Toll-like receptor 4 senses oxidative stress mediated by the oxidation of phospholipids in extracellular vesicles.

Oxidative stress produced in response to infection or sterile injury activates the innate immune response. We found that extracellular vesicles (EVs) isolated from the plasma of patients with rheumatoid arthritis or secreted from cells subjected to oxidative stress contained oxidized phospholipids that stimulated cells expressing Toll-like receptor 4 (TLR4) in a manner dependent on its co-receptor MD-2. EVs from healthy subjects or reconstituted synthetic EVs subjected to limited oxidation gained the ability to stimulate TLR4-expressing cells, whereas prolonged oxidation abrogated this property. Furthermore, we found that 15-lipoxygenase generated hydro(pero)xylated phospholipids that stimulated TLR4-expressing cells. Molecular modeling suggested that the mechanism of activation of TLR4 by oxidized phospholipids in EVs was structurally similar to that of the TLR4 ligand lipopolysaccharide (LPS). This was supported by experiments showing that EV-mediated stimulation of cells required MD-2, that mutations that block LPS binding to TLR4 abrogated the stimulatory effect of EVs, and that EVs induced TLR4 dimerization. On the other hand, analysis of gene expression profiles showed that genes encoding factors that resolve inflammation were more abundantly expressed in responses to EVs than in response to LPS. Together, these data suggest that EVs act as an oxidative stress-induced endogenous danger signal that underlies the pervasive role of TLR4 in inflammatory diseases.

Development of patient-centred standards of care for osteoarthritis in Europe: the eumusc.net-project.

OBJECTIVE: The eumusc.net project is an initiative founded by the European Community and the European League Against Rheumatism. One aim of the project was to facilitate equal standards for musculoskeletal health across Europe. The aim of this work-package was to develop patient-centred and consensus based standards of care (SOC) for osteoarthritis (OA), which should be available in a professional and a patient version. METHODS: A systematic review concerning guidelines dealing with OA was conducted. Furthermore, experts in musculoskeletal diseases were contacted to ensure that 'grey' literature was not excluded. Documents that fulfilled predefined inclusion/exclusion criteria were included and all interventions for OA were extracted and categorised. Based on this list of interventions, a three round Delphi exercise with an international and multidisciplinary expert panel, including patient research partners, was performed to achieve expert consensus. RESULTS: Six documents were included and used for further analysis. Out of them, 46 interventions have been extracted and 10 consensus based SOC were formulated. In addition, a patient version, written in a lay-understandable wording and in the format of checklist questions was developed. An example is SOC 5: "People with OA should achieve optimal pain control using pharmacological and non-pharmacological means." The matching patient-centred checklist question reads: "Do I know how to control pain associated with OA?" CONCLUSIONS: The SOC for OA will be available in the 23 languages of the European Union to enhance unified information to patients and professionals and to further harmonise the treatment/care of OA within Europe.

Detection of antiphosphatidylserine/prothrombin antibodies and their potential diagnostic value.

Antiprothrombin antibodies, measured with phosphatidylserine/prothrombin complex (aPS/PT) ELISA, have been reported to be associated with antiphospholipid syndrome (APS). They are currently being evaluated as a potential classification criterion for this autoimmune disease, characterized by thromboses and obstetric complications. Given the present lack of clinically useful tests for the accurate diagnosis of APS, we aimed to evaluate in-house and commercial assays for determination of aPS/PT as a potential serological marker for APS. We screened 156 patients with systemic autoimmune diseases for antibodies against PS/PT, ß2-glycoprotein I, cardiolipin and for lupus anticoagulant activity. We demonstrated a high degree of concordance between the concentrations of aPS/PT measured with the in-house and commercial assays. Both assays performed comparably relating to the clinical manifestations of APS, such as arterial and venous thromboses and obstetric complications. IgG aPS/PT represented the strongest independent risk factor for the presence of obstetric complications, among all tested aPL. Both IgG and IgM aPS/PT were associated with venous thrombosis, but not with arterial thrombosis. Most importantly, the association between the presence of IgG/IgM aPS/PT and lupus anticoagulant activity was highly significant. Taken together, aPS/PT antibodies detected with the in-house or commercial ELISA represent a promising serological marker for APS and its subsets.

Influence of ionic strength and beta2-glycoprotein I concentration on agglutination of like-charged phospholipid membranes.

The effect of ionic strength on adhesion between negatively charged giant unilamellar vesicles induced by beta2-glycoprotein I (ß2-GPI) was studied experimentally and theoretically. Measuring the effective angle of contact between adhering vesicles indicated that the strength of adhesion between vesicles decreases with increasing ionic strength, and increases with concentration of ß2-GPI. In the theoretical part we focused on the study of the average orientation of ß2-GPI near the charged membrane and its role in mediating the attractive interactions between the vesicles. ß2-GPI proteins were modelled as rods with internal distribution of electric charge. The predictions of Monte Carlo simulations show orthogonal orientation of some of the membrane attached ß2-GPI in narrow gap between two vesicles. On the contrary, at larger distances between vesicles the proteins are parallelly attached to the membrane surface. A local minimum of the free energy corresponding to ß2-GPI-mediated adhesion of two neighbouring vesicles was predicted. The strength of adhesion was confirmed to decrease at high ionic strength.

Hyperferritinemia is associated with serologic antiphospholipid syndrome in SLE patients.

Ferritin may play a direct role on the immune system. We sought to determine if elevated levels of ferritin in lupus patients correlate with disease activity and organ involvement in a large cohort. Ferritin levels (gender and age adjusted) were assessed in 274 lupus serum samples utilizing the LIASON Ferritin automated immunoassay method. Significant disease activity was determined if European Consensus Lupus Activity Index (ECLAM)>2 or Systemic Lupus Erythematosus Disease Activity Index (SLEDAI)>4. Utilizing an EXCEL database, we compared elevated ferritin levels to manifestations grouped by organ involvement, serology, and previous therapy. The patients were predominantly female (89%), median age was 37 years old, and disease duration was 10.6 ± 7.7 years. Hyperferritinemia was found in 18.6% of SLE patients. Compared to subjects with normal ferritin levels, a significantly greater proportion of patients with hyperferritinemia had thrombocytopenia (15.4% vs. 33.3%, p=0.003) and lupus anticoagulant (11.3% vs. 29.0%, p=0.01). Additionally, compared to normoferritinemic subjects, hyperferritinemic subjects had significantly higher total aCL (99.7 ± 369 vs. 30.9 ± 17.3 GPI, p=0.02) and aCL IgM antibody levels (75.3 ± 357.4 vs. 9.3 ± 10.3 GPI, p=0.02), and marginally lower aCL IgG antibody levels (9.2 ± 4.9 vs. 9.7 ± 3.9 GPI, p = 0.096). While the ECLAM score significantly correlated with hyperferritinemia (p=0.04), the SLEDAI score was marginally associated with hyperferritinemia (p = 0.1). Serositis was marginally associated with hyperferritinemia, but not with other manifestations. An association with serologic APS was encountered. Hyperferritinemia was associated with thrombocytopenia, lupus anticoagulant, and anti-cardiolipin antibodies suggest that it may be an early marker for secondary antiphospholipid syndrome in SLE patients.

Low levels of vitamin-D are associated with neuropathy and lymphoma among patients with Sjögren's syndrome.

BACKGROUND/PURPOSE: Primary Sjögren's syndrome (SS) is a chronic autoimmune disease primarily involving the exocrine glands. The clinical picture of SS ranges from exocrinopathy to systemic disease affecting the lung, kidney, liver, skin, musculockeletal and nervous systems. The morbidity of SS is mainly determined by extraglandular disease and increased prevalence of lymphoma. Environmental and hormonal factors, such as vitamin-D may play a role in the pathogenic process and disease expression. Thus, we aimed to evaluate levels of vitamin-D and their association with manifestations of SS. METHODS: Vitamin-D levels were determined in 176 primary SS patients and 163 matched healthy volunteers utilizing the LIAISON chemiluminescent immunoassays (DiaSorin-Italy). A correlation between vitamin-D levels and clinical and serological manifestations of SS was performed. RESULTS: Mean vitamin-D levels were comparable between SS patients and control 21.2 ± 9.4 ng/ml and 22.4 ± 10 ng/ml, respectively. Peripheral neuropathy was diagnosed in 23% of SS patients and associated with lower vitamin-D levels (18.6 ± 5.5 ng/ml vs. 22.6±8 ng/ml (p = 0.04)). Lymphoma was diagnosed in 4.3% of SS patients, who had lower levels of vitamin-D (13.2 ± 6.25 ng/ml), compared to SS patients without lymphoma (22 ± 8 ng/ml), (p = 0.03). Other clinical and serological manifestations did not correlate with vitamin-D status. CONCLUSIONS: In this study, low levels of vitamin-D correlated with the presence of peripheral neuropathy and lymphoma among SS patients. The link between vitamin-D and neuropathy or lymphoma was reported in other conditions, and may support a role for vitamin-D in the pathogenesis of these processes. Plausible beneficial effect for vitamin-D supplementation may thus be suggested.

Antiphospholipid antibodies as non-traditional risk factors in atherosclerosis based cardiovascular diseases without overt autoimmunity. A critical updated review.

The role of antiphospholipid antibodies (aPL) associated with cardiovascular diseases has been extensively studied in autoimmune patients, however it was largely unknown whether and how aPL associate with coronary artery disease (CAD), ishemic stroke (IS) and peripheral artery disease (PAD) in non-autoimmune patients. The current review attempts to prioritize for the first time clinical studies based on cause-outcome and strengths relationships in reference to aPL and CAD/PAD, in addition to supplementing Brey's comprehensive review on IS with other, additional studies. Our overview indicates that all case-control and cross-sectional studies found an aPL association with CAD, PAD and IS, while cohort and nested case-control studies reported a prevailing negative risk association between aPL and IS (confirming Brey), with an unclear/unresolved risk association between aPL and CAD. The only cohort, follow-up study found in PAD reported on positive risk association between aPL and disease. The most frequently associated aPL in all studies reported, irrespective of disease, was aCL, with a less frequent association reported for LA, aß2GPI and other aPL.

International cohort study of 73 anti-Ku-positive patients: association of p70/p80 anti-Ku antibodies with joint/bone features and differentiation of disease populations by using principal-components analysis.

INTRODUCTION: An international cohort study of 73 anti-Ku-positive patients with different connective tissue diseases was conducted to differentiate the anti-Ku-positive populations of patients based on their autoantibody profile and clinical signs/symptoms and to establish possible correlations between antibodies against Ku p70 and Ku p80 with autoimmune diseases. METHODS: Sera of anti-Ku-positive patients were collected from six European centers and were all secondarily tested (in the reference center); 73 were confirmed as positive. Anti-Ku antibodies were detected with counter-immunoelectrophoresis (CIE), line immunoassay (LIA), and immunoblot analyses. All clinical and laboratory data were follow-up cumulative data, except for anti-Ku antibodies. Statistical analyses were performed by using R (V 2.12.1). The Fisher Exact test was used to evaluate the association between anti-Ku antibodies and diagnosis, gender, clinical signs, and other observed antibodies. The P values were adjusted for multiple testing. Separation of disease populations based on the presence of antibodies and clinical signs was investigated by principal-components analysis, which was performed by using thr// R's prcomp function with standard parameters. RESULTS: A 16% higher prevalence of anti-Ku p70 was found over anti-Ku p80 antibodies. In 41 (57%) patients, a combination of both was detected. Five (7%) patients, who were CIE and/or LIA anti-Ku positive, were negative for both subsets, as detected with the immunoblot; 31% of the patients had undifferentiated connective tissue disease (UCTD); 29% had systemic sclerosis (SSc); 18% had systemic lupus erythematosus (SLE); 11% had rheumatoid arthritis; 7% had polymyositis; and 3% had Sjögren syndrome. CONCLUSIONS: A significant positive association was found between female patients with anti-Ku p70 and joint/bone features, and a significant negative association was found between female patients with anti-Ku p80 only and joint/bone features (P = 0.05, respectively). By using the first and the third components of the principal-component analysis (PCA) with 29 parameters evaluated, we observed that the anti-Ku-positive population of UCTD patients had overlapping parameters, especially with SLE, as opposed to SSc, which could be helpful in delineating UCTD patients.

Gastrointestinal-associated autoantibodies in different autoimmune diseases.

BACKGROUND: Gastrointestinal (GI)-related autoantibodies (Abs) are rarely evaluated in autoimmune diseases (AID) other than inflammatory bowel disease, autoimmune hepatitis and celiac disease. Our aim was to determine the prevalence of these antibodies in a wide spectrum of AID. METHODS: We examined 923 serum samples representing 18 AID and compared them with 338 samples from healthy subjects. We used the BioPlex 2200-immunoassay (Bio-Rad, USA) to test samples for the presence of IgA and IgG directed at gliadin (AGA), tissue-transglutaminase (tTG), and Saccharomyces cerevisiae (ASCA). RESULTS: Prevalence of IgA AGA was significantly higher in antiphospholipid syndrome (APS) (7.1 %, P=0.012) and in pemphigus vulgaris (25%, P =0.008) patients, as compared with healthy controls. Presence of IgG-AGA was more common among Crohn's disease (20.5%, P = 0.023) and rheumatoid arthritis (6.5%, P=0.027) patients. IgG anti tTG were frequently observed in APS (6.1%, P=0.012), in giant cell arteritis (11.5%, P=0.013) and in ulcerative colitis (11.1%, P=0.018) patients, and as expected, higher prevalence of ASCA (IgA 19.3% and IgG 27.7%) was found in Crohn's disease. IgG ASCA were also found in systemic lupus erythematosus (SLE) (4.5%, P=0.01), in Graves' disease (5.7%, P=0.018), in cryoglobulinemia (7.1%, P=0.006), and in patients with vasculitides (6.5%, P=0.002). In contrast, lower prevalence of IgG type AGA was found in SLE (P=0.034), cryoglobulinemia (P=0.019) and vasculitides (P=0.013) patients. CONCLUSIONS: Our findings suggest an association between GI-related- Abs and a wide spectrum of AID. The clinical implication of these findings is yet to be determined.

Prolactin and autoimmunity: hyperprolactinemia correlates with serositis and anemia in SLE patients.

Evidence points to an association of prolactin to autoimmune diseases. We examined the correlation between hyperprolactinemia and disease manifestations and activity in a large patient cohort. Age- and sex-adjusted prolactin concentration was assessed in 256 serum samples from lupus patients utilizing the LIASON prolactin automated immunoassay method (DiaSorin S.p.A, Saluggia, Italy). Disease activity was defined as present if European Consensus Lupus Activity Measurement (ECLAM) > 2 or Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) > 4. Lupus manifestations were grouped by organ involvement, laboratory data, and prescribed medications. Hyperprolactinemia was presented in 46/256 (18%) of the cohort. Hyperprolactinemic patients had significantly more serositis (40% vs. 32.4%, p = 0.03) specifically, pleuritis (33% vs. 17%, p = 0.02), pericarditis (30% vs. 12%, p = 0.002), and peritonitis (15% vs. 0.8%, p = 0.003). Hyperprolactinemic subjects exhibited significantly more anemia (42% vs. 26%, p = 0.02) and marginally more proteinuria (65.5% vs. 46%, p = 0.06). Elevated levels of prolactin were not significantly associated with other clinical manifestations, serology, or therapy. Disease activity scores were not associated with hyperprolactinemia. Hyperprolactinemia in lupus patients is associated with all types of serositis and anemia but not with other clinical, serological therapeutic measures or with disease activity. These results suggest that dopamine agonists may be an optional therapy for lupus patients with hyperprolactinemia.

Nanoparticles isolated from blood: a reflection of vesiculability of blood cells during the isolation process.

BACKGROUND: Shedding of nanoparticles from the cell membrane is a common process in all cells. These nanoparticles are present in body fluids and can be harvested by isolation. To collect circulating nanoparticles from blood, a standard procedure consisting of repeated centrifugation and washing is applied to the blood samples. Nanoparticles can also be shed from blood cells during the isolation process, so it is unclear whether nanoparticles found in the isolated material are present in blood at sampling or if are they created from the blood cells during the isolation process. We addressed this question by determination of the morphology and identity of nanoparticles harvested from blood. METHODS: The isolates were visualized by scanning electron microscopy, analyzed by flow cytometry, and nanoparticle shapes were determined theoretically. RESULTS: The average size of nanoparticles was about 300 nm, and numerous residual blood cells were found in the isolates. The shapes of nanoparticles corresponded to the theoretical shapes obtained by minimization of the membrane free energy, indicating that these nanoparticles can be identified as vesicles. The concentration and size of nanoparticles in blood isolates was sensitive to the temperature during isolation. We demonstrated that at lower temperatures, the nanoparticle concentration was higher, while the nanoparticles were on average smaller. CONCLUSION: These results indicate that a large pool of nanoparticles is produced after blood sampling. The shapes of deformed blood cells found in the isolates indicate how fragmentation of blood cells may take place. The results show that the contents of isolates reflect the properties of blood cells and their interaction with the surrounding solution (rather than representing only nanoparticles present in blood at sampling) which differ in different diseases and may therefore present a relevant clinical parameter.

Autoimmune reactivity of IgM acquired after oxidation.

OBJECTIVES: Redox-reactive antibodies, mainly of the IgG class, gained a wide area of interest after their autoimmune reactivity was revealed following the application of chemical and physiological oxidants. In this study, we examined the susceptibility of IgMs to oxidation and evaluated their binding to the autoantigens important in some autoimmune diseases. METHODS: IgM and IgG fractions, isolated from healthy individuals' sera, were oxidized using direct electric current or physiological oxidant hemin. Specificities towards beta-2-glycoprotein I (ß(2)-GPI), cardiolipin (CL), and rheumatoid factor were evaluated with the enzyme-linked immunosorbent assays (ELISAs). Post-translational modification was investigated by 2,4-dinitrophenylhydrazine reaction. RESULTS: Electrochemically oxidized IgM fractions exhibited altered immunoreactivity - low to medium titers in anti-CL and low positive titers in anti-ß(2)-GPI ELISA but exhibited no rheumatoid factor reactivity. Oxidized IgG and IgM fractions exhibited 2.5- and 5-fold increase in the carbonyl content, respectively. DISCUSSION: An increase in the carbonyl content along with increased immunoreactivity after oxidation suggests modifications of the IgM paratopes. These results point towards possible modifications of native IgMs to their autoimmune state despite the fact that IgMs were less susceptible to oxidation than IgGs. The importance of an individual's redox status in maintenance of autoimmune reactions was emphasized by in vitro diagnostic tests.

Antiphospholipid antibodies and atherosclerosis: insights from rheumatoid arthritis--a five-year follow-up study.

OBJECTIVES: Life expectancy in rheumatoid arthritis (RA) patients is reduced by 3-10 years, probably due to cerebrovascular and cardiovascular diseases associated with atherosclerosis. In the present study, we wanted to verify if previously reported IgA anti-beta 2-glycoprotein I (2GPI) antibodies possibly represented an independent risk factor for atherosclerosis in RA patients during a longer period of follow up. METHODS: The follow-up study (after 5.5 years) comprised all initially included patients and controls (premenopausal women, non-diabetic, normotensive at the start of the study), except for two RA patients (one died and one not available). The same clinical, laboratory and ultrasound assessments were performed. RESULTS: Patients and controls were divided into three categories: Intima-media thickness (IMT) progressors, plaque progressors, IMT and plaque progressors. In controls, 55% represented IMT progressors and 5% IMT and plaque progressors. No statistically significant differences were detected comparing the progressors with delta (Δ=difference between follow-up and baseline study for each group in a time span of 5.5 years) LDL cholesterol, homocysteine and IgA anti-ß2GPI. In patients, there were 48.5% IMT progressors, 5.8% plaque progressors and 19.1% IMT and plaque progressors. The progression was statistically significant associated with the levels of Δ homocysteine and Δ apolipoprotein B but not with LDL cholesterol and IgA anti-ß2GPI. CONCLUSIONS: The follow-up study showed advanced atherosclerosis in RA patients compared to sex and age matched controls. However, we were not able to confirm our initial impression that IgA anti-ß2GPI might represent an independent risk factor for atherosclerosis.

Antibodies against acute phase proteins and their functions in the pathogenesis of disease: a collective profile of 25 different antibodies.

The acute phase response is a defense system in which the innate immune response is activated following injury or infection. Positive and negative acute phase proteins (APPs) are crucial for protecting the host organism, as well as returning it to homeostatic levels, the first with elevated concentrations and the latter with decreased concentrations during the acute phase. Reports about the presence of antibodies against APPs are known, however their individual, as well as potentially collective, pathological or physiological roles are still emerging. Some of these autoantibodies are specifically connected with diseases (such as pancreatic secretory trypsin inhibitor and C3, C4 nephritic factors), while others have been reported as natural antibodies. The persistent presence (even if only minor) of autoantibodies in healthy blood donors indicates an overlapping category of autoantibodies, which could become pathogenic, depending on the autoantibody characteristics such as avidity, epitope specificity, changes in the microenvironment leading to different oxidative status and others. This review uses the novel approach of studying the overall autoantibody population against APPs, their functions and connections to diseases. The primary function of autoantibodies against APPs (anti-APPs) is thought to promote their clearance, however autoantibodies against negative APPs have also been found and applying the same role to those is doubtful. There is also the theory of consumption in the stage of inflammation, which could be relevant to anti-APPs. Reports about protective roles of autoantibodies are also emerging, showing lowered levels of antibodies in diseases, which could be interesting for therapeutic intervention.

Immunochemical properties and pathological relevance of anti-ß2-glycoprotein I antibodies of different avidity.

Despite available treatment, there is still significant morbidity and mortality present among patients with the autoimmune thrombophilic condition termed 'antiphospholipid syndrome' (Espinosa, G. and Cervera, R. 2009. Morbidity and mortality in the antiphospholipid syndrome. Curr. Opin. Pulm. Med. 15:413.). High-avidity (HAv) anti-ß(2)-glycoprotein I (anti-ß(2)GPI) antibodies, shown to correlate with thrombotic events in patients, could represent the much needed improved prognostic marker. By studying their effect on crystalline annexin A5 shield on phospholipid surfaces (one of proposed pathogenic mechanisms), with the use of atomic force microscopy, the pathogenic potential of HAv anti-ß(2)GPI antibodies was confirmed. Furthermore, by using surface plasmon resonance and enzyme-linked immunosorbent assays, unique binding characteristics of HAv antibodies in comparison with low avidity antibodies were established. HAv anti-ß(2)GPI were confirmed to (i) recognize ß(2)-glycoprotein I in a solution, (ii) interact predominantly monovalently (much lower dependency on the antigen density) and (iii) form more stable complexes with the antigen. Since enzyme-linked immunosorbent assays currently used in routine diagnostics detect anti-ß(2)GPI antibodies of unknown avidity, our observations are potentially useful for the development of improved diagnostic tests capable of detecting clinically relevant antibodies.

Modified phosphatidylserine-dependent antiprothrombin [corrected] ELISA enables identification of patients negative for other antiphospholipid antibodies and also detects low avidity antibodies.

BACKGROUND: Two approaches for detecting anti-prothrombin antibodies have been described. The first detects antibodies against prothrombin alone and the second, phos-phatidylserine-dependent antiprothrombin antibodies. The latter more often correlate with clinical manifestations of antiphospholipid syndrome and with lupus anticoagulant activity. METHODS: In order to increase the capacity of antibody binding, we modified the previously described phosphatidylser-ine-dependent antiprothrombin ELISA and determined their avidity. We examined 203 patients with systemic autoimmune diseases and 222 blood donors. RESULTS: Our modification resulted in a greater intensity of antibody binding to prothrombin on phosphatidylserine-coated plate surfaces compared to the previously described method. By changing ELISA conditions, we were able to detect with one assay the two, presumably different, populations of antiprothrombin antibodies. Diagnostic specificities of both ELISAs for antiphospholipid syndrome were similar (92.5% vs. 93.1%), while the sensitivity of the modified phosphatidylserine-dependent antiprothrombin ELISA was significantly higher than the anti-prothrombin alone ELISA (59% vs. 25%). Low avidity antiprothrombin antibodies were only detected in the modified phosphatidylserine-dependent antiprothrombin ELISA. Four percent of patients with positive phosphatidylserine-dependent antiprothrombin antibodies, showing clinical manifestations of antiphospholipid syndrome, were negative for all other antiphospholipid antibodies. The risk for antiphospholipid syndrome increased with the number of antiphospholipid antibody positivity. CONCLUSIONS: We conclude that antibodies detected with a modified phosphatidylserine-dependent antiprothrombin ELISA could improve the diagnosis of antiphospholipid syndrome by offering additional information on the risk for thrombosis, especially in patients negative for other antiphospholipid antibodies.

Mechanism of endosomal TLR inhibition by antimalarial drugs and imidazoquinolines.

Endosomal TLRs play an important role in innate immune response as well as in autoimmune processes. In the therapy of systemic lupus erythematosus, antimalarial drugs chloroquine, hydroxychloroquine, and quinacrine have been used for a long time. Their suppression of endosomal TLR activation has been attributed to the inhibition of endosomal acidification, which is a prerequisite for the activation of these receptors. We discovered that chloroquine inhibits only activation of endosomal TLRs by nucleic acids, whereas it augments activation of TLR8 by a small synthetic compound, R848. We detected direct binding of antimalarials to nucleic acids by spectroscopic experiments and determined their cellular colocalization. Further analysis revealed that other nucleic acid-binding compounds, such as propidium iodide, also inhibited activation of endosomal TLRs and colocalized with nucleic acids to endosomes. We found that imidazoquinolines, which are TLR7/8 agonists, inhibit TLR9 and TLR3 even in the absence of TLR7 or TLR8, and their mechanism of inhibition is similar to the antimalarials. In contrast to bafilomycin, none of the tested antimalarials and imidazoquinolines inhibited endosomal proteolysis or increased the endosomal pH, confirming that inhibition of pH acidification is not the underlying cause of inhibition. We conclude that the direct binding of inhibitors to nucleic acids mask their TLR-binding epitope and may explain the efficiency of those compounds in the treatment of autoimmune diseases.

Could antibodies against serum amyloid A function as physiological regulators in humans?

The natural structuring of the immune system is responsible for the functional physiological state of the body. The development of natural autoantibodies involved in homeostasis relies on the ability to distinguish between exposed/masked and altered/non-altered self antigens. The objectives of this article were to address the relationships between antigen and autoantibodies against serum amyloid A (SAA), define SAA protein concentrations in 219 blood donor (BD) sera and determine their autoantibody levels and search for possible clinical associations with autoimmune and thrombotic diseases. Just recently, an increasing number of reports have indicated significantly decreased levels of autoantibodies against pro-inflammatory molecules, such as anti-TNF-alpha, anti-IL-6, or anti-CRP found in diseased conditions, as compared to healthy donors, or even to less severe disease conditions. In accord with this line of thought, our data indicate a predominant presence of anti-SAA autoantibodies in healthy BDs (above 95% as tested by the immunoblot analysis, n = 41). Using ELISA, high levels of anti-SAA antibodies were confirmed with a median OD = 0.996 for the BD group (n = 219). This suggests that anti-SAA antibodies might have a physiological role in homeostasis and/or the innate immune system and could actually be a part of the natural antibody repertoire. Significantly, lower median levels were found in patients with arterial thrombosis. Based on 219 BD sera, we could establish a new median value of 20 µg/ml for SAA antigen and a cut-off value of 114.7 µg/ml (97.5th percentile). Significantly, higher concentrations of SAA were observed for antiphospholipid syndrome, rheumatoid arthritic, and SLE patients.

Thrombomodulatory Effect of Anti-B2-Glycoprotein I Antibodies on Crystalline Annexin A5 on Phospholipid Bilayers, as Observed by Atomic Force Microscopy.

Antibodies against ß2-glycoprotein I are a subset of very heterogeneous family of antiphospholipid antibodies. It is well recognised that anti-ß2-glycoprotein I antibodies are the main pathogenic players in the autoimmune disease known as antiphospholipid syndrome. Many mechanisms have been proposed through which these autoantibodies could cause microplacental, arterial or venous thrombosis. One of the suggested mechanisms is an antiphospholipid antibody-mediated disruption of annexin A5 protective crystalline shield on negatively charged phospholipid membranes. In current report the study of ß2-glycoprotein I, anti-ß2-glycoprotein I antibodies and annexin A5 interactions was performed on in vitro model of planar solid-supported phospholipid bilayers and visualized by atomic force microscopy. Planar phospholipid bilayers comprised 30 % L-α-phosphatidylserine and 70 % L-α-phosphatidylcholine. For the study of interactions 10 mg/l annexin A5, 0.15 g/l ß2-glycoprotein I, 10 g/l of IgG fraction from healthy blood donor, 10 g/l of IgG fraction from a patient with anti-ß2-glycoprotein I antibodies and 0.4 g/l of isolated IgG anti-ß2-glycoprotein I antibodies from the same patients in Hepes buffered saline with 1.5 mM Ca2+ were used. We confirmed the clustering of ß2-glycoprotein I on planar phospholipid bilayers. We also found that in the presence of annexin A5, ß2-glycoprotein I does not bind to planar phospholipid bilayers. However, when adding the anti-ß2-glycoprotein I antibodies, the growth of ß2-glycoprotein I-anti-ß2-glycoprotein I antibodies complexes in the presence of incompletely crystallized annexin A5 on planar phospholipid bilayers was observed. Results confirm the possible thrombomodulatory activity of anti-ß2-glycoprotein antibodies through their effect on crystalline annexin A5. In addition, the hypothesis that the presence of possibly pathologic antigen-antibody pair itself is not sufficient to start the pathological process is confirmed and visualized for the first time.

The use of atomic force microscopy to study the pathologic effects of anti-annexin autoantibodies.

Patients with recurrent pregnancy loss and a history of thrombotic events have often been noted to have autoantibodies directed at annexin A5. However, the relationship of these autoantibodies to immunopathology is still unknown, although it has been proposed that they have a direct effect on the function of annexin A5. Annexin A5 may be a significant immunological target with pathologic implications. Essentially, annexin A5 is an anticoagulant protein that crystallizes over negatively charged phospholipid surfaces and thereby blocks them from availability for coagulation reactions. To address this issue, we have taken advantage of our expertise with atomic force microscopy and studied anti-annexin A5 autoantibodies isolated from patients and focused on the ability of these antibodies to influence annexin A5 crystallization on planar mica-supported phospholipid bilayers. We report herein that such antibodies from patients, but not controls, produced a significant disruption of incomplete annexin A5 crystalline shield on phospholipid bilayer. In addition, the IgG fraction isolated from such patients significantly decreased the velocity of annexin A5 crystallization. Atomic force microscopy is a powerful tool to study the pathologic mechanisms of autoantibodies and the data herein reflect the potential of anti-annexin A5 antibodies that produce pathology in a number of varied but overlapping clinical conditions, including autoimmune thrombosis and antiphospholipid syndrome.