Strong Association of Combined Genetic Deficiencies in the Classical Complement Pathway With Risk of Systemic Lupus Erythematosus and Primary Sjögren's Syndrome

OBJECTIVE

Complete genetic deficiency of the complement component C2 is a strong risk factor for monogenic systemic lupus erythematosus (SLE), but whether heterozygous C2 deficiency adds to the risk of SLE or primary Sjögren's syndrome (SS) has not been studied systematically. This study was undertaken to investigate potential associations of heterozygous C2 deficiency and C4 copy number variation with clinical manifestations in patients with SLE and patients with primary SS.

METHODS

The presence of the common 28-bp C2 deletion rs9332736 and C4 copy number variation was examined in Scandinavian patients who had received a diagnosis of SLE (n = 958) or primary SS (n = 911) and in 2,262 healthy controls through the use of DNA sequencing. The concentration of complement proteins in plasma and classical complement function were analyzed in a subgroup of SLE patients.

RESULTS

Heterozygous C2 deficiency-when present in combination with a low C4A copy number-substantially increased the risk of SLE (odds ratio [OR] 10.2 [95% confidence interval (95% CI) 3.5-37.0]) and the risk of primary SS (OR 13.0 [95% CI 4.5-48.4]) when compared to individuals with 2 C4A copies and normal C2. For patients heterozygous for rs9332736 with 1 C4A copy, the median age at diagnosis was 7 years earlier in patients with SLE and 12 years earlier in patients with primary SS when compared to patients with normal C2. Reduced C2 levels in plasma (P = 2 × 10^-9 ) and impaired function of the classical complement pathway (P = 0.03) were detected in SLE patients with heterozygous C2 deficiency. Finally, in a primary SS patient homozygous for C2 deficiency, we observed low levels of anti-Scl-70, which suggests a risk of developing systemic sclerosis or potential overlap between primary SS and other systemic autoimmune diseases.

CONCLUSION

We demonstrate that a genetic pattern involving partial deficiencies of C2 and C4A in the classical complement pathway is a strong risk factor for SLE and for primary SS. Our results emphasize the central role of the complement system in the pathogenesis of both SLE and primary SS.

The Complex Relationship between C4b-Binding Protein, Warfarin, and Antiphospholipid Antibodies

BACKGROUND

 Low levels of total C4b-binding protein (C4BPt), a circulating inhibitor of the classical/lectin complement pathways, were observed in patients with antiphospholipid antibodies (aPLs) and during warfarin treatment.

OBJECTIVES

 To investigate the associations between aPL and C4BPt in patients with persistently positive (++) aPL, with/without clinical manifestations and systemic lupus erythematosus (SLE), and in controls. Furthermore, we explored the impact of anticoagulation on C4BPt and in relation to complement activation.

METHODS

 In a cross-sectional design we investigated defined subgroups: primary (p) antiphospholipid syndrome (APS, N = 67), aPL++ individuals without clinical manifestations (aPL carriers, N = 15), SLE-aPL++ (N = 118, among them, secondary [s] APS, N = 56), aPL negative (-) SLE (SLE-aPL-, N = 291), and 322 controls. Clinical characteristics, including treatment, were tabulated. C4BPt was determined with a magnetic bead method. Complement proteins (C1q, C2, C3, C4, C3a, C3dg, sC5b-9, factor I [FI]) were measured. A mediation analysis was performed to decompose the total effect of aPL++ on C4BPt into the direct and indirect effects of aPL++ through warfarin.

RESULTS

 Overall, C4BPt is 20% decreased in aPL++ patients, regardless of SLE, APS, clinical manifestations, and aPL profile. C4BPt levels associate positively with complement proteins C1q, C2, C3, and C4, and negatively with complement activation product C3dg. In the SLE group, warfarin treatment contributes to approximately half of the C4BPt reduction (9%) CONCLUSION:  Both aPLs and warfarin are associated with C4BPt reduction. Complement activation in aPL++ patients may partly be explained by impaired inhibition through depressed C4BPt levels. Further studies are needed to understand the clinical implications.

Newborn Screening for Presymptomatic Diagnosis of Complement and Phagocyte Deficiencies

The clinical outcomes of primary immunodeficiencies (PIDs) are greatly improved by accurate diagnosis early in life. However, it is not common to consider PIDs before the manifestation of severe clinical symptoms. Including PIDs in the nation-wide newborn screening programs will potentially improve survival and provide better disease management and preventive care in PID patients. This calls for the detection of disease biomarkers in blood and the use of dried blood spot samples, which is a part of routine newborn screening programs worldwide. Here, we developed a newborn screening method based on multiplex protein profiling for parallel diagnosis of 22 innate immunodeficiencies affecting the complement system and respiratory burst function in phagocytosis. The proposed method uses a small fraction of eluted blood from dried blood spots and is applicable for population-scale performance. The diagnosis method is validated through a retrospective screening of immunodeficient patient samples. This diagnostic approach can pave the way for an earlier, more comprehensive and accurate diagnosis of complement and phagocytic disorders, which ultimately lead to a healthy and active life for the PID patients.

Inherited Classical and Alternative Pathway Complement Deficiencies in Children: A Single Center Experience

BACKGROUND

Primary complement deficiencies are rare diseases.

OBJECTIVE

To retrospectively evaluate the clinical and laboratory findings and complications of patients to increase awareness of pediatricians about complement deficiencies, which are rarely encountered.

METHODS

In this study, the clinical and immunological characteristics of 21 patients who consulted the Immunology Department of our hospital between 2003 and 2017 and were diagnosed with classical or alternative pathway complement deficiency were obtained from the file records.

RESULTS

Ten patients with C1 inhibitor deficiency, four patients with factor I deficiency, three patients with properdin deficiency, two patients with C8 deficiency, one patient with C1q deficiency, and one patient with C4B deficiency were assessed. The mean age of the patients at diagnosis was 11.4±4.7 years, the age of onset of symptoms was 7.9±3.9 years, and the follow-up period was 6.7±3.9 years. Fourteen cases had a similar medical history in the family. All patients with C1q, factor I, properdin, C8, and C4B deficiencies presented with an infection, and vasculitic rash was present in two patients with factor I deficiency. In addition, immune complex glomerulonephritis was present in one patient with factor I deficiency. Meningococcal, Haemophilus influenzae type B, and pneumococcal vaccines were administered and prophylactic antibiotic treatment was initiated in all patients except patients with C1 inhibitor deficiency.

CONCLUSIONS

Early diagnosis of complement deficiencies can facilitate prevention of life-threatening complications such as severe bacterial infections by considering prophylactic antibiotics and vaccines. In patients with C1 inhibitor deficiency, achieving an acurate early diagnosis will assist in the management and timely treatment of life-threatening attacks such as upper airway obstruction and improve outcomes.

Two subgroups in systemic lupus erythematosus with features of antiphospholipid or Sjögren's syndrome differ in molecular signatures and treatment perspectives

Background

Previous studies and own clinical observations of patients with systemic lupus erythematosus (SLE) suggest that SLE harbors distinct immunophenotypes. This heterogeneity might result in differences in response to treatment in different subgroups and obstruct clinical trials. Our aim was to understand how SLE subgroups may differ regarding underlying pathophysiology and characteristic biomarkers.

Methods

In a cross-sectional study, including 378 well-characterized SLE patients and 316 individually matched population controls, we defined subgroups based on the patients’ autoantibody profile at inclusion. We selected a core of an antiphospholipid syndrome-like SLE (aPL+ group; positive in the lupus anticoagulant (LA) test and negative for all three of SSA (Ro52 and Ro60) and SSB antibodies) and a Sjögren’s syndrome-like SLE (SSA/SSB+ group; positive for all three of SSA (Ro52 and Ro60) and SSB antibodies but negative in the LA test). We applied affinity-based proteomics, targeting 281 proteins, together with well-established clinical biomarkers and complementary immunoassays to explore the difference between the two predefined SLE subgroups.

Results

The aPL+ group comprised 66 and the SSA/SSB+ group 63 patients. The protein with the highest prediction power (receiver operating characteristic (ROC) area under the curve = 0.89) for separating the aPL+ and SSA/SSB+ SLE subgroups was integrin beta-1 (ITGB1), with higher levels present in the SSA/SSB+ subgroup. Proteins with the lowest p values comparing the two SLE subgroups were ITGB1, SLC13A3, and CERS5. These three proteins, rheumatoid factor, and immunoglobulin G (IgG) were all increased in the SSA/SSB+ subgroup. This subgroup was also characterized by a possible activation of the interferon system as measured by high KRT7, TYK2, and ETV7 in plasma. In the aPL+ subgroup, complement activation was more pronounced together with several biomarkers associated with systemic inflammation (fibrinogen, α-1 antitrypsin, neutrophils, and triglycerides).

Conclusions

Our observations indicate underlying pathogenic differences between the SSA/SSB+ and the aPL+ SLE subgroups, suggesting that the SSA/SSB+ subgroup may benefit from IFN-blocking therapies while the aPL+ subgroup is more likely to have an effect from drugs targeting the complement system. Stratifying SLE patients based on an autoantibody profile could be a way forward to understand underlying pathophysiology and to improve selection of patients for clinical trials of targeted treatments.

Electronic supplementary material

The online version of this article (10.1186/s13075-019-1836-8) contains supplementary material, which is available to authorized users.

Analysis of Anti-C1q Autoantibodies by Western Blot

Anti-C1q autoantibodies may be found in many conditions, most commonly in systemic lupus erythematosus (SLE) and hypocomplementemic urticarial vasculitis syndrome (HUVS), and are diagnostic markers as well as disease activity markers in lupus nephritis. Sera from patients with SLE and HUVS show partly distinct autoantibody reactivities to separated protein chains B and C of the first component of complement, C1q. These different binding specificities can be detected by Western blot analysis of the autoantibodies under reducing conditions. Results may help clinicians to differentiate between SLE and HUVS.

Age and Sex-Associated Changes of Complement Activity and Complement Levels in a Healthy Caucasian Population

Introduction: The complement system is essential for an adequate immune response. Much attention has been given to the role of complement in disease. However, to better understand complement in pathology, it is crucial to first analyze this system under different physiological conditions. The aim of the present study was therefore to investigate the inter-individual variation in complement activity and the influences of age and sex.

Methods: Complement levels and functional activity were determined in 120 healthy volunteers, 60 women, 60 men, age range 20–69 year. Serum functional activity of the classical pathway (CP), lectin pathway activated by mannan (MBL-LP) and alternative pathway (AP) was measured in sera, using deposition of C5b-9 as readout. In addition, levels of C1q, MBL, MASP-1, MASP-2, ficolin-2, ficolin-3, C2, C4, C3, C5, C6, C7, C8, C9, factor B, factor D, properdin, C1-inhibitor and C4b-binding protein, were determined. Age- and sex-related differences were evaluated.

Results: Significantly lower AP activity was found in females compared to males. Further analysis of the AP revealed lower C3 and properdin levels in females, while factor D concentrations were higher. MBL-LP activity was not influenced by sex, but MBL and ficolin-3 levels were significantly lower in females compared to males. There were no significant differences in CP activity or CP components between females and males, nevertheless females had significantly lower levels of the terminal components. The CP and AP activity was significantly higher in the elderly, in contrast to MBL-LP activity. Moreover, C1-inhibitor, C5, C8, and C9 increased with age in contrast to a decrease of factor D and C3 levels. In-depth analysis of the functional activity assays revealed that MBL-LP activity was predominantly dependent on MBL and MASP-2 concentration, whereas CP activity relied on C2, C1-inhibitor and C5 levels. AP activity was strongly and directly associated with levels of C3, factor B and C5.

Conclusion: This study demonstrated significant sex and age-related differences in complement levels and functionality in the healthy population. Therefore, age and sex analysis should be taken into consideration when discussing complement-related pathologies and subsequent complement-targeted therapies.

Flavonoid treatment in patients with healed venous ulcer: flow cytometry analysis suggests increased CD11b expression on neutrophil granulocytes in the circulation

The objective was to determine the activation of white blood cells (WBCs) and endothelial cells in patients with healed venous ulcer and the influence of the standing position and of treatment with flavonoids. Ten patients with a healed venous ulcer were treated with flavonoid substance (90% diosmin), 1000 mg three times daily for 30 days. Blood samples were taken from arm and dorsal foot veins before and after standing for 30 minutes. Blood sampling was performed before treatment, after three days, one month and three months. The activation of WBCs was determined by measuring adhesion molecule CD11b and CD18 expression on the surface of granulocytes and monocytes. In addition, interleukin 6 (IL-6), IL-8, soluble E-selectin (sE-selectin), sL-selectin and sICAM-1 levels in serum were quantified. The results showed that standing did not influence any of the measured parameters significantly. Expression of CD11b adhesion molecules on granulocytes was significantly up-regulated (p = 0.044) after treatment with flavonoids for one month, but this increase was not significant (p = 0.056) two months after the treatment period compared with the baseline level. The expression of CD18 remained unchanged. Baseline expression of CD11b or CD18 on monocytes did not change significantly during the study period. Neither was any significant change observed in the levels of IL-6, IL- 8 or the soluble adhesion molecules. It was concluded that flavonoid treatment for 30 days increased the expression of CD11b adhesion molecules on circulating granulocytes. No general effect on the inflammatory process could be observed as assessed by levels of cytokines and soluble adhesion molecules. Possible explanations for these findings could be that a decreased number of primed granulocytes leave the circulation due to a changed WBC/endothelial cell interaction or that flavonoids have a direct effect on granulocytes. Further studies are needed to clarify the mode of action of flavonoids in chronic venous disease.

Inflammatory markers and IL-6 polymorphism in peripheral arterial disease with and without diabetes mellitus

Peripheral arterial disease (PAD) is a manifestation of systemic atherosclerosis, recognized as an inflammatory disease of the vessel wall, probably accelerated by diabetes mellitus (DM). Elevated interleukin (IL)-6 levels have been associated with increased cardiovascular morbidity and a common polymorphism has been identified in the promoter region of the IL-6 gene. The aim of this prospective study was to investigate inflammatory mediators in PAD patients (±DM) and to investigate a possible relationship to the IL-6 gene polymorphism. Five groups of patients (DM, intermittent claudication ±DM, critical limb ischemia (CLI) ±DM) and a control group of 20 individuals each were included. Hemoglobin, high sensitive C-reactive protein (hsCRP), creatinine, blood lipids, white blood cells (WBC); CD11b/CD18; vascular cell adhesion molecule (sVCAM-1), intercellular adhesion molecule (sICAM-1), sE-selectin, sP-selectin; IL-6, IL-8, tumour necrosis factor (TNF)α, sTNFα-R1 and sTNFα-R2 were analysed. The IL-6 gene polymorphism was determined in all groups and also compared with 200 healthy controls from a larger study of blood donors. In a multiple regression analysis, adjusted for gender, smoking and age, the effect of CLI was significantly ( p < 0.05) associated with elevated levels of the WBC count, hsCRP, proinflammatory cytokines (IL-6, TNFα-R1-2) and endothelial (sICAM, sVCAM) and WBC (CD11b gran) markers. The effect of less advanced PAD (intermittent claudication) was related to an increased concentration of sVCAM-1 and the number of monocytes and granulocytes. DM or leg ulcers were not significantly related to any of the markers. No significant difference in frequency of the various IL-6 genotypes was found between the groups or when compared with the group of 200 blood donors ( p > 0.3). Activation of cytokines, endothelial cells and WBC was related to the Fontaine stage of PAD but not to the presence of DM or ulcers. No association was found between the polymorphism in the IL-6 promoter region and PAD.

Genetically determined mannan-binding lectin deficiency is of minor importance in determining susceptibility to severe infections and vascular organ damage in systemic lupus erythematosus

Deficiency of mannan-binding lectin (MBL) has been reported to impact susceptibility to severe infections and atherosclerosis in systemic lupus erythematosus (SLE). In this study, MBL gene polymorphisms were analysed in 143 SLE patients and the frequency of severe infections and organ damage according to SLICC/ACR Damage Index regarding cerebrovascular accidents, angina pectoris, coronary by-pass surgery, myocardial infarction and peripheral arterial disease leading to significant tissue loss, were recorded during a mean follow-up time of 15 years from diagnosis. In a multiple logistic regression model, smoking ( P = 0.001), hypertension ( P = 0.030), alcohol intake ( P = 0.027) and higher triglyceride concentration ( P = 0.026) were associated with cerebrovascular, cardiovascular and peripheral arterial organ damage (CPAD), while the association with MBL deficiency did not reach significance ( P = 0.098). Alcohol intake (>15 g/month) was inversely correlated with CPAD (OR = 0.29, 95%CI 0.096—0.87). MBL deficiency was not significantly more common in SLE patients with severe infections in a multivariate analysis ( P > 0.3). In conclusion, classical risk factors such as smoking, hypertension, low alcohol intake and elevated triglyceride concentration were relatively more important for development of CPAD than MBL deficiency in SLE. Furthermore, MBL deficiency did not contribute to development of major infections in SLE. Lupus (2007) 16, 245—253.

The assessment of serum-mediated phagocytosis of necrotic material by polymorphonuclear leukocytes to diagnose and predict the clinical features of systemic lupus erythematosus: an observational longitudinal study

BACKGROUND

Serum-mediated phagocytosis of antibody- and complement-opsonized necrotic cell material (NCM) by polymorphonuclear leukocytes can be quantified by using a flow cytometry-based assay. The phagocytosis of necrotic cell material (PNC) assay parallels the well-known lupus erythematosus cell test. In this study, we aimed to investigate the diagnostic accuracy of the assay and the relationship with clinical manifestations and disease activity in systemic lupus erythematosus (SLE).

METHODS

The diagnostic accuracy for SLE diagnosis of the PNC assay was studied by cross-sectional assessment of blood samples from 148 healthy control subjects and a multicenter rheumatic group (MRG) of 529 patients with different rheumatic symptoms. A cohort of 69 patients with an established SLE diagnosis (SLE cohort) underwent longitudinal clinical and laboratory follow-up for analysis of the temporal relationships between PNC positivity and specific clinical manifestations.

RESULTS

In 35 of 529 MRG patients, 13 of whom had SLE, the PNC assay result was positive. Combined positivity of the PNC assay and anti-double-stranded DNA antibodies increased specificity and positive predictive value for SLE diagnosis to 0.99 and 0.67, respectively. In the longitudinal study, 42 of 69 SLE cohort patients had positive results in the PNC assay at least once. PNC assay positivity was associated with current hematological manifestations and could predict mucocutaneous manifestations. When combined with hypocomplementemia, PNC positivity preceded increased Systemic Lupus Erythematosus Disease Activity Index 2000 score, glomerulonephritis, and alopecia.

CONCLUSIONS

Serum-mediated PNC by polymorphonuclear leukocytes is commonly but not exclusively seen in patients with SLE. The PNC assay may be used in follow-up of patients with SLE and, especially in combination with other routinely assessed laboratory tests, may help to predict flares and different clinical manifestations, including glomerulonephritis. Our results encourage further development of the PNC assay as a complementary laboratory tool in management of patients with SLE.

Novel treatment of severe combined immunodeficiency utilizing ex-vivo T-cell depleted haploidentical hematopoietic stem cell transplantation and CD45RA+ depleted donor lymphocyte infusions

BACKGROUND

Allogeneic hematopoietic stem cell transplantation (HSCT) is the only curative treatment available for severe combined immunodeficiency (SCID); although, there is a high incidence of severe infections and an increased risk of graft-versus host-disease (GvHD) with HSCT. Early intervention is a crucial prognostic factor and a HLA-haploidentical parental donor is often available. Haploidentical HSCT protocols utilizing extensively ex vivo T-cell depleted grafts (CliniMACs system) have proven efficient in preventing GvHD, but cause a delay in early T-cell recovery that increases the risk of viral infections. Here, we present a novel approach for treating SCID that combines selective depletion of GvHD-inducing alpha/beta (α/β) T-cells from the haploidentical HSCT graft with a subsequent donor lymphocyte infusion (DLI) enriched for CD45RO+ memory T-cells.

RESULTS

Our patient was diagnosed with SCID (T-B + NK+ phenotype). At 9 months of age, he received a T cell receptor(TCR)α/β-cell depleted graft from his haploidentical mother, following a reduced intensity conditioning regimen with no additional GvHD prophylaxis. Engraftment was rapid with complete donor chimerism and no signs of GvHD. However, at 12 weeks post HSCT, the patient was still T-cell lymphopenic with clinical symptoms of multiple severe viral infections. Consequently, therapeutic DLIs were initiated for enhanced anti-viral immunity. The patient was treated with CD45RA+ depleted haploidentical maternal donor lymphocytes enriched from unmobilized whole blood, and a total T-cell dose of no more than 25 x10(3) CD3+ cells/kg with >99.9% purity of CD3 + CD45RO+ memory T-cells was transferred. Following the DLI, a prompt increase in CD3 + CD4+ and CD3 + CD8+ counts was observed with a subsequent clearance of viral infections. No acute or chronic GvHD was observed.

CONCLUSIONS

Automated depletion of CD45RA+ naïve T-cells from unmobilized whole blood is a simple and rapid strategy to provide unmanipulated DLIs, with a potentially broad repertoire of pathogen specific memory T-cells. In the haploidentical setting, CD45RA+ depleted DLIs can be safely administered at low T-cell doses for efficient enhancement of viral immunity and limited risk of GvHD. We demonstrate the successful use of this approach following TCR-α/β-cell depleted HSCT for the treatment of SCID.

CD81 and CD48 show different expression on blood eosinophils in systemic sclerosis: new markers for disease and pulmonary inflammation?

OBJECTIVES

In systemic sclerosis (SSc)-related interstitial lung disease (ILD), elevated eosinophil counts in bronchoalveolar lavage are associated with a worse outcome. We hypothesized that eosinophils may be activated in the peripheral circulation, thereby increasing their recruitment to affected tissues and contributing to inflammation and fibrosis. The aim of this study was to characterize the blood eosinophils in SSc patients.

METHOD

Expression levels of surface markers CD11b, CD44, CD48, CD54, CD69, CD81, and HLA-DR on CD16(low)CD9(high)-expressing eosinophils were measured by flow cytometry in whole blood from SSc patients (n = 32) and controls (n = 11).

RESULTS

Expression levels of CD54, CD69, and HLA-DR were undetectable in all groups. CD44 and CD11b expression levels were similar between groups. CD81 expression was lower in patients compared to controls independent of disease duration (p = 0.001). CD48 expression was increased in patients with a short disease duration (< 2 years) compared to both controls (p = 0.042) and patients with longer disease duration (≥ 2 years; p = 0.027). In patients with short disease duration, increased CD48 expression was associated with alveolar inflammation as measured by an increased concentration of alveolar nitric oxide (r = 0.76, p = 0.003).

CONCLUSIONS

Blood eosinophils change phenotype during disease evolution in SSc, and CD48 expression may be used as a biomarker for pulmonary inflammation.

Marked variability in clinical presentation and outcome of patients with C1q immunodeficiency

OBJECTIVE

Globally approximately 60 cases of C1q deficiency have been described with a high prevalence of Systemic Lupus Erythematosus (SLE). So far treatment has been guided by the clinical presentation rather than the underlying C1q deficiency. Recently, it was shown that C1q production can be restored by allogeneic hematopoietic stem cell transplantation. Current literature lacks information on disease progression and quality of life of C1q deficient persons which is of major importance to guide clinicians taking care of patients with this rare disease.

METHODS

We performed an international survey, of clinicians treating C1q deficient patients. A high response rate of >70% of the contacted clinicians yielded information on 45 patients with C1q deficiency of which 25 are published.

RESULTS

Follow-up data of 45 patients from 31 families was obtained for a median of 11 years after diagnosis. Of these patients 36 (80%) suffer from SLE, of which 16 suffer from SLE and infections, 5 (11%) suffer from infections only and 4 (9%) have no symptoms. In total 9 (20%) of the C1q deficient individuals had died. All except for one died before the age of 20 years. Estimated survival times suggest 20% case-fatality before the age of 20, and at least 50% of patients are expected to reach their middle ages.

CONCLUSION

Here we report the largest phenotypic data set on C1q deficiency to date, revealing high variance; with high mortality but also a subset of patients with an excellent prognosis. Management of C1q deficiency requires a personalized approach.

Classical pathway deficiencies - A short analytical review

Deficiencies in the classical pathway of complement activation have some common features but show also great differences. Deficiencies of each of the components (C1q, C1s, C1r, C4 and C2) imply increased susceptibility to bacterial infections. They are also associated with increased risk to develop systemic lupus erythematosus where deficiency of C1q is strongly associated to the disease while C4 less and C2 much less. Deficiency of C1q affects only activation of the classical pathway while deficiency of C4 and C2 also prevent activation of the lectin pathway. Bypass mechanisms may result in complement activation also in absence of C2 but not in absence of C1q or C4. The genes for C2 and C4 isotypes are closely located within the MHC class III region on chromosome 6p and the genes for the 3 C1q chains are on chromosome 1p. Deficiencies of C1q and of C4 show genetic heterogeneity while deficiency of C2 in the great majority of cases is caused by a specific deletion. The production of C4 and C2 is mainly by the hepatocytes in the liver while C1q is produced by monocytic bone marrow derived cells. This has implications for the possibility to treat the deficiency and hematopoietic stem cell transplantation has been tried in C1q deficiency.

European Union funded project on the development of a whole complement deficiency screening ELISA-A story of success and an exceptional manager: Mohamed R. Daha

A whole complement ELISA-based assay kit, primarily designed to screen for deficiencies in components of the complement system was developed during a European Union grant involving more than a dozen European scientists and a small-medium enterprise company (Wieslab, which later merged into Eurodiagnostica). The consortium was led by Prof. Mohamed R. Daha who had already guided a preceding European grant which prepared the ground for this endeavor to create a novel and sophisticated complement measurement tool. The final result of the grant was a scientific publication (Seelen et al., 2005, J. Immunol. Methods 296, 187-198) and a commercially available complement deficiency screening kit, WIESLAB(®) Complement system Screen. Thereafter, the group decided to carry on with a grant, located at Innsbruck Medical University, and supported by royalties and unrestricted educational grants from Eurodiagnostica, Malmö, entitled "Search for Applications for WIESLAB(®) Complement system Screen (SAW)" with the aim to look for further applications of this assay. During the latter project the group organized several scientific meetings aimed at evaluating the use of the assay as well as developing further branches of its platform. A look back over almost two decades reveals a great story of excellent research which was also commercially successful, fulfilling the aims of European Union grants. It is also a story of ageless friendship, only possible due to the vision and guidance of an exceptional manager: Moh Daha.

The association between antibody levels before and after 7-valent pneumococcal conjugate vaccine immunization and subsequent pneumococcal infection in chronic arthritis patients

INTRODUCTION

The aim of present study is to inverstigate the association between antibody levels after vaccination with 7-valent pneumococcal conjugate vaccine (PCV7) and subsequent serious pneumococcal infections in rheumatoid arthritis (RA) and spondylarthropathy (SpA) patients.

METHODS

A cohort of 497 patients (RA=248 and SpA=249) received a single dose of PCV7. At vaccination, patients were treated with methotrexate (MTX; n=85), anti-tumour necrosis factor (anti-TNF) + MTX (n=169), anti-TNF monotherapy (n=158) and non-steroidal anti-inflammatory drugs (NSAIDs)/analgesics (n=85). Antibody levels of serotypes 6B and 23B were analyzed before and 4 to 6 weeks after vaccination using standard enzyme-linked immunosorbent assay (ELISA). Serious pneumococcal infections (pneumonia/lower respiratory tract infection, meningitis, sepsis, septic arthritis) occurring within 4.5 years after vaccination were identified in the Skåne Healthcare Register using the International Classification of Diseases, tenth revision (ICD-10) codes. The association between post-vaccination antibody levels and protection against infections and determination of protective cutoff levels was explored using receiver operating characteristic (ROC) curves. Predictors of infection were studied using regression analyses.

RESULTS

Eighteen infections were registered in 15 patients before vaccination and 27 infections in 23 patients after vaccination. Patients with serious infections after vaccination had significantly lower post-vaccination antibody titres for both 6B (P=0.04) and 23 F (P=0.04). Post-vaccination antibody levels of at least 1.29 mg/L and 1.01 mg/L for 6B and 23, respectively, were associated with better protection from serious infections. Higher age, concomitant prednisolone but not MTX or anti-TNF were associated with such infections.

CONCLUSIONS

Patients with more robust antibody responses after vaccination with pneumococcal conjugate vaccine were less likely to suffer from serious infections. High age and prednisolone at vaccination were associated with putative serious pneumococcal infections in this cohort.

TRIAL REGISTRATION NUMBER

EudraCT EU 2007-006539-29 and NCT00828997 . Registered 23 January 2009.

Novel Genetic Mutations in the First Swedish Patient with Purine Nucleoside Phosphorylase Deficiency and Clinical Outcome After Hematopoietic Stem Cell Transplantation with HLA-Matched Unrelated Donor

Purine nucleoside phosphorylase (PNP) is an enzyme active in the purine salvage pathway. PNP deficiency caused by autosomal recessive mutations in the PNP gene leads to severe combined immunodeficiency (SCID) and in two thirds of cases also to neurological effects such as developmental delay, ataxia, and motor impairment.PNP deficiency has a poor outcome, and the only curative treatment is allogenic hematopoietic stem cell transplantation (HSCT). We present the first Swedish patient with PNP deficiency with novel mutations in the PNP gene and the immunological results of the HSCT and evaluate the impact of HSCT on the neurological symptoms. The patient presented early in life with neurological symptoms and suffered later from repeated serious respiratory tract infections. Biochemical tests showed severe reduction in PNP activity (1% residual activity). Genetic testing revealed two new mutations in the PNP gene: c.729C>G (p.Asn243Lys) and c.746A>C (p.Tyr249Cys). HSCT was performed with an unrelated donor, resulting in prompt and sustained engraftment and complete donor chimerism. There was no further aggravation of the patient's neurological symptoms at 21 months post HSCT, and appropriate developmental milestones were achieved. HSCT is curative for the immunological defect caused by PNP deficiency, and our case strengthens earlier reports that HSCT is effective as a treatment even for neurological symptoms in PNP deficiency.

Primary immunodeficiency in infection-prone children in southern Sweden: occurrence, clinical characteristics and immunological findings

Background

Primary immunodeficiency diseases (PIDs) comprise a heterogeneous group of disorders mainly characterized by increased susceptibility to infections. The aims of this study were to estimate the occurrence rate of PID in the paediatric (age ≤ 18 years) population of southern Sweden (approx. 265,000 children) and to describe their demographic, clinical and immunological characteristics. During a period of 4 years, in four paediatric speciality clinics in Skåne County in southern Sweden, children being seen for infections and fulfilling specific criteria were evaluated according to a predefined examination schedule. The initial analysis consisted of complete blood counts with analysis of lymphocyte subpopulations (T, B, NK cells), measurement of immunoglobulins (IgG, IgA, IgM, IgE and IgG subclasses), and assessment of the complement system (classical, alternative and lectin pathways). In addition, results of these immunological analyses in other children from the same area and time period were evaluated.

Results

In total, 259 children (53.6% males) met the criteria and were included. The most common infection was recurrent otitis media. Immunological analyses results for about two thirds of the patients were outside age-related reference intervals. Further examination in this latter group identified 15 children with PID (9 males); 7 (2.7%) had genetically defined PID, representing 4 different diagnoses, and another 8 (3.1%) had a clinically defined PID - common variable immunodeficiency. No additional PID patient was identified from the evaluation of laboratory results in children not included in the study. The median age at diagnosis was 3.5 years (range 1–12 years).

Conclusions

The occurrence rate of PID was about 4 new cases per year in this population. Several different PID diagnoses were found, and the application of specified criteria to identify PID patients was useful. In children who are prone to infection, the use of a predefined set of immunological laboratory analyses at their first examination was beneficial for early identification of patients with PID.

Anti-C1q antibodies in systemic lupus erythematosus

OBJECTIVE

Anti-C1q has been associated with systemic lupus erythematosus (SLE) and lupus nephritis in previous studies. We studied anti-C1q specificity for SLE (vs rheumatic disease controls) and the association with SLE manifestations in an international multicenter study.

METHODS

Information and blood samples were obtained in a cross-sectional study from patients with SLE (n = 308) and other rheumatologic diseases (n = 389) from 25 clinical sites (84% female, 68% Caucasian, 17% African descent, 8% Asian, 7% other). IgG anti-C1q against the collagen-like region was measured by ELISA.

RESULTS

Prevalence of anti-C1q was 28% (86/308) in patients with SLE and 13% (49/389) in controls (OR = 2.7, 95% CI: 1.8-4, p < 0.001). Anti-C1q was associated with proteinuria (OR = 3.0, 95% CI: 1.7-5.1, p < 0.001), red cell casts (OR = 2.6, 95% CI: 1.2-5.4, p = 0.015), anti-dsDNA (OR = 3.4, 95% CI: 1.9-6.1, p < 0.001) and anti-Smith (OR = 2.8, 95% CI: 1.5-5.0, p = 0.01). Anti-C1q was independently associated with renal involvement after adjustment for demographics, ANA, anti-dsDNA and low complement (OR = 2.3, 95% CI: 1.3-4.2, p < 0.01). Simultaneously positive anti-C1q, anti-dsDNA and low complement was strongly associated with renal involvement (OR = 14.9, 95% CI: 5.8-38.4, p < 0.01).

CONCLUSIONS

Anti-C1q was more common in patients with SLE and those of Asian race/ethnicity. We confirmed a significant association of anti-C1q with renal involvement, independent of demographics and other serologies. Anti-C1q in combination with anti-dsDNA and low complement was the strongest serological association with renal involvement. These data support the usefulness of anti-C1q in SLE, especially in lupus nephritis.

Platelet activation and anti-phospholipid antibodies collaborate in the activation of the complement system on platelets in systemic lupus erythematosus

Anti-phospholipid (aPL) antibodies are important contributors to development of thrombosis in patients with the autoimmune rheumatic disease systemic lupus erythematosus (SLE). The underlying mechanism of aPL antibody-mediated thrombosis is not fully understood but existing data suggest that platelets and the complement system are key components. Complement activation on platelets is seen in SLE patients, especially in patients with aPL antibodies, and has been related to venous thrombosis and stroke. The aim of this study was to investigate if aPL antibodies could support classical pathway activation on platelets in vitro as well as in SLE patients. Furthermore, we investigated if complement deposition on platelets was associated with vascular events, either arterial or venous, when the data had been adjusted for traditional cardiovascular risk factors. Finally, we analyzed if platelet complement deposition, both C1q and C4d, was specific for SLE. We found that aPL antibodies supported C4d deposition on platelets in vitro as well as in SLE patients (p = 0.001 and p<0.05, respectively). Complement deposition on platelets was increased in SLE patients when compared with healthy individuals (p<0.0001). However, high levels of C4d deposition and a pronounced C1q deposition were also seen in patients with rheumatoid arthritis and systemic sclerosis. In SLE, C4d deposition on platelets was associated with platelet activation, complement consumption, disease activity and venous (OR = 5.3, p = 0.02), but not arterial, thrombosis, observations which were independent of traditional cardiovascular risk factors. In conclusion, several mechanisms operate in SLE to amplify platelet complement deposition, of which aPL antibodies and platelet activation were identified as important contributors in this investigation. Complement deposition on platelets was identified as a marker of venous, but not arterial thrombosis, in SLE patients independently of traditional risk factors and aPL antibodies. Further studies are needed to elucidate the role of complement deposition on platelets in development of venous thrombosis.

Pathogenic mechanisms in lupus nephritis: Nucleosomes bind aberrant laminin β1 with high affinity and colocalize in the electron-dense deposits

OBJECTIVE

Apoptotic nucleosomes are structurally and immunologically involved in lupus nephritis. The purpose of this study was to examine the expression and function of laminins and their interactions with nucleosomes in the kidneys of patients with lupus nephritis, using surface plasmon resonance (SPR) analysis.

METHODS

SPR interaction analysis was used to quantify the strength of laminin-nucleosome interactions. Electron microscopy techniques were used to determine in vivo colocalization of IgG, chromatin, and laminin β1, as well as to characterize nucleosome-laminin interactions in vitro.

RESULTS

Nucleosomes were found to possess high affinity for laminin β1-containing laminins and to have the potential to form stable molecular complexes with these structures. In vivo, laminin β1 was aberrantly expressed in the glomerular basement membrane (GMB) of lupus nephritis patients, and in situ, it acted as a nucleosome ligand, selectively colocalizing with nucleosomes within electron-dense deposits (EDDs). Normal adult laminin 11, which contains laminin β2, did not bind nucleosomes, and it did not colocalize in vivo with the nucleosomes in the nephritic GBM. In addition, TGFβ1 was expressed by the glomerular mesangium, glomerular endothelial cells, and by podocytes in patients with lupus nephritis. It was trapped in situ within EDDs by an as-yet-unknown ligand. As was recently described in a transgenic mouse model, paracrine kidney glomerular TGFβ1 may thereby contribute to the development of glomerulopathy via the induction of laminin β1 incorporation in the GBM, whereas systemic blood vessel-derived TGFβ1 could be trapped during filtration.

CONCLUSION

Our findings of the specific high-affinity binding of nucleosomes to aberrantly expressed laminin β1 in the GBM and their colocalization in the GBM may explain important features of the initial steps in the pathogenesis of lupus nephritis, the planted antigen hypothesis.

Serological assessment for celiac disease in IgA deficient adults

PURPOSE

Selective immunoglobulin A deficiency is the most common primary immunodeficiency disorder that is strongly overrepresented among patients with celiac disease (CD). IgG antibodies against tissue transglutaminase (tTG) and deamidated gliadin peptides (DGP) serve as serological markers for CD in IgA deficient individuals, although the diagnostic value remains uncertain. The aim of this study was to investigate the prevalence of these markers in a large cohort of IgA deficient adults with confirmed or suspected CD and relate the findings to gluten free diet.

METHODS

Sera from 488,156 individuals were screened for CD in seven Swedish clinical immunology laboratories between 1998 and 2012. In total, 356 out of 1,414 identified IgA deficient adults agreed to participate in this study and were resampled. Forty-seven IgA deficient blood donors served as controls. Analyses of IgG antibodies against tTG and DGP as well as HLA typing were performed and a questionnaire was used to investigate adherence to gluten free diet. Available biopsy results were collected.

RESULTS

Out of the 356 IgA deficient resampled adults, 67 (18.8%) were positive for IgG anti-tTG and 79 (22.2%) for IgG anti-DGP, 54 had biopsy confirmed CD. Among the 47 IgA deficient blood donors, 4 (9%) were positive for IgG anti-tTG and 8 (17%) for anti-DGP. Four were diagnosed with biopsy verified CD, however, 2 of the patients were negative for all markers. Sixty-eight of 69 individuals with positive IgG anti-tTG were HLA-DQ2/DQ8 positive whereas 7 (18.9%) of the 37 individuals positive for IgG anti-DGP alone were not.

CONCLUSIONS

IgG anti-tTG seems to be a more reliable marker for CD in IgA deficient adults whereas the diagnostic specificity of anti-DGP appears to be lower. High levels of IgG antibodies against tTG and DGP were frequently found in IgA deficient adults despite adhering to gluten free diet.

Clinical phenotype associations with various types of anti-dsDNA antibodies in patients with recent onset of rheumatic symptoms. Results from a multicentre observational study

Despite anti-dsDNA antibodies constitute a wide range of specificities, they are considered as the hallmark for systemic lupus erythematosus (SLE).

Rituximab and abatacept but not tocilizumab impair antibody response to pneumococcal conjugate vaccine in patients with rheumatoid arthritis

Introduction

The objective of the study was to investigate the impact of newer biologic treatments including rituximab, abatacept and tocilizumab on antibody response following pneumococcal vaccination using a 7-valent conjugate vaccine in patients with established rheumatoid arthritis (RA).

Methods

Patients with RA receiving rituximab, abatacept or tocilizumab as monotherapy or combined with methotrexate (MTX) participated in the study. Specific IgG antibodies against 23F and 6B serotypes were measured at vaccination and 4 to 6 weeks after vaccination using standardised ELISA. Geometric mean antibody levels (GML) were calculated. Antibody response (AR) was defined as the ratio between post- and pre-vaccination antibody levels and a positive antibody response (posAR) was AR ≥2.

Results

In total, 88 patients were enrolled in the study. Of 55 patients treated with rituximab, 26 (46%) were on concomitant MTX. Of patients receiving abatacept (n = 17) and tocilizumab (n = 16) biologic treatment was given in combination with MTX in 13 (76%) and 9 (56%) patients, respectively. Patients treated with rituximab had significantly lower AR compared to those on tocilizumab, as well as compared to previously reported RA patients on MTX and controls (spondylarthropathy patients treated with NSAIDs and/or analgesics). In total, 10.3% of patients on rituximab monotherapy and no patient on rituximab + MTX had posAR for both serotypes. For abatacept and tocilizumab the corresponding figures were 17.6% and 50%.

Conclusion

In this cohort of patients with established RA, treatment with rituximab and abatacept was associated with diminished antibody response but this was most pronounced for rituximab. Pneumococcal conjugate vaccine administrated during ongoing tocilizumab treatment seems to be associated with sufficient antibody response. Pneumococcal vaccination should preferably be encouraged before initiation of rituximab or abatacept treatment.

Trial registration

NCT00828997 and EudraCT EU 2007-006539-29.

Increased serum levels of S100A8/A9 and S100A12 are associated with cardiovascular disease in patients with inactive systemic lupus erythematosus

OBJECTIVES

Patients with SLE have an increased morbidity and mortality from cardiovascular disease (CVD). The reason for this is not entirely understood, but is believed to be partly related to the long-lasting inflammatory process seen in SLE. The aim of the present study was to investigate whether there is an association between CVD and serum levels of the proinflammatory proteins S100A8/A9 and S100A12 in SLE.

METHODS

Serum levels of S100A8/A9 and S100A12 were measured with ELISA in 237 SLE patients with clinically inactive disease and without infections, as well as in 100 healthy individuals. Cardiovascular manifestations were defined according to the SLICC/ACR Damage Index (SLICC/ACR-DI).

RESULTS

Serum levels of S100A8/A9 were elevated in our inactive SLE patients as compared with healthy individuals (P < 0.0001), which was not seen for S100A12 (P = 0.12). SLE patients with a history of CVD had increased serum levels of both S100A8/A9 and S100A12 compared with patients with no CVD or venous thromboembolism (P = 0.003 and P = 0.006, respectively). The presence of organ damage according to SLICC/ACR-DI was associated with an increase in both S100A8/A9 and S100A12 serum levels (P = 0.001 and P = 0.006, respectively).

CONCLUSION

Elevated serum levels of S100A8/A9 and S100A12 may be used as an indicator of severe disease and CVD in SLE, suggesting that SLE patients with elevated serum S100A8/A9 and S100A12 concentrations may benefit from more intense cardiovascular primary preventive strategies and possibly also from more intense and early immunosuppressive treatment.

Increased serum type I interferon activity in early systemic sclerosis patients is associated with antibodies against Sjögren's syndrome antigens and nuclear ribonucleoprotein antigens

OBJECTIVE

To study serum type I interferon (IFN) activity in patients with early systemic sclerosis (SSc).

METHOD

Serum type I IFN activity was measured in 33 consecutive patients with SSc and a disease duration of < 2 years and in 13 healthy individuals by calculating a type I IFN score according to the induction of six IFN-α regulated genes in a reporter cell line.

RESULTS

Twenty-seven per cent of the SSc patients had an increased type I IFN score compared to none of the healthy individuals (p < 0.05). The clinical SSc phenotype associated with high serum type I IFN activity did not differ from patients with low serum type I IFN activity regarding the presence of skin or lung fibrosis, pulmonary hypertension, or digital complications. Patients with high serum type I IFN activity were younger (p < 0.01) and had a lower frequency of cardiac involvement (p = 0.053), lower leucocyte count (p < 0.001), higher immunoglobulin (Ig)G levels (p < 0.05), and a higher amount of antibodies against extractable nuclear antigens (p < 0.01) than patients with low serum type I IFN activity. The presence of antibodies against topoisomerase I, Sjögren's syndrome antigen, and nuclear ribonucleoprotein antigens was associated with higher type I IFN activity (p < 0.05 for all comparisons).

CONCLUSIONS

Our study indicates that increased serum type I IFN activity in early SSc patients is associated with an antibody and laboratory profile that may reflect a subclinical overlap of SSc with other type I IFN-driven connective tissue diseases (CTDs).

Genes identified in Asian SLE GWASs are also associated with SLE in Caucasian populations

Recent genome-wide association studies (GWASs) conducted in Asian populations have identified novel risk loci for systemic lupus erythematosus (SLE). Here, we genotyped 10 single-nucleotide polymorphisms (SNPs) in eight such loci and investigated their disease associations in three independent Caucasian SLE case–control cohorts recruited from Sweden, Finland and the United States. The disease associations of the SNPs in ETS1, IKZF1, LRRC18-WDFY4, RASGRP3, SLC15A4, TNIP1 and 16p11.2 were replicated, whereas no solid evidence of association was observed for the 7q11.23 locus in the Caucasian cohorts. SLC15A4 was significantly associated with renal involvement in SLE. The association of TNIP1 was more pronounced in SLE patients with renal and immunological disorder, which is corroborated by two previous studies in Asian cohorts. The effects of all the associated SNPs, either conferring risk for or being protective against SLE, were in the same direction in Caucasians and Asians. The magnitudes of the allelic effects for most of the SNPs were also comparable across different ethnic groups. On the contrary, remarkable differences in allele frequencies between Caucasian and Asian populations were observed for all associated SNPs. In conclusion, most of the novel SLE risk loci identified by GWASs in Asian populations were also associated with SLE in Caucasian populations. We observed both similarities and differences with respect to the effect sizes and risk allele frequencies across ethnicities.

Fine mapping and conditional analysis identify a new mutation in the autoimmunity susceptibility gene BLK that leads to reduced half-life of the BLK protein

OBJECTIVES

To perform fine mapping of the autoimmunity susceptibility gene BLK and identify functional variants involved in systemic lupus erythematosus (SLE).

METHODS

Genotyping of 1163 European SLE patients and 1482 controls and imputation were performed covering the BLK gene with 158 single-nucleotide polymorphisms. Logistic regression analysis was done using PLINK and conditional analyses using GENABEL's test score. Transfections of BLK constructs on HEK293 cells containing the novel mutation or the wild type form were analysed for their effect on protein half-life using a protein stability assay, cycloheximide and western blot. CHiP-qPCR for detection of nuclear factor κ B (NFkB) binding.

RESULTS

Fine mapping of BLK identified two independent genetic effects with functional consequences: one represented by two tightly linked associated haplotype blocks significantly enriched for NFκB-binding sites and numerous putative regulatory variants whose risk alleles correlated with low BLK mRNA levels. Binding of NFkBp50 and p65 to an associated 1.2 Kb haplotype segment was confirmed. A second independent genetic effect was represented by an Ala71Thr, low-frequency missense substitution with an OR=2.31 (95% CI 1.38 to 3.86). The 71Thr decreased BLK protein half-life.

CONCLUSIONS

These results show that rare and common regulatory variants in BLK are involved in disease susceptibility and both, albeit independently, lead to reduced levels of BLK protein.

Increased C1q, C4 and C3 deposition on platelets in patients with systemic lupus erythematosus--a possible link to venous thrombosis?

OBJECTIVE

Patients with systemic lupus erythematosus (SLE) have an increased risk of developing vascular diseases (VD) such as myocardial infarction, stroke and venous thrombosis, which can only partly be explained by traditional risk factors. The role of platelets in this process has not been extensively studied. Platelet activation supports complement binding to the platelet surface, and increased C4d has been seen on platelets in SLE patients as well as in non-rheumatic patients with stroke. In this study we investigated in vivo platelet deposition of the classical complement pathway components C1q, C4d and C3d in relation to VD in SLE patients. Furthermore, the ability of serum to support in vitro complement deposition on fixed heterologous platelets was analyzed.

METHODS

Blood from 69 SLE patients and age- and sex-matched healthy individuals was collected in sodium-citrate tubes and platelets isolated by centrifugation. Complement deposition on platelets was detected by flow cytometry.

RESULTS

We could demonstrate that SLE patients had increased C1q, C3d and C4d deposition on platelets as compared to healthy controls (p < 0.0001). SLE patients with a history of venous thrombosis had increased complement deposition on platelets as compared to SLE patients without this manifestation (p < 0.05). In vitro studies demonstrated that serum from patients with lupus anticoagulant, venous thrombosis or antiphospholipid antibody syndrome supported increased platelet C4d deposition in vitro as compared to SLE patients without these manifestations (p < 0.05). Our data support the hypothesis that platelet activation and the subsequent complement deposition on platelets are central in the development of venous thrombosis in SLE.

CONCLUSIONS

Altogether we suggest that complement deposition on platelets could reflect important pathogenetic events related to the development of venous thrombosis in SLE and might be used as a marker for venous thrombosis in SLE.

Sensitive and specific assays for C3 nephritic factors clarify mechanisms underlying complement dysregulation

C3 nephritic factors are autoantibodies that prolong the half-life or prevent regulation of the alternative pathway C3 convertase, resulting in uncontrolled complement activation. They are strongly associated with renal disease but their role in pathogenesis remains controversial. Here we optimized and compared a panel of assays to identify and interrogate nephritic factor activities. Of 101 patients with histologic or clinically evident disease, 48 were positive in some or all assays. In the presence of properdin, binding of autoantibody was detected in 39 samples and convertase stabilization was detected in 36. Forty-two of 48 nephritic factors tested prevented convertase decay by factor H, and most of these by decay accelerating factor (28) and complement receptor 1 (34). Representative properdin-independent nephritic factors had no effect on C5 cleavage and terminal pathway activity, while properdin-dependent nephritic factors enhanced activity. Biacore analysis of four purified IgG samples confirmed resistance to decay and showed that properdin-independent nephritic factors increased convertase half-life over 50-fold, whereas properdin-dependent nephritic factors increased the half-life 10- to 20-fold and also increased activity of the C3 convertase up to 10-fold. Thus, our study provides a rational approach to detect and characterize nephritic factors in patients.

The effect of smoking and alcohol consumption on markers of systemic inflammation, immunoglobulin levels and immune response following pneumococcal vaccination in patients with arthritis

Introduction

The purpose of this research was to study the influence of cigarette smoking and alcohol consumption on immune response to heptavalent pneumococcal conjugate vaccine, immunoglobulin levels (Ig) and markers of systemic inflammation in patients with rheumatoid arthritis (RA) or spondylarthropathy (SpA).

Methods

In total, 505 patients were vaccinated. Six pre-specified groups were enrolled: RA on methotrexate (MTX) treatment in some cases other disease-modifying antirheumatic drugs (DMARDs) (I); RA on anti-tumour necrosis factor (TNF) as monotherapy (II); RA on anti-TNF+MTX+ possibly other DMARDs (III); SpA on anti-TNF as monotherapy (IV); SpA on anti-TNF+MTX+ possibly other DMARDs (V); and SpA on nonsteroidal anti-inflammatory drugs (NSAIDs) and/or analgesics (VI). Smoking (pack-years) and alcohol consumption (g/week) were calculated from patient questionnaires. Ig, C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) were determined at vaccination. IgG antibodies against serotypes 23F and 6B were measured at vaccination and after four to six weeks using standard ELISA. Immune response (ratio between post- and pre-vaccination antibodies; immune response (IR)) and positive immune response (≥2-fold increase in pre-vaccination antibodies; posIR) were calculated.

Results

Eighty-eight patients (17.4%) were current smokers. Smokers had higher CRP and ESR, lower IgG and lower IR for both serotypes (P between 0.012 and 0.045). RA patients on MTX who smoked ≥1pack-year had lower posIR for both serotypes (P = 0.021; OR 0.29; CI 0.1 to 0.7) compared to never-smokers. Alcohol consumption was associated with lower CRP (P = 0.05) and ESR (P = 0.003) but did not influence IR or Ig levels.

Conclusion

Smoking predicted impaired immune response to pneumococcal conjugate vaccine in RA patients on MTX. Smokers with arthritis had higher inflammatory markers and lower IgG regardless of diagnosis and treatment. Low to moderate alcohol consumption was related to lower levels of inflammation markers but had no impact on immune response.

Trial registration

EudraCT EU 2007-006539-29 and NCT00828997

Combination of autoantibodies against different histone proteins influences complement-dependent phagocytosis of necrotic cell material by polymorphonuclear leukocytes in systemic lupus erythematosus

OBJECTIVE

Polymorphonuclear leukocytes (PMN) with autoantibody-coated engulfed necrotic cell material (NC) are frequently seen in systemic lupus erythematosus (SLE). We evaluated the roles of complement, different antihistone antibodies (anti-H ab), and oxidative burst in the phagocytosis of NC by PMN, as well as association to disease activity and clinical phenotype in SLE.

METHODS

ELISA and immunoblot were used to measure antibodies to different histone proteins in sera from patients with SLE and complement-deficient individuals. Phagocytosis of NC by PMN and oxidative burst activity was assessed by flow cytometry.

RESULTS

A clearly increased phagocytosis of NC was seen in patients with active SLE, which was associated with high levels of anti-H ab concentrations and oxidative burst activity. The complement system contributed to efficient phagocytosis of NC by PMN through activation of the classical pathway, and the phagocytosis was mediated by FcγRIIA, FcγRIIIB, and CR1 in combination. A pattern of high phagocytosis, consumption of classical pathway components, and a broad anti-H ab repertoire was seen particularly in patients with nephritis and serositis. The combination of antibodies to several different histone proteins, often with anti-DNA antibodies, promoted an efficient uptake of NC, whereas antibodies against only histone H1 or a few histones seemed to be of less importance.

CONCLUSION

The distributions of specificities among anti-H ab are of great importance in the complement-dependent phagocytosis of debris from NC in SLE. Measurement of anti-H ab could be useful in monitoring of this disease and contribute to improved understanding of the autoimmune process.

Neutrophil extracellular traps that are not degraded in systemic lupus erythematosus activate complement exacerbating the disease

Ongoing inflammation including activation of the complement system is a hallmark of systemic lupus erythematosus (SLE). Antimicrobial neutrophil extracellular traps (NETs) are composed of secreted chromatin that may act as a source of autoantigens typical for SLE. In this study, we investigated how complement interacts with NETs and how NET degradation is affected by complement in SLE patients. We found that sera from a subset of patients with active SLE had a reduced ability to degrade in vitro-generated NETs, which was mostly restored when these patients were in remission. Patients that failed to degrade NETs had a more active disease and they also displayed lower levels of complement proteins C4 and C3 in blood. We discovered that NETs activated complement in vitro and that deposited C1q inhibited NET degradation including a direct inhibition of DNase-I by C1q. Complement deposition on NETs may facilitate autoantibody production, and indeed, Abs against NETs and NET epitopes were more pronounced in patients with impaired ability to degrade NETs. NET-bound autoantibodies inhibited degradation but also further increased C1q deposition, potentially exacerbating the disease. Thus, NETs are a potent complement activator, and this interaction may play an important role in SLE. Targeting complement with inhibitors or by removing complement activators such as NETs could be beneficial for patients with SLE.

Increased IgG on cell-derived plasma microparticles in systemic lupus erythematosus is associated with autoantibodies and complement activation

OBJECTIVE

To quantify immunoglobulin and C1q on circulating cell-derived microparticles (MPs) in patients with systemic lupus erythematosus (SLE) and to determine whether immunoglobulin and C1q levels are correlated with clinical and serologic parameters.

METHODS

Sixty-eight clinically well-characterized SLE patients, 38 healthy controls, 6 patients with systemic sclerosis (SSc), and 6 patients with rheumatoid arthritis (RA) were included. The numbers of annexin V-binding MPs displaying IgG, IgM, or C1q were enumerated by flow cytometry. MP protein levels were determined by mass spectrometry in clinically defined subsets of SLE patients and controls. The MP IgG load was determined by flow cytometric analysis of all samples from SLE patients and healthy controls.

RESULTS

SLE patients had significantly increased total and relative numbers of IgG-positive MPs (P = 0.0004), with a much higher average IgG load per MP (P < 0.0001) than healthy controls. Quantitative mass spectrometry of purified MPs verified significantly increased IgG, IgM, and C1q levels in SLE patients. In RA and SSc patients, the average IgG load per MP was significantly lower than in SLE patients (P = 0.006 and P = 0.05, respectively). Also, the IgM load and C1q load per MP were significantly higher in SLE patients than in the control groups (P < 0.05), except for IgM in the RA group. IgG-positive MPs were significantly associated with the presence of anti-double-stranded DNA, anti-extractable nuclear antigen, and antihistone antibodies, with total IgG, and with decreased leukocyte counts. Average IgG load per MP was associated with lower concentrations of MPs, the presence of anti-C1q antibodies, and complement consumption.

CONCLUSION

Our findings indicate that circulating cell-derived MPs in SLE patients carry increased loads of IgG, IgM, and C1q and that IgG MPs are associated with autoantibodies and complement activation. The findings link immunologic reactions on MPs with the etiology of SLE.

Genetic association of miRNA-146a with systemic lupus erythematosus in Europeans through decreased expression of the gene

A recent genome-wide association study revealed a variant (rs2431697) in an intergenic region, between the pituitary tumor-transforming 1 (PTTG1) and microRNA (miR-146a) genes, associated with systemic lupus erythematosus (SLE) susceptibility. Here, we analyzed with a case-control design this variant and other candidate polymorphisms in this region together with expression analysis in order to clarify to which gene this association is related. The single-nucleotide polymorphisms (SNPs) rs2431697, rs2910164 and rs2277920 were genotyped by TaqMan assays in 1324 SLE patients and 1453 healthy controls of European ancestry. Genetic association was statistically analyzed using Unphased. Gene expression of PTTG1, the miRNAs miR-3142 and primary and mature forms of miR-146a in peripheral blood mononuclear cells (PBMCs) were assessed by quantitative real-time PCR. Of the three variants analyzed, only rs2431697 was genetically associated with SLE in Europeans. Gene expression analysis revealed that this SNP was not associated with PTTG1 expression levels, but with the microRNA-146a, where the risk allele correlates with lower expression of the miRNA. We replicated the genetic association of rs2341697 with SLE in a case-control study in Europeans and demonstrated that the risk allele of this SNP correlates with a downregulation of the miRNA 146a, potentially important in SLE etiology.