Analysis of CD80 and CD86 expression on peripheral blood B lymphocytes reveals increased expression of CD86 in lupus patients

Implications of CD154 and Its Receptors in the Pathogenesis and Treatment of Systemic Lupus Erythematosus

CD154, also known as CD40 ligand, is a costimulatory molecule involved in humoral and adaptive immune responses upon pairing with its classical receptor, CD40. The CD154/CD40 dyad is a key participant in the pathogenesis of many autoimmune diseases, including systemic lupus erythematosus (SLE). In SLE, the major cells at play, T and B lymphocytes, are shown to overexpress CD154 and CD40, respectively. Subsequently, these cells and other CD40-positive cells engage in numerous effector functions contributing to SLE development. With the recent identification of additional receptors for CD154, all belonging to the integrin family, the role of CD154 in SLE is more complex and calls for deeper investigation into its biological significance. Many therapeutic strategies directed against the CD154/CD40 couple have been deployed for the treatment of SLE and proved efficient in animal models and human studies. However, the incidence of thromboembolic complications in patients treated with these anti-CD154/CD40 antibodies halted their further clinical assessments and called for another class of therapies targeting these molecules. Second-generation antibodies directed against CD154 or CD40 are showing promising results in the advanced stages of clinical testing. Our review presents a thorough description of CD154 and its receptors, CD40 and the integrin family members in SLE pathogenesis. All these elements of the CD154 system represent important therapeutic targets for the treatment of SLE.

Potential role of EBV and Toll-like receptor 9 ligand in patients with systemic lupus erythematosus

SLE is a multisystem autoimmune disease characterized by multiple immunological abnormalities including production of autoantibodies. While the etiology of SLE is largely unknown, it is generally accepted that both genetic and environmental factors contribute to disease risk and immune dysregulation. Production of IFN-α is important for protecting the host against infections; however, over stimulation of innate immune pathways can induce autoimmune disease. Environmental factors, particularly Epstein-Barr virus (EBV), have been proposed to play an important role in SLE disease. Improper engagement of Toll-like receptor (TLR) pathways by endogenous or exogenous ligands may lead to the initiation of autoimmune responses and tissue injury. EBV is shown to be a potent stimulant of IFN-α by TLR signaling cascades. Given the highlighted role of IFN-α in SLE pathogenesis and potential role of EBV infection in this disease, the present study is aimed at exploring the in vitro effects of EBV infection and CPG (either alone or in combination) on IFN-α. We also examined the expression level of CD20 and BDCA-4 and CD123 in PBMCs in 32 SLE patients and 32 healthy controls. Our results showed PBMCs treated with CPG-induced higher levels of IFN-α and TLR-9 gene expression fold change compared to cells treated with either EBV or EBV-CPG. Moreover, PBMCs treated with CPG produced significantly higher IFN-α concentration in supernatant compared to cells treated with EBV but not EBV-CPG. Our results further highlight the potential role of EBV infection and TLRs in SLE patients although more studies are warranted to ascertain the global imprint that EBV infection can have on immune signature in patients with SLE.

A pregnancy hormone-cell death link promotes enhanced lupus-specific immunological effects

Women of reproductive age demonstrate an increased incidence of systemic lupus erythematosus, and reproductive hormones have been implicated in disease progression. Additionally, pregnancy can be associated with disease "flares", the reasons for which remain obscure. While apoptotic bodies are believed to provide an autoantigenic trigger in lupus, whether autoantigenic constituents vary with varying cellular insults, and whether such variations can be immunologically consequential in the context of pregnancy, remains unknown. As assessed by antigenicity and mass spectrometry, apoptotic bodies elicited by different drugs demonstrated the differential presence of lupus-associated autoantigens, and varied in the ability to elicit lupus-associated cytokines from lupus splenocytes and alter the phenotype of lupus B cells. Immunization of tamoxifen-induced apoptotic bodies in lupus-prone mice generated higher humoral autoreactive responses than did immunization with cisplatin-induced apoptotic bodies, and both apoptotic bodies were poorly immunogenic in healthy mice. Incubation of lupus splenocytes (but not healthy splenocytes) with the pregnancy hormone human chorionic gonadotropin (hCG) along with tamoxifen-induced apoptotic bodies (but not cisplatin-induced apoptotic bodies) induced increases in the secretion of lupus-associated cytokines and in the up-modulation of B cell phenotypic markers. In addition, levels of secreted autoantibodies (including of specificities linked to lupus pathogenesis) were enhanced. These events were associated with the heightened phosphorylation of several signaling intermediates. Observations suggest that hCG is a potential disease-promoting co-stimulant in a lupus-milieu; when combined with specific apoptotic bodies, it enhances the intensity of multiple lupus-associated events. These findings deepen mechanistic insight into the hormone's links with autoreactive responses in lupus-prone mice and humans.

B Cell Aberrance in Lupus: the Ringleader and the Solution

Systemic lupus erythematosus (SLE) is a prototypical autoimmune disease with high heterogeneity but the common characterization of numerous autoantibodies and systemic inflammation which lead to the damage of multiple organs. Aberrance of B cells plays a pivotal role in the immunopathogenesis of SLE via both antibody-dependent and antibody-independent manners. Escape of autoreactive B cells from the central and peripheral tolerance checkpoints, over-activation of B cells and their excessive cytokines release which drive T cells and dendritic cells stimulation, and dysregulated surface molecules, as well as intracellular signal pathways involved in B cell biology, are all contributing to B cell aberrance and participating in the pathogenesis of SLE. Based on that rationale, targeting aberrance of B cells and relevant molecules and pathways is expected to be a promising strategy for lupus control. Multiple approaches targeting B cells through different mechanisms have been attempted, including B-cell depletion via monoclonal antibodies against B-cell-specific molecules, blockade of B-cell survival and activation factors, suppressing T-B crosstalk by interrupting costimulatory molecules and inhibiting intracellular activation signaling cascade by targeting pathway molecules in B cells. Though most attempts ended in failure, the efficacy of B-cell targeting has been encouraged by the FDA approval of belimumab that blocks B cell-activating factor (BAFF) and the recommended use of anti-CD20 as a remedial therapy in refractory lupus. Still, quantities of clinical trials targeting B cells or relevant molecules are ongoing and some of them have displayed promising preliminary results. Additionally, advances in multi-omics studies help deepen our understandings of B cell biology in lupus and may promote the discovery of novel potential therapeutic targets. The combination of real-world data with basic research achievements may pave the road to conquering lupus.

A novel monoclonal antibody against human B7-1 protects against chronic graft-vs.-host disease in a murine lupus nephritis model

Lupus nephritis (LN) is the most common complication that causes mortality in patients with systemic lupus erythematosus. The B7-1/B7-2 and CD28/cytotoxic T-lymphocyte associated protein 4 co-stimulatory pathway serves a key role in autoimmune disease and organ transplantation. The aim of the present study was to generate and characterize a monoclonal antibody (mAb; clone 4E5) against human B7-1 and to investigate its potential use for the treatment of LN. The results demonstrated that the 4E5 mAb was successfully generated and able to recognize both human and mouse B7-1. After injection of this mAb into a mouse model with chronic graft-vs.-host disease (cGVHD)-induced lupus-like disease, the expression of CD21, CD23, CD80 and CD86 on B220⁺ B-cells in the spleen, and the concentrations of serum autoantibodies and urine protein, were decreased. Direct immunofluorescence analysis of the kidneys revealed that immunofluorescence of immune complex deposits was weaker in the 4E5-treated mice and electron microscopy analyses of renal tissues indicated that pathological injury of the kidneys of 4E5-treated mice was decreased compared with that in the model control mice. The results of the present study demonstrated that inhibition of the B7-1/CD28 co-stimulatory signaling pathway with the 4E5 mAb may represent a promising strategy to decelerate the progression of LN that is induced by cGVHD with potential for use in the treatment of other autoimmune diseases.

Patients with systemic lupus erythematosus show increased proportions of CD19+CD20- B cells and secretion of related autoantibodies

BACKGROUND

At present, anti-CD20 monoclonal antibody treatments targeting systemic lupus erythematosus (SLE) are complex, variable, and often have disappointing outcomes. High levels of programmed cell death-1 (PD-1) and its ligands (PD-L1, PD-L2) or CD80/CD86 on B cell surfaces are markers of increased B cell activity. However, their expression levels on CD19⁺CD20^+/- B cells and their clinical significance for SLE dynamics have not been carefully investigated.

METHODS

Flow cytometry was used to detect the expression levels of PD-1, PD-L1, PD-L2, CD80, and CD86 on CD19⁺CD20^+/- B cells in peripheral blood from SLE patients and healthy controls (HCs). The amount of anti-dsDNA and immunoglobin G (IgG) secreted by CD19⁺CD20^+/- B cells was measured by enzyme-linked immunosorbent assay.

RESULTS

CD19⁺CD20^- B cell frequency was significantly higher in SLE patients than in HCs (P < 0.001), and was positively correlated with disease activity. In SLE patients, frequencies of PD-1, PD-L1, PD-L2, and CD86 on CD19⁺CD20^- B cells were significantly higher than CD19⁺CD20⁺ B cells (P ≤ 0.002) and were significantly correlated with individual laboratory and clinically based parameters (P < 0.05). In vitro tests, we found that the levels of anti-dsDNA and IgG secreted by CD19⁺CD20^- B cells from patients with SLE were significantly higher than the HC group (P < 0.05).

CONCLUSIONS

We found abnormal frequency of CD19⁺CD20^- B cells and increased expression of surface markers on these cells from SLE patients. And the CD19⁺CD20^- B cells had the ability to proliferate and secrete anti-dsDNA and IgG. Additionally, our results suggested that CD19⁺CD20^- B cells from SLE patients may be the activated B cells and caused poor efficacy of rituximab. Key Points • CD19⁺CD20^- B cell frequencies were significantly higher in SLE patients. • Frequencies of PD-1 and its ligands on CD19⁺CD20^- B cells increased significantly in SLE patients. • CD19⁺CD20^- B cells in SLE patients had the ability to secrete anti-dsDNA and IgG. • CD19⁺CD20^- B cells in SLE patients may be the activated B cells and caused poor efficacy of rituximab.

Autoreactive B cells in SLE, villains or innocent bystanders?

The current concepts for development of autoreactive B cells in SLE (systemic lupus erythematosus) focus on extrinsic stimuli and factors that provoke B cells into tolerance loss. Traditionally, major tolerance loss pathways are thought to be regulated by factors outside the B cell including autoantigen engagement of the B-cell receptor (BCR) with simultaneous type I interferon (IFN) produced by dendritic cells, especially plasmacytoid dendritic cells (pDCs). Later, in autoreactive follicles, B-cells encounter T-follicular helper cells (Tfh) that produce interleukin (IL)-21, IL-4 and pathogenic cytokines, IL-17 and IFN gamma (IFNɣ). This review discusses these mechanisms and also highlights recent advances pointing to the peripheral transitional B-cell stage as a major juncture where transient autocrine IFNβ expression by developing B-cells imprints a heightened susceptibility to external factors favoring differentiation into autoantibody-producing plasmablasts. Recent studies highlight transitional B-cell heterogeneity as a determinant of intrinsic resistance or susceptibility to tolerance loss through the shaping of B-cell responsiveness to cytokines and other environment factors.

The Role of Immune Checkpoint Receptors in Regulating Immune Reactivity in Lupus

Immune checkpoint receptors with co-stimulatory and co-inhibitory signals are important modulators for the immune system. However, unrestricted co-stimulation and/or inadequate co-inhibition may cause breakdown of self-tolerance, leading to autoimmunity. Systemic lupus erythematosus (SLE) is a complex multi-organ disease with skewed and dysregulated immune responses interacting with genetics and the environment. The close connections between co-signaling pathways and SLE have gradually been established in past research. Also, the recent success of immune checkpoint blockade in cancer therapy illustrates the importance of the co-inhibitory receptors in cancer immunotherapy. Moreover, immune checkpoint blockade could result in substantial immune-related adverse events that mimic autoimmune diseases, including lupus. Together, immune checkpoint regulators represent viable immunotherapeutic targets for the treatment of both autoimmunity and cancer. Therefore, it appears reasonable to treat SLE by restoring the out-of-order co-signaling axis or by manipulating collateral pathways to control the pathogenic immune responses. Here, we review the current state of knowledge regarding the relationships between SLE and the co-signaling pathways of T cells, B cells, dendritic cells, and neutrophils, and highlight their potential clinical implications. Current clinical trials targeting the specific co-signaling axes involved in SLE help to advance such knowledge, but further in-depth exploration is still warranted.

Selenium supplementation suppresses immunological and serological features of lupus in B6.Sle1b mice

Systemic lupus erythematosus (SLE) is a debilitating multi-factorial immunological disorder characterized by increased inflammation and development of anti-nuclear autoantibodies. Selenium (Se) is an essential trace element with beneficial anti-cancer and anti-inflammatory immunological functions. In our previous proteomics study, analysis of Se-responsive markers in the circulation of Se-supplemented healthy men showed a significant increase in complement proteins. Additionally, Se supplementation prolonged the life span of lupus prone NZB/NZW-F1 mice. To better understand the protective immunological role of Se in SLE pathogenesis, we have investigated the impact of Se on B cells and macrophages using in vitro Se supplementation assays and the B6.Sle1b mouse model of lupus with an oral Se or placebo supplementation regimen. Analysis of Se-treated B6.Sle1b mice showed reduced splenomegaly and splenic cellularity compared to untreated B6. Sle1b mice. A significant reduction in total B cells and notably germinal center (GC) B cell numbers was observed. However, other cell types including T cells, Tregs, DCs and pDCs were unaffected. Consistent with reduced GC B cells there was a significant reduction in autoantibodies to dsDNA and SmRNP of the IgG2b and IgG2c subclass upon Se supplementation. We found that increased Se availability leads to impaired differentiation and maturation of macrophages from mouse bone marrow derived progenitors in vitro. Additionally, Se treatment during in vitro activation of B cells with anti-CD40L and LPS inhibited optimal B cell activation. Overall our data indicate that Se supplementation inhibits activation, differentiation and maturation of B cells and macrophages. Its specific inhibitory effect on B cell activation and GC B cell differentiation could be explored as a potential therapeutic supplement for SLE patients.

Growth of B Cell Receptor Microclusters Is Regulated by PIP2 and PIP3 Equilibrium and Dock2 Recruitment and Activation

The growth of B cell receptor (BCR) microclusters upon antigen stimulation drives B cell activation. Here, we show that PI3K-mediated PIP₃ production is required for the growth of BCR microclusters. This growth is likely inhibited by PTEN and dependent on its plasma membrane binding and lipid phosphatase activities. Mechanistically, we find that PIP₃-dependent recruitment and activation of a guanine nucleotide exchange factor, Dock2, is required for the sustained growth of BCR microclusters through remodeling of the F-actin cytoskeleton. As a consequence, Dock2 deficiency significantly disrupts the structure of the B cell immunological synapse. Finally, we find that primary B cells from systemic lupus erythematosus (SLE) patients exhibit more prominent BCR and PI3K microclusters than B cells from healthy controls. These results demonstrate the importance of a PI3K- and PTEN-governed PIP₂ and PIP₃ equilibrium in regulating the activation of B cells through Dock2-controlled growth of BCR microclusters.

Procainamide-induced autoimmunity: Relationship to T-helper 2-type T-cell activation

Drug-induced autoimmunity (DIA) refers to a group of adverse drug reactions, and they remain unpredictable largely due to the limited understanding of the mechanisms involved. There is evidence that procainamide can cause autoimmune reactions in humans but the mechanisms involved remain unclear. To examine the cellular and genetic factors involved in the procainamide-induced autoimmune response, we compared rats that are genetically T-helper (Th)2-predisposed (Brown Norway (BN)), Th1-predisposed (Lewis (LEW)) or not genetically predisposed (Sprague Dawley (SD)). We revealed significant differences in response to autoimmunity induced by procainamide among three strains rats, BN was the most sensitive one, SD exhibited less sensitive, while LEW resistance to procainamide. Much more pronounced of Th2-type responses and more complex differentially expressed genes involved in immune regulation and response in BN might contribute to its susceptibleness to DIA. Moreover, similar immune mechanisms were found between BN and SD, which suggesting that these changes would serve as the potential bridge biomarkers to predict DIA among species. This study may also benefit to further understand the toxicological mechanism of drug-induced autoimmune reactions.

Enhanced Bruton's Tyrosine Kinase Activity in Peripheral Blood B Lymphocytes From Patients With Autoimmune Disease

OBJECTIVE

Bruton's tyrosine kinase (BTK) transmits crucial survival signals from the B cell receptor (BCR) in B cells. Pharmacologic BTK inhibition effectively diminishes disease symptoms in mouse models of autoimmunity; conversely, transgenic BTK overexpression induces systemic autoimmunity in mice. We undertook this study to investigate BTK expression and activity in human B cells in the context of autoimmune disease.

METHODS

Using intracellular flow cytometry, we quantified BTK expression and phosphorylation in subsets of peripheral blood B cells from 30 patients with rheumatoid arthritis (RA), 26 patients with primary Sjögren's syndrome (SS), and matched healthy controls.

RESULTS

In circulating B cells, BTK protein expression levels correlated with BTK phosphorylation. BTK expression was up-regulated upon BCR stimulation in vitro and was significantly higher in CD27+ memory B cells than in CD27-IgD+ naive B cells. Importantly, BTK protein and phospho-BTK were significantly increased in B cells from anti-citrullinated protein antibody (ACPA)-positive RA patients but not in B cells from ACPA-negative RA patients. BTK was increased both in naive B cells and in memory B cells and correlated with frequencies of circulating CCR6+ Th17 cells. Likewise, BTK protein was increased in B cells from a major fraction of patients with primary SS and correlated with serum rheumatoid factor levels and parotid gland T cell infiltration. Interestingly, targeting T cell activation in patients with primary SS using the CTLA-4Ig fusion protein abatacept restored BTK protein expression in B cells to normal levels.

CONCLUSION

These data indicate that autoimmune disease in humans is characterized by enhanced BTK activity, which is linked not only to autoantibody formation but also to T cell activity.

Antigen presenting cell abnormalities in the Cln3(-/-) mouse model of juvenile neuronal ceroid lipofuscinosis

Mutations of the CLN3 gene lead to juvenile neuronal ceroid lipofuscinosis (JNCL), an autosomal recessive lysosomal storage disorder that causes progressive neurodegeneration in children and adolescents. There is evidence of immune system involvement in pathology that has been only minimally investigated. We characterized bone marrow stem cell-derived antigen presenting cells (APCs), peritoneal macrophages, and leukocytes from spleen and blood, harvested from the Cln3(-/-) mouse model of JNCL. We detected dramatically elevated CD11c surface levels and increased total CD11c protein in Cln3(-/-) cell samples compared to wild type. This phenotype was specific to APCs and also to a loss of CLN3, as surface levels did not differ from wild type in other leukocyte subtypes nor in cells from two other NCL mouse models. Subcellularly, CD11c was localized to lipid rafts, indicating that perturbation of surface levels is attributable to derangement of raft dynamics, which has previously been shown in Cln3 mutant cells. Interrogation of APC function revealed that Cln3(-/-) cells have increased adhesiveness to CD11c ligands as well as an abnormal secretory pattern that closely mimics what has been previously reported for Cln3 mutant microglia. Our results show that CLN3 deficiency alters APCs, which can be a major contributor to the autoimmune response in JNCL.

Genome-wide search followed by replication reveals genetic interaction of CD80 and ALOX5AP associated with systemic lupus erythematosus in Asian populations

OBJECTIVES

Genetic interaction has been considered as a hallmark of the genetic architecture of systemic lupus erythematosus (SLE). Based on two independent genome-wide association studies (GWAS) on Chinese populations, we performed a genome-wide search for genetic interactions contributing to SLE susceptibility.

METHODS

The study involved a total of 1 659 cases and 3 398 controls in the discovery stage and 2 612 cases and 3 441 controls in three cohorts for replication. Logistic regression and multifactor dimensionality reduction were used to search for genetic interaction.

RESULTS

Interaction of CD80 (rs2222631) and ALOX5AP (rs12876893) was found to be significantly associated with SLE (OR_int=1.16, P_int_all=7.7E-04 at false discovery rate<0.05). Single nuclear polymorphism rs2222631 was found associated with SLE with genome-wide significance (P_all=4.5E-08, OR=0.86) and is independent of rs6804441 in CD80, whose association was reported previously. Significant correlation was observed between expression of these two genes in healthy controls and SLE cases, together with differential expression of these genes between cases and controls, observed from individuals from the Hong Kong cohort. Genetic interactions between BLK (rs13277113) and DDX6 (rs4639966), and between TNFSF4 (rs844648) and PXK (rs6445975) were also observed in both GWAS data sets.

CONCLUSIONS

Our study represents the first genome-wide evaluation of epistasis interactions on SLE and the findings suggest interactions and independent variants may help partially explain missing heritability for complex diseases.

Use of biomarkers in the management of children with lupus

Childhood systemic lupus erythematosus (SLE) is known to have a worse prognosis than adult-onset disease, and monitoring and treatment of the disease are still a challenge. Thus, there is an urgent need for highly reliable, non-invasive biomarkers for early detection of relapses, to avoid long-term complications and to optimize the management of children with LN. Recent studies of pediatric patients have yielded novel specific biomarkers for SLE diagnosis which can be used for monitoring disease activity and response to treatment. The most promising biomarkers in juvenile-onset SLE include cell-bound complement activation products, some genomic profiles, and urinary proteins such as neutrophil gelatinase-associated lipocalin, monocyte chemoattractant protein-1, and alpha-1-acid glycoprotein. None of these might be suitable for use as a single SLE-biomarker. More likely a combination of novel biomarkers with traditionally used data, including autoantibodies and complement, might help to enhance sensitivity and specificity for early diagnosis, disease monitoring, and prediction of relapses.cp.

MicroRNA expression in chronic lymphocytic leukemia developing autoimmune hemolytic anemia

Chronic lymphocytic leukemia (CLL) is frequently associated with autoimmune hemolytic anemia (AIHA). However, the mechanisms governing the association between CLL and AIHA are poorly understood. MicroRNAs (miRNAs) have been associated with different clinico-biological forms of CLL and are also known to play a substantial role in autoimmunity. However, there are no studies correlating miRNA expression with the likelihood that patients with CLL will develop AIHA. In this study, we found that malignant B-cells from patients with CLL subsequently developing AIHA present nine down-regulated (i.e. miR-19a, miR-20a, miR-29c, miR-146b-5p, miR-186, miR-223, miR-324-3p, miR-484 and miR-660) miRNAs. Interestingly, two of these miRNAs (i.e. miR-20a and miR-146b-5p) are involved in autoimmune phenomena, and one (i.e. miR-146b-5p) in both autoimmunity and CLL. Furthermore, we demonstrated that miR-146b-5p modulates CD80, a molecule associated with the B-T-cell synapse and in restoration of the antigen presenting cell capacity of CLL cells.

Increased production of circulating soluble co-stimulatory molecules CTLA-4, CD28 and CD80 in patients with rheumatoid arthritis

Co-stimulatory molecules are key immunoregulatory mediators in regulating T lymphocyte-mediated immune responses and inflammatory reactions. Here we investigated whether there is altered expression and the clinical significance of circulating soluble co-stimulatory molecules in rheumatoid arthritis (RA) patients. Serum concentrations of sCTLA-4, sCD28, sCD80 and sCD86 in 56 RA patients, and 32 sex- and age-matched control subjects were measured by enzyme-linked immunosorbent assay (ELISA). Results showed that serum sCTLA-4, sCD28, and CD80 but not CD86 concentrations in all RA patients were significantly higher than concentrations in healthy control subjects. And there was significant and positive correlation between serum CTLA-4 and sCD28, sCD28 and sCD80, or sCTLA-4 and sCD80 in all RA patients. Serum sCTLA-4 concentration in all RA patients correlated significantly with disease activity score in 28 joints (DAS28). Moreover, immunosuppressant treatment with leflunomide could downregulate the increased levels of sCTLA-4, sCD28, and CD80 in RA patients. Therefore, the elevated production of circulating soluble T-cell co-stimulatory molecules should contribute to the pathogenesis of RA, and serum sCTLA-4 could potentially serve as a new marker of RA disease activity.

Lymphocyte phenotypes in wild-caught rats suggest potential mechanisms underlying increased immune sensitivity in post-industrial environments

The immune systems of wild rats and of laboratory rats can been utilized as models of the human immune system in pre-industrial and post-industrial societies, respectively. In this study, lymphocyte phenotypes in wild rats were broadly characterized, and the results were compared to those obtained by us and by others using cells derived from various strains of laboratory rats. Although not expected, the production of regulatory T cells was not apparently different in wild rats compared to laboratory rats. On the other hand, differences in expression of markers involved in complement regulation, adhesion, signaling and maturation suggest increased complement regulation and decreased sensitivity in wild-caught rats compared to laboratory rats, and point toward complex differences between the maturation of T cells. The results potentially lend insight into the pathogenesis of post-industrial epidemics of allergy and autoimmune disease.

Type I interferon-dependent CD86(high) marginal zone precursor B cells are potent T cell costimulators in mice

OBJECTIVE

To investigate the role of CD86(high) marginal zone (MZ) precursor B cells in type I interferon (IFN)-induced T cell-dependent responses in autoimmune BXD2 mice.

METHODS

Confocal microscopic imaging was used to determine the location of plasmacytoid dendritic cells (DCs), MZ precursor B cells, and CD4 T cells in the spleens of BXD2 and BXD2-Ifnar(-/-) mice. Immunohistochemical staining was used to determine IgG(bright) cells in the spleens of BXD2 and BXD2-Ifnar(-/-) mice. Enzyme-linked immunosorbent assay was used to determine serum levels of IFNα and autoantibodies, and 4-hydroxy-3-nitrophenylacetyl hapten (NP)-chicken γ-globulin (CGG) (NP-CGG)- or NP-Ficoll-induced anti-NP2 antibody titers. Real-time quantitative polymerase chain reaction was used to determine the levels of type I IFN transcripts. T cell proliferation was measured using (3) H-thymidine. The expression of CD86 and CD80 was determined by fluorescence-activated cell sorting analysis.

RESULTS

The deletion of type I IFN receptor abrogated the development of IgG(bright) cells and suppressed a T cell-dependent antibody response. Type I IFN signaling was associated with the expression of CD86, but not CD80, on follicular, MZ, and MZ precursor B cells. However, MZ precursor B cells demonstrated the highest expression of CD86 and the highest capacity for T cell costimulation with intact type I IFN receptor. This effect was blocked by an antibody that neutralizes CD86. In IFN receptor-intact BXD2 mouse spleens, MZ precursor B cells clustered at the T cell-B cell border. CD86 deletion suppressed germinal center formation, autoantibody production, and development of autoimmune diseases in BXD2 mice.

CONCLUSION

Type I IFN can promote autoimmune responses in BXD2 mice through up-regulation of CD86(high) expression on MZ precursor B cells and trafficking of MZ precursor B cells to the T cell-B cell border to provide costimulation of CD4 T cells.

Treatment of systemic lupus erythematosus with epratuzumab

Systemic lupus erythematosus is a prototypic autoimmune disease characterized by abnormalities in the activity of B-cells and T-cells. A novel specific treatment for autoimmune diseases is B-cell depletion with monoclonal antibodies. Epratuzumab is a monoclonal antibody that targets CD22 antigen on B-cells. Initial phase II and two terminated early phase III studies suggest that treatment of systemic lupus erythematosus with this immunomodulatory agent is effective, well tolerated and significantly improves the patient's quality of life. In vitro studies and clinical trials with non-Hodgkin lymphoma patients indicate epratuzumab can potentially serve as a complementary drug in combination therapy with another inhibitor of B-cell activity, rituximab, which is a monoclonal anti-CD20 antibody.

Suppression of autoimmunity and organ pathology in lupus-prone mice upon inhibition of calcium/calmodulin-dependent protein kinase type IV

OBJECTIVE

Systemic lupus erythematosus (SLE) is a chronic inflammatory disease associated with aberrant immune cell function. Treatment involves the use of indiscriminate immunosuppression, which results in significant side effects. SLE T cells express high levels of calcium/calmodulin-dependent protein kinase type IV (CaMKIV), which translocates to the nucleus upon engagement of the T cell receptor-CD3 complex and accounts for abnormal T cell function. The purpose of this study was to determine whether inhibition of CaMKIV would improve disease pathology.

METHODS

We treated MRL/lpr mice with KN-93, a CaMKIV inhibitor, starting at week 8 or week 12 of age and continuing through week 16 and evaluated skin lesions, proteinuria, kidney histopathology, proinflammatory cytokine production, and costimulatory molecule expression. We also determined the effect of silencing of CAMK4 on interferon-γ (IFNγ) expression by human SLE T cells.

RESULTS

CaMKIV inhibition in MRL/lpr mice resulted in significant suppression of nephritis and skin disease, decreased expression of the costimulatory molecules CD86 and CD80 on B cells, and suppression of IFNγ and tumor necrosis factor α production. In human SLE T cells, silencing of CAMK4 resulted in suppression of IFNγ production.

CONCLUSION

We conclude that suppression of CaMKIV mitigates disease development in lupus-prone mice by suppressing cytokine production and costimulatory molecule expression. Specific silencing of CAMK4 in human T cells results in similar suppression of IFNγ production. Our data justify the development of small-molecule CaMKIV inhibitors for the treatment of patients with SLE.

B Cell Abnormalities in Wegener’s Granulomatosis and Microscopic Polyangiitis: Role of CD25+-expressing B Cells

Objective.

The use of rituximab in vasculitis has increased interest in B cell biology. A subpopulation of B cells expressing CD25 shows antigen-presenting properties and may have regulatory functions. We assessed subpopulations of B cell maturation (Bm) and markers related to activity and antigen presentation, and related the findings to disease activity.

Methods.

Multiparameter flow cytometry was used to assess numbers and proportions of circulating lymphocytes from 34 patients with vasculitis (16 remission, 18 active) and 20 controls.

Results.

Active vasculitis samples showed decreased proportions of Bm1 (7.8% vs 11%; p = 0.041), Bm2’ (0.2% vs 0.7%; p = 0.002), and Bm3/Bm4 (0.1% vs 0.3%; p = 0.006), compared with controls; Bm2 cells were the most frequently occurring B cells but they were not significantly different in active vasculitis (74% vs 62%; p = 0.083). In patients with remission the proportion of CD25+ B cells was increased compared to controls (48% vs 29%, respectively; p = 0.006) and also compared to active vasculitis (23%; p = 0.006). The proportion of CD86+ B cells was also increased (31%) compared to active vasculitis (8%; p = 0.001), and to controls (6%; p = 0.0003). In multivariate analysis, Bm2’ cells and CD25+27– B cells were independently influencing the patient group.

Conclusion.

In active vasculitis, a lower proportion of Bm1 cells may indicate activated B cells. Patients in remission had higher proportions of CD25+ (α-chain of interleukin 2 receptor) and CD86+ (costimulatory molecule) B cells. We suggest that these B cells may have a regulatory role, or alternatively may result from previous treatment.

Characterization of the metabolic phenotype of chronically activated lymphocytes

Activated lymphocytes proliferate, secrete cytokines, and can make antibodies. Normally activated B and T cells meet the bioenergetic demand for these processes by up-regulating aerobic glycolysis. In contrast, several lines of evidence suggest that pathogenic lymphocytes in autoimmune diseases like lupus meet ATP demands through oxidative phosphorylation. Using (13)C-glucose as a stable tracer, we found that splenocytes from mice with lupus derive the same fraction of lactate from glucose as control animals, suggesting comparable levels of glycolysis and non-oxidative ATP production. However, lupus splenocytes increase glucose oxidation by 40% over healthy control animals. The ratio between pentose phosphate cycle (PPC) activity and glycolysis is the same for each group, indicating that increased glucose oxidation is due to increased activity of the TCA cycle in lupus splenocytes. Repetitive stimulation of cultured human T cells was used to model chronic lymphocyte activation, a phenotype associated with lupus. Chronically activated T cells rely primarily on oxidative metabolism for ATP synthesis suggesting that chronic antigen stimulation may be the basis for the metabolic findings observed in lupus mice. Identification of disease-related bioenergetic phenotypes should contribute to new diagnostic and therapeutic strategies for immune diseases.

The immunological basis of B-cell therapy in systemic lupus erythematosus

Loss of B-cell tolerance is a hallmark feature of the pathogenesis in systemic lupus erythematosus (SLE), an autoimmune disease that is characterized by hypergammaglobulinemia and autoantibody production. These autoantibodies lead to formation of immune-complex deposition in internal organs causing inflammation and damage. Autoreactive B-cells are believed to be central in the pathophysiology of SLE. Other than its role in the production of antibodies that mediate humoral immune response, B-cells also function as antigen-presenting cells and are capable of activating T-cells. Activated B-cells may also produce pro-inflammatory cytokines that aggravate local inflammation. Abnormal B-cell homeostasis has been described in SLE patients. This may occur as a result of intrinsic B-cell defect or from aberrant regulation by maturation and survival signals. B-cell-based therapy is the current mainstream of research and development of novel therapies in SLE patients with severe and refractory disease. Potential cellular and molecular targets for B-cell therapies include cell surface molecules such as CD20 (rituximab) and CD22 (epratuzumab); co-stimulatory molecules involved in B-cell-T-cell interaction such as CTLA4 and B7 molecules (abatacept); maturation and growth factors such as B-cell activating factor and a proliferation-inducing ligand (belimumab, briobacept, atacicept) and B-cell tolerogen (abetimus). This article provides an overview on normal B-cell physiology and abnormal B-cell biology in SLE that form the immunological basis of B-cell-targeted therapy in the treatment of these patients with refractory diseases.

Validation of a high-throughput methodology to assess the effects of biomaterials on dendritic cell phenotype

A variety of combination products composed of biomaterials and biologics have been developed for tissue regeneration or vaccine delivery. The host immune response to the immunogenic biological components in such products may be modulated by the biomaterial component. Distinct biomaterials have been shown to differentially affect the maturation of dendritic cells (DCs). DCs are professional antigen-presenting cells (APCs) that bridge innate and adaptive immunity and play a central role in inducing immunity or initiating immune tolerance. However, the biomaterials systems used to study DC response thus far have been insufficient to draw a clear conclusion as to which biomaterial properties are the key to controlling DC phenotype. In this study, we developed a 96-well filter plate-based high-throughput (HTP) methodology to assess DC maturation upon biomaterial treatment. Equivalent biomaterial effects on DC phenotype were measured using the conventional flow cytometric and filter-plate method, which validated the HTP methodology. This methodology will be used to screen a large number of biomaterials simultaneously and to draw correlations between material properties and DC phenotype, thereby providing biomaterial design criteria and immunomodulatory strategies for both tissue engineering and vaccine delivery applications.

B cells from rheumatoid arthritis patients show important alterations in the expression of CD86 and FcgammaRIIb, which are modulated by anti-tumor necrosis factor therapy

Introduction

Several molecules help preserve peripheral B cell tolerance, but when altered, they may predispose to autoimmunity. This work studied the expression of the costimulatory molecule CD86 and the inhibitory receptor for IgG immune complexes FcγRIIb (CD32b), on B cells from rheumatoid arthritis (RA) patients, and the influence of anti-tumor necrosis factor (TNF) therapy.

Methods

Peripheral B cells from 18 RA patients and 13 healthy donors were characterized using flow cytometry. Eleven patients who underwent a six-month adalimumab therapy were further assessed for phenotypic changes on their B cells.

Results

RA patients exhibited a high percentage of naïve and memory B cells expressing CD86. In contrast, expression of FcγRIIb was significantly reduced on RA memory B cells and plasmablasts as compared to healthy donors, probably due to downregulation of this receptor when differentiating from naïve to memory cells. These alterations on FcγRIIb were associated with high levels of anti-citrullinated vimentin autoantibodies. In addition, treatment with adalimumab normalized the expression of CD86 on memory B cells and reduced the expression of FcγRIIb, mainly on naïve B cells.

Conclusions

Our findings show that peripheral B cells from RA patients have an altered expression of key molecules, such as CD86 and FcγRIIb. Because this latter receptor is required for feedback inhibition, a deficient expression might contribute to humoral autoimmune responses. Furthermore, these molecules are likely to be influenced by inflammatory factors, since they were modulated by TNF inhibition.

Reduced proportions of natural killer T cells are present in the relatives of lupus patients and are associated with autoimmunity

Introduction

Systemic lupus erythematosus is a genetically complex disease. Currently, the precise allelic polymorphisms associated with this condition remain largely unidentified. In part this reflects the fact that multiple genes, each having a relatively minor effect, act in concert to produce disease. Given this complexity, analysis of subclinical phenotypes may aid in the identification of susceptibility alleles. Here, we used flow cytometry to investigate whether some of the immune abnormalities that are seen in the peripheral blood lymphocyte population of lupus patients are seen in their first-degree relatives.

Methods

Peripheral blood mononuclear cells were isolated from the subjects, stained with fluorochrome-conjugated monoclonal antibodies to identify various cellular subsets, and analyzed by flow cytometry.

Results

We found reduced proportions of natural killer (NK)T cells among 367 first-degree relatives of lupus patients as compared with 102 control individuals. There were also slightly increased proportions of memory B and T cells, suggesting increased chronic low-grade activation of the immune system in first-degree relatives. However, only the deficiency of NKT cells was associated with a positive anti-nuclear antibody test and clinical autoimmune disease in family members. There was a significant association between mean parental, sibling, and proband values for the proportion of NKT cells, suggesting that this is a heritable trait.

Conclusions

The findings suggest that analysis of cellular phenotypes may enhance the ability to detect subclinical lupus and that genetically determined altered immunoregulation by NKT cells predisposes first-degree relatives of lupus patients to the development of autoimmunity.

Lentivirus-induced immune dysregulation

FIV/HIV infections are associated with an early robust humoral and cellular anti-viral immune response followed by a progressive immune suppression that eventually results in AIDS. Several mechanisms responsible for this immune dysfunction have been proposed including cytokine dysregulation, immunologic anergy and apoptosis, and inappropriate activation of immune regulatory cells. Studies on FIV infection provide evidence for all three. Cytokine alterations include decreases in IL2 and IL12 production and increases in IFNgamma and IL10 in FIV(+) cats compared to normal cats. The elevated IL10:IL12 ratio is associated with the inability of FIV(+) cats to mount a successful immune response to secondary pathogens. Additionally, chronic antigenic (FIV) stimulation results in an increase in the percent of activated T cells expressing B7 and CTLA4 co-stimulatory molecules in infected cats. The expression of these molecules is associated with T cells that are undergoing apoptosis in the lymph nodes. As ligation of CTLA4 by B7 transduces a signal for induction of anergy, one can speculate that the activated T cells are capable of T cell-T cell interactions resulting in anergy and apoptosis. The inability of CD4(+) cells from FIV(+) cats to produce IL2 in response to recall antigens and the gradual loss of CD4(+) cell numbers could be due to B7-CTLA4 interactions. The chronic antigenemia may also lead to activation of CD4(+)CD25(+) T regulatory cells. Treg cells from FIV(+) cats are chronically activated and inhibit the mitogen-induced proliferative response of CD4(+)CD25(-) by down-regulating IL2 production. Although Treg cell activation can be antigen-specific, the suppressor function is not, and thus activated Treg cells would suppress responses to secondary pathogens as well as to FIV. Concomitant with the well-known virus-induced immune suppression is a progressive immune hyper-activation. Evidence for immune hyper-activation includes polyclonal B cell responses, gradual replacement of naïve CD4(+) and CD8(+) T cell phenotypes with activation phenotypes (CD62L(-), B7(+), CTLA4(+)), and the chronic activation of CD4(+)CD25(+) Treg cells. Thus lentivirus infections lead to severe immune dysregulation manifested as both chronic immune suppression and chronic immune activation. FIV infection of cats provides a number of advantages over other lentivirus infections as a model to study this immune dysregulation. It is a natural infection that has existed in balance with the cat's immune system for thousands of years. As such, the natural history and pathogenesis provides an excellent model to study the long-term relationships between AIDS lentivirus and host immune system function/dysregulation.

Analyses of CD27++ plasma cells in peripheral blood from patients with bacterial infections and patients with serum antinuclear antibodies

The number of CD27⁺⁺ plasma cells (PCs) in peripheral blood may be a valuable biomarker for systemic lupus erythematosus (SLE) disease management. More insights into the behavior of the PC population are, however, required to validate CD27 as a reliable biomarker. In the current study, we have monitored the PC compartment of patients with acute bacterial infections and patients with SLE and, in addition, examined the relationship between the presence of serum antinuclear antibodies (ANAs) and the number of peripheral PCs. Kinetic analyses in patients with bacterial infection revealed a 10–60-fold expansion of the CD27⁺⁺ PC compartment that peaked at day 2–5 and returned toward normal values at day 7–9 after hospital admission. The transient expansion of the PC population appeared to be a late phenomenon in the process of recovering from a bacterial infection. SLE subjects had significantly increased frequencies of PCs compared with patients suspected of a connective tissue disease and healthy controls. In patients suspected of a connective tissue disease, no relationship was found between the presence of serum ANAs and the number of CD27⁺⁺ PCs. Additionally, the presence of serum ANAs was not associated with abnormalities in other peripheral B-cell subsets. It remains to be established at which stage of SLE development the expansion of the PC compartment is initiated.

A unique T cell subset described as CD4loCD40+ T cells (TCD40) in human type 1 diabetes

Human T1D pancreatic lymph nodes contain diabetes-autoantigen responsive T cells but identification of such T cells in the periphery has proven difficult. Here we describe a unique T cell subset defined by CD4(lo) and CD40 expression (T(CD40)) that is significantly expanded in peripheral blood of T1D but not control or T2D subjects. The HLA-DR3 and DR4 alleles are considered high risk factors for T1D and T(CD40) expansion occurs in T1D subjects carrying HLA DR3 or DR4 haplotypes but, T1D subjects who do not carry either DR3 or DR4 haplotypes still have an expanded percentage of T(CD40) cells. Non-autoimmune subjects, even DR3(+) and DR4(+), do not have elevated percentages of T(CD40) cells. The majority of T(CD40) cells in T1D carry a memory phenotype and a portion of those proliferates when exposed to diabetes-associated self-antigens. A greater number of memory T(CD40) cells express CXCR3 when compared to CD40(-) memory cells and that number is significantly expanded in T1D compared to control subjects. If only total CD4(+) T cells are compared no difference in CXCR3 is seen. Furthermore, T(CD40) cells produce a Th1, pro-inflammatory cytokine profile. In healthy controls, T(CD40) cells have equally Th1 and Th2 profiles.

Similar CD19 dysregulation in two autoantibody-associated autoimmune diseases suggests a shared mechanism of B-cell tolerance loss

: We report here that dysregulation of CD19, a coreceptor that augments B-cell receptor (BCR) signaling, occurs at two B-cell differentiative stages in patients with systemic lupus erythematosus (SLE) and antineutrophil cytoplasmic autoantibody (ANCA) associated small vessel vasculitis (SVV). The naïve B cells of nearly all SLE and ANCA-SVV patients express approximately 20% less CD19 than healthy control (HC) B cells. In contrast, a subset of memory B cells of some SLE and ANCA-SVV Pts (25-35%) express two to fourfold more CD19 than HC B cells. These CD19(hi) memory B cells are activated and exhibit evidence of antigen selection. Proteome array analysis of 67 autoantigens indicates that CD19(hi) SLE Pts exhibit a distinct autoantibody profile characterized by high levels of antibodies to small nuclear ribonucleoproteins and low levels of antiglomerular autoantibodies. These findings have implications for autoreactive B-cell activation and suggest a shared mechanism of B-cell tolerance loss in these two diseases.

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.

Efficacy of rituximab (anti-CD20) for refractory systemic lupus erythematosus involving the central nervous system

AIM

Neuropsychiatric systemic lupus erythematosus (NPSLE) is a serious treatment-resistant phenotype of systemic lupus erythematosus. A standard treatment for NPSLE is not available. This report describes the clinical and laboratory tests of 10 patients with NPSLE before and after rituximab treatment, including changes in lymphocyte phenotypes.

METHODS

Rituximab was administered at different doses in 10 patients with refractory NPSLE, despite intensive treatment.

RESULTS

Treatment with rituximab resulted in rapid improvement of central nervous system-related manifestations, particularly acute confusional state. Rituximab also improved cognitive dysfunction, psychosis and seizure, and reduced the SLE Disease Activity Index Score at day 28 in all 10 patients. These effects lasted for >1 year in five patients. Flow cytometric analysis showed that rituximab down regulated CD40 and CD80 on B cells and CD40L, CD69 and inducible costimulator on CD4+ T cells.

CONCLUSIONS

Rituximab rapidly improved refractory NPSLE, as evident by resolution of various clinical signs and symptoms and improvement of radiographic findings. The down regulation of functional molecules on B and T cells suggests that rituximab modulates the interaction of activated B and T cells through costimulatory molecules. These results warrant further analysis of rituximab as treatment for NPSLE.

Update on the treatment of lupus nephritis

Lupus nephritis (LN) is a major cause of morbidity and mortality in patients with systemic lupus erythematosus. Although the use of aggressive immunosuppression has improved both patient and renal survival over the past several decades, the optimal treatment of LN remains challenging. Improved outcomes have come at the expense of significant adverse effects owing to therapy. Moreover with long-term survival, the chronic adverse effects of effective therapies including risk of malignancy, atherosclerosis, infertility, and bone disease all become more important. Finally, some patients fail to achieve remission with standard cytotoxic therapy and others relapse when therapy is reduced. For these reasons, recent clinical trials have attempted to define alternate treatment protocols that appear to be efficacious in achieving and maintaining remission, but with less toxicity than standard regimens. This paper discusses established and newer treatment options for patients with proliferative and membranous LN, with an emphasis on the results of these recent clinical trials. We also review the experimental and human data regarding some of the novel targeted forms of therapy that are under investigation and in different phases of clinical trials.

Autoimmunity in systemic lupus erythematosus: integrating genes and biology

Susceptibility to the autoimmune phenotype of systemic lupus erythematosus (SLE) is heritable. Linkage analysis and recent advances in the field of single nucleotide polymorphisms (SNPs) have resulted in the identification of several genetic loci and functional allelic variants of signaling proteins which have become the mainstay of understanding disease susceptibility and exploring the basis of autoimmunity in SLE. However, genetic heterogeneity and possible epistatic interactions among genetic elements have precluded replication of these findings in multiple population groups and thus complicated their interpretation. In this regard, the discovery that a plethora of normal signaling proteins are expressed in abnormal amounts in immune cells from patients with SLE has gained significance. Thus, the key to precise elucidation of the pathologic basis of autoimmunity in SLE lies in tying genetics and disease biology. This review highlights recent discoveries of important functional genetic variants and altered expression of normal signaling proteins that network together to disrupt peripheral tolerance and initiate the autoimmune process in SLE.

Usefulness of liver infiltrating CD86-positive mononuclear cells for diagnosis of autoimmune hepatitis

AIM: Although the pathogenic mechanism underlying autoimmune hepatitis (AIH) remains unclear, the immune system is thought to be critical for the progression of the disease. Cellular immune responses may be linked to the hepatocellular damage in AIH. Recently, much attention has been focused on the critical functions of costimulatory molecules expressed on mononuclear cells in the generation of effective T cell-mediated immune responses. Analysis of costimulatory molecule expressed on mononuclear cells from the patients with AIH may give us insight into the pathogenic mechanism of hepatocellular damage in AIH.

METHODS: Peripheral blood mononuclear cells (PBMC) were taken from the patients with AIH (34 cases) and healthy controls (25 cases). Liver infiltrating mononuclear cells (LIMCs) were taken from the patients with AIH (18 cases), the patient with chronic hepatitis C (CH-C) (13 cases) and the patients with fatty liver (2 cases). Using flow cytometry, the cells were analyzed for the expression of costimulatory molecules, such as CD80, CD86, and CD152 (CTLA-4). The results were compared with clinical data such as the level of gammaglobulin, histological grade, presence or absence of corticosteroids administration and the response to corticosteroids.

RESULTS: The levels of CD80+, CD86+ and CD152+ PBMC were significantly reduced in the patients with AIH as compared with healthy controls. By contrast, those cells were significantly higher in LIMC than in PBMC of the patients with AIH. Especially, the level of CD86+ LIMC showed a marked increase irrespective of the degree of disease activity in the patients with AIH, although CD86+ cells were rarely present in PBMC. The levels of CD86+ cells were present in significantly higher frequency in patients with AIH than in the patients with CH-C. Furthermore, the patients with AIH with high levels of CD86+ LIMC showed good responses to corticosteroids, whereas 2 cases of AIH with low levels of CD86+ LIMC did not respond well.

CONCLUSION: These results suggest that LIMC over-expressing costimulatory molecules such as CD80 and CD86 appears to play a role in the pathogenesis of AIH. Especially, CD86 molecule expressed on the LIMC may be useful for the diagnosis of AIH and for the prediction of the therapeutic effects of corticosteroids on AIH.

Ligation of CD28 by its natural ligand CD86 in the absence of TCR stimulation induces lipid raft polarization in human CD4 T cells

Stimulation of resting CD4 T cells with anti-CD3/CD28-coated beads leads to rapid polarization of lipid rafts (LRs). It has been postulated that a major role of costimulation is to facilitate LR aggregation. CD86 is up-regulated or expressed aberrantly on immune cells in a wide array of autoimmune and infectious diseases. Using an Ig fusion with the extracellular domain of CD86 (CD86Ig) bound to a magnetic bead or K562 cells expressing CD86, we demonstrated that ligation of CD28 by its natural ligand, but not by Ab, induced polarization of LRs at the cell-bead interface of fresh human CD4 T cells in the absence of TCR ligation. This correlated with activation of Vav-1, increase of the intracellular calcium concentration, and nuclear translocation of NF-kappaB p65, but did not result in T cell proliferation or cytokine production. These studies show, for the first time, that LR polarization can occur in the absence of TCR triggering, driven solely by the CD28/CD86 interaction. This result has implications for mechanisms of T cell activation. Abnormalities in this process may alter T and B cell tolerance and susceptibility to infection.

Monocyte-derived dendritic cells over-express CD86 in patients with systemic lupus erythematosus

OBJECTIVES

Dendritic cells (DCs) play a key role in regulating immune responses, especially in priming naïve T-cells. Recently, DCs have been suggested to be involved in systemic lupus erythematosus (SLE) development by activating autoreactive T-helper lymphocytes. As a consequence, we compared the activation state of human monocyte-derived DCs (MDDCs) obtained from lupus patients and normal individuals.

METHODS

The MDDCs were generated in vitro from blood from healthy donors and lupus patients. Immature and mature MDDCs were analysed by flow cytometry for several cell surface molecules. In parallel, cytokine secretion was determined by ELISA before and after MDDC activation. In each experiment, lupus DCs were compared with normal DCs.

RESULTS

Here, we show for the first time that lupus MDDCs spontaneously over-express CD86 in the absence of any DC activation signal as compared with normal MDDCs (P = 0.025). Moreover, activation-induced IL-6 secretion was increased in lupus DCs with high CD86 over-expression as compared with normal DCs (P = 0.010). Interestingly, the percentage of MDDCs in lupus preparations is negatively correlated with disease activity scores (SLEDAI; P = 0.031).

CONCLUSIONS

Lupus MDDCs are pre-activated suggesting that they might be more efficient antigen-presenting cells. This result might partly explain how the peripheral tolerance is broken in SLE.

Functional Interplay between Intrinsic B and T Cell Defects Leads to Amplification of Autoimmune Disease in New Zealand Black Chromosome 1 Congenic Mice

Genetic loci on New Zealand Black (NZB) chromosome 1 play an important role in the development of lupus-like autoimmune disease. We have shown previously that C57BL/6 mice with an introgressed NZB chromosome 1 interval extending from approximately 35 to 106 cM have significantly more severe autoimmunity than mice with a shorter interval extending from approximately 82 to 106 cM. Comparison of the cellular phenotype in these mice revealed that both mouse strains had evidence of increased T cell activation; however, activation was more pronounced in mice with the longer interval. Mice with the longer interval also had increased B cell activation, leading us to hypothesize that there were at least two independent lupus susceptibility loci on chromosome 1. In this study, we have used mixed hemopoietic radiation chimeras to demonstrate that autoimmunity in these mice arises from intrinsic B and T cell functional defects. We further show that a T cell defect, localized to the shorter interval, leads to spontaneous activation of T cells specific for nucleosome histone components. Despite activation of self-reactive T cells in mixed chimeric mice, only chromosome 1 congenic B cells produce anti-nuclear Abs and undergo class switching, indicating impaired B cell tolerance mechanisms. In mice with the longer chromosome 1 interval, an additional susceptibility locus exacerbates autoimmune disease by producing a positive feedback loop between T and B cell activation. Thus, T and B cell defects act in concert to produce and amplify the autoimmune phenotype.

EBV and systemic lupus erythematosus: a new perspective

We have proposed that EBV uses mature B cell biology to access memory B cells as a site of persistent infection. A central feature of this model is that EBV adapts its gene expression profile to the state of the B cell it resides in and that the level of infection is stable over time. This led us to question whether changes in the behavior or regulation of mature B cells would alter the state of EBV persistence. To investigate this, we studied the impact of systemic lupus erythematosus (SLE), a disease characterized by immune dysfunction, on EBV infection. We show that patients with SLE have abnormally high frequencies of EBV-infected cells in their blood, and this is associated with the occurrence of SLE disease flares. Although patients with SLE have frequencies of infected cells comparable to those seen in immunosuppressed patients, in SLE the effect was independent of immunosuppressive therapy. Aberrant expression of viral lytic (BZLF1) and latency (latency membrane proteins 1 and 2a) genes was also detected in the blood of SLE patients. We conclude that the abnormal regulation of EBV infection in SLE patients reflects the sensitivity of the virus to perturbation of the immune system.

Rituximab improves peripheral B cell abnormalities in human systemic lupus erythematosus

OBJECTIVE

B lymphocyte depletion has recently emerged as a promising approach to the treatment of systemic lupus erythematosus (SLE). As part of a phase I/II dose-ranging trial of rituximab in the treatment of SLE, we evaluated the fate of discrete B cell subsets in the setting of selective depletion by anti-CD20 monoclonal antibody and during the B cell recovery phase.

METHODS

B cell depletion and phenotype were examined by flow cytometry of peripheral blood mononuclear cells for CD19, CD20, CD27, IgD, and CD38 expression. Changes in autoreactive B lymphocytes and plasma cells were assessed by determination of serum autoantibody levels (anti-double-stranded DNA and VH4.34) and by direct monitoring of a unique autoreactive B cell population bearing surface antibodies whose heavy chain is encoded by the VH4.34 gene segment.

RESULTS

Compared with normal controls, SLE patients displayed several abnormalities in peripheral B cell homeostasis at baseline, including naive lymphopenia, expansion of a CD27-,IgD- (double negative) population, and expansion of circulating plasmablasts. Remarkably, these abnormalities resolved after effective B cell depletion with rituximab and immune reconstitution. The frequency of autoreactive VH4.34 memory B cells also decreased 1 year posttreatment, despite the presence of low levels of residual memory B cells at the point of maximal B cell depletion and persistently elevated serum autoantibody titers in most patients.

CONCLUSION

This study is the first to show evidence that in SLE, specific B cell depletion therapy with rituximab dramatically improves abnormalities in B cell homeostasis and tolerance that are characteristic of this disease. The persistence of elevated autoantibody titers may reflect the presence of low levels of residual autoreactive memory B cells and/or long-lived autoreactive plasma cells.