From T to B and back again: positive feedback in systemic autoimmune disease

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.

Myeloid cells, BAFF, and IFN-gamma establish an inflammatory loop that exacerbates autoimmunity in Lyn-deficient mice

Autoimmunity is traditionally attributed to altered lymphoid cell selection and/or tolerance, whereas the contribution of innate immune cells is less well understood. Autoimmunity is also associated with increased levels of B cell–activating factor of the TNF family (BAFF; also known as B lymphocyte stimulator), a cytokine that promotes survival of self-reactive B cell clones. We describe an important role for myeloid cells in autoimmune disease progression. Using Lyn-deficient mice, we show that overproduction of BAFF by hyperactive myeloid cells contributes to inflammation and autoimmunity in part by acting directly on T cells to induce the release of IFN-γ. Genetic deletion of IFN-γ or reduction of BAFF activity, achieved by either reducing myeloid cell hyperproduction or by treating with an anti-BAFF monoclonal antibody, reduced disease development in lyn^−/− mice. The increased production of IFN-γ in lyn^−/− mice feeds back on the myeloid cells to further stimulate BAFF release. Expression of BAFF receptor on T cells was required for their full activation and IFN-γ release. Overall, our data suggest that the reciprocal production of BAFF and IFN-γ establishes an inflammatory loop between myeloid cells and T cells that exacerbates autoimmunity in this model. Our findings uncover an important pathological role of BAFF in autoimmune disorders.

A common polymorphism in the caspase recruitment domain of RIG-I modifies the innate immune response of human dendritic cells

Infection of human dendritic cells (DCs) by negative-strand RNA viruses, such as Newcastle disease virus, leads to the induction of the IFNbeta gene, IFNB1, through the activation of the RNA helicase RIG-I, which is encoded by DDX58. Expression levels of IFNB1 and DDX58 in infected DCs showed positive correlations at the population and the single-cell levels. DDX58 has a common and potentially functional single nucleotide polymorphism, rs10813831 (A/G), encoding an Arg7Cys amino acid change in the RIG-I protein caspase recruitment domain (CARD). Quantitative RT-PCR analysis on Newcastle disease virus-infected primary DCs from 130 individuals revealed a significant association of the Arg7Cys single nucleotide polymorphism with increased IFNB1 and DDX58 transcription. Allelic imbalance analysis ruled out allele-specific DDX58 message levels and suggested that the observed association between Arg7Cys and IFNB1 and DDX58 transcription originated from a functional change in RIG-I due to the amino acid substitution in the CARD. DDX58 transfection experiments in 293T cells confirmed a biological functional difference between RIG-I 7Cys and the more common RIG-I 7Arg. Taken together, these data indicate that the innate immune response to viral infection of human cells is modified by a functional polymorphism in the RIG-I CARD.

Rituximab in autoimmune hematologic diseases: not just a matter of B cells

Rituximab, a chimeric monoclonal antibody that depletes B cells by binding to the CD20 cell-surface antigen, has been investigated extensively in autoimmune disorders. Following the encouraging results in immune thrombocytopenia (ITP), the use of this agent was explored in other autoimmune hematologic diseases, most notably autoimmune hemolytic anemia (AIHA) and thrombotic thrombocytopenic purpura (TTP), characterized by the presence of pathogenetic autoantibodies. Although randomized clinical trials are lacking, the cumulative data would suggest that rituximab has a beneficial role in their treatment. Response to B-cell-depleting therapy is actually associated with a significant decrease of circulating autoantibodies. However, several lines of evidence indicate that the T-cell compartment may also be modulated by these interventions. The doses and the duration of rituximab treatment in patients with autoimmune diseases are still unclear. The incidence of severe side effects is low but not insignificant. In particular, the risk of systemic infections and viral reactivation is a major concern.

T cells as therapeutic targets in SLE

T cells contribute to the initiation and perpetuation of autoimmunity in systemic lupus erythematosus (SLE), and seem to be directly involved in the development of related organ pathology. Defects associated with CD8(+) and T-regulatory (T(REG)) cell function manifest in parallel with the expanded CD3(+)CD4(-)CD8(-) T cell lineage. The cytokine expression pattern is uniquely characterized by decreased expression of interleukin (IL)-2 and increased production of IL-17 and related cytokines. Therapeutic approaches that limit the cognate interaction between T cells and B cells, prevent inappropriate tissue homing and restore T(REG) cell function and the normal cytokine milieu have been entertained. Biochemical characterization of SLE T cells has revealed distinct early and late signaling aberrations, and has enabled the identification of novel molecular targets that can be corrected with small molecules, and biomarkers that may foretell disease activity and predict organ damage.

Donor CD8 T cell activation is critical for greater renal disease severity in female chronic graft-vs.-host mice and is associated with increased splenic ICOS(hi) host CD4 T cells and IL-21 expression

Lupus-like renal disease in DBA/2-into-F1 (DBA --> F1) mice is driven by donor CD4 T cells and is more severe in females. Donor CD8 T cells have no known role. As expected, we observed that females receiving unfractionated DBA splenocytes (CD8 intact --> F1) exhibited greater clinical and histological severities of renal disease at 13 weeks compared to males. Surprisingly, sex-based differences in renal disease severity were lost in CD8 depleted --> F1 mice due to an improvement in females and a worsening in males. CD8 intact --> F1 female mice exhibited significantly greater donor and host effector (CD44(hi), CD62L(lo)) CD4 T cells and ICOS(hi) CD4 T follicular helper cells than males. CD8 depleted --> F1 female mice exhibited a reduction in the absolute numbers of host, but not donor CD4 Tfh cells and lost the significant increase in host CD4 effector cells vs. males. Greater female IL-21 expression, a product of Tfh cells, was seen in CD8 intact --> F1 and although reduced was still greater than male CD8 depleted --> F1 mice. Thus, donor CD8 T cells have a critical role in mediating sex-based differences in lupus renal disease severity possibly through greater host ICOS(hi) CD4 T cell involvement.

Mouse Models of Systemic Lupus Erythematosus Reveal a Complex Pathogenesis

The mammalian immune system is remarkable in that it can respond to an essentially infinite number of foreign antigens. The ability to mount a long-lasting (adaptive) immune response against foreign antigen requires the participation of cells selected from an enormously diverse population of B and T cells. Because the B and T cell receptors expressed by these cells are generated at random, a significant percentage of B and T cells are invariably directed against self-antigen. Under normal circumstances, autoreactive B and T cells are eliminated, reprogrammed, or inactivated in the primary and secondary lymphoid organs. Despite these checks and balances, a small but significant number of people and animals still develop autoimmune disease. One such autoimmune disease—systemic lupus erythematosus—is characterized by the loss of B- and T-cell tolerance to self-antigens (principally nuclear), culminating in multisystemic inflammation. Multiple genetic defects, drug exposure, infectious agents, and environmental factors can contribute to the pathogenesis of the disease. Loss of B- and T-cell tolerance precipitates activation of plasmacytoid and myeloid dendritic cells; collectively, these cells cooperate to form a complex positive feedback loop, continually stimulated by the persistence of self-antigen. Novel treatment strategies now focus on specific inhibition of various aspects of the feedback loop. These specific inhibitors have the potential to be more effective and lack the side effects associated with generalized immunosuppression.

Autoimmune diseases: MIF as a therapeutic target

IMPORTANCE OF THE FIELD

Autoimmune inflammatory diseases occur commonly in developed countries. The treatment of these diseases is usually non-curative and is aimed at suppressing inflammatory end-organ damage. Macrophage migration inhibitory factor (MIF) is a multipotent cytokine that has been implicated in the pathogenesis of numerous autoimmune inflammatory disorders. The selective targeting of MIF with either anti-MIF antibody or specific MIF antagonists may offer new therapeutic avenues for these diseases.

AREAS COVERED IN THIS REVIEW

Our aim is to discuss MIF-directed therapies as a novel therapeutic approach. The review covers literature from the past 10 years.

WHAT THE READER WILL GAIN

MIF inhibition has been shown to be efficacious in many experimental and pre-clinical studies of autoimmune inflammatory diseases. The close regulatory relationship between MIF and glucocorticoids makes therapeutic antagonism of MIF a potential steroid-sparing therapy in patients with refractory autoimmune diseases.

TAKE HOME MESSAGE

We expect that MIF antagonism by either small-molecule- or antibody-based approaches will find wide application in the treatment of autoimmune inflammatory diseases. Such therapy also may be informed by the MIF genotype of affected patients.

Prevention of murine antiphospholipid syndrome by BAFF blockade

OBJECTIVE

This study was undertaken to determine whether BAFF blockade can be used to prevent or treat antiphospholipid syndrome in a mouse model.

METHODS

Eight- and 12-week-old (NZW x BXSB)F(1) mice were treated with BAFF-R-Ig or TACI-Ig alone or in addition to a short course of CTLA-4Ig. Mice were monitored for thrombocytopenia and proteinuria. Sera were tested for anticardiolipin antibodies (aCL), BAFF levels, and levels of soluble vascular cell adhesion molecule and E-selectin. Mice were killed at 17, 22, or 32 weeks of age, and kidneys and hearts were subjected to histologic examination. Spleen cells were phenotyped and enzyme-linked immunospot assays for autoantibody-producing B cells were performed.

RESULTS

Both BAFF-R-Ig and TACI-Ig prevented disease onset and significantly prolonged survival. Treated mice had significantly smaller spleens than controls, with fewer B cells and fewer activated and memory T cells. BAFF blockade did not prevent the development of aCL, and there was only a modest delay in the development of thrombocytopenia. However, treated mice had significantly less nephritis and myocardial infarcts than did controls.

CONCLUSION

Our findings suggest that aCL are generated in the germinal center, which is relatively independent of BAFF. Effector function of antiplatelet antibodies was only modestly affected by BAFF blockade. In contrast, myocardial infarctions were prevented, suggesting that triggering of thromboses requires both autoantibodies and mediators of inflammation. Similarly, renal damage requires both immune complexes and effector cells. The dissociation between autoantibody production and inflammation that may occur with B cell-depleting therapies underscores the role of B cells as effector cells in the autoimmune response.

Antibodies to the desmoglein 1 precursor proprotein but not to the mature cell surface protein cloned from individuals without pemphigus

In pemphigus foliaceus (PF), autoantibodies against desmoglein 1 (Dsg1) cause blisters. Using Ab phage display, we have cloned mAbs from a PF patient. These mAbs, like those from a previous patient, were directed against mature Dsg1 (matDsg1) on the cell surface of keratinocytes and precursor Dsg1 (preDsg1) in the cytoplasm. To determine whether individuals without pemphigus have B cell tolerance to Dsg1, we cloned mAbs from two patients with thrombotic thrombocytopenic purpura and a healthy person. We found mAbs against preDsg1, but not matDsg1. All but 1 of the 23 anti-preDsg1 mAbs from PF patients and those without PF used the VH3-09 (or closely related VH3-20) H chain gene, whereas no PF anti-matDsg1 used these genes. V(H) cDNA encoding anti-preDsg1 had significantly fewer somatic mutations than did anti-matDsg1 cDNA, consistent with chronic Ag-driven hypermutation of the latter compared with the former. These data indicate that individuals without PF do not have B cell tolerance to preDsg1 and that loss of tolerance to matDsg1 is not due to epitope shifting of anti-preDsg1 B cells (because of different V(H) gene usage). However, presentation of peptides from Dsg1 by preDsg1-specific B cells may be one step in developing autoimmunity in PF.

CTLA4Ig alters the course of autoimmune disease development in Lyn-/- mice

Lyn-deficient (Lyn(-/-)) mice develop an age-dependent autoimmune disease similar to systemic lupus erythematosus, characterized by the production of IgG anti-nuclear Ab. To determine the extent to which this autoimmune phenotype is driven by T cell costimulation, we generated Lyn(-/-) mice expressing a soluble form of the T cell inhibitory molecule, CTLA4 (CTLA4Ig). Surprisingly, although CTLA4Ig prevented myeloid hyperplasia, splenomegaly and IgG anti-nuclear Ab production in Lyn(-/-) mice, it did not inhibit immune complex deposition and tissue destruction in the kidney. In fact, regardless of CTLA4Ig expression, Lyn(-/-) serum contained elevated titers of IgA anti-nuclear Ab, although generally IgA deposition in the kidney was only revealed in the absence of self-reactive IgG. This demonstrated that activation of autoreactive B cell clones in Lyn(-/-) mice can still occur despite impaired costimulation. Indeed, CTLA4Ig did not alter perturbed Lyn(-/-) B cell development and behavior, and plasma cell frequencies were predominantly unaffected. These results suggest that when self-reactive B cell clones are unimpeded in acquiring T cell help, they secrete pathogenic IgG autoantibodies that trigger the fulminant autoimmunity normally observed in Lyn(-/-) mice. The absence of these IgG immune complexes reveals an IgA-mediated axis of autoimmunity that is not sufficient to cause splenomegaly or extramedullary myelopoiesis, but which mediates destructive glomerulonephritis. These findings have implications for the understanding of the basis of Ab-mediated autoimmune diseases and for their treatment with CTLA4Ig.

Baseline autoantibody profiles predict normalization of complement and anti-dsDNA autoantibody levels following rituximab treatment in systemic lupus erythematosus

B cells are thought to play a major role in the pathogenesis of systemic lupus erythematosus (SLE). Rituximab (RTX), a chimeric anti-CD20 mAb, effectively depletes CD20( +) peripheral B cells. Recent results from EXPLORER, a placebo-controlled trial of RTX in addition to aggressive prednisone and immunosuppressive therapy, showed similar levels of clinical benefit in patients with active extra-renal SLE despite effective B cell depletion. We performed further data analyses to determine whether significant changes in disease activity biomarkers occurred in the absence of clinical benefit. We found that RTX-treated patients with baseline autoantibodies (autoAbs) had decreased anti-dsDNA and anti-cardiolipin autoAbs and increased complement levels. Patients with anti-dsDNA autoAb who lacked baseline RNA binding protein (RBP) autoAbs showed increased complement and decreased anti-dsDNA autoAb in response to RTX. Other biomarkers, such as baseline BAFF levels or IFN signature status did not predict enhanced effects of RTX therapy on complement or anti-dsDNA autoAb levels. Finally, platelet levels normalized in RTX-treated patients who entered the study with low baseline counts. Together, these findings demonstrate clear biologic activity of RTX in subsets of SLE patients, despite an overall lack of incremental clinical benefit with RTX in the EXPLORER trial.

Hematopoietic cell transplantation for autoimmune disease: updates from Europe and the United States

Considerable advances have been made in our understanding of the immunobiology of autoimmune disease and its treatment with hematopoietic cell transplantation (HCT). In autoimmune disorders, the reconstituted immune system following lymphoablation and autologous HCT yields qualitative changes in immune defects and modifications in adaptive immune responses. Seminal experiments in animals demonstrated that allogeneic or autologous HCT could prevent progression or reverse organ damage from inherited (genetic) or acquired (antigen induced) autoimmune diseases. Convincing animal and clinical data now show that after HCT, the immune system is normalized and "reset". Following autologous transplantation, this resetting occurs via repertoire replacement. It is currently being studied whether and to what extent suppression of inflammation after HCT is due to reregulation of function or due to the eradication of disease associated T and/or B cell populations. There are now a number of published clinical reports with sufficient follow-up for determinations of safety and efficacy of HCT for autoimmune diseases. On behalf of colleagues in the European League Against Rheumatism (EULAR) and the European Group for Blood and Marrow Transplantation (EBMT), we review the experience with more than 1000 transplants for autoimmune disease in Europe along with the three major multinational randomized trials in for systemic sclerosis (SSc, the ASTIS study), multiple sclerosis (MS, the ASTIMS study), and Crohn's disease (CD, the ASTIC study). Completed phase II studies in the USA of transplantation for severe SSc, SLE and MS yield promising results. For individuals with SSc, there is dramatic improvement/resolution of dermal fibrosis and stabilization/improvement of pulmonary dysfunction reported up to 8 years after lymphoablative conditioning and autologous HCT. Currently, randomized phase III studies are recruiting subjects in the USA with SSc, MS and CD. In addition, 9 other phase I and II trials in the USA are recruiting patients with autoimmune diseases for nonmyeloablative transplants from allogeneic stem cell donors. Research opportunities abound, but recruitment challenges restrict study entry due to organ impairment from advanced autoimmune disease or insurance denial of coverage for HCT. However, within several NIH sponsored trials there are ongoing immunologic, genomic and mechanistic studies to further understand the molecular mechanisms of autoimmunity, immune regulation and response to treatment. These clinical trials will provide basic scientists with insight into immunoregulatory pathways and clinicians with a context to weigh the progress and evidence in this evolving treatment for autoimmune diseases.

B cells from glatiramer acetate-treated mice suppress experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system (CNS) thought to be primarily mediated by T cells. However, emerging evidence supports an important role for B cells in the pathogenesis and inhibition of MS. Glatiramer acetate (GA), a Food and Drug Administration-approved drug for the treatment of MS, has a good safety profile. But GA's mechanism of action in MS is still elusive. In this study, we showed that B cells from GA-treated mice increased production of IL-10 and reduced expression of co-stimulatory molecules viz.: CD80 and CD86. B cells from GA-treated mice also diminished proliferation of myelin oligodendrocyte glycoprotein (MOG(35-55)) specific T cells. Purified B cells transferred from GA-treated mice suppressed experimental autoimmune encephalomyelitis (EAE) in recipient mice compared with B cells transferred from mice treated with PBS or ovalbumin. The treatment effect of GA in EAE was abrogated in B cell-deficient mice. Transfer of B cells from GA-treated mice inhibited the proliferation of autoreactive T cells as well as the development of Th1 and Th17 cells but promoted IL-10 production in recipient mice. The number of peripheral CD11b(+) macrophages in recipient mice also decreased after transfer of B cells from GA-treated mice; however, the number of dendritic cells and regulatory T cells remained unaltered. These results suggest that B cells are important to the protective effects of GA in EAE.

Rituximab treatment of patients with severe, corticosteroid-resistant thyroid-associated ophthalmopathy

PURPOSE

To study the effectiveness of anti-CD20 (rituximab [RTX]; Rituxan; Genentech, Inc., South San Francisco, CA) therapy in patients with severe, corticosteroid (CS)-resistant thyroid-associated ophthalmopathy (TAO).

DESIGN

Retrospective, interventional case series.

PARTICIPANTS

Six consecutive subjects with severe, progressive TAO unresponsive to CS.

METHODS

Electronic medical record review of consecutive patients receiving RTX during the previous 18 months. Responses to therapy were graded using standard clinical assessment and flow cytometric analysis of peripheral lymphocytes.

MAIN OUTCOME MEASURES

Clinical activity score (CAS), proptosis, strabismus, treatment side effects, and quantification of regulatory T cells.

RESULTS

Six patients were studied. Systemic CS failed to alter clinical activity in all patients (mean CAS+/-standard deviation, 5.3+/-1.0 before vs. 5.5+/-0.8 during therapy for 7.5+/-6.4 months; P = 1.0). However, after RTX treatment, CAS improved from 5.5+/-0.8 to 1.3+/-0.5 at 2 months after treatment (P<0.03) and remained quiescent in all patients (CAS, 0.7+/-0.8; P<0.0001) at a mean follow-up of 6.2+/-4.5 months. Vision improved bilaterally in all 4 patients with dysthyroid optic neuropathy (DON). None of the 6 patients experienced disease relapse after RTX infusion, and proptosis remained stable (Hertel measurement, 24+/-3.7 mm before therapy and 23.6+/-3.7 mm after therapy; P = 0.17). The abundance of T regulatory cells, assessed in 1 patient, increased within 1 week of RTX and remained elevated at 18 months of follow-up.

CONCLUSIONS

In progressive, CS-resistant TAO, rapid and sustained resolution of orbital inflammation and DON followed treatment with RTX.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

B cells as a target of immune modulation

B cells have recently been identified as an integral component of the immune system; they play a part in autoimmunity through antigen presentation, antibody secretion, and complement activation. Animal models of multiple sclerosis (MS) suggest that myelin destruction is partly mediated through B cell activation (and plasmablasts). MS patients with evidence of B cell involvement, as compared to those without, tend to have a worse prognosis. Finally, the significant decrease in new gadolinium-enhancing lesions, new T2 lesions, and relapses in MS patients treated with rituximab (a monoclonal antibody against CD20 on B cells) leads us to the conclusion that B cells play an important role in MS and that immune modulation of these cells may ameliorate the disease. This article will explore the role of B cells in MS and the rationale for the development of B cell-targeted therapeutics. MS is an immune-mediated disease that affects over 2 million people worldwide and is the number one cause of disability in young patients. Most therapeutic targets have focused on T cells; however, recently, the focus has shifted to the role of B cells in the pathogenesis of MS and the potential of B cells as a therapeutic target.

Differences in baseline lymphocyte counts and autoreactivity are associated with differences in outcome of islet cell transplantation in type 1 diabetic patients

OBJECTIVE

The metabolic outcome of islet cell transplants in type 1 diabetic patients is variable. This retrospective analysis examines whether differences in recipient characteristics at the time of transplantation are correlated with inadequate graft function.

RESEARCH DESIGN AND METHODS

Thirty nonuremic C-peptide-negative type 1 diabetic patients had received an intraportal islet cell graft of comparable size under an ATG-tacrolimus-mycophenolate mofetil regimen. Baseline patient characteristics were compared with outcome parameters during the first 6 posttransplant months (i.e., plasma C-peptide, glycemic variability, and gain of insulin independence). Correlations in univariate analysis were further examined in a multivariate model.

RESULTS

Patients that did not become insulin independent exhibited significantly higher counts of B-cells as well as a T-cell autoreactivity against insulinoma-associated protein 2 (IA2) and/or GAD. In one of them, a liver biopsy during posttransplant year 2 showed B-cell accumulations near insulin-positive beta-cell aggregates. Higher baseline total lymphocytes and T-cell autoreactivity were also correlated with lower plasma C-peptide levels and higher glycemic variability.

CONCLUSIONS

Higher total and B-cell counts and presence of T-cell autoreactivity at baseline are independently associated with lower graft function in type 1 diabetic patients receiving intraportal islet cells under ATG-tacrolimus-mycophenolate mofetil therapy. Prospective studies are needed to assess whether control of these characteristics can help increase the function of islet cell grafts during the first year posttransplantation.

Activating systemic autoimmunity: B's, T's, and tolls

A recent advance in the treatment and understanding of autoimmune disease has been the efficacy of B-cell-targeted therapy. Such therapies are effective for several such diseases, with systemic autoimmunity being a prototypical example. The mechanism of action is not fully defined, but blocking B cell Ag presentation to T cells is likely to be important. T-B interactions probably engender a positive feedback loop that amplifies and sustains autoimmunity. But how is self-tolerance first broken to initiate this loop? I propose, based on recent data, a model in which autoreactive B cells are activated first, independent of T cells, but dependent upon BCR and TLR signals. These activated B cells then break T cell tolerance, resulting in full-blown autoimmunity.

Type I IFNs and their role in the development of autoimmune diseases

BACKGROUND

Since their initial use in the 1980s, IFNs have become an essential component of the therapy for many diseases such as hepatitis and multiple sclerosis. Although they have been extremely useful in conditions that pose therapeutic challenges, complications associated with their use have been widely reported including emerging reports of several autoimmune diseases. Many of these reports have shed light on the pathogenesis of autoimmune disorders and helped to highlight not only the critical role of type I IFNs in defense against viral infections but also the pivotal role they occupy in the interface between innate and adaptive immunity. Many patients with autoimmune disease have increased responsiveness to type I IFNs (alpha/beta), and therapy with these cytokines has induced or unmasked autoimmune disease in many additional patients.

OBJECTIVE

The objective of this paper is to discuss the role of type I IFNs in autoimmunity.

METHODS

The literature regarding type I IFNs and autoimmunity was reviewed using the Medline database from 1950 to 2009. Search terms included 'interferon alpha' and 'autoimmune disease' and 'interferon beta' and 'autoimmune disease'. Case reports, case series, reviews and prospective studies were included in the analysis.

RESULTS/CONCLUSIONS

In the literature a variety of autoimmune disorders have reportedly been induced by the use of type I IFNs, being used, although these are primarily in the form of case reports and case series. Nevertheless, there is a growing body of molecular evidence to support the clinical association. The role of IFNs in the induction of autoimmunity is complex with interplay of many genetic and environmental factors that influence the balance between normal and aberrant immune responsiveness, ultimately leading to the observed clinical manifestations.

A perspective on B-cell-targeting therapy for SLE

In recent years, large controlled trials have tested several new agents for systemic lupus erythematosus (SLE). Unfortunately, none of these trials has met its primary outcome. This does not mean progress has not been made. In fact, a great deal has been learned about doing clinical trials in lupus and about the biological and clinical effects of the drugs being tested. Many of these drugs were designed to target B cells directly, e.g., rituximab, belimumab, epratuzumab, and transmembrane activator and calcium modulator and cyclophilin ligand interactor-immunoglobulin (TACI-Ig). The enthusiasm for targeting B cells derives from substantial evidence showing the critical role of B cells in murine models of SLE, as well promising results from multiple open trials with rituximab, a chimeric anti-CD20 monoclonal antibody that specifically depletes B cells (Martin and Chan in Immunity 20(5):517-527, 2004; Sobel et al. in J Exp Med 173:1441-1449, 1991; Silverman and Weisman in Arthritis Rheum 48:1484-1492, 2003; Silverman in Arthritis Rheum 52(4):1342, 2005; Shlomchik et al. in Nat Rev Immunol 1:147-153, 2001; Looney et al. in Arthritis Rheum 50:2580-2589, 2004; Lu et al. in Arthritis Rheum 61(4):482-487, 2009; Saito et al. in Lupus 12(10):798-800, 2003; van Vollenhoven et al. in Scand J Rheumatol 33(6):423-427, 2004; Sfikakis et al. Arthritis Rheum 52(2):501-513, 2005). Why have the controlled trials of B-cell-targeting therapies failed to demonstrate efficacy? Were there flaws in design or execution of these trials? Or, were promising animal studies and open trials misleading, as so often happens? This perspective discusses the current state of B-cell-targeting therapies for human lupus and the future development of these therapies.

Cutting edge: Regulatory T cells directly suppress B cells in systemic lupus erythematosus

In systemic lupus erythematosus (SLE), adaptive CD4(+)CD25(+)Foxp3(+) regulatory T cells (Tregs) suppress Th cells that help autoantibody (autoAb)-producing B cells. It is not known whether naturally occurring Tregs can directly suppress B cells in SLE without an intermediate suppression of Th cells. This aspect is important for its implications in the natural course of SLE, because most if not all of the clinical and pathologic effects in SLE are associated with a dysregulated production of autoAbs. In this study, we show that natural Tregs can inhibit B cell activity in vitro and in vivo in SLE through cell contact-mediated mechanisms that directly suppress autoAb-producing B cells, including those B cells that increase numerically during active disease. These results indicate that one way by which natural Tregs attempt to limit humoral autoimmunity in SLE is by directly targeting autoreactive B cells.

Targeting the B cell in vasculitis

The treatment of severe vasculitides, such as antineutrophil cytoplasmic autoantibodies (ANCA)-associated vasculitis, is associated with both short- and long-term toxicities that limit its use in paediatric patients and is complicated by refractory and relapsing disease that requires increased exposure to these toxic therapies. B cells have been implicated in the pathogenesis of autoimmune diseases, including vasculitis, and represent a potential target for new therapies that may have a more acceptable toxicity profile. The use of rituximab, a biologic therapy directed against B cells, has provided valuable insight into the potential role of B-cell targeted therapies for vasculitis. Rituximab appears to be a potentially useful treatment for vasculitis in adult patients, but randomized evidence comparing it to cyclophosphamide in terms of both efficacy and toxicity is lacking, as is long-term safety data. Several other B-cell-directed therapies are in development and may offer rational alternatives or adjunctives to traditional treatments.

Generation of monoclonal antibodies against highly conserved antigens

Background

Therapeutic antibody development is one of the fastest growing areas of the pharmaceutical industry. Generating high-quality monoclonal antibodies against a given therapeutic target is very crucial for the success of the drug development. However, due to immune tolerance, some proteins that are highly conserved between mice and humans are not very immunogenic in mice, making it difficult to generate antibodies using a conventional approach.

Methodology/Principal Findings

In this report, the impaired immune tolerance of NZB/W mice was exploited to generate monoclonal antibodies against highly conserved or self-antigens. Using two highly conserved human antigens (MIF and HMGB1) and one mouse self-antigen (TNF-alpha) as examples, we demonstrate here that multiple clones of high affinity, highly specific antibodies with desired biological activities can be generated, using the NZB/W mouse as the immunization host and a T cell-specific tag fused to a recombinant antigen to stimulate the immune system.

Conclusions/Significance

We developed an efficient and universal method for generating surrogate or therapeutic antibodies against “difficult antigens” to facilitate the development of therapeutic antibodies.

How the study of children with rheumatic diseases identified interferon-alpha and interleukin-1 as novel therapeutic targets

SUMMARY

Our studies in children with rheumatic diseases have led to the identification of two of the oldest cytokines, type I interferon (IFN) and interleukin 1 (IL-1), as important pathogenic players in systemic lupus erythematosus (SLE) and systemic onset juvenile arthritis (SoJIA), respectively. These findings were obtained by studying the transcriptional profiles of patient blood cells and by assessing the biological and transcriptional effect(s) of active patient sera on healthy blood cells. We also identified a signature that can be used to promptly diagnose SoJIA from other febrile conditions. Finally, our pilot clinical trials using IL-1 blockers have shown remarkable clinical benefits in SoJIA patients refractory to other medications.

Th17 cells in rheumatoid arthritis and systemic lupus erythematosus

Recent work has implicated a novel Th effector cell subset, the Th17 cell subset, in the development of both rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) because of the ability of Th17 cells to produce cytokines like IL-17 and IL-21 that can drive both inflammatory and humoral responses. In this review, we will discuss recent studies that have begun elucidating the factors that regulate the development of Th17 cells and provide a brief overview of the role of Th17 cells in RA and SLE.

[Immunoablation followed by autologous stem cell transplantation in lupus: a clinical update]

Systemic lupus erythematosus (SLE) is a classic systemic autoimmune disease. Standard treatment consists of chronic therapy with antimalarials, glucocorticoids and immunosuppressive/cytotoxic drugs, which is associated with considerable side effects. In contrast, immunoablation of autoreactive immunologic memory followed by autologous stem cell transplantation (ASCT) has been the only regimen capable of inducing long-term remission of up to 10 years after cessation of immunosuppressive therapy, even in severely affected patients. Introduced in 1996, the procedure has since been performed in 147 patients with severe SLE refractory to standard treatment in clinical studies worldwide. Most of these patients achieved clinical long-term remission. However, SLE relapses and secondary autoimmune disorders have been reported. Transplant-related mortality occurred in 6% of the 147 cases, with a wide center effect (2-13%). Here we summarise the results published in the literature on immunoablation followed by ASCT in SLE and discuss future perspectives for optimising this therapeutic approach. It may be possible to improve the outcome and reduce the risks of treatment by identifying patients with a poor prognosis at an early stage, before irreversible organ damage has taken place.

A single helper T cell clone is sufficient to commit polyclonal naive B cells to produce pathogenic IgG in experimental pemphigus vulgaris

The development of naive B cells into IgG-producing memory B cells requires cognate T cell-B cell interaction in Ag-specific immune responses. It is unknown whether a single T cell clone is sufficient or whether multiple clones are necessary to induce polyclonal IgG production in vivo. We addressed this issue using a mouse model of pemphigus vulgaris, a fatal autoimmune blistering skin disease caused by IgG autoantibodies against desmoglein (Dsg) 3. We previously isolated several Dsg3-reactive T cell clones from Dsg3(-/-) mice. Among these, two pathogenic T cell clones induced anti-Dsg3 IgG production and the development of a pemphigus phenotype when adoptively transferred with unprimed B cells from Dsg3(-/-) mice. IgG Abs harvested from recipient mice reacted with at least three parts of the extracellular domain of Dsg3, as determined using domain-swapped Dsg3/Dsg1 molecules. The anti-Dsg3 IgGs included at least two subclasses among IgG1, IgG2a, IgG2b, and IgG3 in each mouse. The anti-Dsg3 IgG induced by Dsg3-reactive T cell clones with primed B cells from Dsg3(-/-) mice also showed reactivity against different parts of the molecule, with a similar epitope distribution. Together, these results indicate that a single potent Dsg3-reactive T cell is sufficient to commit polyclonal naive B cells to produce pathogenic anti-Dsg3 IgG Abs and induce the PV phenotype. These findings provide an important framework for examining immunological mechanisms in Ab-mediated autoimmune diseases.

Elevated ATG5 expression in autoimmune demyelination and multiple sclerosis

Multiple sclerosis (MS) is an inflammatory central nervous system (CNS) disorder characterized by T cell-mediated demyelination. In MS, prolonged T cell survival and increased T cell proliferation have been linked to disease relapse and progression. Recently, the autophagy-related gene 5 (Atg5) has been shown to modulate T cell survival. In this study, we examined the expression of Atg5 using both a mouse model of autoimmune demyelination as well as blood and brain tissues from MS cases. Quantitative real-time PCR analysis of RNA isolated from blood samples of experimental autoimmune encephalomyelitis (EAE) mice revealed a strong correlation between Atg5 expression and clinical disability.Analysis of protein extracted from these cells confirmed both upregulation and post-translational modification of Atg5, the latter of which was positively correlated with EAE severity. Analysis of RNA extracted from T cells isolated by negative selection indicated that Atg5 expression was significantly elevated in individuals with active relapsing-remitting MS compared to non-diseased controls. Brain tissue sections from relapsing-remitting MS cases examined by immunofluorescent histochemistry suggested that encephalitogenic T cells are a source of Atg5 expression in MS brain samples. Together these data suggest that increased T cell expression of Atg5 may contribute to inflammatory demyelination in MS.

[Targeting B cells in multiple sclerosis. Current concepts and strategies]

Multiple sclerosis (MS) is a chronic inflammatory demyelinating autoimmune disease of the CNS and a leading cause of lasting neurological disability in younger adults. In the last decade our knowledge of its immunopathogenesis expanded vastly. It is now widely appreciated that B cells are key players in the autoreactive immune network. They exert far more functions than merely being the precursors of antibody-producing plasma cells. B cells act as efficient antigen-presenting cells and may stimulate an autoreactive immune response through secretion of proinflammatory cytokines. It is thus only logical to test therapeutic strategies targeting B cells in MS. Rituximab is a depleting chimeric monoclonal antibody directed against CD20 and expressed on developing, naïve, and memory B cells but not stem or plasma cells. Several smaller studies have been conducted that led to a placebo controlled, double blind phase II study on efficacy which was reported recently. The results are very promising, meeting not only the primary endpoint of reduction of the surrogate MRI marker of contrast-enhancing lesions but also showing a reduction in clinical relapse rate of patients treated with rituximab. This review discusses the role of autoreactive B cells in the context of MS, analyzes the B-cell-depleting treatment studies reported, and provides information on planned and future B-cell-directed therapeutic strategies in MS.

Central tolerance regulates B cells reactive with Goodpasture antigen alpha3(IV)NC1 collagen

Patients and rodents with Goodpasture's syndrome (GPS) develop severe autoimmune crescentic glomerulonephritis, kidney failure, and lung hemorrhage due to binding of pathogenic autoantibodies to the NC1 domain of the alpha3 chain of type IV collagen. Target epitopes are cryptic, normally hidden from circulating Abs by protein-protein interactions and the highly tissue-restricted expression of the alpha3(IV) collagen chain. Based on this limited Ag exposure, it has been suggested that target epitopes are not available as B cell tolerogens. To determine how pathogenic anti-GPS autoantibody responses are regulated, we generated an Ig transgenic (Tg) mouse model that expresses an Ig that binds alpha3(IV)NC1 collagen epitopes recognized by serum IgG of patients with GPS. Phenotypic analysis reveals B cell depletion and L chain editing in Tg mice. To determine the default tolerance phenotype in the absence of receptor editing and endogenous lymphocyte populations, we crossed Tg mice two generations with mice deficient in Rag. Resulting Tg Rag-deficient mice have central B cell deletion. Thus, development of Tg anti-alpha3(IV)NC1 collagen B cells is halted in the bone marrow, at which point the cells are deleted unless rescued by a Rag enzyme-dependent process, such as editing. The central tolerance phenotype implies that tolerizing self-Ag is expressed in bone marrow.

Fas expression on antigen-specific T cells has costimulatory, helper, and down-regulatory functions in vivo for cytotoxic T cell responses but not for T cell-dependent B cell responses

Fas-mediated apoptosis is an important contributor to contraction of Ag-driven T cell responses acting only on activated Ag-specific T cells. The effects of targeted Fas deletion on selected cell populations are well described however little is known regarding the consequences of Fas deletion on only activated Ag-specific T cells. We addressed this question using the parent-into-F(1) (P-->F(1)) model of acute or chronic (lupus-like) graft-vs-host disease (GVHD) as a model of either a CTL-mediated or T-dependent B cell-mediated response, respectively. By transferring Fas-deficient lpr donor T cells into Fas-intact F(1) hosts, the in vivo role of Ag-specific T cell Fas can be determined. Our results demonstrate a novel dichotomy of Ag-specific T cell Fas function in that: 1) Fas expression on Ag-activated T cells has costimulatory, helper, and down-regulatory roles in vivo and 2) these roles were observed only in a CTL response (acute GVHD) and not in a T-dependent B cell response (chronic GVHD). Specifically, CD4 T cell Fas expression is important for optimal CD4 initial expansion and absolutely required for help for CD8 effector CTL. Donor CD8 T cell Fas expression played an important but not exclusive role in apoptosis and down-regulation. By contrast, CD4 Fas expression played no detectable role in modulating chronic GVHD induction or disease expression. These results demonstrate a novel role for Ag-specific T cell Fas expression in in vivo CTL responses and support a review of the paradigm by which Fas deficiency accelerates lupus in MRL/lpr lupus-prone mice.

Immuno-therapeutic potential of haematopoietic and mesenchymal stem cell transplantation in MS

In the last few years there has been extraordinary progress in the field of stem cell research. Two types of stem cells populate the bone marrow: haematopoietic stem/progenitor cells (HSC) and mesenchymal stem cells (MSC). The capacity of HSC to repopulate the blood has been known and exploited therapeutically for at least four decades. Today, haematopoietic stem cell transplantation (HSCT) holds a firm place in the therapy of some haematological malignancies, and a potential role of HSCT for treatment of severe autoimmune diseases has been explored in small-scale clinical studies. Multiple sclerosis (MS) is the noncancerous immune mediated disease for which the greatest number of transplants has been performed to date. The results of clinical studies are double-faced: on the one hand, HSCT has demonstrated powerful effects on acute inflammation, arresting the development of focal CNS lesions and clinical relapses; on the other hand, the treatment did not arrest chronic worsening of disability in most patients with secondary progressive MS, suggesting limited or no beneficial effects on the chronic processes causing progressive disability. MSC are a more recent addition to the range of experimental therapies being developed to treat MS. While interest in MSC usage was originally raised by their potential capacity to differentiate into different cell lineages, recent work showing their interesting immunological properties has led to a revised concept, envisioning their utilization for immuno-modulatory purposes. In this review we will summarize the current clinical and experimental evidence on HSC and MSC and outline some key questions warranting further investigation in this exciting research area.

Altered dendritic cells with tolerizing phenotype in patients with systemic lupus erythematosus

Earlier we showed the generation of tolerizing human monocyte-derived DC following interaction with iC3b-opsonized apoptotic cells. In this study we examine the generation of DC with our previously described tolerogenic phenotype in patients with the systemic autoimmune disease systemic lupus erythematosus (SLE). Monocyte-derived DC were generated in 71 SLE patients, characterized, and then tested for clearance of iC3b-opsonized 1,1'-dioctadecyl-3,3,3',3'-tetramethyl-indocarbocyanineperchlorate-stained apoptotic cells using flow cytometry, and for autologous T-cell activation using autologous mixed lymphocyte reaction (AMLR), at the same time as controls. Compared with healthy, age- and gender-matched controls, SLE patients showed upregulation of MHC class II, with a mean expression of 130.5%+/-36.8% (p < 0.007); CD86 in immature DC from SLE patients, generated in autologous human or control plasma, were also upregulated, with mean expression 106.6%+/-18.0% (p < 0.03). A significant (> 20%) reduction in iC3b-apoptotic cell uptake, together with increased autologous mixed lymphocyte reaction, was seen in 75% of SLE patients. Mean 1,1'-dioctadecyl-3,3,3',3'-tetramethyl-indocarbocyanineperchlorate-stained apoptotic cell acquisition was 70.0%+/-24% (p < 0.0001) compared with healthy controls. Altered generation of a tolerizing DC phenotype was seen in at least one third of SLE patients following interaction with iC3b-opsonized apoptotic cells. These results suggest that a substantial portion of SLE patients fail to generate DC with a tolerizing phenotype.

A common repertoire of autoantibodies is shared by cancer and autoimmune disease patients: Inflammation in their induction and impact on tumor growth

The repertoire of autoantibodies found in cancer patients partly overlaps with that typical of patients with autoimmune diseases. Beside the biochemical and immunological properties of the target antigens and their altered expression in tumor tissues, the intratumoral inflammatory context can play a key role in the induction of autoimmune disease-associated autoantibodies in cancer patients. Furthermore, the impact of such antibodies on cancer growth and progression can be deeply influenced by the interplay with inflammation. The characterization of the spontaneous humoral responses occurring in cancer patients, of the mechanisms that trigger and sustain the autoantibody response and of the biological effects of such autoantibodies may help the rational design of anti-cancer immunotherapeutic protocols.

T cell-independent and toll-like receptor-dependent antigen-driven activation of autoreactive B cells

On the lupus-prone MRL-lpr/lpr (MRL-lpr) background, AM14 rheumatoid factor (RF) B cells are activated, differentiate into plasmablasts, and undergo somatic hypermutation outside of follicles. Using multiple strategies to impair T cells, we found that such AM14 B cell activation did not require T cells but could be modulated by them. In vitro, the signaling adaptor MyD88 is required for IgG anti-chromatin to stimulate AM14 B cell proliferation when T cells are absent. However, the roles of Toll-like receptors (TLRs) in AM14 B cell activation in vivo have not been investigated. We found that activation, expansion, and differentiation of AM14 B cells depended on MyD88; however, mice lacking either TLR7 or TLR9 displayed partial defects, indicating complex roles for these receptors. T cell-independent activation of certain autoreactive B cells, which gain stimuli via endogenous TLR ligands instead of T cells, may be the initial step in the generation of canonical autoantibodies.

B cells drive lymphocyte activation and expansion in mice with the CD45 wedge mutation and Fas deficiency

CD45 and Fas regulate tyrosine phosphorylation and apoptotic signaling pathways, respectively. Mutation of an inhibitory wedge motif in CD45 (E613R) results in hyperresponsive thymocytes and B cells on the C57BL/6 background, but no overt autoimmunity, whereas Fas deletion results in a mild autoimmune disease on the same genetic background. In this study, we show that these two mutations cooperate in mice, causing early lethality, autoantibody production, and substantial lymphoproliferation. In double-mutant mice, this phenotype was dependent on both T and B cells. T cell activation required signaling in response to endogenous or commensal antigens, demonstrated by the introduction of a transgenic T cell receptor. Genetic deletion of B cells also prevented T cell activation. Similarly, T cells were necessary for B cell autoantibody production. However, B cells appeared to be intrinsically activated even in the absence of T cells, suggesting that they may drive the phenotype of these mice. These results reveal a requirement for careful control of B cell signaling and cell death in preventing inappropriate lymphocyte activation and autoimmunity.

Mapping similarities in mTOR pathway perturbations in mouse lupus nephritis models and human lupus nephritis

Introduction

Treatment with sirolimus, a mammalian target of rapamycin (mTOR) inhibitor, has been shown to be efficacious in the MRL/lpr and NZB × NZW F1 mouse models of lupus nephritis, indicating a critical role for the mTOR pathway in both models. This type of demonstration of efficacy in animal models is usually a pre-requisite for advancement into clinical development. However, efficacy in an animal model often has not translated to the desired activity in the clinic. Therefore, a more profound understanding of the mechanistic similarities and differences between various animal models and human diseases is highly desirable.

Methods

Transcriptional profiling was performed on kidneys from mice with lupus nephritis; from mice who had efficacious drug treatment; and from mice before they developed nephritis. Analysis of variance with false discovery rate adjusted to p < 0.05 and an average fold change of two or more was used to identify transcripts significantly associated with disease and response to therapy. Pathway analyses (using various bioinformatics tools) were carried out to understand the basis for drug efficacy in the mouse model. The relevance in human lupus of the pathways identified in the mouse model was explored using information from several databases derived from the published literature.

Results

We identified a set of nephritis-associated genes in mouse kidney. Expression of the majority of these returned to asymptomatic levels on sirolimus treatment, confirming the correlation between expression levels and symptoms of nephritis. Network analysis showed that many of these nephritis genes are known to interact with the mTOR pathway. This led us to ask what human diseases are linked to the mTOR pathway. We constructed the mTOR pathway interactome consisting of proteins that interact with members of the mTOR pathway and identified a strong association between mTOR pathway genes and genes reported in the literature as being involved in human lupus.

Conclusions

Our findings implicate the mTOR pathway as a critical contributor to human lupus. This broad pathway-based approach to understanding the similarities in, and differences between, animal models and human diseases may have broader utility.

Depletion of autoreactive immunologic memory followed by autologous hematopoietic stem cell transplantation in patients with refractory SLE induces long-term remission through de novo generation of a juvenile and tolerant immune system

Clinical trials have indicated that immunoablation followed by autologous hematopoietic stem cell transplantation (ASCT) has the potential to induce clinical remission in patients with refractory systemic lupus erythematosus (SLE), but the mechanisms have remained unclear. We now report the results of a single-center prospective study of long-term immune reconstitution after ASCT in 7 patients with SLE. The clinical remissions observed in these patients are accompanied by the depletion of autoreactive immunologic memory, reflected by the disappearance of pathogenic anti-double-stranded DNA (dsDNA) antibodies and protective antibodies in serum and a fundamental resetting of the adaptive immune system. The latter comprises recurrence of CD31(+)CD45RA(+)CD4(+) T cells (recent thymic emigrants) with a doubling in absolute numbers compared with age-matched healthy controls at the 3-year follow-up (P = .016), the regeneration of thymic-derived FoxP3(+) regulatory T cells, and normalization of peripheral T-cell receptor (TCR) repertoire usage. Likewise, responders exhibited normalization of the previously disturbed B-cell homeostasis with numeric recovery of the naive B-cell compartment within 1 year after ASCT. These data are the first to demonstrate that both depletion of the autoreactive immunologic memory and a profound resetting of the adaptive immune system are required to reestablish self-tolerance in SLE.

B cells as therapeutic targets in autoimmune neurological disorders

B cells have a fundamental role in the pathogenesis of various autoimmune neurological disorders, not only as precursors of antibody-producing cells, but also as important regulators of the T-cell activation process through their participation in antigen presentation, cytokine production, and formation of ectopic germinal centers in the intermeningeal spaces. Two B-cell trophic factors-BAFF (B-cell-activating factor) and APRIL (a proliferation-inducing ligand)-and their receptors are strongly upregulated in many immunological disorders of the CNS and PNS, and these molecules contribute to clonal expansion of B cells in situ. The availability of monoclonal antibodies or fusion proteins against B-cell surface molecules and trophic factors provides a rational approach to the treatment of autoimmune neurological diseases. This article reviews the role of B cells in autoimmune neurological disorders and summarizes the experience to date with rituximab, a B-cell-depleting monoclonal antibody against CD20, for the treatment of relapsing-remitting multiple sclerosis, autoimmune neuropathies, neuromyelitis optica, paraneoplastic neurological disorders, myasthenia gravis, and inflammatory myopathies. It is expected that ongoing controlled trials will establish the efficacy and long-term safety profile of anti-B-cell agents in several autoimmune neurological disorders, as well as exploring the possibility of a safe and synergistic effect with other immunosuppressants or immunomodulators.

B cell depletion with anti-CD79 mAbs ameliorates autoimmune disease in MRL/lpr mice

MRL/lpr mice develop a spontaneous systemic lupus erythematosus-like autoimmune syndrome due to a dysfunctional Fas receptor, with contributions from other less well-defined genetic loci. The removal of B cells by genetic manipulation not only prevents autoantibody formation, but it also results in substantially reduced T cell activation and kidney inflammation. To determine whether B cell depletion by administration of Abs is effective in lupus mice with an intact immune system and established disease, we screened several B cell-specific mAbs and found that a combination of anti-CD79alpha and anti-CD79beta Abs was most effective at depleting B cells in vivo. Anti-CD79 therapy started at 4-5 mo of age in MRL/lpr mice significantly decreased B cells (B220(+)CD19(+)) in peripheral blood, bone marrow, and spleens. Treated mice also had a significant increase in the number of both double-negative T cells and naive CD4(+) T cells, and a decreased relative abundance of CD4(+) memory cells. Serum anti-chromatin IgG levels were significantly decreased compared with controls, whereas serum anti-dsDNA IgG, total IgG, or total IgM were unaffected. Overall, survival was improved with lower mean skin scores and significantly fewer focal inflammatory infiltrates in submandibular salivary glands and kidneys. Anti-CD79 mAbs show promise as a potential treatment for systemic lupus erythematosus and as a model for B cell depletion in vivo.

Therapeutic benefit of treatment with anti-thymocyte globulin and latent TGF-β1 in the MRL/lpr lupus mouse model

The pathogenesis of systemic lupus erythematosus is believed to involve defects in regulatory T cell (Treg) activity and abnormal activation of B and T lymphocytes. The purpose of this study was to test the therapeutic potential of rabbit anti-mouse thymocyte globulin (ATG), a lymphocyte-depleting agent, in conjunction with transforming growth factor (TGF)-β1, a factor involved in the induction and expansion of Tregs. MRL/lpr mice with active disease were treated with ATG followed by a 12-day course of latent TGF-β1 during the period of lymphocyte repopulation. Treatment with ATG + latent TGF-β1 synergistically inhibited the progression of proteinuria and albuminuria and provided a significant improvement in long-term survival. This therapeutic benefit correlated histologically with reduced glomerular pathology and protein cast formation. The mechanism of action did not involve suppression of autoantibody formation but may involve the activity of CD4+CD25+FoxP3+ Tregs, which were found to be induced by ATG + TGF-β1 treatment in vitro.