fcgamma receptors.

Autoantibodies in autism spectrum disorders (ASD)

Autism spectrum disorders (ASD) are a heterogeneous group of neurodevelopmental disorders defined behaviorally by abnormalities in social, verbal, and nonverbal communication. The etiologies of ASD are unknown, likely to be the result of a variety of numerous genetic, neurological, environmental, and immunological interactions that lead to a general behavioral phenotype defined as ASD. This review will focus on the various immune system anomalies, in particular, autoantibodies, which have been reported in subjects with ASD. In addition, we will discuss recent studies performed by our group concerning the presence of autoantibodies directed against neural antigens, which are observed in patients with ASD.

Apoptosis of melanocytes in vitiligo results from antibody penetration

Vitiligo is a rather common disease characterized by depigmentation of skin and mucosae due to the loss of melanocytes, most likely as a result of autoimmune phenomena. In this study we demonstrated apoptotic markers in residual melanocytes in skin biopsies of patients with vitiligo, as well as the presence of serum antibodies to melanocyte-specific antigens in the vast majority of patients. Moreover, we were able to prove that serum IgG antibodies from vitiligo patients, but not from healthy controls, were capable to penetrate into cultured melanocytes in vitro, and trigger them to engage in apoptosis. Our results are consonant with the theory that melanocyte-specific antibodies are responsible for the deletion of melanocytes through antibody penetration and apoptosis.

IgG deposits can be detected in cell nuclei of patients with both lupus erythematosus and malignancy

The purpose was to find immunological disturbances in lupus erythematosus (LE) patients with concomitant malignancy. 159 LE patients have been analyzed. Routine laboratory analyses including screening of serum autoantibodies and analyzing peripheral blood mononuclear cells by using flow cytometry have been performed. Malignant diseases have been revealed in 12 (7.5%) cases. All patients suffered from internal malignancies. LE patients with vs without malignancy had significantly decreased anti-double stranded DNA (16.6 vs 31.6%; p < 0.05) and increased anti-SSA/SSB (83.3 vs 32.2%/26.4%; p < 3 x 10(-12)) antibodies. Patients with neoplastic disease had increased IgG within the cell nuclei (76.6% +/- 9.6 vs 51.8 +/- 4.6%; p < 2 x 10(-7)). IgG penetrating living cells has been shown previously in SLE but has so far not been found in association to LE patients with malignant disease.

Apoptosis: the link between autoantibodies and leuko-/lymphocytopenia in patients with lupus erythematosus

OBJECTIVE

To analyse the relation between serum autoantibodies and leuko-/lymphocytopenia in patients with lupus erythematosus (LE).

METHODS

Laboratory routine analyses (white blood cell counts, autoantibody detection), and flow cytometry (annexin V, CD3, CD4, CD8, CD95, F(ab)2 anti-human IgG) have been performed in LE-patients versus healthy controls. In vitro, the influence of pooled serum containing anti-dsDNA antibodies has been analysed on the CD95 expression.

RESULTS

Leukocytes, lymphocytes, CD3+, CD3+ CD4+, and CD3+ CD8+ cells from LE-patients were significantly reduced compared with controls. Patients with autoantibodies had significantly lower absolute cell counts than those without. Apoptosis was increased in LE versus controls (p < 0.04). The percentage of CD95+ T-cells was increased, and the absolute number of CD95+ cells was reduced in LE. In vitro up-regulation of CD95 could be detected on T-cells of healthy donors. Induction of CD95 seems to be donor-dependent.

CONCLUSION

The data suggest that autoantibodies may be associated with blood cytopenias. CD95 seems to play a central role in this signalling cascade. The underlying mechanism is unclear, but seems to be autoantibody-related apoptosis induction.

Nuclear-targeting autoantibodies induced nuclear PARP cleavage accompanied by more pronounced decrease of peripheral white blood cells than Ro/SSA and La/SSB antigen-targeting autoantibodies

Autoantibody production and leukocytopenia may be linked in patients with lupus erythematosus (LE). Unclear is the ability of different autoantibody species to induce apoptosis and cell loss. Laboratory routine analyses (white blood cell counts, autoantibody detection), and flow cytometry (annexin V, CD3, CD4, CD8) have been performed in 126 consecutive LE-patients. Nuclei of PBMC were investigated flow cytometrically for the presence of the 85 kDa poly-(ADP-ribose)-polymerase (PARP) fragment. Peripheral total white blood cells (WBC), lymphocytes, T-cells, CD3+ CD4+, and CD3+ CD8+ cells were significantly decreased in patients with LE (P from 1.2 x 10(-14) to P < .0008). In the presence of either antinuclear (P from 1.2 x 10(-14) to P < .0008) or anti-dsDNA antibodies (P from 2.9 x 10(-12) to P < .007) were significantly diminished. Differences in cell numbers in LE patients with versus without anti-Ro/SSA were less pronounced: significant differences could be only obtained in lymphocytes and T-cells (P < .02). Anti-La/SSB antibodies were accompanied by significant increased leukocytes (P < .02). PARP cleavage (85 kDa) in nuclei was preferentially observed in cases with nuclear targeting autoantibodies. These results indicate that nuclear targeting autoantibodies are associated to lower peripheral blood cells counts than Ro/SSA, and La/SSB cytoplasmic targeting autoantibodies. This provides an explanation for the pathogenesis of cytopenias associated with SLE.

LE cell phenomenon: nuclear IgG deposits inhibit enzymatic cleavage of the nucleus of damaged cells and support its phagocytic clearance by PMN

Apoptotic cell death, phagocytic uptake, and their interplay may induce/trigger autoantibody production and autoimmunity. Herein the role of immunoglobulin G (IgG) anti-dsDNA autoantibodies in nucleo-phagocytosis by polymorpho-nuclear cells (PMN) has been analyzed. Necrotaxis, phagocytosis and PMN with engulfed nuclei can be imaged by vital microscopy. Vital microscopy revealed dead neutrophils with persistence of nuclei or ingested nuclei in 8/10 patients with lupus erythematosus (LE) and in 4/20 healthy controls (P < 0.0006). The phagocytic clearance of dead cells/nuclei did not correspond to any of the analyzed apoptosis markers (annexin V, CD95, and active caspase 3). IgG staining of isolated PBMC nuclei as detected by flow cytometry was significantly higher in parallel to NUC+ (P < 0.02). In vitro phagocytosis of substrates pre-treated with anti-dsDNA containing serum induced an increased phagocytic capacity as compared to normal serum. These data suggest that anti-dsDNA antibodies seem to inhibit enzymatic cleavage of nuclei from damaged cells, and improve their phagocytic uptake by PMN, which finally results in LE cell formation.

New approaches to the renal pathogenicity of anti-DNA antibodies in systemic lupus erythematosus

Autoantibodies against double stranded (ds) DNA are not only a helpful serological marker for diagnosis of systemic lupus erythematosus (SLE), but have also been shown to be crucial in the pathogenesis of lupus nephritis. However, the question of how anti-dsDNA antibodies contribute to renal damage is unresolved. Many authorities believe that indirect binding (mediated by nuclear antigens) or direct cross-reactivity of anti-dsDNA antibodies with kidney antigens are important determinants of anti-dsDNA nephritogenicity. An alternative hypothesis for the renal pathogenicity of anti-dsDNA antibodies was proposed more than 20 years ago, namely that certain autoantibodies could penetrate into living cells and thus induce damage. Work from several laboratories has recently provided firm support for this iconoclastic theory, which contradicted prevailing immunologic dogma that cell interiors are inaccessible to antibodies. Here, we review the evidence that anti-dsDNA antibodies may penetrate into living cells, and discuss which intracellular events may follow from binding of anti-dsDNA antibodies to the cell surface and subsequent intracellular penetration. Determining the mechanism by which anti-dsDNA antibodies induce renal injury is important for understanding a major disease manifestation of lupus, and may lead to the development of novel approaches to the treatment of lupus renal disease.

Cluster analysis of antinuclear autoantibodies in the prognosis of SLE nephropathy: are anti-extractable nuclear antibodies protective?

To investigate the possible role of anti-ENA autoantibodies in the pathogenesis of SLE nephropathy, we performed a cross sectional clustering study of 91 SLE patients using 75 clinical and laboratory variables examining the presence of anti-dsDNA and ENA autoantibodies by ELISA and Western blot. We applied principal component, hierarchical cluster, multiple correspondence and logistical regression analysis. Two polar forms of SLE nephropathy and five clinical groups were identified: group 1 without overt nephropathy (n = 37), group 2 with nephropathy and only proteinuria (n = 19), group 3 nephropathy and only hematuria (n = 11), group 4 with hematuria and proteinuria (n = 14) and group 5 on renal failure (n = 10). When analyzed individually, levels of anti-dsDNA and single anti-ENA antibodies did not allow us to differentiate between renal and non-renal groups. However, when the anti-ENA autoantibodies were analyzed as a cluster, a high predictive value for clinical nephropathy was obtained. Thus, the absence of ENA antibodies (ENA ve or Venezuelan cluster) increased eleven-fold the odds ratio to develop SLE nephropathy. We suggested that the ENA ve cluster may predict development of the most severe forms of renal lupus while the ENA Sm/RNP and the ENA Ro/La/Sm/RNP clusters could be associated with the absence and the most benign form of SLE nephropathy. It must be interesting to apply similar cluster methodology in an SLE population with different ethnic background.

Nucleosomes are major T and B cell autoantigens in systemic lupus erythematosus

OBJECTIVE

Double-stranded DNA (dsDNA) is a well-known target of autoantibodies in systemic lupus erythematosus (SLE). The majority of these autoantibodies are of the IgG isotype and show affinity maturation, both of which are known hallmarks of T cell help. T cell responses to autoantigens, including DNA, have been reported only incidentally in SLE patients. Nevertheless, in murine SLE, naked DNA and complexed DNA (nucleosomes) are known to be recognized by T cells. This study aimed to characterize the antinucleosome response and its clinical impact on human SLE.

METHODS

Nucleosomes were prepared from chicken erythrocytes. Sera from SLE and control patients were investigated by enzyme-linked immunosorbent assay (ELISA) for nucleosome-specific antibody responses. Peripheral blood mononuclear cells (PBMC) from SLE and control patients were analyzed by a kinetic T cell proliferation assay. PBMC were subsequently analyzed for nucleosome-specific T cell proliferation.

RESULTS

Of 136 SLE patients, 56% were seropositive for antinucleosome antibodies. In contrast, only 3% of 309 control patients (with rheumatoid arthritis, mixed connective tissue disease, undifferentiated connective tissue disease, Lyme borreliosis, scleroderma, Sjögren's syndrome, ulcerative colitis, hepatitis B virus infection, or human immunodeficiency virus infection) were seropositive. Thus, the antinucleosome ELISA had a sensitivity of 56%, a specificity of 97%, and a diagnostic confidence of 90% when applied to SLE. It was therefore superior to an anti-DNA ELISA that demonstrated a 69% diagnostic confidence in the same population. Antinucleosome reactivity in SLE patients correlated significantly with disease activity (P < 0.0001), nephritis (P < 0.002), and psychosis (P < 0.02). When proliferation assays were applied, 14 of 26 SLE patients (54%) were positive for nucleosome-specific T cells that proliferated in response to their cognate antigen. A suppressed response was elicited in 3 SLE patients (12%); in these patients, the PBMC response to nucleosomes was lower than the proliferation of PBMC in the presence of culture medium only. PBMC from the remaining 9 SLE patients (35%) were nonresponsive to nucleosomes in either way. Responding, nonresponding, and suppressed populations differed from each other significantly (P < 0.0001). None of the PBMC from 7 healthy donors and 10 control patients could be stimulated with nucleosomal antigens.

CONCLUSION

We present evidence that nucleosomes are major autoantigens in human SLE and that antinucleosomal antibodies are highly specific for the disease. The antinucleosome ELISA has been shown to be superior to the anti-dsDNA ELISA and may thus be a significantly better tool for diagnosing SLE. Nucleosome-specific T cells in SLE patients may help B cells class switch to IgG and undergo affinity maturation.

Interleukin-8 stimulates the adhesion of endometrial stromal cells to fibronectin

OBJECTIVE

To study the effect of interleukin-8 (IL-8) and mouse anti-human IL-8 monoclonal antibody on endometrial stromal cell adhesion to fibronectin.

DESIGN

Prospective, controlled in vitro study.

SETTING

Academic research laboratory.

PATIENT(S)

Women undergoing benign gynecologic surgery for indications other than endometrial disease.

INTERVENTION(S)

Endometrial stromal cells were treated with IL-8 and mouse anti-human IL-8 monoclonal antibody at different concentrations and adhesion assays were performed by labeling the cells with calcein.

MAIN OUTCOME MEASURE(S)

Fluorescence in calcein-labeled endometrial stromal cells.

RESULT(S)

IL-8 induced a concentration-dependent increase of cell adhesion to fibronectin matrix (twofold at 10 ng/mL; P = .006). Treatment of endometrial stromal cells with anti-IL-8 neutralizing antibody inhibited partially the cell adhesion.

CONCLUSION(S)

IL-8 stimulates the adhesion of endometrial stromal cells to fibronectin in a concentration-dependent manner. IL-8 may thus be relevant for the attachment of endometrial implants in the pathogenesis of endometriosis.