F1 hybrid New Zealand Black (NZB) x New Zealand White (NZM) (NZB/NZW) mice spontaneously develop an autoimmune disease analogous to systemic lupus erythematosus (SLE). Testosterone experts a powerful suppressive effect on this disorder in adult NZB/NZW mice. A series of experiments was designed to determine if disease would also be suppressed by exposing fetal NZB/NZW mice to increased testosterone. A model was developed in which NZB dams carrying NZB/NZW fetuses were treated with testosterone in a dose adequate to masculinize the external genitalia in female fetuses. NZB/NZW mice that were derived from testosterone-treated dams and control NZB/NZW offspring were followed in a longevity study and had serial assays to assess development of SLE. Additional experiments were carried out to measure lymphocyte subsets and responses to mitogens. Results were compared with F1 hybrid offspring of C57BL/6 dams crossed with DBA/2 males, which are not autoimmune and do not develop SLE. Spleen cells from these groups were tested for Thy 1.2, CD4, CD8, and IgM receptors, and for responses to the mitogens Concanavalin A (ConA) and lipopolysaccharide. Control male NZB/NZW fetuses had unexpectedly high serum estradiol, which decreased significantly with maternal testosterone treatment. The testosterone-exposed male NZB/NZW fetuses developed into adults that lived longer than male NZB/NZW controls. Testosterone treatment of the dam was associated with elevated terminal anti-DNA levels but did not alter markers of renal diseases in adult NZB/NZW mice of either sex. Testosterone-exposed NZB/NZW females had altered T-lymphocyte subsets and testosterone-exposed males had increased response to ConA compared to controls. In male NZB/NZW fetuses whose mothers were administered testosterone, the naturally high level of circulating estradiol observed in untreated male fetuses was decreased significantly. This decrease was associated with an increase in longevity. This unique observation has important implications for fetal exposure to endocrine disruptors in the environment.
IFNα is known to play a critical role in the pathogenesis of systemic lupus erythematosus (SLE), but the mechanisms remain unclear. We previously showed that within weeks, exposure to IFNα in vivo induces lupus in pre-autoimmune lupus-prone NZB × NZW F1 (NZB/W) but not in BALB/c mice. In the current study, we show that in vivo expression of IFNα induces sustained B cell proliferation in both BALB/c and NZB/W mice. In NZB/W but not BALB/c mice, B cell proliferation was accompanied by a rapid and unabated production of autoantibody-secreting cells (ASCs) in secondary lymphoid organs, suggesting that a B cell checkpoint is altered in the autoimmune background. The majority (>95%) of ASCs elicited in IFNα-treated NZB/W mice were short-lived and occurred without the induction of long-lived plasma cells. A short course of cyclophosphamide caused a sharp drop in IFNα-elicited short-lived plasma cells, but the levels recovered within days following termination of treatment. Thus, our work provides new insights into effectiveness and limitations of current SLE therapies.
lupus; interferon alpha; B lymphocytes; short-lived plasma cells; cyclophosphamide
Systemic lupus erythematosus (SLE) is considered a prototype of systemic autoimmune diseases; however, despite considerable advances in recent years in the understanding of basic mechanisms in immunology, little progress has been made in elucidating the etiology and pathogenesis of this disease. This even holds for inbred mice, such as the lupus-prone New Zealand Black/New Zealand White (NZB/NZW) F1 mice, which are all genetically programmed to develop lupus at a predetermined age. This frustrating state of affairs calls for a fundamental change in our scientific thinking, and the opening of new directions in lupus research. Here, we suggest that intrinsic B cell tolerance mechanisms are not grossly impaired in lupus-prone mice, but that an unusually strong positive selection event recruits a small number of autoreactive B cells to the germinal centers. This event could be facilitated by nucleic acid–protein complexes that are created by somatic changes in the susceptible animal.
B cell tolerance; Lupus; Anti-DNA; NZB/NZW mice; Retroelements
MRL/MpJ-Faslpr/lpr/J (MRLlpr) mice develop lupus-like disease manifestations in an IL-21–dependent manner. IL-21 is a pleio-tropic cytokine that can influence the activation, differentiation, and expansion of B and T cell effector subsets. Notably, auto-reactive CD4+ T and B cells spontaneously accumulate in MRLlpr mice and mediate disease pathogenesis. We sought to identify the particular lymphocyte effector subsets regulated by IL-21 in the context of systemic autoimmunity and, thus, generated MRLlpr mice deficient in IL-21R (MRLlpr.IL-21R−/−). Lymphadenopathy and splenomegaly, which are characteristic traits of the MRLlpr model were significantly reduced in the absence of IL-21R, suggesting that immune activation was likewise decreased. Indeed, spontaneous germinal center formation and plasma cell accumulation were absent in IL-21R–deficient MRLlpr mice. Correspondingly, we observed a significant reduction in autoantibody titers. Activated CD4+ CD44+ CD62Llo T cells also failed to accumulate, and CD4+ Th cell differentiation was impaired, as evidenced by a significant reduction in CD4+ T cells that produced the pronephritogenic cytokine IFN-γ. T extrafollicular helper cells are a recently described subset of activated CD4+ T cells that function as the primary inducers of autoantibody production in MRLlpr mice. Importantly, we demonstrated that T extrafollicular helper cells are dependent on IL-21R for their generation. Together, our data highlighted the novel observation that IL-21 is a critical regulator of multiple pathogenic B and T cell effector subsets in MRLlpr mice.
Malaria infection is accompanied by the production of a number of autoantibodies, including some that react with DNA. Epidemiological evidence implicates these in the nephritides that arise in human quartan malaria and in experimental malaria infections in mice. Through parallels with the involvement of DNA-reactive antibodies in the autoimmune syndrome systemic lupus erythematosus, a role for DNA-reactive antibodies in forming phlogistic immune deposits in the kidneys is implied. To more fully understand the relationship between antibodies of this specificity made in malaria and systemic lupus erythematosus, we prepared monoclonal DNA-reactive antibodies from BALB/c mice infected with Plasmodium berghei (clone RC) and compared their properties with those of other antibodies previously isolated from lupous MRL/Mp lpr/lpr and (NZB x NZW)F1 mice. Antibodies from malarial mice were all immunoglobulin M class and bound to single-stranded but not double-stranded DNA in an enzyme-linked immunosorbent assay. They also reacted with synthetic polyribonucleotides in the enzyme-linked immunosorbent assay and with parasitized erythrocytes and parasite pigment in kidney sections. None of the antibodies from lupous mice had identical specificities. The potential involvement of the DNA-reactive antibodies in malarial nephritis was demonstrated, by use of immunocytochemical methods, on the basis of their binding to existing immune deposits in kidney sections from malarial mice, a similar property having been previously demonstrated for antibodies from lupous mice. Furthermore, antibodies from malarial mice expressed public idiotypes, notably Id.V-88, which is a member of the Id.16/6 family, commonly found on DNA-reactive antibodies in lupus and other infectious and connective tissue diseases. This study indicates that DNA-reactive antibodies in malaria have immunochemical properties similar but not identical to those of such antibodies in systemic lupus erythematosus and that they have the potential to participate in the formation of immune deposits in nephritic malarial kidneys.
Immunization with portions of a murine antibody to DNA induced Ig peptide-reactive peripheral CD8+ inhibitory T (Ti) cells in non-autoimmune (BALB/c × NZW) F1 (CWF1) mice. Those Ti suppressed in vitro production of IgG anti-DNA by lymphocytes from MHC-matched, lupus-prone (NZB × NZW) F1 (BWF1) mice, primarily via secretion of transforming growth factor-β (TGF-β). 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-β, 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.
Inhibitory CD8+ T cells; Lupus
Autoimmunity leads to the activation of innate effector pathways, pro-inflammatory cytokine production, and end-organ injury. Macrophage migration inhibitory factor (MIF) is an upstream activator of the innate response that mediates the recruitment and retention of monocytes via CD74 and associated chemokine receptors, and it has a role in the maintenance of B lymphocytes. High-expression MIF alleles also are associated with end-organ damage in different autoimmune diseases. We assessed the therapeutic efficacy of ISO-1, an orally bioavailable, MIF antagonist, in two distinct models of systemic lupus erythematosus (SLE): the NZB/NZW F1 and the MRL/lpr mouse strains. ISO-1, like anti-MIF, inhibited the interaction between MIF and its receptor, CD74, and in each model of disease, it reduced functional and histological indices of glomerulonephritis, CD74+ and CXCR4+ leukocyte recruitment, and pro-inflammatory cytokine and chemokine expression. Neither autoantibody production nor T and B cell activation were significantly affected, pointing to the specificity of MIF antagonism in reducing excessive pro-inflammatory responses. These data highlight the feasibility of targeting the MIF–MIF receptor interaction by small molecule antagonism and support the therapeutic value of downregulating MIF-dependent pathways of tissue damage in SLE.
Autoimmunity; Cytokine; Innate Immunity
Systemic lupus erythematosus and its murine equivalent, modelled in the New Zealand Black and New Zealand White (NZB × NZW)F1 hybrid strain, are polygenic inflammatory diseases, probably reflecting an autoimmune response to debris from cells undergoing programmed cell death. Several human and murine loci contributing to disease have been defined. The present study asks whether the proinflammatory purinergic receptor P2X7, an initiator of a form of programmed cell death known as aponecrosis, is a candidate product of murine and human lupus susceptibility loci. One such locus in (NZB × NZW)F1 mice is lbw3, which is situated at the distal end of NZW chromosome 5. We first assess whether NZB mice and NZW mice carry distinct alleles of the P2RX7 gene as expressed by common laboratory strains, which differ in sensitivity to ATP stimulation. We then compare the responses of NZB lymphocytes, NZW lymphocytes and (NZB × NZW)F1 lymphocytes to P2X7 stimulation. NZB and NZW parental strains express the distinct P2X7-L and P2X7-P alleles of P2RX7, respectively, while lymphocytes from these and (NZB × NZW)F1 mice differ markedly in their responses to P2X7 receptor stimulation. NZB mice and NZW mice express functionally distinct alleles of the proinflammatory receptor, P2X7. We show that current mapping suggests that murine and human P2RX7 receptor genes lie within lupus susceptibility loci lbw3 and SLEB4, and we argue that these encode a product with the functional characteristics consistent with a role in lupus. Furthermore, we argue that aponecrosis as induced by P2X7 is a cell death mechanism with characteristics that potentially have particular relevance to disease pathogenesis.
Systemic lupus erythematosus is a complement-mediated autoimmune disease. While genetic deficiencies of classical pathway components lead to an increased risk of developing systemic lupus erythematosus, end organ damage is associated with complement activation and immune complex deposition. The role of classical pathway regulators in systemic lupus erythematosus is unknown. C4 binding protein (C4bp) is a major negative regulator of the classical pathway. In order to study the role of C4bp deficiency in an established murine model of lupus nephritis, mice with a targeted deletion in the gene encoding C4bp were backcrossed into the MRL/lpr genetic background. Compared with control MRL/lpr mice, C4bp knockout MLR/lpr mice had similar mortality and similar degrees of lymphoproliferation. There were no differences in the extent of proteinuria or renal inflammation. Staining for complement proteins and immunoglobulins in the kidneys of diseased mice revealed no significant strain differences. Moreover, there was no difference in autoantibody production or in levels of circulating immune complexes. In comparison with C57BL/6 mice, MRL/lpr mice had depressed C4 levels as early as 3 weeks of age. The absence of C4bp did not impact serum C4 levels or alter classical pathway hemolytic activity. Given that immune complex renal injury in the MRL/lpr mouse is independent of Fc receptors as well as the major negative regulator of the classical pathway, new mechanisms for immune-complex-mediated renal injury need to be considered.
Although systemic lupus erythematosis (SLE) is usually evaluated with regard to autoimmune reactivity toward the kidney, there are multiple psychiatric abnormalities associated with this autoimmune disease. Lupus-prone male NZM88 mice, derived from NZB/NZW F1 mice, develop early neuropsychiatric manifestations without any signs of nephritis. In addition to the usual repertoire of antibody specificities, including autoantibodies to dsDNA and renal antigens, mice of this inbred strain express autoantibodies to numerous brain antigens. Here, we show that autoantibodies to brain antigens, assessed by Western analysis, are as individually varied as are the diverse neuropsychiatric manifestations observed in SLE patients. Additionally, a monoclonal antibody derived from the spleen of an untreated NZM88 male when injected into healthy BALB/cByJ, but not C57BL/6J, mice induced behaviors similar to those of lupus-prone NZM88 mice. This monoclonal antibody, which is specific to dynamin-1, binds preferentially in BALB/cByJ cortex and induces substantial expression of cytokines mainly in the hypothalamus. Thus, an antibody to just one brain antigen can induce multiple behavioral changes, and multiple autoantibodies to different brain antigens exist in lupus-prone mice; however, susceptibility to the induction of neurobehavioral deficits is dependent on host genetics.
lupus; neuropsychiatric; dynamin-1; autoantibody
In murine models of systemic lupus erythematosus (SLE), administration of either prolactin or estradiol (E2) increases autoimmunity, and there is evidence that elevated prolactin in response to E2 administration may contribute substantially to E2 effects. Hormonal influence on SLE can extend to environmental agents, as demonstrated by the ability of estrogenic organochlorine pesticides such as chlordecone to accelerate the development of lupus in female (NZB x NZW)F1 mice. In order to evaluate a potential role for prolactin in chlordecone effects on SLE, it was necessary to first determine whether treatment with chlordecone, like E2, results in elevated prolactin levels. Ovariectomized (NZB x NZW)F1 mice were treated for 5–6 weeks with chlordecone or E2 in doses shown previously to significantly shorten the time to onset of SLE. At the end of the treatment period, serum prolactin levels were increased 10- to 20-fold in E2-treated mice compared to untreated controls, but decreased in an apparent dose-dependent manner in mice treated with chlordecone. Prolactin receptor in purified B and CD4 T cells from treated animals, assessed through measurement of mRNA using quantitative real-time PCR, was increased by E2 treatment but unchanged in response to chlordecone. These observations suggest that the role of prolactin in eliciting autoimmunity in E2-treated animals is absent in the case of chlordecone, and by implication, that chlordecone possesses other actions that can replace the contribution of prolactin to development of SLE.
prolactin; estradiol; systemic lupus erythematosus; chlordecone; organochlorine pesticides
Systemic lupus erythematosus (SLE) is an autoimmune disorder that affects women more frequently than men. In the (NZB × NZW)F1 mouse, a murine SLE model, the presence or absence of estrogen markedly influences the rate of progression of disease. Three organochlorine pesticides with estrogenic effects were administered chronically to ovariectomized female (NZB × NZW)F1 mice, and we measured the time to development of renal disease, the principal clinical manifestation of lupus in this model. Treatment with chlordecone, methoxychlor, or o,p′-dichlorodiphenyl-trichloroethane (o,p′-DDT) significantly decreased the time to onset of renal impairment, as did treatment with 17β-estradiol used as a positive control. In an expanded study of chlordecone, we found a dose-related early appearance of elevated anti–double-strand DNA autoantibody titers that corresponded with subsequent development of glomerulonephritis. Immunohistofluorescence confirmed early deposition of immune complexes in kidneys of mice treated with chlordecone. These observations are consistent with an effect of these organochlorine pesticides to accelerate the natural course of SLE in the (NZB × NZW)F1 mouse. Although we originally hypothesized that the effect on progression of autoimmunity was due to estrogenic properties of the pesticides, autoimmune effects and estrogenicity, assessed through measurement of uterine hypertrophy, were not well correlated. This may indicate that uterine hypertrophy is a poor indicator of comparative estrogenic effects of organochlorine pesticides on the immune system, or that the pesticides are influencing autoimmunity through a mode of action unrelated to their estrogenicity.
autoimmunity; chlordecone; DDT; estrogenicity; glomerulonephritis; kepone; methoxychlor; organochlorine pesticides; systemic lupus erythematosus
Systemic lupus erythematosus is a systemic inflammatory disease characterized by antibodies to nuclear molecules in association with immune complex deposition. As shown previously, microparticles (MPs), which are small membrane-bound vesicles released from dying and activated cells, contain nucleic acids and can form immune complexes found in patient blood. To assess the role of MPs in murine lupus, we used flow cytometry to measure the presence of MPs with bound IgG in the blood of MRL-lpr/lpr and NZB/W mice. These studies showed much higher numbers of MPs with bound IgG in the blood of MRL lpr/lpr compared to NZB/W mice. Furthermore, these studies showed that antibodies from MRL-lpr/lpr mice bound better to MPs from apoptotic cells than those from NZB/W mice. Together, these studies indicate important differences in the serological features of the two strains as reflected by the capacity of antibodies to bind to MPs.
autoimmunity; animal models; apoptosis; molecular immunology
The acute-phase plasma protein response to disease activity in murine models of autoimmune lupus-like disease was investigated by measurement of the concentration of serum amyloid P component (SAP) in NZB X W and MRL/l mice. The levels of SAP, which is a major acute-phase protein in mice, did not rise at all in response to progression of disease in NZB X W mice between the ages of 1 and 9 mo. This resembles the behavior of acute-phase proteins such as C-reactive protein and serum amyloid A protein in human systemic lupus erythematosus, and just as in human lupus, where the occurrence of intercurrent microbial infection can stimulate an acute-phase response, so injection of bacterial lipopolysaccharide or casein into the NZB X W mice stimulated "normal" acute-phase SAP production. In marked contrast, MRL/l mice developed greatly increased levels of SAP, which correlated closely with progression of their pathology as they aged. The disease profile of the MRL/l strain includes rheumatoid factors and spontaneous polyarthritis and their SAP response resembles the behavior of acute phase proteins in human rheumatoid arthritis. Different patterns of acute-phase response in different autoimmune disorders may thus be a reflection of the genetic predisposition to particular diseases and/or contribute to their pathogenesis. The existence of animal counterparts for the various clinical patterns of human acute-phase protein production will assist in experimental investigation of the underlying mechanisms and of the biological role of the acute-phase response.
Long-term administration of CTLA4Ig prevents the onset of disease in systemic lupus erythematosus–prone (SLE-prone) NZB/NZW F1 mice. To determine the mechanism of this effect, we engineered an adenovirus that expresses murine CTLA4Ig. Administration of a single high dose of this virus results in long-term expression of CTLA4Ig in the serum and absence of an immune response to the adenoviral vector. We administered Ad-CTLA4Ig to 19- to 22-week-old NZB/NZW F1 mice and evaluated the effect on anti-DNA antibody–producing B cells. We show that CTLA4Ig has a beneficial effect on murine SLE for as long as it is present in the serum. This effect is associated with decreased expansion of both the IgM and IgG autoreactive B-cell population, inhibition of immunoglobulin class switching, decreased frequency and altered pattern of somatic mutation, and a marked decrease in the numbers of activated CD4-positive T cells. In contrast, intrinsic B-cell hyperreactivity and the survival of plasma cells in the bone marrow, both of which are less dependent on T-cell help, appear to be unaffected by CTLA4Ig. High-dose CTLA4Ig did not induce permanent tolerance in this autoimmune disease model. Furthermore, although the mice survived in a conventional housing facility, treatment with Ad-CTLA4Ig was immunosuppressive.
Prolactin is secreted from the pituitary gland and other organs, as well as by cells such as lymphocytes. Prolactin has an immunostimulatory effect and is associated with autoimmune diseases that are characterised by abnormal B cell activation, such as systemic lupus erythematosus (SLE). Our aim was to determine if different splenic B cell subsets express the prolactin receptor and if the presence of prolactin influences these B cell subsets and correlates with development of lupus.
Using real-time PCR and flow cytometry, we found that different subsets of immature (transitional) and mature (follicular, marginal zone) B cells express different levels of the prolactin receptor and are differentially affected by hyperprolactinaemia. We found that transitional B cells express the prolactin receptor at higher levels compared to mature B cells in C57BL/6 mice and the lupus-prone MRL/lpr and MRL mouse strains. Transitional-1 (T1) B cells showed a higher level of prolactin receptor expression in both MRL/lpr and MRL mice compared to C57BL/6 mice. Hyperprolactinaemia was induced using metoclopramide, which resulted in the development of early symptoms of SLE. We found that T1 B cells are the main targets of prolactin and that prolactin augments the absolute number of T1 B cells, which reflects the finding that this B cell subpopulation expresses the highest level of the prolactin receptor.
We found that all B cell subsets express the prolactin receptor but that transitional B cells showed the highest prolactin receptor expression levels. Hyperprolactinaemia in mice susceptible to lupus accelerated the disease and increased the absolute numbers of T1 and T3 B cells but not of mature B cells, suggesting a primary effect of prolactin on the early stages of B cell maturation in the spleen and a role of prolactin in B cell differentiation, contributing to SLE onset.
Spleen tyrosine kinase (Syk) is involved in membrane-mediated signaling in various cells, including immune cells. It is overexpressed in T cells from patients with systemic lupus erythematosus (SLE), and its inhibition has been shown to improve T cell function as well as to improve disease manifestations in (NZB × NZW)F1 lupus-prone mice and in patients with rheumatoid arthritis. While clinical trials examining Syk inhibition in patients with SLE are being considered, the aim of our experiments was to determine whether the therapeutic effects of Syk inhibition extend to other strains of lupus-prone mice and whether they result in improvement in skin disease and modification of established disease.
Female MRL/lpr or BAK/BAX mice were studied. Starting either at age 4 weeks (before disease) or at age 16 weeks (after established disease) and continuing for up to 16 weeks, mice were fed chow containing the Syk inhibitor R788 or control chow.
We found that inhibition of Syk in MRL/lpr and BAK/BAX mice prevented the development of skin disease and significantly reduced established skin disease. Similarly, Syk inhibition reduced the size of the spleen and lymph nodes, suppressed the development of renal disease, and suppressed established renal disease. Discontinuation of treatment resulted in extended suppression of skin disease for at least 8 weeks and suppression of renal disease for 4 weeks.
Syk inhibition suppresses the development of lupus skin and kidney disease in lupus-prone mice, suppresses established disease in lupus-prone mice, and may represent a valuable treatment for patients with SLE.
Interleukin 23 receptor expressing IL-17 producing T cells have been shown to be important in the development of murine lupus. The usefulness of IL-23 inhibition in ameliorating lupus nephritis is unknown. We hypothesized that inhibition of IL-23 will ameliorate nephritis in lupus-prone mice. To this end, we treated MRL/lpr lupus-prone mice for 6 weeks with a rat anti-IL-23p19 antibody, which resulted in delaying the onset of nephritis without affecting the production of anti-dsDNA antibodies. The effect of the treatment was hampered by the production of murine anti-rat IgG antibodies. The amelioration of murine lupus by IL-23 inhibition strengthens the rationale for targeting IL-23 in patients with systemic lupus erythematosus.
Autoantigen presentation to T cells is crucial for the development of autoimmune disease. However, the mechanisms of autoantigen presentation are poorly understood. In this study, we show that splenic phagocytes play an important role in autoantigen presentation in murine lupus. Nucleosomes are major autoantigens in systemic lupus erythematosus. We found that nucleosome-specific T cells were stimulated dominantly in the spleen, compared with lymph nodes, lung, and thymus. Among splenic APCs, F4/80+macrophages and CD11b+CD11c+ dendritic cells were strong stimulators for nucleosome-specific T cells. When splenic phagocytes were depleted in (NZB × NZW) F1 (NZB/W F1) mice, nucleosome presentation in the spleen was dramatically suppressed. Moreover, depletion of splenic phagocytes significantly suppressed anti-nucleosome Ab and anti-dsDNA Ab production. Proteinuria progression was delayed and survival was prolonged in phagocyte-depleted mice. The numbers of autoantibody-secreting cells were decreased in the spleen from phagocyte-depleted mice. Multiple injections of splenic F4/80+ macrophages, not those of splenic CD11c+ dendritic cells, induced autoantibody production and proteinuria progression in NZB/W F1 mice. These results indicate that autoantigen presentation by splenic phagocytes including macrophages significantly contributes to autoantibody production and disease progression in lupus-prone mice.
The current view holds that chronic autoimmune diseases are driven by the continuous activation of autoreactive B and T lymphocytes. However, despite the use of potent immunosuppressive drugs designed to interfere with this activation the production of autoantibodies often persists and contributes to progression of the immunopathology. In the present study, we analyzed the life span of (auto)antibody-secreting cells in the spleens of NZB × NZW F1 (NZB/W) mice, a murine model of systemic lupus erythematosus. The number of splenic ASCs increased in mice aged 1–5 mo and became stable thereafter. Less than 60% of the splenic (auto)antibody-secreting cells were short-lived plasmablasts, whereas 40% were nondividing, long-lived plasma cells with a half-life of >6 mo. In NZB/W mice and D42 Ig heavy chain knock-in mice, a fraction of DNA-specific plasma cells were also long-lived. Although antiproliferative immunosuppressive therapy depleted short-lived plasmablasts, long-lived plasma cells survived and continued to produce (auto)antibodies. Thus, long-lived, autoreactive plasma cells are a relevant target for researchers aiming to develop curative therapies for autoimmune diseases.
plasma cell; autoimmunity; SLE; antibodies; anti-DNA
Some T cells react with lipid antigens bound to antigen-presenting molecule CD1d. Numbers and functions of a subset of such lipid-reactive T cells are reduced in patients with systemic lupus erythematosus (SLE) and their relatives, as well as in genetically susceptible and chemically induced animal models of lupus-like disease. We have reported that the germline deletion of CD1d exacerbates lupus, suggesting a protective role of these cells in the development of lupus. The use of a knockout mouse model in this study, however, did not allow examination of the role of these cells at different stages of disease. Here, we describe an approach to deplete CD1d-dependent T cells, which allowed us to investigate the role of these cells at different stages of disease in genetically lupus-prone NZB/NZW F1 (BWF1) mice. Repeated intravenous injections of large numbers of CD1d-transfected cells resulted in ~50–75% reduction in these cells, as defined by the expression of CD4, NK1.1 and CD122, and lack of expression of CD62 ligand. TCR γδ +NK1.1+ cells were also reduced in the recipients of CD1d-transfected cells as compared with control recipients. Such depletion of CD1d-reactive T cells in preclinical BWF1 mice resulted in disease acceleration with a significant increase in proteinuria and mortality. In older BWF1 mice having advanced nephritis, however, such depletion of CD1d-reactive T cells resulted in some disease improvement. Taken together, these data as well as our published studies suggest that CD1d-reactive T cells protect against the development of lupus in animal models. However, these cells appear to be unable to suppress established lupus nephritis in these animals, and might even play a disease aggravating role in late stages of disease.
animal models; antigen-presenting molecule; autoantibody; lupus nephritis
Systemic lupus erythematosus is an autoimmune disease with a high morbidity and nephritis is a common manifestation. Previous studies in murine lupus models have suggest a role for Toll-like receptor 2 and 4. We examined the role of these molecules in MRL lpr mice which is one of the most established and robust murine models. We compared disease parameters in Toll-like receptor 2 or Toll-like receptor 4 deficient mice with their littermate controls. We found no difference in the severity of glomerulonephritis as assessed by histology, serum creatinine and albuminuria when Toll-like receptor 2 or Toll-like receptor 4 deficient MRLlpr mice were compared with Toll-like receptor sufficient controls. We also found similar levels of anti-dsDNA and anti-ssDNA antibodies. These results show that Toll-like receptor 2 and Toll-like receptor 4 do not play a significant role in MRLlpr mice, and therefore they may not be important in human lupus.
Patients with systemic lupus erythematosus (SLE) have an impairment in phenotype and function of endothelial progenitor cells (EPCs) which is mediated by interferon α (IFN-α). We assessed whether murine lupus models also exhibit vasculogenesis abnormalities and their potential association with endothelial dysfunction. Phenotype and function of EPCs and type I IFN gene signatures in EPC compartments were assessed in female New Zealand Black/New Zealand White F1 (NZB/W), B6.MRL-Faslpr/J (B6/lpr) and control mice. Thoracic aorta endothelial and smooth muscle function were measured in response to acetylcholine or sodium nitropruside, respectively. NZB/W mice displayed reduced numbers, increased apoptosis and impaired function of EPCs. These abnormalities correlated with significant decreases in endolthelium-dependent vasomotor responses and with increased type I IFN signature in EPC compartments. In contrast, B6/lpr mice showed improvement in endothelium-dependent and endothelium-independent responses, no abnormalities in EPC phenotype or function and downregulation of type I IFN signatures in EPC compartments. These results indicate that NZB/W mice represent a good model to study the mechanisms leading to endothelial dysfunction and abnormal vasculogenesis in lupus. These results further support the hypothesis that type I IFNs may play an important role in premature vascular damage and, potentially, atherosclerosis development in SLE.
endothelial progenitor cells; endothelium; interferon-alpha; systemic lupus erythematosus
T cells that express IL-17 infiltrate the kidneys of patients with systemic lupus erythematosus. A significant proportion of these cells are CD3+CD4−CD8− double-negative T cells. In this study, we show that double-negative T cells from MRL/lpr mice express high amounts of IL-17 and that as disease progressively worsens, the expression of IL-17 and of IL-23 receptor in lymphocytes from these mice increases. Lymph node cells from lupus-prone mice, but not control mice, treated in vitro with IL-23 induce nephritis when transferred to non-autoimmune, lymphocyte-deficient Rag-1−/− mice. Kidney specimens from these recipient mice show significant Ig and complement deposition. The data indicate that an aberrantly active IL-23/IL-17 axis contributes to the development of nephritis in lupus-prone mice.
Systemic lupus erythematosus (SLE) is a multiphenotypic autoimmune disease. The hallmark of SLE is the production of anti-double-stranded DNA autoantibodies and the deposition of immune complexes in target tissues such as the kidney, skin, and brain. Additional phenotypic traits are the presence of arthritis, anemia, central nervous system involvement, and a variety of autoantibodies. Females of childbearing age are particularly at risk. Recent genetic analysis of murine SLE shows that susceptibility is under complex polygenic control. It is also apparent that environmental factors contribute to the induction and exacerbation of SLE. We describe here the genotypic and phenotypic characterization of a group of recombinant inbred strains of SLE-prone mice that were derived from NZB and NZW progenitors, the parental strains of the classic female F1 hybrid lupus model. Recombination and reassortment of these ancestral genomes resulted in the NZM (New Zealand mixed) strains with strain-specific patterns of renal disease penetrance and other autoimmune traits such as Coombs positive anemia and neurologic deficits. Multiple susceptibility loci of the ancestral strains demonstrate that SLE is inherited as a threshold trait. Because some of these loci co-localize with the susceptibility loci of the insulin-dependent diabetes of nonobese diabetic strain, it is apparent that there are disease-specific as well as autoimmunity-promoting genes. It is proposed that the NZM strains, particularly those with reduced disease penetrance or partial genotypes, provide an improved genetic model for assessment of the effects of environmental agents on SLE and autoimmunity.