In vitro apoptosis and expression of apoptosis-related molecules in lymphocytes from patients with systemic lupus erythematosus and other autoimmune diseases

Assessing the COX-2/PGE2 Ratio and Anti-Nucleosome Autoantibodies as Biomarkers of Autism Spectrum Disorders: Using Combined ROC Curves to Improve Diagnostic Values

Autism spectrum disorder (ASD) is a neurodevelopmental condition marked by restricted and repetitive behaviors as well as difficulties with social interaction. Numerous studies have revealed aberrant lipid mediators and autoimmunity as a recognized etiological cause of ASD that is amenable to therapeutic intervention. In this study, the relationship between the relative cyclooxygenase-2/prostaglandin E2 ratio (COX-2/PGE2) as a lipid mediator marker and anti-nucleosome autoantibodies as an autoimmunity marker of ASD was investigated using multiple regression and combined receiver operating characteristic (ROC) curve analyses. The study also sought to identify the linear combination of these variables that optimizes the partial area under the ROC curves. There were forty ASD children and forty-two age- and gender-matched controls included in the current study. Using combined ROC curve analysis, a notable increase in the area under the curve was seen in the patient group, using the control group as a reference group. Additionally, it was reported that the combined markers had improved specificity and sensitivity. This study demonstrates how the predictive value of particular biomarkers associated with lipid metabolism and autoimmunity in children with ASD can be measured using a ROC curve analysis. This technique should help us better understand the etiological mechanism of ASD and how it may adversely affect cellular homeostasis, which is essential to maintaining healthy metabolic pathways. Early diagnosis and intervention may be facilitated by this knowledge.

Major low-energy trauma results in non-specific immunoglobulin generation without evidence for specific autoantibody production: A prospective cohort study

Cellular debris resulting from large trauma might overwhelm the scavenger mechanisms and lead to autoimmune reactions. We analysed whether a major well-defined trauma in humans induces laboratory signs of transient autoimmunity in the months after the insult. We included 50 patients with pertrochanteric femur fracture undergoing intramedullary nail osteosynthesis in a prospective cohort study and followed them at 3-4 days, 6 weeks, 12 weeks and 12 months postoperatively. By standard techniques, we assessed levels of total immunoglobulins, anti-nuclear antibodies (ANA), anti-cardiolipin antibodies, anti-dsDNA antibodies and anti-C1q antibodies, as well as antibodies against cytomegalovirus (CMV) as a control. Blood leukocyte differential and lymphocyte subpopulations were determined at baseline and in the first two postoperative samples. The mean age of the patients reached 80.1 years, and 23 (46%) completed all visits. Serum concentrations of total IgG, IgM and IgA increased at all follow-up time points. The ANA fluorescence light intensity units increased at 12 weeks and 12 months postoperatively (p < 0.0001), but the proportion of ANA-positive patients did not change (35%). The values of anti-C1q mildly increased at all follow-up visits, but not the ratio to total IgG. Anti-dsDNA remained negative in all patients, and anti-cardiolipin IgG/IgM antibodies did not change. Anti-CMV IgG antibodies increased significantly at all follow-up visits, without change in the ratio to total IgG. Flow cytometry showed an increased proportion of B-cells 3-4 days postoperatively. In conclusion, major musculoskeletal trauma in elderly patients induces a generalized non-specific increase in immunoglobulin production without laboratory signs for enhanced systemic autoimmunity.

CD4 T lymphocyte subsets display heterogeneous susceptibility to apoptosis induced by serum from patients with systemic lupus erythematosus

BACKGROUND

Serum from systemic lupus erythematosus (SLE) patients has been shown to induce T-lymphocyte (TL) apoptosis. Given that different cells of the immune system display different sensitivity to apoptosis, we set to evaluate the in vitro effect of SLE serum on regulatory T-cells (Treg), Th17, Th1 and Th2 from SLE patients and healthy controls.

METHODS

Peripheral blood mononuclear cells from SLE patients or normal controls were exposed to a pool of sera from SLE patients or normal controls. Annexin V was used to label cells in apoptosis or necrosis. Annexin V-labeled Treg, Th17, Th1 and Th2 cells were determined using flow cytometry.

RESULTS

Total CD3 + and CD4 + cells from SLE patients showed higher frequency of spontaneous apoptosis/necrosis, whereas Th1 cells from SLE patients presented reduced spontaneous apoptosis/necrosis rate as compared with cells from controls. Incubation with SLE serum induced increased frequency of apoptotic/necrotic CD3 + , CD4 + and Th2 cells from normal controls or from SLE patients as compared with cultures incubated with normal human serum (NHS) or without human serum at all. Incubation with SLE serum did not increase the apoptosis/necrosis rate in Th1 or Th17 cells. Treg cells from SLE patients were more prone to apoptosis/necrosis induced by SLE serum than Treg cells from normal individuals. Th1, Th2, and Th17 cells presented increased apoptosis rates in cultures without human serum.

CONCLUSION

Our findings indicate that the serum of patients with active SLE stimulates apoptosis of CD4 + T cells in general and exhibit differentiated effects on CD4 + T-cell subsets.

Blood transcriptome analysis in a buck-ewe hybrid points towards an nuclear factor-kappa B lymphoproliferative autoimmune disorder

Mammal hybridization is a speciation mechanism and an evolutionary driver. Goat-sheep, especially buck-ewe hybrids, are very rare with only one case reported in 2016, which is the subject of the work presented here. Blood transcriptome analysis revealed that the hybrid largely deviated from imprinting schemes previously described in sheep and other mammals. Furthermore, transcriptome regulation seems to differ from the parent transcriptomes, which is most likely a product of partially incompatible imprinting mechanisms from two closely related species. To gain a deeper understanding of hybridization in mammals we re-analyzed the RNA sequencing data of the buck-ewe hybrid and its parents. We found parent-of-origin-specific expression of genes that functionally clustered, which we explain with the Dobzhansky-Muller incompatibility (DMI) model. According to the DMI model, proteins which interact have a high probability of being barrier loci and hence are prone to monoallelic expression. We discovered enrichment of genes uniquely expressed by the buck-ewe hybrid, which implicate that it suffered from an NF-κB lymphoproliferative autoimmune disorder. Similar findings were reported in the F1 generation of hybrid mice. We propose that hybridization of two related species may lead to an autoimmune phenotype, due to immunoglobulin incompatibilities and incomplete silencing of barrier loci.

Longitudinal monitoring of circulating immune cell phenotypes in large vessel vasculitis

Giant cell arteritis (GCA) and Takayasu arteritis (TAK) are two types of primary large vessel vasculitis (LVV). LVV is an intractable, rare disease with a high relapse rate. Disease progression in asymptomatic patients is an important issue in the clinical management of LVV. Useful biomarkers associated with clinical phenotypes, disease activity, and prognosis may be present in peripheral blood. In this review, we focused on peripheral leukocyte counts, surface markers, functions, and gene expression in LVV patients. In particular, we explored longitudinal changes in circulating immune cell phenotypes during the active phase of the disease and during treatment. The numbers and phenotypes of leukocytes in the peripheral blood were different between LVV and healthy controls, GCA and TAK, LVV in active versus treatment phases, and LVV in treatment responders versus non-responders. Therefore, biomarkers obtained from peripheral blood immune cells may be useful for longitudinal monitoring of disease activity in LVV.

Phenotypic and functional alterations of peritoneal macrophages in lupus-prone mice

Background

Several studies have demonstrated the contribution of innate immune cells, including macrophages, in promoting systemic lupus erythematosus (SLE). Macrophages, one of the most abundant cell populations in the peritoneal cavity, are considered multifunctional cells with phenotypic plasticity. However, the functional properties of peritoneal macrophages in steady-state and during the progression of SLE remain poorly defined.

Methods and results

Using the [NZB × NZW]F1 (BWF1) murine model of SLE, we analyzed the phenotype and function of peritoneal macrophages during the disease’s onset. We found a higher frequency of peritoneal macrophages and B1a cells in BWF1-diseased mice than age-matched controls. Additionally, macrophages from diseased animals expressed lower levels of CD206, MHC-II, and Sirpα. RNAseq analysis identified 286 differentially expressed genes in peritoneal macrophages from diseased-BWF1 mice compared to control mice. Functional experiments demonstrate that peritoneal macrophages from diseased-BWF1 mice secrete higher levels of pro-inflammatory cytokines when activated with TLR7 and TLR9 agonists, and they were less efficient in suppressing the activation and proliferation of peritoneal LPS-activated B cells. These data demonstrate that peritoneal macrophages from BWF1-diseased mice present phenotypic and functional alterations shifting to a more pro-inflammatory state.

Conclusions

The increase of macrophages with an altered phenotype and function together with the accumulation of B1a cells in the peritoneal cavity of diseased-BWF1 mice may promote the progression of the disease. Advancing awareness of the role and phenotype of peritoneal macrophages in SLE may contribute to a better understanding of these types of diseases and the development of novel therapies.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11033-022-07252-0.

Lymphopenia at diagnosis of ANCA-vasculitis with renal involvement is correlated with severity and renal prognosis

BACKGROUND

Lymphopenia is commonly observed in autoimmune diseases, where it has been associated with disease activity or prognosis. However, in ANCA-associated vasculitis (AAV) only few, small-scale studies have been targeted to this issue. Research has not yet focused on AAV with renal involvement (AAV-RI) patients. Thus, the aim of this study was to analyze the association between lymphocyte counts and outcomes in a large cohort of AAV-RI patients.

METHODS

We used the Maine-Anjou AAV registry that retrospectively gathers data on consecutive patients affected by AAV in four French Nephrology Centers, recorded since January 2000. We analyzed clinical, biological, and histological data at diagnosis of AAV-RI. Risk factors for end-stage kidney disease (ESKD) were analyzed. Event-free survival was also assessed.

RESULTS

Among the 145 patients included in the study, those with lymphopenia at diagnosis had a lower renal function at baseline (eGFR 13 mL/min vs 26 mL/min, p = 0.002) and were more likely to require kidney replacement therapy (51% vs 25%, p = 0.003). Lymphopenia was correlated with histological lesions and especially with the percentage of sclerotic glomeruli (p = 0.0027). ESKD-free survival was lower in lymphopenic patients (p < 0.0001). In multivariate Cox analysis, lymphopenia was an independent risk factor for ESKD (HR 4.47 (95% confidence interval: [2.06-9.72], p < 0.001).

CONCLUSION

Lymphopenia correlates with the severity of AAV glomerulonephritis at diagnosis and predicts poor renal outcome. In this view, lymphopenia could be used as a simple and cost-effective biomarker to assess renal prognosis at AAV-RI diagnosis.

Cell Survival Failure in Effector T Cells From Patients With Systemic Lupus Erythematosus Following Insufficient Up-Regulation of Cold-Shock Y-Box Binding Protein 1

OBJECTIVE

The importance of cold-shock Y-box binding protein 1 (YB-1) for cell homeostasis is well-documented based on prior observations of its association with certain cancer entities. This study was undertaken to explore the role of YB-1 in T cell homeostasis and survival and the potential contribution of YB-1 to the pathogenesis of systemic lupus erythematosus (SLE).

METHODS

In the peripheral blood from 25 SLE patients and 25 healthy donors, the expression of YB-1 and frequency of T cell apoptosis was analyzed by quantitative polymerase chain reaction (qPCR) and fluorescence-activated cell sorting of CD4+ T cells ex vivo and also analyzed in T cells in vitro after 6 days of stimulation with anti-CD3-coupled or anti-CD3/anti-CD28-coupled microspheres. YB-1 was overexpressed using lentiviral transduction with wild-type green fluorescent protein (wtGFP) YB-1, and knockdown of YB-1 was achieved using specific short hairpin RNA (shRNA) (3-fold reduction; P < 0.0001).

RESULTS

YB-1 expression was significantly lower in apoptosis-prone T cells and in activated T cells from SLE patients compared to YB-1 expression in nonapoptotic T cells and activated T cells from healthy donors (P = 0.001). Knockdown of YB-1 in T cells consequently led to expression of proapoptotic molecules and caspase 3 activation (1.6-fold), and subsequently, to apoptosis. Furthermore, YB-1 promoted survival pathways involving enhanced protein expression of the kinase Akt (2-fold) and Bcl-2 (3-fold), even when Fas/CD95 was triggered. YB-1-mediated T cell survival was reversed by Akt and phosphatidylinositol 3-kinase (PI3K) inactivation. In SLE patients, rescue of YB-1 expression strongly promoted survival of T cells and even prevented cell death in T cells that were extremely apoptosis-prone.

CONCLUSION

Our data show that failure of YB-1 up-regulation in T cells from SLE patients led to enhanced apoptosis. These findings imply that YB-1 plays a crucial role in the disturbed homeostasis of activated T cells leading to hematopoietic alterations in SLE. These insights may help facilitate the development of new treatment strategies for SLE.

Aggregatibacter actinomycetemcomitans Leukotoxin (LtxA; Leukothera®): Mechanisms of Action and Therapeutic Applications

Aggregatibacter actinomycetemcomitans is an oral pathogen that produces the RTX toxin, leukotoxin (LtxA; Leukothera^®). A. actinomycetemcomitans is strongly associated with the development of localized aggressive periodontitis. LtxA acts as a virulence factor for A. actinomycetemcomitans to subvert the host immune response by binding to the β₂ integrin lymphocyte function-associated antigen-1 (LFA-1; CD11a/CD18) on white blood cells (WBCs), causing cell death. In this paper, we reviewed the state of knowledge on LtxA interaction with WBCs and the subsequent mechanisms of induced cell death. Finally, we touched on the potential therapeutic applications of LtxA (trade name Leukothera^®) toxin therapy for the treatment of hematological malignancies and immune-mediated diseases.

Non-erythropoietic erythropoietin-derived peptide protects mice from systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease, which results in various organ pathologies. However, current treatment towards SLE is suboptimal. Erythropoietin (EPO) has been shown to promote SLE recovery, but clinical application can be limited by its haematopoiesis-stimulating effects. EPO-derived helix-B peptide (ARA290) is non-erythrogenic but has been reported to retain the anti-inflammatory and tissue-protective functions of EPO. Therefore, here we investigated the effects and potential mechanisms of ARA290 on SLE. The administration of ARA290 to pristane-induced SLE and MRL/lpr mice significantly suppressed the level of serum antinuclear autoantibodies (ANAs) and anti-dsDNA autoantibodies, reduced the deposition of IgG and C3, and ameliorated the nephritis symptoms. Moreover, the serum concentrations of inflammatory cytokine IL-6, MCP-1 and TNF-α in SLE mice were reduced by ARA290. Further, ARA290 decreased the number of apoptotic cells in kidney. In vitro experiment revealed that ARA290 inhibited the inflammatory activation of macrophages and promoted the phagocytotic function of macrophages to apoptotic cells. Finally, ARA290 did not induce haematopoiesis during treatment. In conclusion, ARA290 ameliorated SLE, which at least could be partly due to its anti-inflammatory and apoptotic cell clearance promoting effects, without stimulating haematopoiesis, suggesting that ARA290 could be a hopeful candidate for SLE treatment.

Role of MiR-98 and Its Underlying Mechanisms in Systemic Lupus Erythematosus

Objective.

T-lymphocyte apoptosis plays a critical role in the pathogenesis of systemic lupus erythematosus (SLE). However, the underlying regulatory mechanisms of apoptosis in SLE remain unclear. The aim of this study was to explore the role of miR-98 in SLE and its underlying mechanisms.

Methods.

Western blotting and quantitative reverse transcription PCR (qRT-PCR) were used to analyze miR-98 and Fas expression. Luciferase reporter assays were performed to identify miR-98 targets. To modify miRNA levels, miR-98 mimics and inhibitor were transfected into cells. A lentiviral construct was used to overexpress the level of Fas in SLE CD4+ T cells. Gene and protein expression were determined by qRT-PCR and Western blotting. Apoptosis levels were evaluated by annexin V staining and flow cytometry.

Results.

Compared to those of healthy donors, miR-98 was downregulated in SLE CD4+ T cells, whereas Fas mRNA and protein expression were upregulated. Upregulation of miR-98 by mimic transfection protected Jurkat cells against Fas-mediated apoptosis at both mRNA and protein levels, while miR-98 inhibitor induced the completely opposite effect. Luciferase reporter assays demonstrated that miR-98 directly targeted Fas mRNA. Further, miR-98 inhibitor induced apoptosis in primary healthy CD4+ T cells through the Fas-caspase axis, while upregulation of miR-98 in SLE CD4+ T cells led to the opposite effect.

Conclusion.

The current study revealed that downregulation of miR-98 induces apoptosis by modulating the Fas-mediated apoptotic signaling pathway in SLE CD4+ T cells. These results suggest that miR-98 might serve as a potential target for SLE treatment.

Impaired phagocytosis of apoptotic cell material in serologically active clinically quiescent patients with systemic lupus erythematosis

AIM

Serologically active clinically quiescent (SACQ) patients with systemic lupus erythematosus (SLE) account for 8-12% of all patients with SLE, but there is disagreement about whether such patients are indeed clinically stable. Patients with clinically active SLE have decreased macrophage function, although the status of SACQ patients with SLE is unclear.

METHOD

This study compared 18 patients who met the diagnostic criteria for SACQ SLE with 18 healthy volunteers with regard to the capability of macrophages to clear apoptotic bodies by use of a modified serum-free phagocytosis test. Macrophages that naturally differentiated from monocytes were used to engulf apoptotic cells developed from polymorphonuclear neutrophils.

RESULTS

The results showed that macrophages from SACQ patients with SLE had less phagocytotic capability than those from healthy controls.

CONCLUSION

The significant reduction of macrophage phagocytotic capability in these patients suggests the potential for disease recurrence. The use of a serum-free method confirmed the presence of intrinsic factors that modulate the decrease of macrophage function in SLE.

Influenza A (H1N1) virus infection triggers severe pulmonary inflammation in lupus-prone mice following viral clearance

Each year, up to one fifth of the United States population is infected with influenza virus. Although mortality rates are low, hundreds of thousands are hospitalized each year in the United States. Specific high risk groups, such as those with suppressed or dysregulated immune systems, are at greater danger for influenza complications. Respiratory infections are a common cause of hospitalizations and early mortality in patients with systemic lupus erythematosus (SLE); however, whether this increased infection risk is a consequence of the underlying dysregulated immune background and/or immunosuppressing drugs is unknown. To evaluate the influenza immune response in the context of lupus, as well as assess the effect of infection on autoimmune disease in a controlled setting, we infected lupus-prone MRL/MpJ-Fas(lpr) mice with influenza virus A PR/8/34 H1N1. Interestingly, we found that Fas(lpr) mice generated more influenza A virus specific T cells with less neutrophil accumulation in the lung during acute infection. Moreover, Fas(lpr) mice produced fewer flu-specific IgG and IgM antibodies, but effectively cleared the virus. Further, increased extrinsic apoptosis during influenza infection led to a delay in autoimmune disease pathology with decreased severity of splenomegaly and kidney disease. Following primary influenza A infection, Fas(lpr) mice had severe complications during the contraction and resolution phase with widespread severe pulmonary inflammation. Our findings suggest that influenza infection may not exacerbate autoimmune pathology in mice during acute infection as a direct result of virus induced apoptosis. Additionally, autoimmunity drives an enhanced antigen-specific T cell response to clear the virus, but persisting pulmonary inflammation following viral clearance may cause complications in this lupus animal model.

IFN priming is necessary but not sufficient to turn on a migratory dendritic cell program in lupus monocytes

Blood monocytes from children with systemic lupus erythematosus (SLE) behave similar to dendritic cells (DCs), and SLE serum induces healthy monocytes to differentiate into DCs in a type I IFN-dependent manner. In this study, we found that these monocytes display significant transcriptional changes, including a prominent IFN signature, compared with healthy controls. Few of those changes, however, explain DC function. Exposure to allogeneic T cells in vitro reprograms SLE monocytes to acquire DC phenotype and function, and this correlates with both IFN-inducible (IP10) and proinflammatory cytokine (IL-1β and IL6) expression. Furthermore, we found that both IFN and SLE serum induce the upregulation of CCR7 transcription in these cells. CCR7 protein expression, however, requires a second signal provided by TLR agonists such as LPS. Thus, SLE serum "primes" a subset of monocytes to readily (<24 h) respond to TLR agonists and acquire migratory DC properties. Our findings might explain how microbial infections exacerbate lupus.

Serum antinucleosome-specific antibody as a marker of autoimmunity in children with autism

Background

Increasing evidence of autoimmune phenomena in some individuals with autism could represent the presence of altered or inappropriate immune responses in this disorder. The role of the nucleosome in the induction of antibody response in some autoimmune-mediated tissue damage may provide novel targets for treatment. Due to the paucity of studies investigating the frequency of systemic auto-antibodies in autism, we are the first to investigate the frequency of antinucleosome-specific antibodies in a group of autistic children.

Methods

Serum antinucleosome-specific antibodies were measured by ELISA in 60 autistic children, between the ages of 3 and 12 years, in comparison to 60 healthy children. Autistic severity was assessed using the Childhood Autism Rating Scale (CARS).

Results

Autistic children had significantly higher serum antinucleosome-specific antibodies than healthy children (P <0.001). The seropositivity of antinucleosome-specific antibodies was found in 46.7% of autistic children. Autistic children with a family history of autoimmunity (40%) had a significantly higher frequency of serum antinucleosome-specific antibodies (83.3%) than patients without such a history (22.2%, P <0.001).

Conclusions

Serum levels of antinucleosome-specific antibodies were increased in some autistic children. However, these data should be treated with caution until further investigations are performed with a larger subject population to determine whether these antibodies have a role in the induction of autoimmunity in a subgroup of autistic children. The role of immunotherapy in children with autism should be also studied.

High occurrence of in vitro apoptosis of lymphocytes induced by serum from systemic lupus erythematosus patients is associated with increased serum levels of anti-C1q autoantibodies

BACKGROUND

The ethiopathogenesis of increased apoptosis of lymphocytes in systemic lupus erythematosus (SLE) is still incompletely understood but anti-C1q autoantibodies have been shown to induce apoptosis in lymphocytes from healthy donors and certain cell lines.

AIM

This study was undertaken to investigate the relationship between peripheral lymphocyte apoptosis and serum levels of anti-C1q autoantibodies in SLE patients.

METHODS

The sera of 124 patients with SLE involving 62 active SLE and 62 inactive SLE, fulfilling America College of Rheumatology (ACR) classification criteria for SLE (1997) were incubated with peripheral blood lymphocytes of healthy donors. The results were compared with 124 sex- and age-matched normal controls. Apoptotic lymphocytes (AL) were detected by flow cytometry using annexin V and propidium iodide binding. Anti-C1q autoantibodies were detected by an enzyme-linked immunoassay kit for all SLE patients.

RESULTS

Results demonstrated that the percentage of AL in the peripheral blood of active SLE patients was significantly higher (n = 62, 34.95 ± 12.78%) than that of the inactive SLE patients (n = 62, 30.69 ± 10.13%, P = 0.042, 95%CI = 0.16-8.36) and normal controls (n = 124, 27.92 ± 10.22%, P = 0.001, 95%CI = 3.33-10.73). The percentage of AL significantly correlated with serum levels of anti-C1q autoantibodies in the active SLE patients (r = 0.263, P = 0.039) but not in the inactive SLE patients (r = 0.170, P = 0.185).

CONCLUSION

The results of this study suggest that increased serum levels of anti-C1q autoantibodies are responsible for apoptosis and may play a pathogenic role in SLE patients, especially in active disease.

Reduced expressions of Fas and Bcl-2 proteins in CD14+ monocytes and normal CD14 soluble levels in juvenile systemic lupus erythematosus

In order to evaluate Fas and Bcl-2 expressions in CD14+ monocytes, to measure soluble CD14 serum levels and to analyze the relationships with lupus nephritis and disease activity, we enrolled 41 patients with juvenile systemic lupus erythematosus (JSLE) and 27 healthy volunteers. Disease activity was determined by SLEDAI score. Peripheral monocytes were stained for CD14, Fas and Bcl-2 molecules, and cellular expressions were determined by flow cytometry. Soluble CD14 levels were measured by a quantitative ELISA kit. JSLE patients, those with active disease and those with nephritis, presented significantly reduced expressions of Fas and Bcl-2 proteins in CD14+ monocytes compared with healthy controls. Significant inverse correlations between percentages of CD14+Fas+ cells, SLEDAI score and anti-dsDNA antibodies were observed. JSLE patients had soluble CD14 levels similar to controls, although sCD14 levels positively correlated with ESR, but not with SLEDAI score. JSLE patients with nephritis also presented sCD14 levels similar to controls. In conclusion, the reduced expressions of Fas and Bcl-2 proteins in CD14+ monocytes from JSLE patients depict that monocyte apoptotic mechanisms may be important in lupus pathogenesis.

Apoptotic-cell-derived membrane vesicles induce an alternative maturation of human dendritic cells which is disturbed in SLE

The clearance of apoptotic cells occurs in a non-inflammatory context. Defects in this clearance process have been linked to the emergence of human autoimmune diseases like systemic lupus erythematosus (SLE). A characteristic of apoptotic cell death is the shedding of membrane coated vesicles from the cellular surfaces. Those vesicles have recently been recognized as mediators of intercellular communication or as adjuvant in the pathogenesis of autoimmune diseases. We analyzed the interactions between these apoptotic cell-derived membrane vesicles and professional antigen presenting cells. These vesicles were engulfed by monocyte-derived dendritic cells (mDC) and stimulated their maturation towards a phenotype comprising an upregulation of CD80, CD83, CD86, and a remarkable downregulation of MHC class II molecules. We observed only a minor release of proinflammatory cytokines from these mDC when compared to LPS stimulation. mDC stimulated by apoptotic vesicles did not cause significant T-cell expansion. Interestingly, when compared to normal healthy donors SLE patients-derived dendritic cells showed a significantly different phenotype lacking the downregulation of MHC class II, which correlated to disease activity.

Prolonged apoptotic cell accumulation in germinal centers of Mer-deficient mice causes elevated B cell and CD4+ Th cell responses leading to autoantibody production

Mer receptor tyrosine kinase is a member of the Tyro-3/Axl/Mer (TAM) subfamily of receptor tyrosine kinases, and its expression on phagocytes facilitates their clearance of apoptotic cells (ACs). Mer expression in germinal centers (GCs) occurs predominantly on tingible body macrophages. B and T cells do not express Mer. In this study, we show that Mer deficiency ((Mer(-/-)) resulted in the long-term accumulation of ACs primarily in GCs and not in the T cell zone, marginal zone, or red pulp areas of the spleen. AC accumulation in GCs led to augmented Ab-forming cell, GC, and IgG2 Ab responses in Mer(-/-) mice, which were sustained for at least 80 d. Enhanced responses in Mer(-/-) mice were due to increased activation and proliferation of B cells and CD4(+) Th cells, including follicular helper T cells, which resulted in high titers of anti-nuclear Abs in Mer(-/-) mice compared with wild-type controls. Secondary IgG-producing Ab-forming cell, total IgG, and IgG2 Ab responses were also increased in Mer(-/-) mice. Finally, compared with wild-type controls, Mer(-/-) mice had increased percentage of IFN-γ-producing CD4(+) Th cells and elevated levels of Th1 (i.e., IL-2 and IFN-γ) and proinflammatory (i.e., TNF and IL-6) cytokines, consistent with elevated levels of Th1-biased IgG2 Abs in Mer(-/-) mice. Together, our results demonstrate that Mer deficiency induces prolonged accumulation of ACs in GCs, resulting in dysregulation of GC B cell and CD4(+) Th cell responses and Th1 cytokine production, leading to alteration of B cell tolerance and the development of autoantibodies.

Germinal center kinase-like kinase (GLK/MAP4K3) expression is increased in adult-onset Still's disease and may act as an activity marker

BACKGROUND

Germinal center kinase-like kinase (GLK, also termed MAP4K3), a member of the MAP4K family, may regulate gene transcription, apoptosis and immune inflammation in response to extracellular signals. The enhanced expression of GLK has been shown to correspond with disease severity in patients with systemic lupus erythematosus. We investigated the role of GLK in the pathogenesis of adult-onset Still's disease, which shares some similar clinical characteristics with systemic lupus erythematosus.

METHODS

The frequencies of circulating GLK-expressing T-cells in 24 patients with active adult-onset Still's disease and 12 healthy controls were determined by flow cytometry analysis. The expression levels of GLK proteins and transcripts were evaluated in peripheral blood mononuclear cells by immunoblotting and quantitative PCR. Serum levels of T helper (Th)17-related cytokines, including IL-1β, IL-6, IL-17 and TNF-α, were measured by ELISA.

RESULTS

Significantly higher median frequencies of circulating GLK-expressing T-cells were observed in patients with adult-onset Still's disease (31.85%) than in healthy volunteers (8.93%, P <0.001). The relative expression levels of GLK proteins and transcripts were also significantly higher in patients with adult-onset Still's disease (median, 1.74 and 2.35, respectively) compared with those in healthy controls (0.66 and 0.92, respectively, both P <0.001). The disease activity scores were positively correlated with the frequencies of circulating GLK-expressing T-cells (r = 0.599, P <0.005) and the levels of GLK proteins (r = 0.435, P <0.05) or GLK transcripts (r = 0.452, P <0.05) in patients with adult-onset Still's disease. Among the examined Th17-related cytokines, elevated levels of serum IL-6 and IL-17 were positively correlated with the frequencies of circulating GLK-expressing T-cells and the levels of GLK proteins as well as transcripts in patients with adult-onset Still's disease. GLK expression levels decreased significantly after effective therapy in these patients.

CONCLUSIONS

Elevated expression levels of GLK and their positive correlation with disease activity in patients with adult-onset Still's disease indicate that GLK may be involved in the pathogenesis and act as a novel activity biomarker of this disease.

The genetics of lupus: a functional perspective

Systemic lupus erythematosus (SLE) is an autoimmune disease with a strong genetic component and is characterized by chronic inflammation and the production of anti-nuclear auto-antibodies. In the era of genome-wide association studies (GWASs), elucidating the genetic factors present in SLE has been a very successful endeavor; 28 confirmed disease susceptibility loci have been mapped. In this review, we summarize the current understanding of the genetics of lupus and focus on the strongest associated risk loci found to date (P <1.0 × 10−8). Although these loci account for less than 10% of the genetic heritability and therefore do not account for the bulk of the disease heritability, they do implicate important pathways, which contribute to SLE pathogenesis. Consequently, the main focus of the review is to outline the genetic variants in the known associated loci and then to explore the potential functional consequences of the associated variants. We also highlight the genetic overlap of these loci with other autoimmune diseases, which indicates common pathogenic mechanisms. The importance of developing functional assays will be discussed and each of them will be instrumental in furthering our understanding of these associated variants and loci. Finally, we indicate that performing a larger SLE GWAS and applying a more targeted set of methods, such as the ImmunoChip and next generation sequencing methodology, are important for identifying additional loci and enhancing our understanding of the pathogenesis of SLE.

Impaired clearance of apoptotic cells in germinal centers: implications for loss of B cell tolerance and induction of autoimmunity

Germinal centers (GCs) comprise lymphoid microenvironments where antigen-stimulated B cells undergo rapid proliferation and somatic hypermutation (SHM), resulting in the generation of B cells with high affinity for antigen. However, this process also generates B cell clones with low antigen affinity and with the potential for autoreactivity. It has been suggested that GC B cells with low antigen affinity and autoreactivity are eliminated via apoptosis and are rapidly cleared by tingible body macrophages (TBMφs). Inefficient clearance of apoptotic cells (ACs) results in autoimmunity that is thought to be mediated by various intracellular molecules possessing danger-associated molecular patterns (DAMPs), including nuclear self-Ags. DAMPs can be released from ACs undergoing "secondary necrosis" due to a disruption in AC clearance within GCs. This review discusses the role and mechanisms associated with impaired clearance of ACs in GCs in loss of B cell tolerance leading to autoantibody production and the development of autoimmunity.

Assessment of mitochondrial dysfunction in lymphocytes of patients with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is characterized by abnormal activation and cell death signaling within the immune system. Activation, proliferation, or death of cells of the immune system is dependent on controlled reactive oxygen intermediates (ROI) production and ATP synthesis in mitochondria. The mitochondrial transmembrane potential (∆ψ (m)) reflects the energy stored in the electrochemical gradient across the inner mitochondrial membrane which, in turn, is used by F(0)F(1)-ATPase to convert ADP to ATP during oxidative phosphorylation. Mitochondrial hyperpolarization (MHP) and transient ATP depletion represent early and reversible steps in T cell activation and apoptosis. By contrast, T lymphocytes of patients with SLE exhibit elevated ∆ψ (m), i.e., persistent mitochondrial hyperpolarization (MHP), cytoplasmic alkalinization, increased ROI production, as well as diminished levels of intracellular glutathione and ATP. Increased production of nitric oxide has been identified as a cause of MHP and increased mitochondrial biogenesis. Oxidative stress affects signaling through the T cell receptor as well as activity of redox--sensitive caspases. ATP depletion causes diminished activation-induced apoptosis and sensitizes lupus T cells to necrosis. Activation of the mammalian target of rapamycin (mTOR) has recently emerged as a key sensor of MHP and mediator of enhanced Ca(2+) flux in lupus T cells.

Immunopathogenesis of primary biliary cirrhosis: an old wives' tale

Primary biliary cirrhosis (PBC) is a cholestatic liver disease characterised by the autoimmune destruction of the small intrahepatic bile ducts. The disease has an unpredictable clinical course, but may progress to fibrosis and cirrhosis. Although medical treatment with urseodeoxycholic acid is largely successful, some patients may progress to liver failure requiring liver transplantation. PBC is characterised by the presence of disease specific anti-mitochondrial (AMA) antibodies, which are pathognomonic for PBC development. The disease demonstrates an overwhelming female preponderance and virtually all women with PBC present in middle age. The reasons for this are unknown; however several environmental and immunological factors may be involved. As the immune systems ages, it become less self tolerant, and mounts a weaker response to pathogens, possibly leading to cross reactivity or molecular mimicry. Some individuals display immunological changes which encourage the development of autoimmune disease. Risk factors implicated in PBC include recurrent urinary tract infection in females, as well as an increased prevalence of reproductive complications. These risk factors may work in concert with and possibly even accelerate, immune system ageing, contributing to PBC development. This review will examine the changes that occur in the immune system with ageing, paying particular attention to those changes which contribute to the development of autoimmune disease with increasing age. The review also discusses risk factors which may account for the increased female predominance of PBC, such as recurrent UTI and oestrogens.

Constitutive abnormal expression of RasGRP-1 isoforms and low expression of PARP-1 in patients with systemic lupus erythematosus

OBJECTIVE

Defective expression of Ras guanil releasing protein-1 (RasGRP-1) and increased apoptosis have been reported in lymphocytes from SLE patients. Whether these aberrations are correlated and linked to disease activity has not been elucidated.

METHODS

Expression of normal 90 kDa RasGRP-1, its most prevalent 86 kDa isoform and full PARP-1 116 kDa and its cleavage fragment 84 kDa were determined in whole protein lysates of peripheral blood mononuclear cells (PBMC) in correlation with mitogen activated protein kinase (MAPK) activity and SLE clinical status in a large group of SLE patients during 1 year follow-up.

RESULTS

Expression of normal 90 kDa RasGRP-1 was comparable in patients and controls. However, SLE patients demonstrated a constitutively increased 86 kDa/90 kDA ratio (p < 0.01) and decreased full poly (ADP-ribose) polymerase protein-1 (PARP-1) expression (p < 0.002) compared with controls who were disease-independent. A remission in disease activity was associated with decreased RasGRP-1 expression. Expression of 84 kDa PARP-1 cleavage fragment was found in 15% of patients but in none of the controls. In addition, expression of PARP-1 correlated positively with normal 90 kDa RasGRP-1 expression and negatively with the RasGRP-1 86 kDa/90 kDA ratio.

CONCLUSIONS

These data suggest that constitutive aberrant expression of PARP-1 and RasGRP-1 ratio may act in concert to impair survival of lymphocytes in SLE patients.

The pathway of estradiol-induced apoptosis in patients with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a disease with unknown etiology. The pathologic role of sex hormones and apoptosis in SLE has often been discussed. We studied the effects of estradiol in the pathway of induced apoptosis in Iranian SLE patients. T lymphocytes from 35 SLE patients and 20 age-matched controls were isolated and cultured in the presence of 10(-8) M 17-β estradiol. The expression levels of Fas, Fas ligand (FasL), Bcl-2, caspase-8, and caspase-9 mRNAs were determined semiquantitatively in comparison to the expression level of beta actin RNA. Estradiol exposure did not have any significant effects on the expression levels of Fas, Bcl-2, and caspase-9 in SLE patients and controls. However, the expression levels of FasL and caspase-8 were significantly increased in SLE patients, but not in controls. This suggests the probable involvement of extrinsic apoptosis pathway in estradiol-induced apoptosis in SLE.

Inefficient clearance of dying cells in patients with SLE: anti-dsDNA autoantibodies, MFG-E8, HMGB-1 and other players

Systemic lupus erythematosus (SLE) is a complex disease resulting from inflammatory responses of the immune system against several autoantigens. Inflammation is conditioned by the continuous presence of autoantibodies and leaked autoantigens, e.g. from not properly cleared dying and dead cells. Various soluble molecules and biophysical properties of the surface of apoptotic cells play significant roles in the appropriate recognition and further processing of dying and dead cells. We exemplarily discuss how Milk fat globule epidermal growth factor 8 (MFG-E8), biophysical membrane alterations, High mobility group box 1 (HMGB1), C-reactive protein (CRP), and anti-nuclear autoantibodies may contribute to the etiopathogenesis of the disease. Up to date knowledge about these key elements may provide new insights that lead to the development of new treatment strategies of the disease.

Autoimmunity and chronic inflammation - two clearance-related steps in the etiopathogenesis of SLE

Systemic lupus erythematosus (SLE) is an autoimmune disease with very prominent chronic inflammatory aspects that render into multiple symptoms and clinical signs. The precise etiology of SLE remains elusive; however, it is known that its etiopathogenesis is of multifactorial nature. The production of autoantibodies (AAb) targeting double stranded DNA (dsDNA) and other nuclear autoantigens is the main characteristic of this disease. These target antigens are often modified and/or translocated when apoptotic cells undergo secondary necrosis as a consequence of the clearance deficiency in patients with SLE. In healthy individuals, dead and dying cells are rapidly removed by macrophages in an anti-inflammatory context; this does not elicit immune responses. In SLE, apoptotic cells are often not properly cleared; autoantigens leak out, and are subsequently presented to B cells by follicular dendritic cells (FDC) in secondary lymphoid tissues. This defect challenges the peripheral self-tolerance. Autoreactive B cell activation and production of anti-nuclear AAb result as the first step in the etiopathogenesis of SLE. The second step is the formation of immune complexes (IC) with apoptotic cell-derived nuclear remnants either in situ or deposited in various tissues. Nucleic acid-containing IC may also be ingested by phagocytes, which subsequently produce pro-inflammatory cytokines. Both processes result in chronic organ and tissue damage, development and maintenance of the systemic autoimmune disease. In conclusion, clearance deficiency may contribute to SLE in two ways: first, in germinal centres it enables the affinity maturation of autoreactive B cells and second, in peripheral tissues it leads to the accumulation of accessible nuclear autoantigens. Chronic inflammation in SLE is consequently promoted by the persistently binding of AAb with their cognate autoantigens forming a binary weapon: the nucleic acid-containing IC.

IAN5 polymorphisms are associated with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a representative autoimmune disease, which is frequently associated with lymphopenia. Biobreeding (BB) rat is a typical animal model which develops autoimmune diseases with lymphopenia which results from a frame-shift mutation in the immune-associated nucleotide (IAN) 5 gene. IAN5 is involved in the regulation of T-cell activation and survival. To examine the association of IAN5 gene with SLE, we scrutinised the single nucleotide polymorphisms (SNPs) in the IAN5 gene. We conducted a case-control study where 132 SLE patients, 505 rheumatoid arthritis (RA) patients, and 546 controls were genotyped for four SNPs in the IAN5 gene. Two SNPs (+2071C > T and +2677G > A) were associated with susceptibility to SLE (P = 0.040 and 0.045, respectively), and -4432G > A SNP was associated with the development of leukopenia (P = 0.028) and the requirement of steroid pulse therapy (P = 0.040) in SLE patients. Haplotype analyses showed that Ht1(CTCG) was associated with susceptibility to SLE (P = 0.036), and Ht4(ACCG), Ht5(ACTA) and Ht6(GCCG) were associated with the development of nephritis (P = 0.017, 0.019, 0.022, respectively). In conclusion, the IAN5 polymorphisms were associated with susceptibility to SLE and the development of clinical disease manifestations in a strictly Korean population.

Disparate distribution of activating and inhibitory killer cell immunoglobulin-like receptor genes in patients with systemic lupus erythematosus

The genes of killer cell immunoglobulin-like receptors (KIRs), which are involved in the activation of T cells and natural killer cells, are highly variable. In recent years, the role of KIRs in autoimmune diseases has received increasing attention. The present study was undertaken to determine the association of the polymorphism of KIR genes with the susceptibility to systemic lupus erythematosus (SLE). The polymorphism of KIR genes of 93 patients with SLE together with 123 healthy donors as the control group was determined by polymerase chain reaction with sequence-specific primers. Twenty-seven novel gene combinations were found. Genotypic frequencies of KIR2DL2 (p < 0.001) and KIR2DS1 (p < 0.001) were much higher in patients with SLE than in control subjects. Individuals with two and more than two activating KIR genes were found more frequently in patients than in control subjects (80.7% versus 66.7%, p = 0.022). The results suggest that a genetic disturbance between activating and inhibitory KIR genes may be one of the key factors underlying the pathogenesis of SLE.

Increased T-lymphocyte apoptosis in lupus correlates with disease activity and may be responsible for reduced T-cell frequency: a cross-sectional and longitudinal study

Apoptosis of lymphocytes is increased in patients with lupus. This may be pathogenic leading to increased load of autoantigens or may be a bystander effect of immune activation. A major unresolved issue is whether apoptosis is related to disease activity. Also its association with lymphocyte frequencies, anti-nucleosomal antibodies and serum IL 10 levels needs to be explored further. The aims of this study are to measure T- and B-lymphocyte apoptosis in patients with lupus and look at the effect of disease activity in a cross-sectional and longitudinal design and to determine frequency of T and B cells, level of anti-nucleosomal antibodies and serum IL 10 and assess their relationship with apoptosis. This study included 41 patients with SLE and 20 controls. A cutoff value of 4 in systemic lupus erythematosus disease activity index (SLEDAI) was used to separate active from inactive SLE. The frequency and degree of apoptosis of T and B lymphocyte were enumerated by flow cytometry using peripheral blood mononuclear cells (PBMCs) stained with CD3/CD19 and annexin V/PI. The data for T/B cell frequency are represented as % of these cells in the PBMC population, whereas percentage of apoptotic cells is out of total T or B cells. Serum anti-nucleosomal antibodies and IL 10 were assayed using ELISA. A repeat assessment of these parameters was carried out in 11 active patients when they became inactive. We found higher T-lymphocyte apoptosis in patients with SLE versus controls (14.8 +/- 9.2, 7.2 +/- 3.0; P < 0.05) and a lower frequency of T cells (72.7 +/- 12.6, 79.9 +/- 5.8; P < 0.05). T-lymphocyte apoptosis was higher in patients with active disease compared with inactive (18.5 +/- 11.3, 11.6 +/- 5.4; P = 0.05). Further, T-lymphocyte apoptosis directly correlated with SLEDAI (r = 0.37, P < 0.05) and inversely with T-cell frequency (r = -0.29, P < 0.05). Anti-nucleosomal antibodies correlated with SLEDAI but not apoptosis. On longitudinal follow-up, a decline in T-cell apoptosis was seen in patients with SLE, however this was not statistically significant. We confirmed a higher degree of apoptosis in T-lymphocytes in patients with SLE and found a direct correlation of T-cell apoptosis with disease activity. Patients had reduced T-cell frequency, which inversely correlated with T-cell apoptosis and may suggest a cause-effect relationship.

Gene expression in systemic lupus erythematosus: bone marrow analysis differentiates active from inactive disease and reveals apoptosis and granulopoiesis signatures

OBJECTIVE

The cells of the immune system originate from the bone marrow, where many of them also mature. This study was undertaken to examine gene expression in the bone marrow of patients with systemic lupus erythematosus (SLE), in order to better understand the aberrant immune response in this disease.

METHODS

Bone marrow mononuclear cells (BMMCs) from 20 SLE patients (11 with active disease and 9 with inactive disease) and peripheral blood mononuclear cells (PBMCs) from 27 patients (16 with active disease and 11 with inactive disease) were studied; BMMCs and PBMCs from 7 healthy individuals and 3 osteoarthritis patients were studied as controls. Samples were analyzed on genome-scale DNA microarrays, with 21,329 genes represented.

RESULTS

We identified 102 genes involved in various biologic processes that were differentially expressed between patient and control BMMCs; 53 of them are genes that are involved in major networks, including cell death, growth, signaling, and proliferation. Comparative analysis revealed 88 genes that were differentially expressed between bone marrow and blood, the majority of which are involved in cell growth and differentiation, cellular movement and morphology, immune response, and other hematopoietic cell functions. Unsupervised clustering of highly expressed genes revealed 2 major SLE patient clusters (active disease and inactive disease) based on gene expression in bone marrow, but not in peripheral blood. The up-regulated genes in the bone marrow of patients with active disease included genes involved in cell death and granulopoiesis.

CONCLUSION

Microarray analysis of the bone marrow differentiated active from inactive SLE and provided further evidence of the role of apoptosis and granulocytes in the pathogenesis of the disease.

Altered T and B lymphocyte signaling pathways in lupus

Systemic lupus erythematosus (SLE) has long been recognized to be characterized by dysregulated signaling pathways in T and B lymphocytes, beginning with observations of cellular hyperactivity and hyperresponsiveness, and evolving to recent studies focused upon the genetic and molecular bases of such phenomena. This review focuses on recently elucidated signaling abnormalities currently thought to be intrinsic to T and/or B cells in human SLE.

SLE serum induces classical caspase-dependent apoptosis independent of death receptors

The main source of autoantigens in systemic lupus erythematosus (SLE) is most likely apoptotic material. We have previously shown that sera from SLE patients can induce apoptosis in monocytes and lymphocytes, and here we characterized mechanisms of apoptosis induced by SLE serum. SLE serum seems to induce caspase-dependent classical apoptosis since cells exposed to SLE serum displayed morphology consistent with classical apoptosis as demonstrated by confocal microscopy, and pan-caspase inhibitor Z-VAD.fmk significantly reduced SLE serum-induced apoptosis. Death-receptor-independent pathways seemed to be involved since SLE serum induced apoptosis equally in FADD-mutant and wild-type Jurkat cell lines, and blocking of Fas and TNFR1 did not reduce apoptosis induction. Importantly, apoptosis was significantly reduced in a Bcl-2 overexpressing Jurkat cell line indicating involvement of mitochondrial pathways. Thus, based on morphology and caspase inhibition experiments, we have demonstrated that SLE serum induce classical caspase-dependent apoptosis, and this was independent of death receptor pathways.

Autoantigens are translocated into small apoptotic bodies during early stages of apoptosis

A dysregulation of apoptosis or an ineffective clearance of apoptotic material is suspected to be involved in the pathogenesis of systemic lupus erythematodes. Subcellular fragments such as apoptotic bodies (ABs) have been recognized as modulators of intercellular communication and immune function. In this context, we have been interested whether nuclear and cytoplasmic antigens are relocated into ABs. In the present study, we characterized ABs isolated from apoptozing lymphoblasts. We found an accumulation of the linker-histone (histone 1) as well as the core-histones (histone 2A, histone 2B, histone 3, histone 4) in ABs. Further, they contained DNA, RNA and the ribonuclear protein La/SSB. Proteins such as cytochrome c, HSP 70, prohibitin, p53, nuclear matrix antigen or lamin B were excluded from ABs. The content of ABs differed from that observed in membrane microparticles isolated from viable cells. Formation of ABs occurred early during apoptosis. It was observed before DNA-degradation or phosphatidylserine exposure was detected. ABs were engulfed by monocyte-derived phagocytes. These findings suggest that immunogenic molecules are actively translocated into ABs followed by a rapid engulfment of the latter by environmental phagocytes. In autoimmune diseases, a defect in the clearance of ABs or AB formation may contribute to the development of autoimmunity.

Decreased expressions of the TNF-alpha signaling adapters in peripheral blood mononuclear cells (PBMCs) are correlated with disease activity in patients with systemic lupus erythematosus

Tumor necrosis factor (TNF)-alpha is a pleiotropic cytokine. Systemic lupus erythematosus (SLE) is an autoimmune and inflammatory disease. However, until now, the expression and pathophysiological role of TNF adapters in SLE have been poorly understood. This study aims to investigate the expression of mRNA for the TNF adapter proteins including TNF receptor-associated death domain (TRADD) protein, Fas-associated death domain (FADD) protein, receptor-interacting protein 1 (RIP-1), and TNF receptor-associated factor-2 (TRAF-2) in peripheral blood mononuclear cells (PBMCs) from patients with SLE and to explore the relationship between the expression of these adapters and the SLE disease activity. PBMCs were isolated from the venous blood of 51 SLE patients and 17 healthy subjects. The expression of mRNA for TNF adapter molecules such as TRADD, FADD, RIP-1, and TRAF-2 in PBMCs were analyzed by semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) and quantitative real-time RT-PCR. There were constitutive expressions of mRNA for TRADD, FADD, RIP-1, and TRAF-2 in PBMCs from healthy subjects. The expression of mRNA for all the adapter molecules significantly decreased in PBMCs from patients with SLE, which were 0.38-, 0.69-, 0.59-, and 0.55-fold, respectively, compared to those of control subjects (P < 0.05). The expression of Caspase 3 was significantly increased in SLE patients (P < 0.01); however, the expression of IL-1beta was not significantly different between SLE and control subjects. The expression of TRADD, FADD, RIP-1, and TRAF-2 in PBMCs from patients with SLE were negatively correlated with SLEDAI, the correlation coefficient of which was -0.285, -0.280, -0.307, and -0.298, respectively (P < 0.05). The expression of mRNA for TNF adapter molecules TRADD, FADD, RIP-1, and TRAF-2 decreased significantly in PBMCs from patients with SLE, and the expression of these adapters were negatively correlated with the SLE activity index. These abnormalities may be involved in the immunopathogenic injury mediated by the aberration TNF-alpha signaling pathway in SLE.

Systemic lupus erythematosus: multiple immunological phenotypes in a complex genetic disease

Systemic lupus erythematosus (SLE) is a complex polygenic autoimmune disease characterized by the presence of anti-nuclear autoantibodies (ANAs) that are often detectable years prior to the onset of clinical disease. The disease is associated with a chronic activation of the immune system, with the most severe forms progressing to inflammatory damage that can impact multiple organ systems in afflicted individuals. Current therapeutic strategies poorly control disease manifestations and are generally immunosuppressive. Recent studies in human patient populations and animal models have associated elements of the innate immune system and abnormalities in the immature B lymphocyte receptor repertoires with disease initiation. A variety of cytokines, most notably type I interferons, play important roles in disease pathogenesis and effector mechanisms. The genetic basis for disease susceptibility is complex, and analyses in humans and mice have identified multiple susceptibility loci, several of which are located in genomic regions that are syntenic between humans and mice. The complexities of the genetic interactions that mediate lupus have been investigated in murine model systems by characterizing the progressive development of disease in strains expressing various combinations of susceptibility alleles. These analyses indicate that genetic epistasis dramatically impact disease development and support the feasibility of identifying molecular pathways that can suppress disease progression without completely impairing normal immune function.

Inefficient clearance of dying cells and autoreactivity

Dying cells were basically unnoticed by scientists for a long time and only came back into the spotlight roughly 10 years ago. The process of recognition and uptake of apoptotic and necrotic cells is complex and failures in this process can contribute to the pathogenesis of autoimmune diseases such as systemic lupus erythematosus (SLE). Here, we discuss the recognition and uptake molecules which are involved in an efficient clearance of dying cells in early and late phases of cell death. The exposure of phosphatidylserine (PS) is an early surface change of apoptosing cells recognized by several receptors and adaptor molecules. We demonstrated that dying cells have cell membranes with high lateral mobility of PS, which contribute to their efficient clearance. Changes of the glycoprotein composition of apoptotic cells occur later than the exposure of PS. We further observed that complement binding is an early event in necrosis and a rather late event in apoptosis. Complement, C-reactive protein (CRP), and serum DNase I act as back-up molecules in the clearance process. Finally, we discuss how the accumulation of secondary necrotic cells and cellular debris in the germinal centers of secondary lymph organs can lead to autoimmunity. It is reasonable to argue that clearance defects are major players in the development of autoimmune diseases such as SLE.

Activation of transforming growth factor-beta1 and early atherosclerosis in systemic lupus erythematosus

The efficiency of activating latent transforming growth factor (TGF)-beta1 in systemic lupus erythematosus (SLE) may control the balance between inflammation and fibrosis, modulating the disease phenotype. To test this hypothesis we studied the ability to activate TGF-beta1 in SLE patients and control individuals within the context of inflammatory disease activity, cumulative organ damage and early atherosclerosis. An Activation Index (AI) for TGF-beta1 was determined for 32 patients with SLE and 33 age-matched and sex-matched control individuals by quantifying the increase in active TGF-beta1 under controlled standard conditions. Apoptosis in peripheral blood mononuclear cells was determined by fluorescence-activated cell sorting. Carotid artery intima-media thickness was measured using standard Doppler ultrasound. These measures were compared between patients and control individuals. In an analysis conducted in patients, we assessed the associations of these measures with SLE phenotype, including early atherosclerosis. Both intima-media thickness and TGF-beta1 AI for SLE patients were within the normal range. There was a significant inverse association between TGF-beta1 AI and levels of apoptosis in peripheral blood mononuclear cells after 24 hours in culture for both SLE patients and control individuals. Only in SLE patients was there a significant negative correlation between TGF-beta1 AI and low-density lipoprotein cholesterol (r = -0.404; P = 0.022) and between TGF-beta1 AI and carotid artery intima-media thickness (r = -0.587; P = 0.0004). A low AI was associated with irreversible damage (SLICC [Systemic Lupus International Collaborating Clinics] Damage Index > or = 1) and was inversely correlated with disease duration. Intima-media thickness was significantly linked to total cholesterol (r = 0.371; P = 0.037). To conclude, in SLE low normal TGF-beta1 activation was linked with increased lymphocyte apoptosis, irreversible organ damage, disease duration, calculated low-density lipoprotein levels and increased carotid IMT, and may contribute to the development of early atherosclerosis.

Peripheral blood lymphocyte apoptosis and circulating dendritic cells in patients with systemic lupus erythematosus: correlation with immunological status and disease-related symptoms

We investigated in vivo the relationship between the degree of peripheral blood lymphocyte apoptosis and circulating dendritic cells (DC) as well as the immunological status in 45 patients with systemic lupus erythematous (SLE). Apoptosis was detected by phosphatidylserine externalization and assays to detect caspase activation. The total DC count (tDC) and their myeloid, mDC1 (BDCA1+) and mDC2 (BDCA3+), and plasmacytoid, pDC (BDCA3+), subtypes were assessed. Moreover, several immunological parameters, such as complement proteins, interferons (IFN), tumor necrosis factor (TNF)-alpha, interleukin (IL)-4, and IL-6 levels were assessed. There were no significant differences in both the intensity of apoptosis and DC counts between active and inactive SLE as well as between untreated patients and those treated with steroids. The incidence of lymphocyte apoptosis correlated positively with T-cell count, both T-helper (p=0.004) and cytotoxic T cells (p=0.001), but not with B or natural killer (NK) cells. The intensity of apoptosis enhanced along with the increase in complement C3 (p=0.016) and decrease in IFN-gamma (p=0.040) levels. The apoptotic cell count correlated with tDC (p=0.031), mDC1 (p=0.007), and pDC (p=0.039) counts. Both tDC and mDC1 counts correlated positively with antinuclear antibody (ANA) titers (p=0.017 and 0.032, respectively). Moreover, tDC correlated with C4 (p=0.039) and pDC with both C3 (p=0.032) and C4 (p=0.007) levels. The DC counts correlated inversely with IFN-gamma (tDC, p=0.038; mDC1, p=0.009), IL-6 (mDC2, p=0.031), or serum IgG levels (tDC, p=0.006; mDC1, p<0.001; mDC2, p=0.001). We found a positive correlation between lymphocyte apoptosis and peripheral blood DC count as well as the level of complement proteins in patients with SLE. The enhanced lymphocyte apoptosis was accompanied by the decrease in concentration of some cytokines, such as IFN-gamma or IL-6, as well as serum IgG level. This finding may reflect pathogenetic events during development of the disease, which include a persistent signal derived from circulating apoptotic lymphocytes, mobilizing the complement system, and attracting peripheral blood DC.

IL-15 and IL-15R in leucocytes from patients with systemic lupus erythematosus

OBJECTIVE

To assess the functional status of the IL-15/IL-15Ralpha cytokine system in different leucocyte subsets from patients with systemic lupus erythematosus (SLE).

METHODS

Eighteen patients with SLE (10 with inactive and eight with active disease) and 14 healthy individuals were studied. Serum levels and in vitro production of IL-15 were determined. In addition, the expression of IL-15 receptor alpha (IL-15Ralpha) and membrane-bound IL-15 was assessed and the in vitro effects of IL-15 on CD69 and CD64 expression, interferon-gamma and TNF-alpha synthesis, respiratory burst induction and apoptosis were studied.

RESULTS

Serum levels of IL-15 were significantly increased in inactive and active patients with SLE. Accordingly, the in vitro synthesis and release of IL-15 by monocytes in response to IFN-gamma+lipopolysaccharide was significantly enhanced in SLE patients with active disease, as was the percentage of membrane-bound IL-15+ monocytes. On the other hand, enhanced basal expression of IL-15Ralpha was detected in leucocytes from SLE patients, with defective induction upon stimulation with phytohaemagglutinin or phorbol myristate acetate/ionomycin. Furthermore, diminished induction of CD69 expression and interferon-gamma and TNF-alpha synthesis by recombinant human IL-15 was detected in peripheral blood mononuclear cells from SLE, and there was defective induction of CD64 and priming for respiratory burst in neutrophils. The anti-apoptotic effect of IL-15 was diminished in leucocytes from SLE patients.

CONCLUSION

Our data indicate that there is enhanced synthesis of IL-15 by immune cells from SLE patients, with a poor response to this cytokine by different leucocyte subsets. This abnormal function of IL-15/IL-15Ralpha may contribute significantly to the pathogenesis of SLE.