T cell determinants from autoantibodies to DNA can upregulate autoimmunity in murine systemic lupus erythematosus

SLE: a cognitive step forward-a synthesis of rethinking theories, causality, and ignored DNA structures

Systemic lupus erythematosus (SLE) is classified by instinctual classification criteria. A valid proclamation is that these formally accepted SLE classification criteria legitimate the syndrome as being difficult to explain and therefore enigmatic. SLE involves scientific problems linked to etiological factors and criteria. Our insufficient understanding of the clinical condition uniformly denoted SLE depends on the still open question of whether SLE is, according to classification criteria, a well-defined one disease entity or represents a variety of overlapping indistinct syndromes. Without rational hypotheses, these problems harm clear definition(s) of the syndrome. Why SLE is not anchored in logic, consequent, downstream interdependent and interactive inflammatory networks may rely on ignored predictive causality principles. Authoritative classification criteria do not reflect consequent causality criteria and do not unify characterization principles such as diagnostic criteria. We need now to reconcile legendary scientific achievements to concretize the delimitation of what SLE really is. Not all classified SLE syndromes are "genuine SLE"; many are theoretically "SLE-like non-SLE" syndromes. In this study, progressive theories imply imperative challenges to reconsider the fundamental impact of "the causality principle". This may offer us logic classification and diagnostic criteria aimed at identifying concise SLE syndromes as research objects. Can a systems science approach solve this problem?

Bischoff D, S Singh S, H. Hahn B. Peptide-based immunotherapy in lupus: Where are we now?

In autoimmune rheumatic diseases, immune hyperactivity and chronic inflammation associate with immune dysregulation and the breakdown of immune self-tolerance. A continued, unresolved imbalance between effector and regulatory immune responses further exacerbates inflammation that ultimately causes tissue and organ damage. Many treatment modalities have been developed to restore the immune tolerance and immmunoregulatory balance in autoimmune rheumatic diseases, including the use of peptide-based therapeutics or the use of nanoparticles-based nanotechnology. This review summarizes the state-of-the-art therapeutic use of peptide-based therapies in autoimmune rheumatic diseases, with a specific focus on lupus.

Therapeutic peptides for the treatment of systemic lupus erythematosus: a place in therapy

INTRODUCTION

Studies in vitro and in vivo have identified several peptides that are potentially useful in treating systemic lupus erythematosus (SLE). The rationale for their use lies in the cost-effective production, high potency, target selectivity, low toxicity, and a peculiar mechanism of action that is mainly based on the induction of immune tolerance. Three therapeutic peptides have entered clinical development, but they have yielded disappointing results. However, some subsets of patients, such as those with the positivity of anti-dsDNA antibodies, appear more likely to respond to these medications.

AREAS COVERED

This review evaluates the potential use of therapeutic peptides for SLE and gives an opinion on how they may offer advantages for SLE treatment.

EXPERT OPINION

Given their acceptable safety profile, therapeutic peptides could be added to agents traditionally used to treat SLE and this may offer a synergistic and drug-sparing effect, especially in selected patient populations. Moreover, they could temporarily be utilized to manage SLE flares, or be administered as a vaccine in subjects at risk. Efforts to ameliorate bioavailability, increase the half-life and prevent immunogenicity are ongoing. The formulation of hybrid compounds, like peptibodies or peptidomimetic small molecules, is expected to yield renewed treatments with a better pharmacologic profile and increased efficacy.

Triggers of Autoimmunity: The Role of Bacterial Infections in the Extracellular Exposure of Lupus Nuclear Autoantigens

Infections are considered important environmental triggers of autoimmunity and can contribute to autoimmune disease onset and severity. Nucleic acids and the complexes that they form with proteins—including chromatin and ribonucleoproteins—are the main autoantigens in the autoimmune disease systemic lupus erythematosus (SLE). How these nuclear molecules become available to the immune system for recognition, presentation, and targeting is an area of research where complexities remain to be disentangled. In this review, we discuss how bacterial infections participate in the exposure of nuclear autoantigens to the immune system in SLE. Infections can instigate pro-inflammatory cell death programs including pyroptosis and NETosis, induce extracellular release of host nuclear autoantigens, and promote their recognition in an immunogenic context by activating the innate and adaptive immune systems. Moreover, bacterial infections can release bacterial DNA associated with other bacterial molecules, complexes that can elicit autoimmunity by acting as innate stimuli of pattern recognition receptors and activating autoreactive B cells through molecular mimicry. Recent studies have highlighted SLE disease activity-associated alterations of the gut commensals and the expansion of pathobionts that can contribute to chronic exposure to extracellular nuclear autoantigens. A novel field in the study of autoimmunity is the contribution of bacterial biofilms to the pathogenesis of autoimmunity. Biofilms are multicellular communities of bacteria that promote colonization during chronic infections. We review the very recent literature highlighting a role for bacterial biofilms, and their major components, amyloid/DNA complexes, in the generation of anti-nuclear autoantibodies and their ability to stimulate the autoreactive immune response. The best studied bacterial amyloid is curli, produced by enteric bacteria that commonly cause infections in SLE patients, including Escherichia coli and Salmonella spps. Evidence suggests that curli/DNA complexes can trigger autoimmunity by acting as danger signals, molecular mimickers, and microbial chaperones of nucleic acids.

Regulatory T cells in immune-mediated renal disease

Regulatory T cells (Tregs) are CD4+ T cells that can suppress immune responses by effector T cells, B cells and innate immune cells. This review discusses the role that Tregs play in murine models of immune-mediated renal diseases and acute kidney injury and in human autoimmune kidney disease (such as systemic lupus erythematosus, anti-glomerular basement membrane disease, anti-neutrophil cytoplasmic antibody-associated vasculitis). Current research suggests that Tregs may be reduced in number and/or have impaired regulatory function in these diseases. Tregs possess several mechanisms by which they can limit renal and systemic inflammatory immune responses. Potential therapeutic applications involving Tregs include in vivo induction of Tregs or inducing Tregs from naïve CD4+ T cells or expanding natural Tregs ex vivo, to use as a cellular therapy. At present, the optimal method of generating a phenotypically stable pool of Tregs with long-lasting suppressive effects is not established, but human studies in renal transplantation are underway exploring the therapeutic potential of Tregs as a cellular therapy, and if successful may have a role as a novel therapy in immune-mediated renal diseases.

Leptin promotes systemic lupus erythematosus by increasing autoantibody production and inhibiting immune regulation

Leptin is an adipocytokine that plays a key role in the modulation of immune responses and the development and maintenance of inflammation. Circulating levels of leptin are elevated in systemic lupus erythematosus (SLE) patients, but it is not clear whether this association can reflect a direct influence of leptin on the propathogenic events that lead to SLE. To investigate this possibility, we compared the extent of susceptibility to SLE and lupus manifestations between leptin-deficient (ob/ob) and H2-matched leptin-sufficient (wild-type, WT) mice that had been treated with the lupus-inducing agent pristane. Leptin deficiency protected ob/ob mice from the development of autoantibodies and renal disease and increased the frequency of immunoregulatory T cells (Tregs) compared with leptin-sufficient WT mice. The role of leptin in the development of SLE was confirmed in the New Zealand Black (NZB) × New Zealand White (NZW)F1 (NZB/W) mouse model of spontaneous SLE, where elevated leptin levels correlated with disease manifestations and the administration of leptin accelerated development of autoantibodies and renal disease. Conversely, leptin antagonism delayed disease progression and increased survival of severely nephritic NZB/W mice. At the cellular level, leptin promoted effector T-cell responses and facilitated the presentation of self-antigens to T cells, whereas it inhibited the activity of regulatory CD4 T cells. The understanding of the role of leptin in modulating autoimmune responses in SLE can open possibilities of leptin-targeted therapeutic intervention in the disease.

BLyS antagonists and peptide tolerance induction

The major impediment to drug development for systemic lupus erythematosus (SLE) is its heterogeneity. The unpredictable manner in which lupus targets different organs at varying intensity makes the study of new drugs and the optimization of their administration extremely difficult. With the advent of novel, targeted biologic agents for SLE, it can be hoped that more strategic, lupus-relevant immune modulation will lead to safer and more effective treatments. Two alternative new approaches to lupus treatment are reviewed. The first involves selective inhibition of a single protein (BLyS), which may play a central role in host defense and in the pathogenesis of SLE. Although this approach is finely targeted to the inhibition of a single protein which is known to be upregulated in SLE patients, the positioning of BLyS at a critical hub in the immune response suggests that more global adverse repercussions on immunity might still occur. The second strategy is the use of peptides designed to specifically induce tolerance in limited autoreactive immune responses. Immune repercussions might, at least in theory, be almost nonexistent with this kind of approach. Concerns that limited induction of tolerance might have equally limited impact on the complex immune disorder of SLE are not borne out in preliminary murine data. Specific development programs are ongoing using both of these strategies and have recently entered human trials.

T cell vaccination in systemic lupus erythematosus with autologous activated T cells

Systemic lupus erythematosus (SLE) is an autoreactive T cell mediated autoimmune disease. Immunization with inactivated autoreactive T cells may induce idiotype anti-idiotypic reaction to deplete specific subsets of autoreactive T cells involved in SLE. Six SLE patients unsuitable or refused to use immunosuppressants were treated with T cell vaccination. Their clinical manifestations and laboratory parameters including mixed lymphocyte reactions were evaluated. Autoreactive T cell clones were derived from peripheral blood mononuclear cells of the patients and 1 × 107 irradiated T cells were inoculated subcutaneously at 0, two, six and eight weeks, respectively. The enrolled patients were followed up for 32-40 months at an interval of three to six months. The clinical characteristics and laboratory abnormalities improved after inoculation without increasing the dose of corticosteroids and immunosuppressants in most patients. SLE disease activity index (SLEDAI) scores decreased. Proliferative responses against the T cell vaccine were observed in four of six patients. At the time of this report, the six patients remain in clinical remission. No significant side effect from the vaccination was noticed during the follow-up period. The results of this pilot study indicate that T cell vaccination is a safe and effective treatment in SLE.

Inhibition of BTK and ITK with Ibrutinib Is Effective in the Prevention of Chronic Graft-versus-Host Disease in Mice

Bruton’s Tyrosine Kinase (BTK) and IL-2 Inducible T-cell Kinase (ITK) are enzymes responsible for the phosphorylation and activation of downstream effectors in the B-cell receptor (BCR) signaling and T cell receptor (TCR) signaling pathways, respectively. Ibrutinib is an FDA-approved potent inhibitor of both BTK and ITK that impairs B-cell and T-cell function. CD4 T cells and B cells are essential for the induction of chronic graft-versus-host disease (cGVHD). We evaluated these targets by testing the ability of Ibrutinib to prevent or ameliorate cGVHD, which is one of the major complications for patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT). We found that Ibrutinib significantly alleviated cGVHD across four different mouse models, accompanied by increased long-term survival and reduced clinical score. The clinical improvements in Ibrutinib-treated recipients were associated with decreased serum-autoantibodies, costimulatory molecule activation, B-cell proliferation, and glomerulonephritis compared to vehicle controls. Ibrutinib was also able to alleviate the clinical manifestations in acute GVHD (aGVHD), where the recipients were given grafts with or without B cells, suggesting that an inhibitory effect of Ibrutinib on T cells contributes to a reduction in both aGVHD and cGVHD pathogenesis. An effective prophylactic regimen is still lacking to both reduce the incidence and severity of human cGVHD following allo-HSCT. Our study shows that Ibrutinib is an effective prophylaxis against several mouse models of cGVHD with minimal toxicity and could be a promising strategy to combat human cGVHD clinically.

Systemic Lupus Erythematosus: Molecular Mimicry between Anti-dsDNA CDR3 Idiotype, Microbial and Self Peptides-As Antigens for Th Cells

Systemic lupus erythematosus (SLE) is marked by a T helper (Th) cell-dependent B cell hyperresponsiveness, with frequent germinal center reactions, and gammaglobulinemia. A feature of SLE is the finding of IgG autoantibodies specific for dsDNA. The specificity of the Th cells that drive the expansion of anti-dsDNA B cells is unresolved. However, anti-microbial, anti-histone, and anti-idiotype Th cell responses have been hypothesized to play a role. It has been entirely unclear if these seemingly disparate Th cell responses and hypotheses could be related or unified. Here, we describe that H chain CDR3 idiotypes from IgG⁺ B cells of lupus mice have sequence similarities with both microbial and self peptides. Matched sequences were more frequent within the mutated CDR3 repertoire and when sequences were derived from lupus mice with expanded anti-dsDNA B cells. Analyses of histone sequences showed that particular histone peptides were similar to VDJ junctions. Moreover, lupus mice had Th cell responses toward histone peptides similar to anti-dsDNA CDR3 sequences. The results suggest that Th cells in lupus may have multiple cross-reactive specificities linked to the IgVH CDR3 Id-peptide sequences as well as similar DNA-associated protein motifs.

Invariant natural killer T cells in lupus patients promote IgG and IgG autoantibody production

IgG autoantibodies, including antibodies to double-stranded DNA (dsDNA), are pathogenic in systemic lupus erythematosus (SLE), but the mechanisms controlling their production are not understood. To assess the role of invariant natural killer T (iNKT) cells in this process, we studied 44 lupus patients. We took advantage of the propensity of PBMCs from patients with active disease to spontaneously secrete IgG in vitro. Despite the rarity of iNKT cells in lupus blood (0.002-0.05% of CD3-positive T cells), antibody blockade of the conserved iNKT TCR or its ligand, CD1d, or selective depletion of iNKT cells, inhibited spontaneous secretion of total IgG and anti-dsDNA IgG by lupus PBMCs. Addition of anti-iNKT or anti-CD1d antibody to PBMC cultures also reduced the frequency of plasma cells, suggesting that lupus iNKT cells induce B-cell maturation. Like fresh iNKT cells, expanded iNKT-cell lines from lupus patients, but not healthy subjects, induced autologous B cells to secrete antibodies, including IgG anti-dsDNA. This activity was inhibited by anti-CD40L antibody, as well as anti-CD1d antibody, confirming a role for CD40L-CD40 and TCR-CD1d interactions in lupus iNKT-cell-mediated help. These results reveal a critical role for iNKT cells in B-cell maturation and autoantibody production in patients with lupus.

Idiotype-specific Th cells support oligoclonal expansion of anti-dsDNA B cells in mice with lupus

Systemic lupus erythematosus (SLE) is marked by a Th cell-dependent B cell hyperresponsiveness, with frequent germinal center reactions and hypergammaglobulinemia. The specificity of Th cells in lupus remains unclear, but B cell Ids have been suggested. A hallmark is the presence of anti-dsDNA, mutated IgG autoantibodies with a preponderance of arginines in CDR3 of the Ig variable H chain (IgVH). B cells can present V region-derived Id peptides on their MHC class II molecules to Id-specific Th cells. We show that Id-specific Th cells support the proliferation of anti-dsDNA Id(+) B cells in mice suffering from systemic autoimmune disease with SLE-like features. Mice developed marked clonal expansions of B cells; half of the IgVH sequences were clonally related. Anti-dsDNA B cells made up 40% of B cells in end-stage disease. The B cells expressed mutated IgVH with multiple arginines in CDR3. Hence, Id-driven T cell-B cell collaboration supported the production of classical anti-dsDNA Abs, recapitulating the characteristics of such Abs in SLE. The results support the concept that Id-specific Th cells may trigger the development of SLE and suggest that manipulation of the Id-specific T cell repertoire could play a role in treatment.

Leptin promotes lupus T-cell autoimmunity

In systemic lupus erythematosus (SLE), the impairment in apoptosis can facilitate the initiation and maintenance of autoimmune responses to self antigens. Here we show that the adipocytokine leptin, which is abnormally elevated in SLE, promotes the survival and proliferation of autoreactive T-cells in mice with an autoreactive T-cell repertoire, including (NZB x NZW)F1 lupus-prone mice. This ability of leptin to promote lupus T-cell autoimmunity suggests the possibility of a therapeutic targeting of leptin in SLE.

Blockade of programmed death-1 in young (New Zealand Black x New Zealand White)F1 mice promotes the suppressive capacity of CD4+ regulatory T cells protecting from lupus-like disease

Programmed death-1 (PD-1) usually acts as a negative signal for T cell activation, and its expression on CD8(+)Foxp3(+) T cells is required for their suppressive capacity. In this study, we show that PD-1 signaling is required for the maintenance of functional regulatory CD4(+)CD25(+)Foxp3(+) regulatory T cells (CD4(+) T(reg)) that can control autoimmunity in (New Zealand Black × New Zealand White)F1 lupus mice. PD-1 signaling induced resistance to apoptosis and prolonged the survival of CD4(+) T(reg). In vivo, the blockade of PD-1 with a neutralizing Ab reduced PD-1 expression on CD4(+) T(reg) (PD1(lo)CD4(+) T(reg)). PD1(lo)CD4(+) T(reg) had an increased ability to promote B cell apoptosis and to suppress CD4(+) Th as compared with CD4(+) T(reg) with elevated PD-1 expression (PD1(hi)CD4(+) T(reg)). When PD-1 expression on CD4(+) T(reg) was blocked in vitro, PD1(lo)CD4(+) T(reg) suppressed B cell production of IgG and anti-dsDNA Ab. Finally, in vitro studies showed that the suppressive capacity of CD4(+) T(reg) depended on PD-1 expression and that a fine-tuning of the expression of this molecule directly affected cell survival and immune suppression. These results indicate that PD-1 expression has multiple effects on different immune cells that directly contribute to a modulation of autoimmune responses.

Germline deletion of β2 microglobulin or CD1d reduces anti-phospholipid antibody, but increases autoantibodies against non-phospholipid antigens in the NZB/W F1 model of lupus

Introduction

β2-microglobulin (β2m) is required for the surface expression of MHC class I and class I-like proteins such as CD1d, Qa1 and neonatal Fc receptor (FcRn), all of which may impact the development of autoimmunity. Since CD1d is known to bind and present phospholipid antigens to T cells, we asked if the deficiency of β2m or CD1d will impact the development of anti-phospholipid antibodies as compared to other aspects of lupus autoimmunity.

Methods

We introgressed the β2m-null genotype onto the NZB and NZW backgrounds for 12 to 14 generations to generate genetically lupus-susceptible (NZB/NZW)F1 (BWF1) mice that are β2m-deficient (β2m°). Circulating immunoglobulins (Ig), rheumatoid factor (RF), anti-DNA and anti-cardiolipin (anti-CL) antibodies, and renal disease were analyzed in these and CD1d-deficient (CD1d°) BWF1 mice that we had previously generated.

Results

Whereas β2m° BWF1 mice had reduced serum IgG, they had increased mortality, nephritis, serum IgG anti-DNA antibody and RF as compared to heterozygous and wild-type littermates. These effects were recapitulated in CD1d° BWF1 mice, except that they also had increased serum IgG as compared to control littermates. Intriguingly, both β2m° and CD1d° mice had lower serum anti-CL antibody levels than in control littermates. Such CD1d dependence of anti-CL antibody production is not mediated by CD1d/glycolipid-reactive iNKT cells, as these cells reduced the production of RF and anti-DNA antibodies but had no effect on anti-CL antibodies.

Conclusions

We report a novel dichotomous role of β2m and CD1d, whereby these molecules differently regulate autoimmunity against phospholipid versus non-phospholipid autoantigens.

Somatic mutagenesis in autoimmunity

Our laboratory investigates systemic autoimmune disease in the context of mouse models of systemic lupus erythematosus (SLE). SLE is associated with high titers of serum autoantibodies of the IgG class that are predominantly directed against nuclear antigens, with pathological manifestations that are considered by many to be characteristic of an immune-complex mediated disease. In this review, we focus on the known and potential roles of somatic mutagenesis in SLE. We will argue that anti-nuclear antibodies (ANA) arise predominantly from nonautoreactive B cells that are transformed into autoreactive cells by the process of somatic hypermutation (SHM), which is normally associated with affinity maturation during the germinal center reaction. We will also discuss the role of SHM in creating antigenic peptides in the V region of the B cell receptor (BCR) and its potential to open an avenue of unregulated T cell help to autoreactive B cells. Finally, we will end this review with new experimental evidence suggesting that spontaneous somatic mutagenesis of genes that regulate B cell survival and activation is a rate-limiting causative factor in the development of ANA.

Fate determination of mature autoreactive B cells

A large antibody repertoire is generated in developing B cells in the bone marrow. Before these B cells achieve immunocompetence, those expressing autospecificities must be purged. To that end, B cells within the bone marrow and just following egress from the bone marrow are subject to tolerance induction. Once B cells achieve immunocompetence, the antibody repertoire can be further diversified by somatic hypermutation of immunoglobulin genes in B cells that have been activated by antigen and cognate T cell help and have undergone a germinal center (GC) response. This process also leads to the generation of autoreactive B cells which must be again purged to protect the host. Thus, B cells within the GC and just following egress from the GC are also subject to tolerance induction. Available data suggest that B cell intrinsic processes triggered by signaling through the B cell receptor activate tolerance mechanisms at both time points. Recent data suggest that GC and post-GC B cells are also subject to B cell extrinsic tolerance mechanisms mediated through soluble and membrane-bound factors derived from various T cell subsets.

Sercarzian immunology--In memoriam. Eli E. Sercarz, 1934-2009

During his long career as a principal investigator and educator, Eli Sercarz trained over 100 scientists. He is best known for developing hen egg white lysozyme (HEL) as a model antigen for immunologic studies. Working in his model system Eli furthered our understanding of antigen processing and immunologic tolerance. His work established important concepts of how the immune system recognizes antigenic determinants processed from whole protein antigens; specifically he developed the concepts of immunodominance and crypticity. Later in his career he focused more on autoimmunity using a variety of established animal models to develop theories on how T cells can circumvent tolerance induction and how an autoreactive immune response can evolve over time. His theory of "determinant spreading" is one of the cornerstones of our modern understanding of autoimmunity. This review covers Eli's entire scientific career outlining his many seminal discoveries.

Aborted germinal center reactions and B cell memory by follicular T cells specific for a B cell receptor V region peptide

A fundamental problem in immunoregulation is how CD4(+) T cells react to immunogenic peptides derived from the V region of the BCR that are created by somatic mechanisms, presented in MHC II, and amplified to abundance by B cell clonal expansion during immunity. BCR neo Ags open a potentially dangerous avenue of T cell help in violation of the principle of linked Ag recognition. To analyze this issue, we developed a murine adoptive transfer model using paired donor B cells and CD4 T cells specific for a BCR-derived peptide. BCR peptide-specific T cells aborted ongoing germinal center reactions and impeded the secondary immune response. Instead, they induced the B cells to differentiate into short-lived extrafollicular plasmablasts that secreted modest quantities of Ig. These results uncover an immunoregulatory process that restricts the memory pathway to B cells that communicate with CD4 T cells via exogenous foreign Ag.

Galectin-1-induced down-regulation of T lymphocyte activation protects (NZB x NZW) F1 mice from lupus-like disease

Systemic lupus erythematosus (SLE) is a complex autoimmune disease characterized by a hyperactive immune system, including activation of autoreactive T and B cells. These studies demonstrate that administration of recombinant galectin-1, a β-galactose binding protein, to SLE-prone (NZB × NZW) F1 mice reduced lymphocyte activation, inhibited serum anti-double-stranded DNA(dsDNA) IgG antibody production, decreased the incidence of proteinuria, and increased survival rate. In addition, recombinant galectin-1'-treated mice had a higher frequency of Foxp3 expression, which suggested an increase in the percentage of peripheral regulatory T cells. Consistent with the finding that there were fewer activated T lymphocytes, ex vivo T cells from mice treated with recombinant galectin-1 exhibited less proliferation in response to TCR stimulation. Furthermore, these cells were less efficient at lipid raft clustering in response to TCR/CD28 engagement, consistent with published reports that galectin-1 can reorganize the synaptic contact to interfere with TCR signaling and activation to prevent T cell activation. Aged galectin-1-deficient mice had higher serum levels of antibodies against dsDNA, elucidating a role for endogenous galectin-1 in decreasing susceptibility to autoimmunity. Together, the findings highlight galectin-1 as a novel potential therapeutic immune modulator for treatment of lupus-like disease.

Invariant NKT cells inhibit autoreactive B cells in a contact- and CD1d-dependent manner

Autoantibody production is a hallmark of autoimmune diseases, such as lupus and rheumatoid arthritis. Accumulating evidence suggests a role of invariant NKT (iNKT) cells in their pathogenesis. Mechanisms underlying the role of iNKT cells in these diseases, however, remain unclear. In this study, we show that iNKT cells suppress IgG anti-DNA Ab and rheumatoid factor production and reduce IL-10-secreting B cells in a contact-dependent manner, but increase total IgG production and enhance activation markers on B cells via soluble factors. In vivo reconstitution with iNKT cells also reduces autoantibody production in iNKT-deficient mice and in SCID mice implanted with B cells. Using an anti-DNA transgenic model, we found that autoreactive B cells spontaneously produce IL-10 and are activated in vivo. In the presence of activated iNKT cells, these autoreactive B cells are selectively reduced, whereas nonautoreactive B cells are markedly activated. Because iNKTs recognize CD1d, we reasoned that CD1d might play a role in the differential regulation of autoreactive versus nonautoreactive B cells by iNKT cells. Indeed, autoreactive B cells express more CD1d than nonautoreactive B cells, and CD1d deficiency in lupus mice exacerbates autoantibody production and enhances Ab response to a self-peptide but not to a foreign peptide. Importantly, iNKT cells fail to inhibit autoantibody production by CD1d-deficient B cells. Thus, iNKT cells inhibit autoreactive B cells in a contact- and CD1d-dependent manner but activate nonautoreactive B cells via cytokines. Such ability of iNKTs to suppress autoantibody production, without causing global suppression of B cells, has important implications for the development of iNKT-based therapy for autoimmune diseases.

Spontaneous autoimmunity in mice that carry an IghV partial transgene: a required arginine in VHCDR3

We describe a unique spontaneous mouse model of autoimmunity, which occurs on a non-autoimmune-prone SWR genetic background. In this model, SWR mice carry an IghV partial transgene (pTg) encoding only the heavy chain variable domain of an antibody directed against chromatin. Autoimmune disease in pTg mice was manifested by some of the features of systemic lupus erythematosus (SLE), including the presence of serum anti-nuclear antibodies, splenomegaly, skin lesions and a moderate degree of kidney pathology, in various combinations among individuals. Autoimmunity was observed in three independent transgenic lines, but not in three control lines carrying a nearly identical pTg, in which a VHCDR3 codon for Arg was replaced by one for Ser to ablate chromatin reactivity. Various features of disease were often but not always accompanied by anti-chromatin antibodies. Unexpectedly, the anti-chromatin antibodies detected in seropositive animals were not encoded by the pTg. These observations strongly implicate a role for the transgene product in disease initiation but not necessarily for end-state pathology, and they raise the possibility that autoreactive B cells may play a previously unappreciated role in initiating the development of systemic autoimmunity.

Tracking early autoimmune disease by bioluminescent imaging of NF-kappaB activation reveals pathology in multiple organ systems

It is desirable to have an early and sensitive detection marker of autoimmune disease in intact animals. Nuclear factor (NF)-kappaB is a transcription factor that is associated with inflammatory responses and immune disorders. Previously, we demonstrated that so-called idiotypic-driven T-B cell collaboration in mice doubly transgenic for paired immunoglobulin and T cell receptor transgenes resulted in a systemic autoimmune disease with systemic lupus erythematosus-like features. Here, we investigated NF-kappaB activation by including an NF-kappaB-responsive luciferase reporter transgene in this animal model. Triply transgenic mice developed bioluminescence signals from diseased organs before onset of clinical symptoms and autoantibody production, and light emissions correlated with disease progression. Signals were obtained from secondary lymphoid organs, inflamed intestines, skin lesions, and arthritic joints. Moreover, bioluminescence imaging and immunohistochemistry demonstrated that a minority of mice suffered from an autoimmune disease of the small intestine, in which light emissions correlated with antibodies against tissue transglutaminase and gliadin. Detection of luciferase by immunohistochemistry revealed NF-kappaB activation in collaborating B and T cells, as well as in macrophages. These results demonstrate that bioluminescent in vivo imaging of NF-kappaB activation can be used for early and sensitive detection of autoimmune disease in an experimental mouse model, offering new possibilities for the evaluation of anti-inflammatory drugs.

Idiotope-specific CD4(+) T cells induce apoptosis of human oligodendrocytes

CD4(+) T cells specific for immunologic non-self determinants on self-IgG, idiotopes (Id), can be raised from cerebrospinal fluid (CSF) and blood of patients with multiple sclerosis (MS). To test if Id-specific CD4(+) T cells have the potential to destroy oligodendrocytes (ODCs), we analyzed their ability to induce apoptosis of human ODC cell lines. Id-specific CD4(+) T cells stimulated with either Id-bearing B cells, Id-peptide presented by other antigen presenting cells, or by anti-CD3/anti-CD28 in the absence of accessory cells induced DNA fragmentation and killed ODCs. Killing required contact between the ODCs and the T cells, it did not depend on the cytokine profile of the T cells, it was independent of other cell types, and was inhibited by a general caspase inhibitor and an anti-Fas antibody. Activated CD4(+) T cells specific for glutamic acid decarboxylase 65 also induced apoptosis, showing that killing does not depend on cognate interaction between T cells and target cells but rather on the activation status of the T cells.

Expansion of immunoglobulin autoreactive T-helper cells in multiple myeloma

Activation and expansion of T helper (Th) cells followed by regulation of activation are essential to the generation of immune responses while limiting concomitant autoreactivity. In order to characterize T cells reactive towards myeloma-derived monoclonal immunoglobulin (mIg), an autologous coculture assay for single-cell analysis of mIg-responding cells was developed. When cultured with dendritic cells loaded with mIg, CD4(+) Th cells from patients with progressing multiple myeloma (MM) showed a proliferative MHC class II-dependent response. CD8(+) T-cell reactivity and Th1 activation were consistently low or absent, and Th2 and regulatory cytokines were expressed. The presence of such non-Th1 CD4(+) T cells in peripheral blood was independent of treatment status, while the frequencies of responding cells varied between patients and reached the same order of magnitude as those measured for tetanus toxoid-specific Th memory cells. Furthermore, investigations of T-cell subpopulations indicated a possible regulatory role on the mIg responsiveness mediated by suppressive CD25(high)FOXP3(+)CD4(+) T cells. It is proposed from the present results that a predominant in vivo activation of non-Th1 mIg-reactive CD4(+) T cells constitute an Ig-dependent autoregulatory mechanism in human MM, with possible tumor growth supporting or permissive effects.

Immunization with peptides derived from the idiotypic region of lupus-associated autoantibodies delays the development of lupus nephritis in the (SWR×NZB)F1 murine model

Systemic lupus erythematosus (SLE) is a multiorgan autoimmune disease affecting 40-50/100,000 Americans. Although most of the research on pathogenic antibodies focuses on antigenic specificity, there is increasing evidence that specific immunoglobulin idiotypes may mediate lupus nephritis independent of autoantigen specificity. In previous work, our laboratory characterized a set of nephritogenic monoclonal antibodies with substantial idiotypic cross-reactivity, produced by the spontaneous SLE model (SWR x NZB)F(1) (SNF(1)), termed Id(LN)F(1). Peptides derived from one of these antibodies, Id540, was previously shown to stimulate pathogenic T-cells from prenephritic SNF(1) mice, similar to what has been seen for pathogenic A6.1 antibody produced by the (NZB x NZW)F(1) model. In this study, we immunized pre-nephritic SNF(1) mice with p62-73, a peptide derived from the variable region of Id540 and, in separate experiments, with p58-69, a peptide derived from the variable region of A6.1. In both cases, immunization resulted in increased survival and delayed nephritis; however, while both peptides affected levels of anti-DNA antibodies, immunization with p62-73 only affected levels of Id(LN)F(1) antibodies. These findings confirm the roles of pathogenic idiotypes in the pathogenesis of lupus nephritis and suggest that therapies that target specific idiotypes might be a potential tool in the management of SLE.

Examining the role of CD1d and natural killer T cells in the development of nephritis in a genetically susceptible lupus model

OBJECTIVE

CD1d-reactive invariant natural killer T (iNKT) cells secrete multiple cytokines upon T cell receptor (TCR) engagement and modulate many immune-mediated conditions. The purpose of this study was to examine the role of these cells in the development of autoimmune disease in genetically lupus-prone (NZBxNZW)F1 (BWF1) mice.

METHODS

The CD1d1-null genotype was crossed onto the NZB and NZW backgrounds to establish CD1d1-knockout (CD1d0) BWF1 mice. CD1d0 mice and their wild-type littermates were monitored for the development of nephritis and assessed for cytokine responses to CD1d-restricted glycolipid alpha-galactosylceramide (alphaGalCer), anti-CD3 antibody, and concanavalin A (Con A). Thymus and spleen cells were stained with CD1d tetramers that had been loaded with alphaGalCer or its analog PBS-57 to detect iNKT cells, and the cells were compared between BWF1 mice and class II major histocompatibility complex-matched nonautoimmune strains, including BALB/c, (BALB/cxNZW)F1 (CWF1), and NZW.

RESULTS

CD1d0 BWF1 mice had more severe nephritis than did their wild-type littermates. Although iNKT cells and iNKT cell responses were absent in CD1d0 BWF1 mice, the CD1d0 mice continued to have significant numbers of interferon-gamma-producing NKT-like (CD1d-independent TCRbeta+,NK1.1+ and/or DX5+) cells. CD1d deficiency also influenced cytokine responses by conventional T cells: upon in vitro stimulation of splenocytes with Con A or anti-CD3, type 2 cytokine levels were reduced, whereas type 1 cytokine levels were increased or unchanged in CD1d0 mice as compared with their wild-type littermates. Additionally, numbers of thymic iNKT cells were lower in young wild-type BWF1 mice than in nonautoimmune strains.

CONCLUSION

Germline deletion of CD1d exacerbates lupus in BWF1 mice. This finding, together with reduced thymic iNKT cells in young BWF1 mice as compared with nonautoimmune strains, implies a regulatory role of CD1d and iNKT cells during the development of lupus.

Immunoregulatory role of Jalpha281 T cells in aged mice developing lupus-like nephritis

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by the emergence of autoreactive T cells. Humans and mice with SLE have reduced numbers of CD1d-restricted invariant natural killer T (iNKT) cells, suggesting a key role for these cells in its immunopathogenesis. This subset uses an invariant TCR constituted by Valpha14 Jalpha281 chains paired with some Vbeta domains. The regulatory role for iNKT cells in non-autoimmune mice was suggested by our previous results showing that aged Jalpha281 knockout (KO) mice produce anti-dsDNA. Here we show that old Jalpha281 KO mice have proteinuria and antibodies against dsDNA and cardiolipin. Histological analysis of Jalpha281 KO mice revealed glomeruli damage and deposition of C3c and IgG, mainly of the IgG3 subclass. In spleens of aged Jalpha281 KO mice there is an increase of activated marginal zone B cells. The evolution of lesions may depend on the age-associated increase of autoantibodies production, preferentially IgG3, mainly secreted by marginal zone B cells. Our results provide the first evidence of a lupus-like syndrome in non-autoimmune mice, supporting an age-related immunoregulatory role of Jalpha281+ cells, probably associated with the activation of marginal zone B cells.

B cells and dendritic cells from V kappa 8 light chain transgenic mice activate MRL-lpr/gld CD4+ T cells

Autoreactive CD4+ T cells are required for full expression of disease in human systemic lupus erythematosus and in spontaneous murine lupus. However, the Ag specificity of these CD4+ T cells remains largely unknown. Rheumatoid factor (RF) B cells function as highly efficient APCs by taking up immune complexes (IC) and presenting IC constituents to T cells. We hypothesized that Ag-specific CD4+ T cells in lupus-prone mice could be identified by stimulating the CD4+ T cells with RF B cells from AM14 RF BCR transgenic mice pulsed with IC containing lupus-associated autoantibodies and autoantigens. This approach identified several independent T cell lines that proliferated robustly in response to IC-pulsed spleen cells from the AM14 RF BCR transgenic mice. However, these T cells did not recognize an IC constituent. Instead, these T cells recognized a determinant dependent on the inheritance of the transgene-encoded Vkappa8 L chain, most likely a neoantigen created by the insertion of the transgene into the genome. Additionally, although the precise nature of the neoantigen is not known, the T cells described in this report may provide a useful tool for examining the role of T cells in the RF autoantibody response.

Regulatory T cells in lupus

Naturally occurring, CD4+ CD25+ regulatory T cells that are exported from the thymus early in life play an important role in controlling organ-specific autoimmune diseases, but they may not be critical for suppressing systemic autoimmunity in lupus. On the other hand, lupus-prone subjects appear to be deficient in generation of adaptive T-regulatory cells that can be induced by various means. We review autoantigen-specific therapeutic approaches that induce such regulatory T cells. Of particular interest are TGF-ss producing CD4+ CD25+ and CD8+ regulatory T cells that are induced by low dose tolerance therapy of lupus-prone mice with nucleosomal histone peptide epitopes, administered subcutaneously in subnanomolar doses. These regulatory T cells are not only efficient in suppressing autoantigen recognition and autoantibody production, but they also inhibit migration/accumulation of pathogenic autoimmune cells in the target organ, such as the kidneys of mice prone to develop lupus nephritis. We discuss why and under what conditions such therapeutic approaches would be beneficial in lupus patients and lupus-prone subjects.

The Unveiling of Hidden T-Cell Determinants of a Native Antigen by Defined Mediators of Inflammation: Implications for the Pathogenesis of Autoimmunity

A major hypothesis for the induction of autoimmunity invokes the enhanced display of previously hidden (cryptic) epitopes under inflammatory conditions leading to the activation of self-reactive T cells. However, there is meager data that directly validate the influence of specific immune mediators on the upregulation of the presentation of cryptic determinants in vivo. We tested the effect on well-defined cryptic epitopes of hen eggwhite lysozyme (HEL) of the availability locally of a cytokine (IL-2, IL-4, IL-6, IL-10, TNF-alpha or granulocyte-macrophage colony-stimulating factor) at the antigen delivery site, or of the pretreatment of the immunogen with a cathepsin (Cat B, D, L or S) prior to use in vivo. Each of the three mouse strains (H-2(b/d/k)) tested revealed a unique profile of T-cell reactivity to different cryptic epitopes of HEL in response to a particular cytokine or cathepsin. These results provide proof of principle for the reversal of crypticity of self-epitopes by immune mediators in the local milieu. Moreover, co-immunization with an antigen and a cytokine offers a simple and reliable tool for studying the role of cryptic epitopes in autoimmunity. Our results also strengthen the rationale for the use of inhibitors of cytokine/cathepsin activity in the treatment of autoimmune diseases.

T cell tolerance to germline-encoded antibody sequences in a lupus-prone mouse

The BCR V region has been implicated as a potential avenue of T cell help for autoreactive B cells in systemic lupus erythematosus. In principle, either germline-encoded or somatically generated sequences could function as targets of such help. Preceding studies have indicated that class II MHC-restricted T cells in normal mice attain a state tolerance to germline-encoded Ab diversity. In this study, we tested whether this tolerance is intact in systemic lupus erythematosus-prone (New Zealand Black x SWR)F1 mice (SNF1). Using a hybridoma sampling approach, we found that SNF1 T cells were tolerant to germline-encoded Ab sequences. Specifically, they were tolerant to germline-encoded sequences derived from a lupus anti-chromatin Ab that arose spontaneously in this strain. This was true both for diseased and prediseased mice. Thus, there does not appear to be a global defect in T cell tolerance to Ab V regions in this autoimmune-prone strain either before or during autoimmune disease.

Insertion of the dibasic motif in the flanking region of a cryptic self-determinant leads to activation of the epitope-specific T cells

Efficient induction of self tolerance is critical for avoiding autoimmunity. The T cells specific for the well-processed and -presented (dominant) determinants of a native self protein are generally tolerized in the thymus, whereas those potentially directed against the inefficiently processed and presented (cryptic) self epitopes escape tolerance induction. We examined whether the crypticity of certain determinants of mouse lysozyme-M (ML-M) could be attributed to the nonavailability of a proteolytic site, and whether it could be reversed to immunodominance by engraftment of a novel cleavage site in the flanking region of the epitope. Using site-directed mutagenesis, we created the dibasic motif (RR or RK; R = arginine, K = lysine), a target of intracellular proteases, in the region adjoining one of the three cryptic epitopes (46-61, 66-79, or 105-119) of ML-M. Interestingly, the mutated lysozyme proteins, but not unmutated ML-M, were immunogenic in mice. The T cell response to the altered lysozyme was attributable to the efficient processing and presentation of the previously cryptic epitope, and this response was both epitope and MHC haplotype specific. In addition, the anti-self T cell response was associated with the generation of autoantibodies against self lysozyme. However, the results using one of three mutated lysozymes suggested that the naturally processed, dibasic motif-marked epitope may not always correspond precisely to the cryptic determinant within a synthetic peptide. This is the first report describing the circumvention of self tolerance owing to the targeted reversal of crypticity to dominance in vivo of a specific epitope within a native self Ag.

Systemic autoimmune disease caused by autoreactive B cells that receive chronic help from Ig V region-specific T cells

B cells present BCR V region-derived Id-peptides on their MHC class II molecules to Id-specific CD4+ T cells. Prolonged Id-driven T-B collaboration could cause autoimmune disease, but this possibility is difficult to test in normal individuals. We have investigated whether mice doubly transgenic for an Id+ Ig L chain and an Id-specific TCR develop autoimmune disease. Surprisingly, T cell tolerance was not complete in these mice because a low frequency of weakly Id-reactive CD4+ T cells accumulated with age. These escapee Id-specific T cells provided chronic help for Id+ B cells, resulting in a lethal systemic autoimmune disease including germinal center reactions, hypergammaglobulinemia, IgG autoantibodies, glomerulonephritis, arthritis, skin affection, and inflammatory bowel disease. Inflamed tissues contained foci of Id-driven T-B collaboration, with deposition of IgG and complement. The disease could be transferred with B and T cells. The results demonstrate a novel mechanism for development of autoimmune disease in which self-reactive Id+ B cells receive prolonged help from Id-specific T cells, thus bypassing the need for help from T cells recognizing conventional Ag.

Tumor necrosis factor-alpha microsatellite polymorphism association with rheumatoid arthritis in Indian patients

BACKGROUND

Level of TNF-alpha increases significantly in synovial fluid of rheumatoid arthritis (RA) patients. It is proposed that tumor necrosis factor (TNF) microsatellite alleles may influence its expression and presumably can contribute to the disease severity. However, there is a lack of such study to predict any such association with RA in an Indian population.

METHODS

In this study, we investigated the differential pattern of distribution of TNF microsatellite alleles in an Indian population and its association with RA. One hundred eighteen RA patients and 120 healthy individuals were genotyped for TNF microsatellite alleles using Genescan. Odds ratio was calculated to demonstrate the correlation between allelic distribution and clinical severity.

RESULTS

The study shows that distribution of TNF microsatellite alleles in an Indian population is very different from other Asian Oriental and Western populations, except for some similarities with an Italian population. Frequency of microsatellite TNFd3 allele (9.24 vs. 3.85%, chi(2)=5.6, p < or =0.0179, OR=0.393, 95% CI=0.177-0.87) and more interestingly TNFd3 containing haplotypes has been found significantly reduced in patients. On the contrary, TNFb5 allele frequency increased in the patients (22.3 vs. 30.8%, chi(2)=4.4, p < or =0.036, OR=1.55, 95% CI=1.027-2.344) as compared to controls. Furthermore, significant increase in frequency of this allele in severe patients (22.3 vs. 33.8%, chi(2)=6.22, p < or =0.013, OR=1.78, 95% CI=1.132-2.798) along with the significant increase in haplotypes containing this allele supports the association of TNFb5 with disease severity.

CONCLUSIONS

In an Indian population, TNFb5 may be considered as a risk factor, whereas TNFd3, unlike others, may be protective for RA.

SLE: translating lessons from model systems to human disease

Systemic lupus erythematosus (SLE, lupus) results from immune-mediated damage to multiple organs. Its pathogenesis should be viewed as a series of steps, beginning with impaired immune regulation that permits self-reactive T-B-cell activation, which results in the production of autoantibodies. Activated T and B cells then infiltrate tissues, which along with autoantibody and immune complex deposition, triggering local events that ultimately cause organ damage. Although improved understanding of early autoimmune events might open up avenues for disease prevention, future investigations must focus on the mechanisms of end-organ damage in model systems and how to translate this knowledge into human disease. Understanding the mechanisms of each pathogenetic step would provide a rational basis for the development of disease stage-specific diagnostic markers and treatments.

Understanding crypticity is the key to revealing the pathogenesis of autoimmunity

In this opinion, we propose that the hierarchy of antigenic determinants within self-antigens is the major influence in molding the potentially autoreactive T-cell repertoire. The well processed and presented determinants constitute a 'dominant self', whereas the poorly processed and/or presented determinants will be invisible to T cells and comprise a 'cryptic self', which we consider a fundamental cornerstone of a theory of autoimmunity. It accounts for the large repertoire of self-reactive clones because a similar hierarchy is established in the thymus and controls positive and negative selection. Furthermore, this residual T-cell repertoire, largely directed against cryptic determinants, will contain some T cells with sufficient affinity for MHC and antigen that enables them to respond under inflammatory conditions, thus facilitating presentation of previously cryptic determinants.

The natural killer T cell ligand alpha-galactosylceramide prevents or promotes pristane-induced lupus in mice

Systemic lupus erythematosus is a systemic autoimmune disease characterized by inflammation in organs such as kidneys and presence of autoantibodies against nuclear antigens. We have previously shown that CD1d deficiency in BALB/c mice exacerbates lupus nephritis and autoantibody production induced by the hydrocarbon oil pristane. Here, we have tested the impact of activating CD1d-restricted natural killer T (NKT) cells on pristane-induced lupus-like autoimmunity in BALB/c and SJL mice. Repeated in vivo treatment of pristane-injected BALB/c mice with the NKT cell ligand alpha-galactosylceramide (alpha-GalCer) prior to the onset of florid disease suppressed proteinuria, in a manner that was dependent on CD1d and IL-4 expression. In sharp contrast, however, similar treatment of pristane-injected SJL mice with alpha-GalCer resulted in increased proteinuria. Consistent with these dichotomous effects of NKT cell activation on the development of lupus-like autoimmunity, NKT cells in BALB/c and SJL/J mice exhibited a mixed Th1/Th2 and a Th1-biased cytokine production profile, respectively. These findings demonstrate that NKT cell activation with alpha-GalCer suppresses or promotes pristane-induced lupus-like autoimmunity in mice, in a strain-dependent manner.

T cell hyperactivity in lupus as a consequence of hyperstimulatory antigen-presenting cells

Sle3 is an NZM2410-derived lupus susceptibility locus on murine chromosome 7. Congenic recombination has resulted in a novel mouse strain, B6.Sle3, associated with serum antinuclear autoantibodies (ANAs), T cell hyperactivity, and elevated CD4/CD8 ratios. An OVA-specific TCR transgene was used as a tool to demonstrate that Sle3 facilitated heightened T cell expansion in vitro, and in vivo, following antigen challenge. Indeed, continued T cell expansion was noted even in response to a tolerogenic signal. However, these phenotypes did not appear to be T cell intrinsic but were dictated by hyperstimulatory B6.Sle3 APCs. Importantly, B6.Sle3-derived DCs and macrophages appeared to be significantly more mature/activated, less apoptotic, and more proinflammatory and were better at costimulating T cells in vitro, compared with the B6 counterparts. Finally, the adoptive transfer of B6.Sle3-derived DCs into healthy B6 recipients elicited increased CD4/CD8 ratios and serum ANAs, 2 cardinal Sle3-associated phenotypes. We posit that their heightened expression of various costimulatory molecules, including CD80, CD106, I-A, and CD40, and their elevated production of various cytokines, including IL-12 and IL-1beta, may explain why Sle3-bearing DCs may be superior at breaching self tolerance. These studies provide mechanistic evidence indicating that intrinsic abnormalities in DCs and possibly other myeloid cells may dictate several of the phenotypes associated with systemic lupus, including ANA formation and T cell hyperactivity.

Cerebrospinal fluid T cell clones from patients with multiple sclerosis: recognition of idiotopes on monoclonal IgG secreted by autologous cerebrospinal fluid B cells

Due to somatic recombination and hypermutation, Ig variable heavy (V(H)) and light (V(L)) regions contain unique immunogenic determinants, idiotopes (Id), which can stimulate T cells. To address the relevance of this in a human disease, monoclonal IgG (mAb)-secreting B cell clones were established from the cerebrospinal fluid (CSF) of two patients with multiple sclerosis (MS). HLA-DR-restricted CD4(+) T cell lines and clones from CSF of both patients specifically recognized autologous CSF mAb. The CSF T cell clones produced IFN-gamma; some also produced TNF-alpha, IL-10 and IL-5. V(H) and V(L) on the monoclonal IgG derived from CSF B cells expressed amino acid replacements due to somatic mutations. A T cell epitope was mapped to a V(H) framework region, where an amino acid replacement was critical for the T cell recognition. The finding of Id-specific T cells and Id-bearing B cells in the CSF indicates that they coexist within the diseased organ, and provide a basis for the study of Id-driven T-B cell collaboration in a human autoimmune disease.

Suppressive oligodeoxynucleotides delay the onset of glomerulonephritis and prolong survival in lupus-prone NZB x NZW mice

OBJECTIVE

Synthetic oligodeoxynucleotides (ODN) expressing TTAGGG motifs suppress the production of proinflammatory cytokines and have been proven effective at blocking the development of certain organ-specific autoimmune diseases. We undertook this study to determine whether suppressive ODN alter the development of systemic autoimmunity, by evaluating their effect on the progression of lupus-like disease in NZB x NZW (NZB/NZW) mice.

METHODS

We repeatedly treated mice with suppressive ODN before or after the onset of proteinuria. We monitored the effect of treatment on the onset, severity, and immunologic correlates of disease.

RESULTS

Treatment with suppressive ODN significantly prolonged lifespan while delaying the onset and progression of glomerulonephritis in NZB/NZW mice. Clinical improvement was accompanied by a significant reduction in anti-double-stranded DNA autoantibody production and by significantly reduced secretion of interferon-gamma and interleukin-12 in vivo.

CONCLUSION

Suppressive ODN may be of benefit in the treatment of chronic systemic autoimmune diseases such as systemic lupus erythematosus.

T-helper cell intrinsic defects in lupus that break peripheral tolerance to nuclear autoantigens

Special populations of T helper cells drive B cells to produce IgG class switched, pathogenic autoantibodies in lupus. The major source of antigenic determinants (epitopes) that trigger interactions between lupus T and B cells is nucleosomes of apoptotic cells. These epitopes can be used for antigen-specific therapy of lupus. Secondly, the autoimmune T cells of lupus are sustained because they resist anergy and activation-induced programmed cell death by markedly upregulating cyclooxygenase (COX) 2 along with the antiapoptotic molecule c-FLIP. Only certain COX-2 inhibitors block pathogenic anti-DNA autoantibody production in lupus by causing death of autoimmune T helper cells. Hence COX-2 inhibitors may work independently of their ability to block the enzymatic function of COX-2, and structural peculiarities of these select inhibitors may lead to better drug discovery and design.

Amelioration of lupus manifestations by a peptide based on the complementarity determining region 1 of an autoantibody in severe combined immunodeficient (SCID) mice engrafted with peripheral blood lymphocytes of systemic lupus erythematosus (SLE) patients

A peptide based on the complementarity determining region (CDR)1 of a human monoclonal anti-DNA autoantibody (hCDR1) was shown to either prevent or treat an already established murine lupus in systemic lupus erythematosus (SLE)-prone mice or in mice with induced experimental SLE. The present study was undertaken to determine the therapeutic potential of hCDR1 in a model of lupus in severe combined immunodeficient (SCID) mice engrafted with peripheral blood lymphocytes (PBL) of patients with SLE. To this end, PBL obtained from lupus patients were injected intraperitoneally into two equal groups of SCID mice that were treated either with the hCDR1 (50 micro g/mouse) once a week for 8 weeks, or with a control peptide. Mice were tested for human IgG levels, anti-dsDNA autoantibodies, anti-tetanus toxoid antibodies and proteinuria. At sacrifice, the kidneys of the successfully engrafted mice were assessed for human IgG and murine complement C3 deposits. Of the 58 mice transplanted with PBL of SLE patients, 38 (66%) were engrafted successfully. The mice that were treated with the control peptide developed human dsDNA-specific antibodies. Treatment with hCDR1 down-regulated the latter significantly. No significant effect of the treatment on the levels of anti-tetanus toxoid antibodies could be observed. Treatment with hCDR1 resulted in a significant amelioration of the clinical features manifested by proteinuria, human IgG complex deposits as well as deposits of murine complement C3. Thus, the hCDR1 peptide is a potential candidate for a novel specific treatment of SLE patients.

Differences between CD8+ T cells in lupus-prone (NZB x NZW) F1 mice and healthy (BALB/c x NZW) F1 mice may influence autoimmunity in the lupus model

Immunization with portions of a murine antibody to DNA induced Ig peptide-reactive peripheral CD8+ inhibitory T (Ti) cells in non-autoimmune (BALB/c x NZW) F1 (CWF1) mice. Those Ti suppressed in vitro production of IgG anti-DNA by lymphocytes from MHC-matched, lupus-prone (NZB x NZW) F1 (BWF1) mice, primarily via secretion of transforming growth factor-beta (TGF-beta). However, splenic CD8+ cells from immunized BWF1 mice failed to suppress anti-DNA. Therefore, BWF1 mice were studied for defects in peripheral CD8+ T cells. The potential to suppress autoimmunity mediated by activated CD4+ helper T and B cells in BWF1 mice was assessed. As BWF1 mice aged, peripheral CD8+ T cells expanded little; fewer than 10% displayed surface markers of activation and memory. In contrast, quantities of splenic CD4+ T and B cells increased; high proportions displayed activation/memory markers. In old compared to young BWF1 mice, splenic cell secretion of two cytokines required for generation of CD8+ T effectors, IL-2 and TGF-beta, was decreased. Immunizing BWF1 mice activated peptide-reactive CD8+ T cells, but their number was decreased compared to young BWF1 or old normal mice. While peptide-reactive splenic CD8+ T cells from immunized BWF1 mice did not survive in short-term cultures, similar CD8+ T cell lines from immunized CWF1 mice expanded and on transfer into BWF1 mice delayed autoimmunity and prolonged survival. Therefore, CD8+ T cells in old BWF1 mice are impaired in expansion, acquisition of memory, secretion of cytokine, and suppression of autoimmunity. Understanding these defects might identify targets for therapy in systemic lupus erythematosus.

MHC-restricted Ig V region-driven T-B lymphocyte collaboration: B cell receptor ligation facilitates switch to IgG production

B cells spontaneously process their endogenous Ig and present V region peptides on their MHC class II molecules. We have here investigated whether B cells collaborate with V region-specific CD4+ T cells in vivo. By use of paired Ig L chain-transgenic and TCR-transgenic mice and cell transfer into normal hosts, we demonstrate that B cell presentation of a V(L) region peptide to CD4+ T cells results in germinal centers, plasma cells, and Ab secretion. Because the transgenic B cells have a fixed L chain but polyclonal H chains, their B cell receptor (BCR) repertoire is diverse and may bind a multitude of ligands. In a hapten-based system, BCR ligation concomitant with V region-driven T-B collaboration induced germinal center formation and an IgM --> IgG isotype switch. In the absence of BCR ligation, mainly IgM was produced. Consistent with this, prolonged V region-driven T-B collaboration resulted in high titers of IgG autoantibodies against ubiquitous self-Ags, while natural-type Abs against exotic bacteria remained IgM. Taken together, V region-driven T-B collaboration may explain induction of natural IgM Abs (absence of BCR ligation) and IgG autoantibodies (BCR ligation by autoantigen) and may be involved in the development of autoimmunity.

Ig-Reactive CD4+CD25+ T Cells from Tolerized (New Zealand Black × New Zealand White)F1 Mice Suppress In Vitro Production of Antibodies to DNA

We have recently shown that tolerogenic administration of an artificial peptide (pConsensus) that is based on sequences within the V(H) regions of several murine anti-dsDNA Ig delays appearance of autoantibodies in female (New Zealand Black (NZB) x New Zealand White (NZW))F(1) (NZB/W F(1)) mice and significantly prolongs their survival. The aim of this study was to characterize the T cell population(s) involved in pConsensus-induced down-regulation of autoimmune responses in tolerized NZB/W F(1) mice. Using MHC class II dimers loaded with tolerogenic peptide, we found that pCons favored expansion of peptide-reactive CD4(+)CD25(+) regulatory T cells (T(R)) that inhibited in vitro production of anti-dsDNA Ab-forming cells. Suppression by T(R) was abrogated by the presence in culture of Ab to glucocorticoid-induced TNFR family member 18 or to TGFbeta latency-associated protein. These findings suggest possible relevance of Ag specificity in the mechanism of T(R)-mediated immune tolerance to Ig-derived peptides in NZB/W F(1) mice.

Activation and tolerance in CD4(+) T cells reactive to an immunoglobulin variable region

Antibody diversity creates an immunoregulatory challenge for T cells that must cooperate with B cells, yet discriminate between self and nonself. To examine the consequences of T cell reactions to the B cell receptor (BCR), we generated a transgenic (Tg) line of mice expressing a T cell receptor (TCR) specific for a κ variable region peptide in monoclonal antibody (mAb) 36-71. The κ epitope was originally generated by a pair of somatic mutations that arose naturally during an immune response. By crossing this TCR Tg mouse with mice expressing the κ chain of mAb 36-71, we found that κ-specific T cells were centrally deleted in thymi of progeny that inherited the κTg. Maternally derived κTg antibody also induced central deletion. In marked contrast, adoptive transfer of TCR Tg T cells into κTg recipients resulted in T and B cell activation, lymphadenopathy, splenomegaly, and the production of IgG antichromatin antibodies by day 14. In most recipients, autoantibody levels increased with time, Tg T cells persisted for months, and a state of lupus nephritis developed. Despite this, Tg T cells appeared to be tolerant as assessed by severely diminished proliferative responses to the Vκ peptide. These results reveal the importance of attaining central and peripheral T cell tolerance to BCR V regions. They suggest that nondeletional forms of T tolerance in BCR-reactive T cells may be insufficient to preclude helper activity for chromatin-reactive B cells.

Germ line tumor-associated immunoglobulin VH region peptides provoke a tumor-specific immune response without altering the response potential of normal B cells

Previous studies have suggested that murine T cells are tolerant to epitopes derived from germ line variable regions of immunoglobulin (Ig) heavy (VH) or light chains. This has lead to the prediction that germ line VH-region epitopes found in neoplastic B cells cannot be used to provoke an antitumor immune response. To test these assumptions and address the question of how such a vaccine may alter the normal B-cell response, an antibody-forming B-cell hybridoma (1H6) expressing a conserved germ line VH gene with specificity for dextran was generated and used as a tumor model. Using algorithms for predicting major histocompatibility complex (MHC) binding, potential MHC class I and II binding peptides were identified within the 1H6 VH region, synthesized, and tested for MHC binding and immunogenicity. We show that germ line VH peptides, when presented by dendritic cells, are immunogenic in vitro and provoke a tumor-specific protective immune response in vivo. We conclude that (1) it is possible to induce a T-cell response to germ line VH peptides; (2) such peptides can be used to generate a B-cell tumor-specific vaccine; and (3) a vaccine targeting VH peptides expressed by the dominant dextran-specific B-cell clonotype had no effect upon the magnitude of the normal B-cell response to dextran.