The interplay of chemokines and dendritic cells in the pathogenesis of lupus nephritis

Identification of driver genes in lupus nephritis based on comprehensive bioinformatics and machine learning

Background

Lupus nephritis (LN) is a common and severe glomerulonephritis that often occurs as an organ manifestation of systemic lupus erythematosus (SLE). However, the complex pathological mechanisms associated with LN have hindered the progress of targeted therapies.

Methods

We analyzed glomerular tissues from 133 patients with LN and 51 normal controls using data obtained from the GEO database. Differentially expressed genes (DEGs) were identified and subjected to enrichment analysis. Weighted gene co-expression network analysis (WGCNA) was utilized to identify key gene modules. The least absolute shrinkage and selection operator (LASSO) and random forest were used to identify hub genes. We also analyzed immune cell infiltration using CIBERSORT. Additionally, we investigated the relationships between hub genes and clinicopathological features, as well as examined the distribution and expression of hub genes in the kidney.

Results

A total of 270 DEGs were identified in LN. Using weighted gene co-expression network analysis (WGCNA), we clustered these DEGs into 14 modules. Among them, the turquoise module displayed a significant correlation with LN (cor=0.88, p<0.0001). Machine learning techniques identified four hub genes, namely CD53 (AUC=0.995), TGFBI (AUC=0.997), MS4A6A (AUC=0.994), and HERC6 (AUC=0.999), which are involved in inflammation response and immune activation. CIBERSORT analysis suggested that these hub genes may contribute to immune cell infiltration. Furthermore, these hub genes exhibited strong correlations with the classification, renal function, and proteinuria of LN. Interestingly, the highest hub gene expression score was observed in macrophages.

Conclusion

CD53, TGFBI, MS4A6A, and HERC6 have emerged as promising candidate driver genes for LN. These hub genes hold the potential to offer valuable insights into the molecular diagnosis and treatment of LN.

Macrophages in Lupus Nephritis: Exploring a potential new therapeutic avenue

Lupus nephritis (LN) is a serious complication of systemic lupus erythematosus (SLE) that occurs in about half of patients. LN is characterized by glomerular deposition of immune complexes, leading to subendothelial, mesangial and subepithelial electron dense deposits, triggering immune cell infiltration and glomerular as well as tubulointerstitial injury. Monocytes and macrophages are abundantly present in inflammatory lesions, both in glomeruli and the tubulointerstitium. Here we discuss how monocytes and macrophages are involved in this process and how monocytes and macrophages may represent specific therapeutic targets to control LN.

Immunomodulatory Activity of Mesenchymal Stem Cells in Lupus Nephritis: Advances and Applications

Lupus nephritis (LN) is a significant cause of various acute and chronic renal diseases, which can eventually lead to end-stage renal disease. The pathogenic mechanisms of LN are characterized by abnormal activation of the immune responses, increased cytokine production, and dysregulation of inflammatory signaling pathways. LN treatment is an important issue in the prevention and treatment of systemic lupus erythematosus. Mesenchymal stem cells (MSCs) have the advantages of immunomodulation, anti-inflammation, and anti-proliferation. These unique properties make MSCs a strong candidate for cell therapy of autoimmune diseases. MSCs can suppress the proliferation of innate and adaptive immune cells, such as natural killer cells (NKs), dendritic cells (DCs), T cells, and B cells. Furthermore, MSCs suppress the functions of various immune cells, such as the cytotoxicity of T cells and NKs, maturation and antibody secretion of B cells, maturation and antigen presentation of DCs, and inhibition of cytokine secretion, such as interleukins (ILs), tumor necrosis factor (TNF), and interferons (IFNs) by a variety of immune cells. MSCs can exert immunomodulatory effects in LN through these immune functions to suppress autoimmunity, improve renal pathology, and restore kidney function in lupus mice and LN patients. Herein, we review the role of immune cells and cytokines in the pathogenesis of LN and the mechanisms involved, as well as the progress of research on the immunomodulatory role of MSCs in LN.

The Immunomodulatory Potential of tolDCs Loaded with Heat Shock Proteins

Disease suppressive T cell regulation may depend on cognate interactions of regulatory T cells with self-antigens that are abundantly expressed in the inflamed tissues. Heat shock proteins (HSPs) are by their nature upregulated in stressed cells and therefore abundantly present as potential targets for such regulation. HSP immunizations have led to inhibition of experimentally induced inflammatory conditions in various models. However, re-establishment of tolerance in the presence of an ongoing inflammatory process has remained challenging. Since tolerogenic DCs (tolDCs) have the combined capacity of mitigating antigen-specific inflammatory responses and of endowing T cells with regulatory potential, it seems attractive to combine the anti-inflammatory qualities of tolDCs with those of HSPs.

Targeting dendritic cell function during systemic autoimmunity to restore tolerance

Systemic autoimmune diseases can damage nearly every tissue or cell type of the body. Although a great deal of progress has been made in understanding the pathogenesis of autoimmune diseases, current therapies have not been improved, remain unspecific and are associated with significant side effects. Because dendritic cells (DCs) play a major role in promoting immune tolerance against self-antigens (self-Ags), current efforts are focusing at generating new therapies based on the transfer of tolerogenic DCs (tolDCs) during autoimmunity. However, the feasibility of this approach during systemic autoimmunity has yet to be evaluated. TolDCs may ameliorate autoimmunity mainly by restoring T cell tolerance and, thus, indirectly modulating autoantibody development. In vitro induction of tolDCs loaded with immunodominant self-Ags and subsequent cell transfer to patients would be a specific new therapy that will avoid systemic immunosuppression. Herein, we review recent approaches evaluating the potential of tolDCs for the treatment of systemic autoimmune disorders.

Human plasmacytoid dendritic cells regulate IFN-α production through activation-induced splicing of IL-18Rα

IFN-α production by pDCs regulates host protection against viruses and is implicated in autoimmune pathology. Human pDCs express high levels of IL-18R, but little is known of its role in pDC function. We report that IL-18R signaling negatively regulates IFN-α production through activation-induced splicing of IL-18Rα in human pDCs. Our data reveal two distinct isoforms of IL-18Rα in human pDCs: the known, full-length receptor (IL-18Rα1) and a novel, truncated variant (IL-18Rα2), which functions as a molecular decoy that competitively inhibits the canonical IL-18Rα1/IL-18Rβ signaling pathway. Whereas NK cells and pDCs both express IL-18Rα1, pDCs express significantly higher levels of IL-18Rα2, resulting in differential responses of these populations to IL-18. Flu exposure increases IL-18Rα1 expression in pDCs, and the blocking of IL-18R enhances pDC production of IFN-α and IP-10; thus, pDCs use activation-induced splicing to regulate IFN-α production in response to flu. These data demonstrate that IL-18R modulates IFN-α release by human pDCs and suggest that IL-18R signaling may represent a promising therapeutic target.

Tolerogenic dendritic cells as a therapy for treating lupus

Systemic lupus erythematosus (SLE) is a chronic autoimmune disorder that is characterized by the over production of auto-antibodies against nuclear components. Thus, SLE patients have increased morbidity and, mortality compared to healthy individuals. Available therapies are not curative and are associated with unwanted adverse effects. During the last few years, important advances in immunology research have provided rheumatologists with new tools for designing novel therapies for treating autoimmunity. However, the complex nature of SLE has played a conflicting role, hindering breakthroughs in therapeutic development. Nonetheless, new advances about SLE pathogenesis could open a fruitful line of research. Dendritic cells (DCs) have been established as essential players in the mechanisms underlying SLE, making them attractive therapeutic targets for fine-tuning the immune system. In this review, we discuss the recent advances made in revealing the mechanisms of SLE pathogenesis, with a focus on the use of DCs as a target for therapy development.

Urinary CXCL-10/IP-10 and MCP-1 as markers to assess activity of lupus nephritis

Objective

IP-10 and MCP-1 are pro-inflammatory chemokines which are involved in the immunopathogenesis of lupus nephritis and may thus be useful biomarkers.

Methods

SLE patients fulfilling ACR 1997 criteria were included. SLEDAI was calculated and blood and urine samples collected. Active lupus was defined as SLEDAI ≥4. Active patients were divided into active renal (proteinuria ≥ 500 mg/day or active sediment in urine) and active non-renal lupus. Patients with active renal lupus were followed until the nephritis became inactive, when a second sample was collected. Serum and urinary levels of MCP-1 and IP-10 (pg/ml) were measured by ELISA. Urinary values were normalized for urinary spot creatinine (in mg/dL. Thus the values were expressed as pg/mg creatinine × 100 creatinine).

Results

A total of 136 patients with SLE including 78 active (46 active renal and 32 active non-renal) were included. Median age was 25 (10–55) years and SLE duration was 23 (six to 48) months. Both serum (data not shown) and urinary levels of MCP-1 (35.2 (12.7–71.7), 9.4 (4.4–17), p < 0.001) and IP-10 (9.5 (4.4–17.9), 3.9 (1.9–9.3), p < 0.001) were higher in active compared to inactive SLE. However, in active renal compared to active non-renal SLE, there was no difference in serum levels; only urinary levels of MCP-1 (46.2 (19.9–125), 12.7 (5.8–43.9), p < 0.001) and IP-10 (12.5 (5.6–22.7), 5.2 (2.3–12.2), p < 0.05) were higher. On longitudinal follow-up of active renal patients ( n = 24), there was a decrease in urinary levels of MCP-1 and IP-10 ( p = 0.005). On ROC analysis, urinary MCP-1 outperformed C4 and urinary IP-10, but was similar to dsDNA and C3 in differentiating active renal from non-renal SLE.

Conclusions

Urinary and serum IP-10 and MCP-1 are potentially useful markers of lupus activity; however, only the urinary levels are indicative of renal activity. However, on ROC analysis, they are not better than conventional markers.

Characterization of 5C11-positive activated interferon-producing cells in patients with systemic lupus erythematosus

OBJECTIVE

5C11 antibody is a novel monoclonal antibody against human BST2 and can be used to detect activation of interferon-producing cells (IPCs). Activated IPCs, which produce large amounts of interferon-α (IFNα), are considered to play an important role in the pathogenesis of systemic lupus erythematosus (SLE). We investigated the characterization of 5C11-positive cells in patients with SLE.

METHODS

The proportions of 5C11-positive cells among blood dendritic cell antigen 2 (BDCA-2)-, CD3-, CD19- and CD14-positive cells in peripheral blood from SLE patients (SLE-PBMCs) and healthy controls (control-PBMCs) were analyzed by flow cytometry. The effect of 5C11 antibody on IFNα production from SLE-PBMCs under stimulation with cytosine-phosphate-guanosine (CpG2216, bacterial oligonucleotide motif) was also examined by enzyme-linked immunosorbent assay (ELISA).

RESULTS

The proportions of 5C11-positive cells among BDCA-2-, CD3- and CD19-, but not CD14-positive cells in SLE-PBMCs were significantly increased compared to those in control-PBMCs (p < 0.0001, all). Especially, the number of 5C11-positive cells among BDCA-2-positive cells was significantly increased in SLE-PBMCs by about six-fold compared to that in control-PBMCs (p < 0.0001). 5C11 antibody inhibited IFNα production by SLE-PBMCs induced by CpG and the inhibition rates was 27% (p < 0.001).

CONCLUSION

SLE patients had a significantly higher proportion of 5C11-positive cells among CD3 and CD19 cells, and especially BDCA-2 positive cells. The ability of 5C11 antibody to inhibit IFNα production from SLE-PBMCs warrants further investigation for its possible clinical application for the treatment of SLE.

Urinary monocyte chemotactic protein-1 and transforming growth factor-β in systemic lupus erythematosus

The purpose of this investigation was to assess the correlation of two biomarkers with the occurrence of renal flares in systemic lupus erythematosus (SLE). Urine levels of monocyte chemotactic protein-1 (MCP-1) and transforming growth factor beta (TGF-β) were measured at baseline, and at two and four months in five groups of patients: 25 lupus nephritis patients with active disease (active LN), 10 lupus nephritis patients with SLE in remission (remission LN), 25 patients with clinical active SLE and without nephritis (active NLN), 10 patients without nephritis with SLE in remission (remission NLN) and 10 healthy controls. We used repeated measurement and ANOVA with Duncan's post hoc to analyze the data; the urine level of the two proteins could distinguish the groups based on the existence of lupus nephritis and/or activity of SLE disease. Furthermore we performed receiver operating curve analysis to identify a cutoff point with a good sensitivity and specificity to diagnose lupus nephritis with either one of the urine proteins. Finally the samples from active LN were grouped according to whether they were Class IV or other classes. Baseline urinary MCP-1, but not TGF-β, was significantly different between the classes. Further investigation into the use of these cytokines in a prospective study is needed to determine their capacity as diagnostic tools for renal flares.

Autoantibodies in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a multifactorial disorder with multigenic inheritance and various environmental factors implicated in its aetiopathogenesis. Despite the multiple mechanisms involved in the aetiology of SLE being elusive, recent studies have made progress in our understanding of the pathogenic mechanisms via abnormal regulation of cell-mediated and humoral immunity that lead to tissue damage. The heterogeneity of the clinical manifestations probably reflects the complexity of the disease pathogenesis itself. The immune system in SLE is characterised by a complex interplay between overactive B cells, abnormally activated T cells and antigen-presenting cells. This interplay leads to the production of an array of inflammatory cytokines, apoptotic cells, diverse autoantibodies and immune complexes that in turn activate effector cells and the complement system, leading to tissue injury and damage which are the hallmarks of the clinical manifestations. SLE patients have dysregulation of inflammatory cytokines, chemokines and immune response-related genes, as well as of the genes involved in apoptosis, signal transduction and the cell cycle.

Monocyte chemoattractant-1 as a urinary biomarker for the diagnosis of activity of lupus nephritis in Brazilian patients

OBJECTIVE

Monocyte chemotactic protein (MCP-1), involved in the pathogenesis of lupus nephritis (LN), has recently been indicated as a new biomarker of kidney activity in systemic lupus erythematosus (SLE). Our aim was to assess urinary MCP-1 (uMCP-1) as a biomarker of renal activity in patients with SLE and to compare it to other disease activity markers, using the ELISA.

METHODS

Seventy-five female Brazilian patients with SLE and a control group participated in our study. Patients with SLE were distributed among 3 groups according to kidney involvement and classified according to disease activity based on clinical and laboratory measures such as urinary sediment, proteinuria, kidney function, C3, C4, anti-dsDNA, disease activity index, and renal SLE disease activity index. The serum and uMCP-1 concentrations were measured by sandwich ELISA.

RESULTS

In the A-LN group (active lupus nephritis: SLE with kidney involvement), the concentration of uMCP-1 was significantly higher than in other groups. A cutoff point was established using the results of the control group to apply this test in the detection of LN. A-LN had a higher frequency of positive results for uMCP-1 in comparison to the other groups (p < 0.001). To detect disease activity in patients with LN, a new cutoff was determined based on the results of patients with SLE with kidney involvement. Setting specificity at 90%, the sensitivity of the test was 50%.

CONCLUSION

The high specificity makes uMCP-1 a useful test as a predictor of kidney activity in SLE, especially when associated to other measures used in clinical practice.

Lipopolysaccharide-pretreated plasmacytoid dendritic cells ameliorate experimental chronic kidney disease

Plasmacytoid dendritic cells play important roles in inducing immune tolerance, preventing allograft rejection, and regulating immune responses in both autoimmune disease and graft-versus-host disease. In order to evaluate a possible protective effect of plasmacytoid dendritic cells against renal inflammation and injury, we purified these cells from mouse spleens and adoptively transferred lipopolysaccharide (LPS)-treated cells, modified ex vivo, into mice with adriamycin nephropathy. These LPS-treated cells localized to the kidney cortex and the lymph nodes draining the kidney, and protected the kidney from injury during adriamycin nephropathy. Glomerulosclerosis, tubular atrophy, interstitial expansion, proteinuria, and creatinine clearance were significantly reduced in mice with adriamycin nephropathy subsequently treated with LPS-activated plasmacytoid dendritic cells as compared to the kidney injury in mice given naive plasmacytoid dendritic cells. In addition, LPS-pretreated cells, but not naive plasmacytoid dendritic cells, convert CD4+CD25− T cells into Foxp3+ regulatory T cells and suppress the proinflammatory cytokine production of endogenous renal macrophages. This may explain their ability to protect against renal injury in adriamycin nephropathy.

Lupus nephritis: current update

Lupus nephritis is a major cause of morbidity and mortality in patients with systemic lupus erythematosus. The general consensus is that 60% of lupus patients will develop clinically relevant nephritis at some time in the course of their illness. Prompt recognition and treatment of renal disease is important, as early response to therapy is correlated with better outcome. The present review summarizes our current understanding of the pathogenic mechanisms underlying lupus nephritis and how the disease is currently diagnosed and treated.

Correlations of urinary biomarkers, TNF-like weak inducer of apoptosis (TWEAK), osteoprotegerin (OPG), monocyte chemoattractant protein-1 (MCP-1), and IL-8 with lupus nephritis

OBJECTIVE

This case-controlled study was designed to correlate urinary biomarkers, TNF-like weak inducer of apoptosis (TWEAK), osteoprotegerin (OPG), monocyte chemoattractant protein-1 (MCP-1), and interleukin-8 (IL-8) levels, with renal involvement in a cohort of systemic lupus erythematosus (SLE) patients to examine their diagnostic performance.

PATIENTS AND METHODS

In 73 SLE patients, and in 23 healthy volunteers, urinary levels of TWEAK, OPG, MCP-1, and IL-8 levels were measured. Disease activity was assessed by total SLE disease activity index, and renal activity by renal activity index (rSLEDAI), and both were correlated with urinary biomarkers. Sensitivity, specificity, and predictive values of individual biomarkers to predict lupus nephritis were also calculated.

RESULTS

Significantly higher levels of urinary biomarkers were observed in SLE patients with lupus nephritis (LN) compared with those without LN (TWEAK, p < 0.001; MCP-1, p < 0.001; OPG, p < 0.001; IL-8, p < 0.032). Other significantly higher levels were observed in SLE patients with LN compared with control subjects (TWEAK, MCP-1, OPG, and IL-8 p < 0.001). Positive correlations were observed between rSLEDAI and TWEAK (r = 0.612 and p < 0.001), MCP-1 (r = 0.635 and p < 0.001), and OPG (r = 0.505 and p < 0.001).

CONCLUSIONS

Urinary levels of TWEAK, OPG, and MCP-1 positively correlate with renal involvement as assessed by rSLEDAI with reasonable sensitivity, specificity, and predictive values to detect lupus nephritis while IL-8 was not significantly associated with global or rSLEDAI.

OX40/OX40L in systemic lupus erythematosus: association with disease activity and lupus nephritis

BACKGROUND AND OBJECTIVES

OX40-OX40L interaction is implicated in the pathogenesis of systemic lupus erythematosus (SLE). We evaluated the role of OX40/OX40L as markers of disease activity and nephritis in SLE patients.

DESIGN AND SETTING

Case-control study conducted in 2009 on SLE patients attending the outpatient clinics of Ain Shams University Hospital, Egypt.

PATIENTS AND METHODS

We assessed the percentage of CD4+ T-lymphocytes expressing OX40 by flowcytometry, and serum OX40 ligand (OX40L) levels in 40 patients with SLE (20 with lupus nephritis and 20 without) and in 20 healthy controls. Disease activity was assessed by the University of Toronto SLE disease activity index (SLEDAI).

RESULTS

The percentage of CD4+ T-lymphocytes expressing OX40 was significantly higher in SLE patients than in controls, and in patients with lupus nephritis than in those without. OX40 expression correlated positively with both serum creatinine levels and SLEDAI. OX40 expression was the highest in patients with class V lupus nephritis and lowest in class II. Serum OX40L levels were significantly higher in SLE patients than in controls, and in patients with nephritis than in those without. Serum OX40L levels correlated with serum creatinine levels but not with SLEDAI. OX40 expression on CD4+ T-cells had a higher sensitivity and specificity in diagnosing lupus nephritis than both OX40L and anti-double-stranded DNA levels.

CONCLUSION

OX40-OX40L interaction plays a role in the pathogenesis of SLE. The expression of OX40 on CD4+ T-lymphocytes and the serum level of OX40L may act as markers of lupus nephritis. Measurements of percentages of CD4+ T-lymphocytes expressing OX40 may serve as an indicator of disease activity in SLE.

Current and emerging strategies for the treatment and management of systemic lupus erythematosus based on molecular signatures of acute and chronic inflammation

Lupus is a chronic, systemic inflammatory condition in which eicosanoids, cytokines, nitric oxide (NO), a deranged immune system, and genetics play a significant role. Our studies revealed that an imbalance in the pro- and antioxidants and NO and an alteration in the metabolism of essential fatty acids exist in lupus. The current strategy of management includes administration of nonsteroidal anti-inflammatory drugs such as hydroxychloroquine and immunosuppressive drugs such as corticosteroids. Investigational drugs include the following: 1) belimumab, a fully human monoclonal antibody that specifically recognizes and inhibits the biological activity of B-lymphocyte stimulator, also known as B-cell-activation factor of the TNF family; 2) stem cell transplantation; 3) rituximab, a chimeric monoclonal antibody against CD20, which is primarily found on the surface of B-cells and can therefore destroy B-cells; and 4) IL-27, which has potent anti-inflammatory actions. Our studies showed that a regimen of corticosteroids and cyclophosphamide, and methods designed to enhance endothelial NO synthesis and augment antioxidant defenses, led to induction of long-lasting remission of the disease. These results suggest that methods designed to modulate molecular signatures of the disease process and suppress inflammation could be of significant benefit in lupus. Some of these strategies could be vagal nerve stimulation, glucose-insulin infusion, and administration of lipoxins, resolvins, protectins, and nitrolipids by themselves or their stable synthetic analogs that are known to suppress inflammation and help in the resolution and healing of the inflammation-induced damage. These strategies are likely to be useful not only in lupus but also in other conditions, such as rheumatoid arthritis, scleroderma, ischemia-reperfusion injury to the myocardium, ischemic heart disease, and sepsis.

Elevated interleukin-18 and skewed Th1:Th2 immune response in lupus nephritis

There is evidence that interleukin-18 plays a role in lupus nephritis (LN). Since interleukin -18 (IL-18) promotes polarization of the immune response toward Th1, we investigated level of IL-18 and assessed the phenotypic distribution of Th1 and Th2 type cells in LN. A predominance of Th1 type (IFN-γ+) cells and significant correlations with serum IL-18 was seen in the patients with LN compared to healthy controls. Although most patients were treated with high dosage of glucocorticoid and other immunosuppressive agents, higher level of IL-18 was found in both serum and glomeruli. However, there was no paralleled upregulation of its gene expression in peripheral blood mononuclear cells. Our findings indicate that the elevated IL-18 should be a symbol of disease activity and play a major role in the pathogenesis of LN by promoting cytokine imbalance towards Th1 type immune response. We conclude that patients with LN would benefit from it while the bioactivity of this cytokine was effectively counteracted.

ZC3H12A (MCPIP1): molecular characteristics and clinical implications

BACKGROUND

ZC3H12A is a gene whose absence is related to autoimmune disorders and to other phenotypical alterations.

METHODS

A comprehensive review of the structure, molecular functions and regulation of ZC3H12A gene and its protein MCPIP1 is done in order to understand their clinical implications.

RESULTS

ZC3H12A, at 1p34.3, has 9860bp, six exons and 61 described SNPs. Eleven are non-synonymous thus leading to changes in MCPIP1, the protein encoded by ZC3H12A. MCPIP1 is induced by MCP-1 and IL-1 whose signals are transduced through the NF-kβ and MAPkinase pathways. This protein acts as an RNAse by degrading chemokine transcripts such as IL-1 as well as its own mRNA and as a transcription factor by reducing the expression of other chemokines induced by NF-kβ such as MCP-1. It also up-regulates genes involved in several differentiation processes and apoptosis. Therefore, ZC3H12A is an equilibrium gatekeeper that not only regulates its own inducers but also controls the regulation by degrading its own mRNA.

CONCLUSION

Understanding ZC3H12A gives a comprehensive panorama that promises to improve our understanding of processes in which this gene is involved including autoimmune, infectious and cardiovascular diseases.

Oversecretion of cytokines and chemokines in lupus nephritis is regulated by intraparenchymal dendritic cells: a review

Lupus nephritis (LN) occurs in more than one-third of patients with systemic lupus erythematosus. Its pathogenesis is attributed to the glomerular deposition of immune complexes as well as to imbalance of the cytokine homeostasis. In this context, high production of cytokines and chemokines by dendritic cells (DCs) may concur to LN. In addition, urinary cytokine excretion may reflect the accumulation of DCs within glomeruli. DCs are differentiated in both myeloid and plasmacytoid (p) subsets in relation to their typical antigen and chemokine expression. Both subsets migrate in response to chemotactic stimuli because pDCs are susceptible to IL-18 expressed by resident glomerular cells. pDCs bear the IL-18R, and it is conceivable that DCs migrate to the kidney under the attraction of IL-18. Therefore, the depletion of DCs reflects the inflammation severity in LN, whereas measurement of Th1 cytokines may represent an effective tool for monitoring the onset of LN.

Type 1 diabetes patients have significantly lower frequency of plasmacytoid dendritic cells in the peripheral blood

Dendritic cells uniquely orchestrate the delicate balance between T cell immunity and regulation and an imbalance favoring immunogenic rather than tolerogenic DC is believed to contribute to the development of autoimmune diseases such as type 1 diabetes (T1D). In this study, we determined the frequencies of three blood DC subsets (pDC, mDC1 and mDC2) in 72 T1D patients and 75 normal controls using the Miltenyi blood DC enumeration kit. The frequency of blood pDC was found to be negatively correlated with subject age in both normal controls and T1D patients (p=0.0007), while the frequency of mDC1 and mDC2 do not change significantly with subject age. More importantly, the mean frequency of pDC in blood was, after adjusting for age, significantly lower in T1D (mean=0.127%) than controls (mean=0.188%) (p<6.0 x 10(-5)), whereas no difference was observed for mDC1 and mDC2 between T1D and controls. Furthermore, T1D patients have a lower proportion of pDC and higher proportion of mDC1 among the total blood DC population than normal controls. These results indicate that the frequency of blood pDC and the pDC/mDC1 ratio are negatively associated with T1D.

Targeting the CD134-CD134L interaction using anti-CD134 and/or rhCD134 fusion protein as a possible strategy to prevent lupus nephritis

Lupus nephritis (LN) is characterized by an increased upregulation of Th1. This study was undertaken to evaluate the role of CD134 in cytokine production in peripheral blood mononuclear cells (PBMCs) from subjects with LN. Percentages of IFN-gamma- (Th1), IL-4-, and IL-10- (Th2) producing cells within the PBMC CD4+ T cell population of LN subjects were found to be higher than those of healthy subjects. Stimulation of PBMC from LN subjects with anti-CD3 epsilon mAb/rIL-2 resulted in further increases in cytokine production. Stimulation in the presence of anti-CD134 mAb resulted in reduced IL-4 and IL-10 production; however, it also resulted in increased IFN-gamma production. Stimulation in the presence of the fusion protein rhCD134:Fc resulted in decreased production of all three cytokines. The possibilities that anti-CD134 therapy may control the extent of IL-4- and IL-10-mediated damage in active LN and that rhCD134:Fc therapy may prevent occurrence of LN are discussed.

Increased IL-18 production by dendritic cells in active inflammatory myopathies

Inflammatory myopathies (IM) are chronic disorders characterized by muscular accumulation of inflammatory cells that promote cytotoxicity and tissue damage. Overexpression of chemokines and cytokines as well as imbalance of dendritic cells (DC) homeostasis have been postulated to exert a role in both dermatomyositis (DM) and polymyositis (PM). We studied the T helper (Th)-1 and Th2 cytokine levels by enzyme linked immunosorbent assay (ELISA) and the muscular expression of IL-18 and its receptor by both histochemistry (HIC) and in situ hybridization (ISH) in both patients and normal controls. Also, the cell populations infiltrating the muscles were investigated. We present evidence that DM and PM are characterized by a predominant Th1 immune response with high production of both interferon (IFN)-gamma and interleukin (IL)-18 in the presence of reduced levels of IL-4 and IL-6. IL-18 was also demonstrated in muscles and produced by both macrophages and DC surrounding either perivascular and perimysium areas or endomysium. IL-18R was highly expressed by T cells and DC as well as by endothelial cells (EC) and smooth muscle cells (SMC). High concentrations of serum and muscular IL-18 suggest that deregulated IL-18/IL-18R pathway may be pathogenetic in IM and measurement of IL-18 might be predictive of the disease activity.

Dendritic cells and the immunopathogenesis of systemic lupus erythematosus

Over the last decade, the role of dendritic cells (DCs) in the immunopathogenesis of systemic lupus erythematosus (SLE) has become apparent. As unique mediators of both tolerance and immunity, aberrant myeloid and plasmacytoid DC function can promote autoimmune responses via a number of mechanisms and proinflammatory pathways. This review provides an overview of DC function, the potential role of DCs in promoting autoimmune responses in SLE, and how other abnormalities in lupus can lead to an enhanced engagement of DCs in immune responses. How medications used to treat SLE and other autoimmune conditions may exert effects on DCs is also explored.

Ionizing radiation stimulates secretion of pro-inflammatory cytokines: dose-response relationship, mechanisms and implications

In previous studies we showed a marked increase in secretion of inflammatory cytokines TNFalpha and interleukin (IL)-1beta by mouse macrophages in response to different doses of ionizing radiation (IR). Here we show the stimulation of IL-12 and IL-18 secretion by mouse peritoneal macrophages after whole-body irradiation with exploration of the possible mechanisms and implications in cancer radiotherapy. Both low (0.075 Gy) and high (2 Gy) doses of IR were found to cause sustained stimulation of IL-12 and IL-18 secretion by mouse macrophages; this paralleled the activation of NF-kappaB as well as up-regulated expression of CD14 and TLR4-MD2 on the macrophage surface and MyD88 in the cytoplasm. The expression of CD14, TLR4-MD2 and MyD88 increased in a dose-dependent manner from radiation doses between 0.05 and 2 Gy. The secretion of IL-12 and IL-18 showed a dose-dependent increase from doses between 0.05 and 4 Gy. It is concluded that IR can stimulate the secretion of IL-12 and IL-18 presumably via activation of the Toll signaling pathway in macrophages. The potential harmful effect of repeated doses of radiation used in radiotherapy for certain cancers is discussed.

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.

Chloroquine treatment influences proinflammatory cytokine levels in systemic lupus erythematosus patients

Systemic lupus erythematosus (SLE) is an autoimmune disease with a complex pathogenesis. Published data have revealed that serum levels of proinflammatory cytokines are increased in SLE patients. The aim of our study was to evaluate whether monotherapy with chloroquine phosphate affects IL-1beta, IL-6, IL-18 and TNF-alpha serum levels in SLE patients. The study group consisted of 25 SLE patients with mild or moderate disease activity and 25 age- and sex-matched healthy control subjects. In SLE patients the cytokine levels were measured just before and three months after starting chloroquine treatment at a dose of 125 mg twice daily. Although the majority of SLE patients had a low systemic lupus activity measure (SLAM) index, the levels of IL-6, IL-18 and TNF-alpha were significantly higher than in the control group. After three-months of chloroquine therapy the mean level of IL-6, IL-18 and TNF-alpha decreased significantly. Minimal erythema doses (MEDs) were significantly increased in SLE patients after three months of chloroquine therapy. The results indicate that chloroquine treatment lowers some proinflammatory cytokines and may provide a photoprotective effect.