Endothelial cell-binding activity of anti-U1-ribonucleoprotein antibodies in patients with connective tissue diseases

Idiopathic and connective tissue disease-associated pulmonary arterial hypertension (PAH): Similarities, differences and the role of autoimmunity

Pre-capillary pulmonary arterial hypertension (PAH) is hemodynamically characterized by a mean pulmonary arterial pressure (mPAP) ≥ 20 mmHg, pulmonary capillary wedge pressure (PAWP) ≤15 mmHg and pulmonary vascular resistance (PVR) > 2. PAH is classified in six clinical subgroups, including idiopathic PAH (IPAH) and PAH associated to connective tissue diseases (CTD-PAH), that will be the main object of this review. The aim is to compare these two PAH subgroups in terms of epidemiology, histological and pathogenic findings in an attempt to define disease-specific features, including autoimmunity, that may explain the heterogeneity of response to therapy between IPAH and CTD-PAH.

Risk factors of pulmonary arterial hypertension in patients with systemic lupus erythematosus: A meta-analysis

OBJECTIVE

To determine the risk factors of pulmonary arterial hypertension (PAH) related to systemic lupus erythematosus (SLE) through systematic reviews and meta-analyses.

METHODS

We undertook electronic search strategies using Medline via PubMed, Embase, Web of Science, and Cochrane Library up to April 11, 2023. Study selection and data extraction were performed by 2 authors independently. We made risk of bias judgments based on the Newcastle-Ottawa Scale (NOS). Pooled risk ratios (RRs) and 95% confidence intervals (CIs) were calculated to estimate the overall effect sizes of potential risk factors for PAH in SLE patients. Univariate and multivariate meta-regression models were used to assess the independent effects of each risk factor on PAH. Sensitivity analyses were also conducted to explore potential sources of heterogeneity.

RESULTS

A total of 19 articles were included in this meta-analysis, and the results showed that gender (female) [RR = 1.04, 95% CI (1.02, 1.06), p = .0001], interstitial lung disease [RR = 4.36, 95% CI (2.42, 7.85), p = .0001], alopecia [RR = 1.39, 95% CI (1.06, 1.83), p = .017], Raynaud's phenomenon [RR = 1.83, 95% CI (1.41, 2.37), p = .0001], systemic hypertension [RR = 1.30, 95% CI (1.07, 1.58), p = .007], serositis [RR = 2.29, 95% CI (1.89, 2.77), p = .0001], pericardial effusion [RR = 3.33, 95% CI (2.20, 5.05), p = .0001], anti-RNP [RR = 1.86, 95% CI (1.19, 2.91), p = .006], anti-SSA [RR = 1.28, 95% CI (1.01, 1.62), p = .041], anti-SSB [RR = 1.38, 95% CI (1.19, 1.60), p = .0001], anti-U1RNP [RR = 1.58, 95% CI (1.07, 2.34), p = .023], thrombocytopenia [RR = 1.38, 95% CI (1.14, 1.68), p = .001], and current smokers [RR = 2.20, 95% CI (1.19, 4.06), p = .012] were all risk factors for PAH related to SLE.

CONCLUSION

PAH is a serious complication of SLE. Since prognosis of SLE patients after the occurrence of PAH is poor, routine examination should be conducted for SLE patients with PAH risk factors.

Basophils beyond allergic and parasitic diseases

Basophils bind IgE via FcεRI-αβγ2, which they uniquely share only with mast cells. In doing so, they can rapidly release mediators that are hallmark of allergic disease. This fundamental similarity, along with some morphological features shared by the two cell types, has long brought into question the biological significance that basophils mediate beyond that of mast cells. Unlike mast cells, which mature and reside in tissues, basophils are released into circulation from the bone marrow (constituting 1% of leukocytes), only to infiltrate tissues under specific inflammatory conditions. Evidence is emerging that basophils mediate non-redundant roles in allergic disease and, unsuspectingly, are implicated in a variety of other pathologies [e.g., myocardial infarction, autoimmunity, chronic obstructive pulmonary disease, fibrosis, cancer, etc.]. Recent findings strengthen the notion that these cells mediate protection from parasitic infections, whereas related studies implicate basophils promoting wound healing. Central to these functions is the substantial evidence that human and mouse basophils are increasingly implicated as important sources of IL-4 and IL-13. Nonetheless, much remains unclear regarding the role of basophils in pathology vs. homeostasis. In this review, we discuss the dichotomous (protective and/or harmful) roles of basophils in a wide spectrum of non-allergic disorders.

Anti-RNP Antibody: A Potential Novel Predictor for Osteonecrosis in Systemic Lupus Erythematosus

Objective

To explore risk factors for developing osteonecrosis in patients with systemic lupus erythematosus (SLE).

Methods

Twenty-six SLE patients with osteonecrosis from January 2018 to December 2019 were described. Fifty SLE patients without osteonecrosis were selected as controls from the SLE database (total 2,680) of our hospital during the same period. Clinical manifestations and laboratory tests were recorded and analyzed, especially antibodies. Univariate and multivariate analyses were used to evaluate possible associated risk factors.

Results

Twenty-six (3 male, 23 female) SLE patients with osteonecrosis were confirmed by X-ray and magnetic resonance imaging. The median course from SLE onset to osteonecrosis onset was 45 (range 2–302) months. Seven (27%) patients had a single joint involved and 19 (73%) patients had two or more joints involved. Besides, the incidence of femoral head osteonecrosis (FHON), knee ON, and humerus head ON were 85% (22/26), 27% (7/26), and 12%(3/26), respectively. The multivariate logistic regression analysis showed that the score of European Consensus Lupus Activity Measurement (ECLAM) at SLE onset [odds ratio (OR) 1.37; 95% confidence interval (CI) 1.07–1.75], a cumulative dose of prednisone above 10 g (OR 15.49; 95% CI 3.38–84.61), and positive of independent anti-RNP antibodies (OR 3.35; 95% CI 0.80–10.73) were significantly associated with osteonecrosis in SLE.

Conclusion

The score of ECLAM at SLE onset, a cumulative dose of prednisone above 10 g, and positive anti-RNP antibodies are associated with osteonecrosis in SLE. Herein, we reported for the first time that anti-RNP antibodies were associated with osteonecrosis in SLE patients and might be a novel predictor.

Basophils and IgE contribute to mixed connective tissue disease development

BACKGROUND

Mixed connective tissue disease (MCTD) is a rare and complex autoimmune disease that presents mixed features with other connective tissue diseases, such as systemic lupus erythematosus, systemic sclerosis, and myositis. It is characterized by high levels of anti-U1 small nuclear ribonucleoprotein 70k autoantibodies and a high incidence of life-threatening pulmonary involvement. The pathophysiology of MCTD is not well understood, and no specific treatment is yet available for the patients. Basophils and IgE play a role in the development of systemic lupus erythematosus and thus represent new therapeutic targets for systemic lupus erythematosus and other diseases involving basophils and IgE in their pathogenesis.

OBJECTIVE

We sought to investigate the role of basophils and IgE in the pathophysiology of MCTD.

METHODS

Basophil activation status and the presence of autoreactive IgE were assessed in peripheral blood of a cohort of patients with MCTD and in an MCTD-like mouse model. Basophil depletion and IgE-deficient animals were used to investigate the contribution of basophils and IgE in the lung pathology development of this mouse model.

RESULTS

Patients with MCTD have a peripheral basopenia and activated blood basophils overexpressing C-C chemokine receptor 3. Autoreactive IgE raised against the main MCTD autoantigen U1 small nuclear ribonucleoprotein 70k were found in nearly 80% of the patients from the cohort. Basophil activation and IgE anti-U1 small nuclear ribonucleoprotein 70k were also observed in the MCTD-like mouse model along with basophil accumulation in lymph nodes and lungs. Basophil depletion dampened lung pathology, and IgE deficiency prevented its development.

CONCLUSIONS

Basophils and IgE contribute to MCTD pathophysiology and represent new candidate therapeutic targets for patients with MCTD.

Synergistic enhancement of production of proinflammatory cytokines of human peripheral blood monocytes by anti-Sm and anti-RNP antibodies

The present study was performed to elucidate the roles of serum anti-Sm antibodies in the pathogenesis of systemic lupus erythematosus (SLE). Highly purified peripheral blood monocytes obtained from healthy donors were cultured in the presence of monoclonal anti-Sm antibody (anti-Sm mAb), monoclonal anti-U1-RNP antibody (anti-RNP mAb) or control murine IgG1 or IgG3. After various periods of incubation, levels of IL-6 and TNF-α in the culture supernatants were measured by ELISA and the expression of mRNA for various molecules in monocytes was determined using RT-PCR. Flow cytometry analysis confirmed the bindings of anti-Sm mAb and anti-RNP mAb on viable human monocytes. Both anti-Sm mAb and anti-RNP mAb significantly increased the production of IL-6 and TNF-α of human monocytes in a dose-dependent manner, although the latter was more potent than the former. Of note, anti-Sm mAb synergistically enhanced the production and mRNA expression of IL-6 and TNF-α of human monocytes in the presence of anti-RNP mAb. Notably, anti-RNP mAb, but not anti-Sm mAb, significantly enhanced the mRNA expression of RelA in human monocytes. Finally, anti-Sm mAb still up-regulated the IL-6 production of monocytes in the presence of anti-RNP mAb under the influence of N-acetyl cysteine or pyrrolidine dithiocarbamate that totally abrogated the IL-6 production provoked by anti-Sm mAb alone in the absence of anti-RNP mAb. These results demonstrate that anti-Sm and anti-RNP antibodies synergistically up-regulate the expression of IL-6 and TNF-α in human monocytes. The data also suggest that the effect of anti-Sm in the synergy with anti-RNP might not involve NFkB activation.

Anti-RNP/Sm antibodies in patients with systemic lupus erythematosus and its role in thrombosis: a case-control study

OBJECTIVE

To validate the association of thrombotic events with positive lupus anticoagulant (LA) and co-presence of anti-RNP/Sm, as well as the diagnostic accuracy of this combination of antibodies for thrombosis.

METHODS

Case-control study of patients with systemic lupus erythematosus (SLE) who presented thrombosis after SLE diagnosis and controls with SLE without thrombosis. Comorbidities, traditional risk factors, clinical variables, and treatment were evaluated. Antiphospholipid (aPL) and anti-RNP/Sm antibodies were determined.

RESULTS

Sixty-three cases and 63 controls were studied, 88% women, median age of 40 years, and disease duration of 135 months at study inclusion. No differences were found between groups regarding age, comorbidities, or clinical characteristics at SLE diagnosis. Patients with thrombosis were more frequently positive for anti-RNP/Sm (p = 0.001), IgG aCL (p = 0.02), IgG anti-B2GPI (p = 0.02), IgM anti-B2GPI (p = 0.02), LA (p < 0.001), the combination of anti-RNP/Sm + LA (p < 0.001), and aPL triple marker (p = 0.002), compared to controls. The combination of anti-RNP/Sm + LA, SLEDAI-2 K, and prednisone dose was associated with thrombosis (p < 0.05). The combination of anti-RNP/Sm + LA showed 56% sensitivity, 79% specificity, 73% positive predictive value, 64% negative predictive value, positive likelihood ratio (LR) 2.69, and negative LR 0.56 for predicting thrombosis. No difference was found in the comparison of area under the curve between LA alone and the combination of anti-RNP/Sm + LA (p = 0.73).

CONCLUSION

Thrombosis was associated with disease activity, dose of prednisone, and the combination of anti-RNP/Sm antibodies and LA. This combination of antibodies could be useful in the identification of SLE patients at risk of thrombosis.

An Autoimmune Basis for Raynaud's Phenomenon: Murine Model and Human Disease

OBJECTIVE

Raynaud's phenomenon (RP) is common in anti-RNP-positive patients with rheumatic diseases but is not itself known to be caused by autoimmunity. The aim of this study was to assess autoantibodies that could mediate this process.

METHODS

Antibodies derived from patient sera and from murine models of anti-RNP autoimmunity were screened for the ability to induce RP-like tissue ischemia and endothelial cell apoptosis in murine models and in vitro systems.

RESULTS

RNP-positive sera from RP patients and murine sera from RNP-positive B cell adoptive transfer recipients induced RP-like tissue ischemia and endothelial cell apoptosis. Proteomic analysis identified cytokeratin 10 (K10) as a candidate autoantigen in RP. Monoclonal anti-K10 antibodies reproduced patterns of ischemic tissue loss and endothelial cell apoptosis; K10 knockout or depletion of anti-K10 activity in serum was protective. Cold exposure enhanced K10 expression and in vivo tissue loss.

CONCLUSION

Anti-K10 antibodies are sufficient to mediate RP-like ischemia in murine models and are implicated in the pathogenesis of RP in patients with anti-RNP autoimmunity.

Increased levels of anti-heat-shock protein 60 (anti-Hsp60) indicate endothelial dysfunction, atherosclerosis and cardiovascular diseases in patients with mixed connective tissue disease

Heat-shock protein 60 (Hsp60) has been shown to provoke inflammation, and anti-Hsp60 may facilitate the development of atherosclerosis. In this study, we have investigated 30 patients with mixed connective tissue disease (MCTD) and assessed anti-Hsp60 and their relationship to cardiovascular diseases (CVD). Out of 30 patients with MCTD, 15 had CVDs. Anti-Hsp60 antibody was determined by enzyme-linked immunosorbent assay. Since endothelial dysfunction and accelerated atherosclerosis are characteristic to MCTD, a wide array of MCTD-, endothelial dysfunction- and CVD-associated parameters was investigated: serum lipid levels, paraoxonase activity (PON1), rich nuclear ribonucleoprotein U1 (anti-U1RNP), anti-endothelial cell antibodies, anti-cardiolipin and anti-β2-glycoprotein I antibody isotypes (anti-CL and anti-β2GPI), endothelin-1 (ET-1) levels, also intima-media thickness (IMT), a quantitative indicator of atherosclerosis. In MCTD, anti-Hsp60 antibody levels were significantly higher than in healthy individuals (p < 0.02). MCTD patients with CVD had significantly higher levels of anti-Hsp60 compared to MCTD without CVD (p = 0.001). Patients with MCTD had significantly lower high-density lipoprotein cholesterol (p = 0.02) and PON activity (p < 0.001), and significantly increased systolic (p < 0.0002) and diastolic (p < 0.001) blood pressure compared to healthy individuals. Anti-U1RNP levels (p < 0.002) and IMT were higher in patients compared to controls (p = 0.002). The CVD-positive MCTD patients had increased anti-Hsp60 (p < 0.0013), anti-CL IgG (p = 0.0005), ET-1 serum concentration (p < 0.05) and IMT levels (p < 0.001) compared to MCTD patients without CVD. Anti-Hsp60 showed a strong correlation with anti-oxLDL (r = 0.36, p = 0.01) and serum ET-1 (r = 0.62, p < 0.001) and negative correlation with PON activity (r = -0.47, p = 0.01). Anti-Hsp60 indicates endothelial injury, CVD, and can function as a novel atherosclerotic risk factor, also a valuable diagnostic marker in patients with MCTD.

Pregnancy Associated with Systemic Lupus Erythematosus: Immune Tolerance in Pregnancy and Its Deficiency in Systemic Lupus Erythematosus--An Immunological Dilemma

Pregnancy is a physiological condition that requires immune tolerance to the product of conception. Systemic lupus erythematosus (SLE) is a disease with well-represented immune mechanisms that disturb immune tolerance. The association of pregnancy with systemic lupus erythematosus creates a particular immune environment in which the immune tolerance specific of pregnancy is required to coexist with alterations of the immune system caused by SLE. The main role is played by T regulatory (Treg) cells, which attempt to regulate and adapt the immune system of the mother to the new conditions of pregnancy. Other components of the immune system also participate to maintain maternal-fetal immune tolerance. If the immune system of pregnant women with SLE is not able to maintain maternal immune tolerance to the fetus, pregnancy complications (miscarriage, fetal hypotrophy, and preterm birth) or maternal complications (preeclampsia or activation of SLE, especially in conditions of lupus nephritis) may occur. In certain situations this can be responsible for neonatal lupus. At the same time, it must be noted that during pregnancy, the immune system is able to achieve immune tolerance while maintaining the anti-infectious immune capacity of the mother. Immunological monitoring of pregnancy during SLE, as well as of the mother's disease, is required. It is important to understand immune tolerance to grafts in transplant pathology.

Neonatal lupus erythematosus

Neonatal lupus erythematosus (NLE) refers to a clinical spectrum of cutaneous, cardiac, and systemic abnormalities observed in newborn infants whose mothers have autoantibodies against Ro/SSA and La/SSB. The condition is rare and usually benign and self-limited but sometimes may be associated with serious sequelae. We review the pathophysiology, clinical features, and management of infants with this condition. Neonates with NLE should be managed at a tertiary care center. Multidisciplinary team involvement may also be indicated. In mothers with anti-Ro/SSA and/or anti-La/SSB antibodies and infants with congenital heart block, the risk of recurrence in subsequent offspring is 17–25%. Therefore, careful monitoring of subsequent pregnancies with serial ultrasonography and echocardiography is essential.

Serum antibodies against the 70k polypeptides of the U1 ribonucleoprotein complex are associated with psychiatric syndromes in systemic lupus erythematosus: a retrospective study

OBJECTIVES

We assessed the association between serum autoantibodies against the 70-kDa polypeptide of the U1-ribonucleoprotein (RNP) complex (U1-70k) and the central nervous system (CNS) syndromes in systemic lupus erythematosus (SLE) patients.

METHODS

We studied 106 hospitalized patients with active SLE, comparing those with (n = 32) and without (n = 74) CNS syndromes. CNS syndromes were further classified into neurologic (n = 21) and psychiatric (n = 15) disorders. Immunoglobulin G (IgG) anti-U1-70k antibodies were measured by enzyme-linked immunosorbent assay (ELISA) using recombinant antigens. IgG antibodies against whole U1-RNP were measured using commercial ELISA kits.

RESULTS

Although there was no significant difference in the levels of serum anti-U1-70k antibodies in SLE patients with or without CNS syndromes (p = 0.83), the levels were significantly elevated in SLE patients compared with patients without psychiatric syndromes (p = 0.030). In contrast, no significant difference was observed in the levels of serum anti-U1-RNP antibodies in SLE patients with or without psychiatric syndromes (p = 0.555).

CONCLUSIONS

These results indicate that serum anti-U1-70k antibodies are associated with psychiatric syndromes in SLE but that they are not associated with CNS syndromes as a whole or with neurologic syndromes. The anti-U1-70k antibodies might be involved in the pathological mechanisms of psychiatric syndromes in SLE.

Nucleic acid-associated autoantigens: pathogenic involvement and therapeutic potential

Autoimmunity to ubiquitously expressed macromolecular nucleic acid-protein complexes such as the nucleosome or the spliceosome is a characteristic feature of systemic autoimmune diseases. Disease-specificity and/or association with clinical features of some of these autoimmune responses suggest pathogenic involvement which, however, has been proven in only a few cases so far. Although the mechanisms leading to autoimmunity against nucleic acid-containing complexes are still far from being fully understood, there is increasing experimental evidence that the nucleic acid component may act as a co-stimulator or adjuvans via activation of nucleic acid-binding receptor systems such as Toll-like receptors in antigen-presenting cells. Dysregulated apoptosis and inappropriate stimulation of nucleic acid-sensing receptors may lead to loss of tolerance against the protein components of such complexes, activation of autoreactive T cells and formation of autoantibodies. This has been demonstrated to occur in systemic lupus erythematosus and seems to represent a general mechanism that may be crucial for the development of systemic autoimmune diseases. This review provides a comprehensive overview of the most thoroughly-characterized nucleic acid-associated autoantigens, describing their structure and biological function, as well as the nature and pathogenic importance of the reactivities directed against them. Furthermore, recent advances in immunotherapy such as antigen-specific approaches targeted at nucleic acid-binding antigens are discussed.

Anti-ribonucleoprotein antibodies mediate enhanced lung injury following mesenteric ischemia/reperfusion inRag-1−/−mice

Natural Abs and autoantibodies bind antigens displayed by ischemia-conditioned tissues, followed by complement activation and enhanced tissue injury during reperfusion. Anti-ribonucleoprotein (RNP) Ab is associated with lung disease in patients with autoimmune disease but it is not known whether these abs contribute to lung injury. Mesenteric I/R in mice leads to local and remote lung injury. Accordingly, we used this model to investigate whether anti-RNP Abs would reconstitute I/R damage with prominent lung damage in injury-resistant Rag1(-/-) animals. Rag1(-/-) mice injected with anti-RNP Ab containing serum and subjected to mesenteric I/R suffered greater intestinal injury than control-treated and sham-operated animals. The magnitude of the reconstituted damage was anti-RNP Ab titer-dependent. Anti-RNP Ab-treated animals demonstrated a dose-dependent increase in lung histologic injury scores compared to control and sham animals. Anti-RNP mediated injury was shown to be complement dependent. These experiments reveal a novel mechanism whereby anti-RNP Abs contributes to the development of pulmonary pathology in patients with autoimmune diseases following exposure of remote organs to I/R injury.

Common inflammatory mediators orchestrate pathophysiological processes in rheumatoid arthritis and atherosclerosis

RA is characterized by a systemic inflammatory state, in which immune cells and soluble mediators play a crucial role. These inflammatory processes resemble those in other chronic inflammatory diseases, such as atherosclerosis. The chronic systemic inflammation in RA can be considered as an independent risk factor for the development of atherosclerosis, and represents an important field to investigate the reasons of the increase of acute cardiovascular events in RA. In the present review, we focused on several mediators of autoimmunity, inflammation and endothelial dysfunction, which can be considered the most promising targets to prevent atherogenesis in RA. Among several mediators, the pro-inflammatory cytokine TNF-alpha has been shown as a crucial factor to induce atherosclerosis in RA patients.

Mixed connective tissue disease: what is behind the curtain?

Although there is still an emotional debate over the existence of mixed connective tissue disease, the evidence from animal models suggests that anti-U1RNP antibodies, similar to other autoantibodies in other connective tissue diseases (such as antisynthetase, anticentromere, and antitopoisomerase), play a pathophysiological role in this disease. Despite an antiendothelial effect of anti-U1RNP antibodies, which is reminiscent of anticentromere antibodies, patients with high-titer autoantibodies to U1RNP in the absence of anti-Sm antibodies do not usually have or develop typical systemic sclerosis. Instead, their severe Raynaud's syndrome is commonly accompanied by arthritis, which can be erosive, and by swollen/puffy hands and myositis. Pulmonary arterial hypertension is the major life-threatening complication in these patients and regular screening for this condition is essential.

Anti-RNP immunity: Implications for tissue injury and the pathogenesis of connective tissue disease

Certain autoantibodies are characteristic of autoimmune disease manifestations and contribute to organ pathology. The presence of high-titer antibodies to U1-RNP are associated with mixed connective tissue disease, although these antibodies may also be present in systemic lupus erythematosus and systemic sclerosis. However, the role of antibodies to U1-RNP in the pathogenesis of connective tissue disease remains unclear. Data from recent experimental studies promote the hypothesis that U1-RNP antibodies participate in both innate and adaptive immune responses, implicating them in the pathogenesis of connective tissue disease.

Clinical and Immunoserological Characteristics of Mixed Connective Tissue Disease Associated with Pulmonary Arterial Hypertension

We investigated the clinical characteristics and immunoserological alterations in patients with mixed connective tissue disease (MCTD) associated with pulmonary arterial hypertension (PAH). Anti-U1RNP autoantibodies, anti-endothelial cell antibodies (AECA) and serum thrombomodulin (TM) as well as von Willebrand factor antigen (vWFAg) concentrations were measured in 25 patients with MCTD associated with PAH and in 154 MCTD patients without PAH. The results showed that the probability of survival was lower in MCTD patients with PAH than in the 154 MCTD-non-PAH patients (5-year survival rate in MCTD with PAH: 73%, versus 96% in MCTD-non-PAH; P < 0.01). AECA were more frequently present in the sera of MCTD patients with PAH than in MCTD-non-PAH (P < 0.001). Serum TM and vWFAg levels were higher in MCTD-PAH patients than in MCTD-non-PAH patients (TM: P < 0.001; vWFAg: P < 0.001). Significant correlation was noticed between the quantity of AECA and TM level (r = 0.466) as well as the quantity of AECA and vWFAg level (r = 0.550). In conclusion, our results suggest that in MCTD the presence of AECA and endothelial cell activation may play a role in the development of PAH and in the maintenance of obliterative vascular processes.

A murine model of mixed connective tissue disease induced with U1 small nuclear RNP autoantigen

OBJECTIVE

To test whether immunizing mice with autoantigens closely linked to mixed connective tissue disease (MCTD) could induce an MCTD-like clinical syndrome distinguishable from systemic lupus erythematosus (SLE).

METHODS

Transgenic and knockout C57BL/6-derived mice were immunized subcutaneously at age 8-12 weeks with U1-70-kd small nuclear RNP (70K) fusion protein along with either Freund's complete adjuvant (CFA) or U1 RNA. After 2 months, mice were killed and analyzed histologically and serologically.

RESULTS

Immunization of C57BL/6-derived mice transgenic for human HLA-DR4 with 70K and either CFA or U1 RNA led to anti-70K antibodies in 62% of mice (21 of 34), and diversified anti-RNP immune responses. MCTD-like lung disease also developed in 50% of immunized mice (17 of 34), and anti-70K antibodies were strongly correlated with lung disease. CFA and U1 RNA were comparably able to induce this syndrome. Mice deficient in Toll-like receptor 3 (TLR-3) also developed this same syndrome when immunized with 70K and CFA. However, TLR-3(-/-) mice failed to develop MCTD-like lung disease when treated with 70K and U1 RNA. Rather, TLR-3(-/-) mice immunized with 70K and U1 RNA developed an autoimmune syndrome characterized by glomerulonephritis typical of SLE.

CONCLUSION

Exposure to 70K in an appropriate context is sufficient to induce autoimmunity and target organ injury consistent with MCTD. This system represents a new model of autoimmune interstitial lung disease, and establishes a closer link between anti-70K immunity and MCTD-like lung disease. Of note, changes in innate immune signaling can cause the same trigger to lead to the development of SLE-like nephritis rather than MCTD-like lung disease.

New target antigens for antiendothelial cell antibodies

Numerous connective tissue diseases, such as systemic lupus erythematosus (SLE), and infectious states, such as leprosy, are characterized by early vascular endothelial cell (EC) damage. There is substantial interest in the role of anti-EC antibodies (AECA) in such an injury. Due to the diversity of AECA-associated conditions, these autoantibodies are likely to be heterogeneous, and, therefore, identification of their antigens (Ag) to be difficult. They may be classified into three groups: membrane components, ligand-receptor complexes and Ag derived from the blood and attached to the cell surface. New technologies have been developed to sort it out, such as expression libraries and two-dimensional electrophoresis. A handful of Ag have hitherto been recognized viz. heat-shock protein 60 in SLE and leprosy, or plasminogen activator inhibitor-1 in SLE and Wegener granulomatosis. In reality, most of the target Ag for AECA remain to be identified.

Epitope spreading within lupus-associated ribonucleoprotein antigens

Autoantibodies reactive with several cellular antigens are present in the sera of patients with systemic lupus erythematosus. Polypeptides within the Ro-RNP complex and the snRNP complex are often targeted by these autoantibodies. One of the mechanisms responsible for their evolution is that of epitope spreading. Experimental animal model systems provide evidence for this. This review discusses the animal model systems of epitope spreading within these ribonucleoprotein antigens, the mechanisms of epitope spreading, and its relevance for disease pathogenesis.

Raynaud's Phenomenon in Mixed Connective Tissue Disease

Raynaud's phenomenon affects most patients who have mixed connective tissue disease (MCTD) and frequently represents the initial manifestation of the disease. It is the cutaneous symptom of a systemic vasculopathy that is characterized by intimal fibrosis and blood vessel obliteration that frequently leads to visceral involvement, particularly pulmonary hypertension. An association between Raynaud's phenomenon and the characteristic autoantibody in MCTD, anti-U1-RNP (ribonucleoprotein), is found across the spectrum of rheumatic diseases, including undifferentiated connective tissue disease, scleroderma, and systemic lupus erythematosus. Capillary nailfold examination represents a valuable tool to identify patients who are at risk for MCTD. The goal in the therapy of Raynaud's phenomenon in MCTD is to decrease the frequency of attacks, to prevent digital ulceration, and to limit progressive vascular damage. Therapeutic regimens include the traditional use of calcium channel blockers and novel vascular therapies.

Mixed Connective Tissue Disease: Still Crazy After All These Years

Mixed connective tissue disease (MCTD) remains a controversial diagnosis. The classification criteria have changed significantly from the original description by Sharp and colleagues in 1972 after follow-up of the original and other MCTD patients. In this article we review the clinical, serologic, and genetic studies of MCTD published in the last 10 years and ask if this term is appropriate.

Screening of an endothelial cDNA library identifies the C-terminal region of Nedd5 as a novel autoantigen in systemic lupus erythematosus with psychiatric manifestations

Anti-endothelial-cell antibodies are associated with psychiatric manifestations in systemic lupus erythematosus (SLE). Our primary aim in this study was to seek and characterize molecules that behave as endothelial autoantigens in SLE patients with psychiatric manifestations. By screening a cDNA library from human umbilical artery endothelial cells with serum from an SLE patient with psychosis, we identified one positive strongly reactive clone encoding the C-terminal region (C-ter) of Nedd5, an intracytoplasmatic protein of the septin family. To evaluate anti-Nedd5 serum immunoreactivity, we analyzed by ELISA specific IgG responses in 17 patients with SLE and psychiatric manifestations (group A), 34 patients with SLE without psychiatric manifestations (group B), 20 patients with systemic sclerosis, 20 patients with infectious mononucleosis, and 35 healthy subjects. IgG specific to Nedd5 C-ter was present in 14 (27%) of the 51 SLE patients. The mean optical density value for IgG immunoreactivity to Nedd5 C-ter was significantly higher in patients of group A than in those of group B, those with infectious mononucleosis, or healthy subjects (0.17 ± 0.14 vs, respectively, 0.11 ± 0.07, P = 0.04; 0.11 ± 0.06, P = 0.034; and 0.09 ± 0.045, P = 0.003, on Student's t-test). Moreover, IgG immunoreactivity to Nedd5 C-ter was significantly higher in patients with systemic sclerosis than in patients of group B or healthy subjects (0.18 ± 0.18 vs, respectively, 0.11 ± 0.07, P = 0.046; and 0.09 ± 0.045, P = 0.003). The percentage of patients with anti-Nedd5 C-ter serum IgG was higher in group A than in group B (8 (47%) of 17, vs 6 (17%) of 34, P = 0.045, on Fisher's exact test). In order to clarify a possible mechanism by which Nedd5 might be autoantigenic, we observed that Nedd5 relocated from cytoplasm to the plasma membrane of EAhy926 endothelial cells after apoptotic stimuli. In conclusion, Nedd5 is a novel autoantigen of potential clinical importance that could be successfully used for a more thorough investigation of the pathogenesis of psychiatric manifestations in SLE. Although anti-Nedd5 autoantibodies are not specific to SLE, they are significantly associated with neuropsychiatric SLE and may represent immunological markers of psychiatric manifestations in this pathology.