Lupus-like Autoimmune Syndrome Research Articles

T helper cells: Top targets for systemic lupus erythematosus treatment?

In the original research article, Parisa R et al. demonstrated that the induction of lupus-like autoimmune syndrome in BALB/c Mice caused disturbance in splenic T cell subpopulations. This study also elucidated those other mechanisms, apart from disturbance in T cells balance, may be responsible for the development of the disease’s symptoms

The Role of Human Fc Gamma Receptors in the Pathophysiology of Lupus Syndrome

Systemic Lupus Erythematosus (SLE) is a chronic autoimmune syndrome, which currently has no curative treatment. The main drivers of this inflammatory disease are the IgG family autoantibodies that are produced against self‐antigens resulting from dysregulated apoptosis. These pathogenic autoantibodies form immune complexes (ICs), which become deposited in various tissues and cause organ damage. IgG ICs mainly interact with target cells by engaging with a family of receptors known as Fc gamma receptors (FcγRs). FcγRs are thought to be important contributors to inflammation in autoimmune diseases such as SLE. These receptors cooperate in modulating antigen processing and presentation, autoantibody production, and the promotion of inflammatory processes. Current mouse models do not adequately produce translatable data regarding the crucial role of FcγRs in SLE pathogenesis because the repertoire of FcγRs in mice is significantly different to that of humans. The human FcγR family consists of FcγRI, FcγRIIa, FcγRIIb, FcγRIIIa, and FcγRIIIb whereas mice express FcγRI, FcγRIIb, FcγRIII and FcγRIV. Furthermore, FcγRIIa, which is absent in wild type (WT) mice, is the only IgG receptor present on human platelets. The present study used the pristane method of lupus induction in WT mice and in mice in which all murine FcγRs have been replaced by human FcγRs (hu‐FcγR mice) to study the role of individual human FcγRs in the initiation and progression of lupus‐like autoimmune syndrome. After chemically inducing SLE in hu‐FcγR mice, we have found that both the initiation and progression of SLE is significantly accelerated compared to WT mice, suggesting that the combination of human FcγRs play a dominant role in the pathogenesis of lupus. Symptoms such as hypothermia, chopped breathing and weight loss was present in 61% of hu‐FcγR mice after 15 days or less after injection compared to only 33% in WT mice (p<0.05). hu‐FcγR mice presented splenomegaly, glomerulonephritis, and lung vasculitis as early as 10 days after injection. Antinuclear antibodies were found in 47% of injected hu‐FcγR mice compared to 28% in WT mice (p<0.05). These results suggest that FcγRs can significantly affect the development of a lupus‐like syndrome in mice. Furthermore, mice with human FcγRs should be considered as a more suitable model to study autoimmune disorders such as SLE. The present study and other necessary investigations in this topic may not only profoundly impact our knowledge of inflammation in SLE, but also identify specific FcγRs as novel therapeutic targets. Ultimately, because of the involvement of FcγRs in modulation of the inflammatory response, our findings have the potential to impact therapeutic approaches for other inflammatory autoimmune disorders, such as rheumatoid arthritis and antiphospholipid syndrome.Support or Funding InformationThis study was supported by Florida Hospital and the Adventist University of Health Sciences.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Immune modulation effects of curcumin in pristane-induced lupus mice

Background: Curcumin, a polyphenolic compound derived from food spice turmeric has been widely used in Asian traditional medicine for its medicinal properties as antitumor, antioxidant, and anti-inflammatory properties. Meanwhile, intraperitoneal (i.p.) injection of the hydrocarbon oil pristane into normal mice leads to a lupus-like autoimmune syndrome. We aimed to investigate the effects of curcumin on systemic lupus erythematosus (SLE) clinical manifestation, adaptive immune system components, proinflammatory cytokines, and autoantibody production in pristane-induced lupus mice. Methods: Fifty female BALB/c mice, 6–8 weeks old were divided into 2 groups: Forty mice received a single i.p. injection of 0.5 cc pristane for lupus induction and ten mice as healthy controls. Starting at 16 weeks after injection, forty pristane-induced lupus mice were divided into four groups based on doses of curcumin received intragastrically: 0, 12.5, 50, and 200 mg/kg bw/day daily for 16 weeks. At 32 weeks after injection, all of mice were assessed for arthritis score, proteinuria level, body weights, adaptive immune system components (Th1, Th2, Th17, and Treg percentages) from spleen using flow cytometry; proinflammatory cytokines and autoantibody production, including interleukin-6 (IL-6), interferon-alpha (IFN-α), and antinuclear antibody (ANA) from serum using enzyme-linked immunosorbent assay. Results: Arthritis score and proteinuria level were decreased in curcumin-treated mice. However, body weights were not significantly different between the groups. The decreased of Th1, Th2, and Th17 percentages were seen after treatment with 200 mg/kg bw/day of curcumin (P = 0.031,P = 0.017, andP = 0.005, respectively). However, only slight increase of Treg percentages was seen after curcumin treatment. Treatment with 200 mg/kg bw/day of curcumin decreased serum IL-6 and IFN-α levels (P = 0.007 andP = 0.003). Furthermore, ANA levels were also decreased significantly after treatment with 200 mg/kg bw/day of curcumin (P = 0.013). Conclusion: Our findings suggested that curcumin could prove useful as a therapeutic intervention in SLE.

Paradoxical Attenuation of Autoimmune Hepatitis by Oral Isoniazid in Wild-Type andN-Acetyltransferase–Deficient Mice

Isoniazid (INH) treatment can cause serious liver injury and autoimmunity. There are now several lines of evidence that INH-induced liver injury is immune mediated, but this type of liver injury has not been reproduced in animals, possibly because immune tolerance is the dominant response of the liver. In this study, we immunized mice with isonicotinic acid (INA)-modified proteins and Freund's adjuvant, which led to mild experimental autoimmune hepatitis (EAH) with an increase in cells staining positive for F4/80, CD11b, CD8, CD4, CD45R, and KI67. We expected that subsequent treatment of mice with oral INH would lead to more serious immune-mediated liver injury, but paradoxically it markedly attenuated the EAH caused by immunization with INA-modified hepatic proteins. In addition, patients of the slow acetylator phenotype are at increased risk of INH-induced liver injury. Treatment of arylamine N-acetyltransferase-deficient Nat1/2(-/-) mice with INH for up to 5 weeks produced mild increases in glutamate and sorbitol dehydrogenase activities, but not severe liver injury. Female Nat1/2(-/-) mice treated with INH for 1, 3, or 7 days developed steatosis, an increase in Oil Red O staining, and abnormal mitochondrial morphology in the liver. A decrease in M1 and an increase in M2a and M2b macrophages was observed in female Nat1/2(-/-) mice treated with INH for 1, 3, or 7 days; these changes returned to baseline levels by day 35. These data indicate that INH has immunosuppressive effects, even though it is also known to induce autoantibody production and a lupus-like autoimmune syndrome in humans.

Polyclonal hypergammaglobulinemia and autoantibody production induced by vaccination in farmed Atlantic salmon

The introduction of oil-adjuvanted vaccines in salmon aquaculture made large-scale production feasible by reducing the impact of infections. Vaccines given intraperitoneally (ip) contain oil adjuvant such as mineral oil. However, in rodents, a single ip injection of adjuvant hydrocarbon oil induces lupus-like systemic autoimmune syndrome. We have recently reported that autoimmune disease in farmed salmon, characterized by production of various autoantibodies, immune complex glomerulonephritis, liver thrombosis, and spinal deformity, are previously unrecognized side effects of vaccination. In the present study, we examined whether vaccination-induced autoantibody production in farmed Atlantic salmon is a mere result of polyclonal B-cell activation. Sera were collected from 205 vaccinated and unvaccinated Atlantic salmon (experimental, 7 farms) and wild salmon. Total IgM levels and autoantibodies to salmon blood cell (SBC) extract in sera were measured by ELISA and the relationship between hypergammaglobulinemia and autoantibody production was analyzed. Comparison of endpoint titers vs levels/units using a single dilution of sera in detection of autoantibodies to SBC showed near perfect correlation, justifying the use of the latter for screening. Both total IgM and anti-SBC antibodies are increased in vaccinated salmon compared with unvaccinated controls, however, they do not always correlate well when compared between groups or between individuals, suggesting the involvement of antigen-specific mechanisms in the production of anti-SBC autoantibodies. The primary considerations of successful vaccine for aquaculture are cost-effectiveness and safety. Vaccination-induced autoimmunity in farmed Atlantic salmon may have consequences on future vaccine development and salmon farming strategy. Evaluation for polyclonal hypergamamglobulinemia and autoimmunity should be included as an important trait when vaccine efficacy and safety are evaluated in future.

Disrupted Mer receptor tyrosine kinase expression leads to enhanced MZ B-cell responses

Control of lymphocyte homeostasis is essential to ensure efficient immune responses and to prevent autoimmunity. Splenic marginal zone B cells are important producers of autoantibodies, and are subject to stringent tolerance mechanisms to prevent autoimmunity. In this paper, we explore the role of the Mer tyrosine kinase (Mertk) in regulating autoreactive B cells. This receptor tyrosine kinase serves to bind apoptotic cells, to mediate their phagocytosis, and to regulate subsequent cytokine production. Mice lacking Mertk suffer from impaired apoptotic cell clearance and develop a lupus-like autoimmune syndrome. Here we show that such Mertk-KO mice have expanded numbers of splenic marginal zone B cells. Mertk-KO mice bearing a DNA-specific immunoglobulin heavy-chain transgene (3H9) produced anti-DNA antibodies that appeared to be secreted largely by marginal zone B cells. Finally, Mertk-KO mice developed greater antibody responses after NP-Ficoll immunization than their B6 counterparts. Taken together, our data show that Mertk has a major effect on the development of the marginal zone B-cell compartment. Mertk is also important in establishing DNA-specific B-cell tolerance in 3H9 anti-DNA transgenic mice.

Differential impact of the CD45 juxtamembrane wedge on central and peripheral T cell receptor responses

The cooperative activity of protein tyrosine kinases and phosphatases plays a central role in regulation of T cell receptor (TCR) signal strength. Perturbing this balance, and thus the threshold for TCR signals, has profound impacts on T cell development and function. We previously generated mice containing a point mutation in the juxtamembrane wedge of the receptor-like protein tyrosine phosphatase CD45. Demonstrating the critical negative regulatory function of the wedge, the CD45 E613R (WEDGE) mutation led to a lymphoproliferative disorder (LPD) and a lupus-like autoimmune syndrome. Using genetic, cellular, and biochemical approaches, we now demonstrate that the CD45 wedge influences T cell development and function. Consistent with increased TCR signal strength, WEDGE mice have augmented positive selection and enhanced sensitivity to the CD4-mediated disease experimental autoimmune encephalitis (EAE). These correspond with hyperresponsive calcium and pERK responses to TCR stimulation in thymocytes, but surprisingly, not in peripheral T cells, where these responses are actually depressed. Together, the data support a role for the CD45 wedge in regulation of T cell responses in vivo and suggest that its effects depend on cellular context.

Rai Acts as a Negative Regulator of Autoimmunity by Inhibiting Antigen Receptor Signaling and Lymphocyte Activation

Rai (ShcC) belongs to the family of Shc adaptor proteins and is expressed in neuronal cells, where it acts as a survival factor activating the PI3K/Akt survival pathway. In vivo, Rai protects the brain from ischemic damage. In this study, we show that Rai is expressed in T and B lymphocytes. Based on the finding that Rai(-/-) mice consistently develop splenomegaly, the role of Rai in lymphocyte homeostasis and proliferation was addressed. Surprisingly, as opposed to neurons, Rai was found to impair lymphocyte survival. Furthermore, Rai deficiency results in a reduction in the frequency of peripheral T cells with a concomitant increase in the frequency of B cells. Rai(-/-) lymphocytes display enhanced proliferative responses to Ag receptor engagement in vitro, which correlates with enhanced signaling by the TCR and BCR, and more robust responses to allergen sensitization in vivo. A high proportion of Rai(-/-) mice develop a lupus-like autoimmune syndrome characterized by splenomegaly, spontaneous peripheral T and B cell activation, autoantibody production, and deposition of immune complexes in the kidney glomeruli, resulting in autoimmune glomerulonephritis. The data identify Rai as a negative regulator of lymphocyte survival and activation and show that loss of this protein results in breaking of immunological tolerance and development of systemic autoimmunity.

Vaccination-Induced Systemic Autoimmunity in Farmed Atlantic Salmon

Over half of the salmon consumed globally are farm-raised. The introduction of oil-adjuvanted vaccines into salmon aquaculture made large-scale production feasible by preventing infections. The vaccines that are given i.p. contain oil adjuvant such as mineral oil. However, in rodents, a single i.p. injection of adjuvant hydrocarbon oil induces lupus-like systemic autoimmune syndrome, characterized by autoantibodies, immune complex glomerulonephritis, and arthritis. In the present study, whether the farmed salmon that received oil-adjuvanted vaccine have autoimmune syndrome similar to adjuvant oil-injected rodents was examined. Sera and tissues were collected from vaccinated or unvaccinated Atlantic salmon (experimental, seven farms) and wild salmon. Autoantibodies (immunofluorescence, ELISA, and immunoprecipitation) and IgM levels (ELISA) in sera were measured. Kidneys and livers were examined for pathology. Autoantibodies were common in vaccinated fish vs unvaccinated controls and they reacted with salmon cells/Ags in addition to their reactivity with mammalian Ags. Diffuse nuclear/cytoplasmic staining was common in immunofluorescence but some had more specific patterns. Serum total IgM levels were also increased in vaccinated fish; however, the fold increase of autoantibodies was much more than that of total IgM. Sera from vaccinated fish immunoprecipitated ferritin and approximately 50% also reacted with other unique proteins. Thrombosis and granulomatous inflammation in liver, and immune-complex glomerulonephritis were common in vaccinated fish. Autoimmunity similar to the mouse model of adjuvant oil-induced lupus is common in vaccinated farmed Atlantic salmon. This may have a significant impact on production loss, disease of previously unknown etiology, and future strategies of vaccines and salmon farming.

A Point Mutation in the Juxtamembrane Wedge of CD45 Impacts Myeloid Development and Generates a Novel Model for Hemophagocytic Disorders in the Context of a MHC I-Restricted Transgene.

The receptor like-protein tyrosine phosphatase CD45 is highly expressed on all nucleated hematopoietic cells and functions by modulating the activity of Src family kinases. We previously generated mice containing a point mutation in the juxtamembrane wedge of CD45 that leads to constitutive phosphatase activity. Demonstrating the critical negative regulatory function of the wedge, the CD45E613R mutation led to a lymphoproliferative disorder, lupus-like autoimmune syndrome, and premature death at 9–12 months of age. To address the intrinsic effects of the wedge mutation on the CD8 T cell lineage, we introduced a CD8 restricted T-cell receptor (TCR) transgene, OT1, specific for the antigen ovalbumin, into CD45E613R mice. Surprisingly, 100% of the CD45E613R/OT1+ mice succumb by 6 weeks of age to a rapidly progressive disease characterized by severe cachexia, hemophagocytosis, and markedly elevated interferon gamma levels. This phenotype shares similarity to the human hemophagocytic syndromes hemophagocytic lymphohistiocytosis (HLH) and macrophage activation syndrome (MAS). The aims of this study are to identify the mechanistic basis and the cell type(s) responsible for this phenotype. Using a genetic approach, we demonstrate that the phenotype is maintained in CD45E613R/OT1+mice on a Rag1−/− background, thus implicating myeloid and/or CD8 T cells in disease pathogenesis. Analysis of myeloid cell development, phagocytic function, and signaling indicate that the wedge mutation operates in this lineage. Despite the intrinsic hyperresponsiveness of CD45E613R macrophages, adoptive transfer experiments demonstrate they are not essential for disease. However, adoptive transfer of purified CD45E613R/OT1+ CD8 T cells into either CD45 mutant or CD45 wildtype (wt) is sufficient to initiate disease. Interestingly, CD45E613R CD8 OT+ T cells are not dominant over CD45wt CD8+ cells. In addition we show that transfer of CD45wt CD8+ T cells into ill mice can delay disease progression. We hypothesize that, in the setting of the wedge mutation, the restricted repertoire of the CD8 T cells in CD45E613R/OT1+ mice might not be able to limit macrophage activation. We believe these mice may represent a useful model for understanding the molecular pathogenesis of hemophagocytic disorders, devastating and often fatal diseases in humans.

Roquin represses autoimmunity by limiting inducible T-cell co-stimulator messenger RNA

Immune responses are normally targeted against microbial pathogens and not self-antigens by mechanisms that are only partly understood. Here we define a newly discovered pathway that prevents autoimmunity by limiting the levels on T lymphocytes of aco-stimulatory receptor, the inducible T-cell co-stimulator(ICOS). In sanroque mice homozygous for an M199R mutation in the ROQ domain of Roquin (also known as Rc3h1), increased Icos expression on T cells causes the accumulation of lymphocytes that is associated with a lupus-like autoimmune syndrome. Roquin normally limits Icos expression by promoting the degradation of Icos messenger RNA.A conserved segment in the unusually long ICOS 3' untranslated mRNA is essential for regulation by Roquin. This segment comprises a 47-base-pair minimal region complementary to T-cell-expressed microRNAs including miR-101, the repressive activity of which is disrupted by base-pair inversions predicted to abrogate miR-101 binding. These findings illuminate a critical post-transcriptional pathway within T cells that regulates lymphocyte accumulation and autoimmunity, and highlights the therapeutic potential of partially antagonising the ICOS pathway.

Expression and regulation of Toll-like receptors in lupus-like immune complex glomerulonephritis of MRL-Fas(lpr) mice

How microbial infections exacerbate immune complex glomerulonephritis remains speculative. Toll-like receptors (TLRs) may be involved in this phenomenon, because TLRs have potent immunostimulatory functions when exposed to selected pathogen-associated molecules. We addressed this issue by characterizing the expression of TLR1-9 in MRLlpr/lpr mice that spontaneously develop immune complex glomerulonephritis as part of a systemic lupus-like autoimmune syndrome. Five-week-old healthy MRLlpr/lpr mice expressed TLR3 mRNA in kidneys at comparable levels as in the spleen, while all other TLRs were expressed at low levels in the kidney. In 20-week-old nephritic MRLlpr/lpr mice, renal mRNA levels had increased for TLR1-9. Renal TLR mRNA originated at least in part from glomeruli as evidenced by real-time RT-PCR from laser capture microdissected glomeruli. Immunostaining for TLR3, TLR7 and TLR9 revealed their expression by F4/80-positive infiltrating macrophages in 20-week-old nephritic MRLlpr/lpr mice. In addition, TLR3 localized to glomerular mesangial cells. Cultured mesangial cells expressed TLR1-4 and TLR6, while murine macrophages expressed TLR1-9. TNF-alpha and IFN-gamma induced TLR2, TLR3 and TLR6 mRNA in mesangial cells, while they down-regulated TLR1-9 mRNA in macrophages. Stimulation of both cell types with ligands for TLR1-4, TLR5, TLR7 and TLR9 induced IL-6 production consistent with their respective TLR expression patterns. TNF-alpha and IFN-gamma enhanced ligand-induced IL-6 production in both cell types irrespective of their modulatory effect on respective TLR mRNA levels. Thus, cell-type-specific expression and regulation of TLRs may be involved in infection-associated exacerbation of immune complex glomerulonephritis of MRLlpr/lpr mice.

Multiorgan Autoimmune Inflammation, Enhanced Lymphoproliferation, and Impaired Homeostasis of Reactive Oxygen Species in Mice Lacking the Antioxidant-Activated Transcription Factor Nrf2

Nuclear factor erythroid 2-related factor 2 (Nrf2) is an antioxidant-activated cap "n" collar basic leucine zipper transcription factor. To assess the function of Nrf2 in the antioxidant response, we examined mice with targeted disruption of the Nrf2 gene. Nrf2-null mice developed complex disease manifestations, with a majority exhibiting a lupus-like autoimmune syndrome characterized by multiorgan inflammatory lesions with a marked female predominance, appearance of anti-double-stranded DNA antibodies in young adulthood, intravascular deposition of immunoglobulin complexes in blood vessels, and premature death due to rapidly progressing membranoproliferative glomerular nephritis. Mechanistic analyses revealed that the null mice showed enhanced proliferative response of CD4+ T cells, altered ratios of CD4+ and CD8+ cells, and increased oxidative lesions in tissues. Analyses of antioxidant-induced gene expression showed that the knockout mice were devoid of the basal and inducible expression of certain phase 2 detoxification enzymes and antioxidant genes in hepatic and lymphoid cells in vivo. Our findings suggest that Nrf2 mediates important antioxidant functions involved in the control of peripheral lymphocyte homeostasis and autoimmune surveillance.

The Juxtamembrane Wedge Negatively Regulates CD45 Function in B Cells

CD45 is a receptor-like protein tyrosine phosphatase highly expressed on all nucleated hematopoietic cells. We previously generated mice containing a point mutation in the juxtamembrane wedge of CD45. Demonstrating the critical negative regulatory function of the wedge, the CD45 E613R mutation led to a lymphoproliferative disorder (LPD) and a lupus-like autoimmune syndrome. Here we show the central role of B cells in this phenotype. Genetic elimination of B cells, but not T cells, ablates the LPD. In contrast to CD45-deficient B cells, the E613R mutation generates hyperresponsive B cells. Comparison of CD45-deficient and CD45 E613R mice reveals dichotomous effects of these mutations on B cell development. Together, the results support a role for CD45 as a rheostat, with both positive and negative regulatory functions, that fine-tunes the signal transduction threshold at multiple checkpoints in B cell development.

Induction of Apoptosis by the Hydrocarbon Oil Pristane: Implications for Pristane-Induced Lupus

Intraperitoneal injection of the hydrocarbon oil pristane into normal mice leads to a lupus-like autoimmune syndrome. Although advances in defining the roles of cellular and humoral mediators involved in this syndrome have been made, the mechanisms that initiate a break in tolerance leading to autoimmunity remain unknown. We describe in this study that pristane induces apoptosis both in vivo and in vitro. Pristane arrests cell growth and induces cell death by apoptosis via the mitochondrial pathway of caspase activation in a dose-dependent manner. Nuclear autoantigens created by pristane-induced apoptosis of lymphoid cells within the peritoneal cavity in the setting of a profoundly altered cytokine milieu may be the initiating event in the development of autoimmunity in this syndrome. These findings suggest that apoptosis may be a critical initial event in the pathogenesis of pristane-induced lupus and are of potential relevance for human systemic lupus erythematosus.

A Critical Role for Sialylation in Cryoglobulin Activity of Murine IgG3 Monoclonal Antibodies

Cryoprecipitating IgG3 autoantibodies have been shown to play a significant role in the development of murine lupus-like autoimmune syndrome. However, the structural basis of IgG3 cryoprecipitation still remains to be defined. In view of the implication of positively charged amino acid residues present in variable regions in IgG3 cryoglobulin activity, we explored the role of terminal sialic acids in oligosaccharide side chains for the cryogenic activity of IgG3 mAb. Comparative oligosaccharide structural analysis of different cryogenic and non-cryogenic IgG3 mAb showed an inverse correlation between the extent of sialylation and cryogenic activity. The inhibitory role of sialylation was further confirmed by the demonstration of enrichment of less and more sialylated IgG3 in cryoprecipitated and noncryoprecipitated fractions, respectively, separated from four different cryogenic IgG3 mAb. Significantly, the sialic acid contents of the latter fraction became comparable to those of non-cryogenic IgG3 mAb. Finally, we observed that highly sialylated non-cryogenic IgG3 mAb was more potent in the inhibition of cryoprecipitation of cryogenic IgG3 mAb. Our results thus suggest that the content of negatively charged sialic acids in oligosaccharide side chains is one of the critical factors to determine IgG3 cryoglobulin activity, along with amino acid sequences of the IgG3 variable regions.

Differential Activation of Anti-Erythrocyte and Anti-DNA Autoreactive B Lymphocytes by the Yaa Mutation

An as-yet-unidentified mutation, Y-linked autoimmune acceleration (Yaa), is responsible for the accelerated development of lupus-like autoimmune syndrome in mice. In view of a possible role for Yaa as a positive regulator of BCR signaling, we have explored whether the expression of the Yaa mutation affects the development and activation of transgenic autoreactive B cells expressing either 4C8 IgM anti-RBC or Sp6 IgM anti-DNA. In this study, we show that the expression of the Yaa mutation induced a lethal form of autoimmune hemolytic anemia in 4C8 transgenic C57BL/6 mice, likely as a result of activation of 4C8 anti-RBC autoreactive B cells early in life. This was further supported, although indirectly, by increased T cell-independent IgM production in spleens of nontransgenic C57BL/6 mice bearing the Yaa mutation. In contrast, Yaa failed to induce activation of Sp6 anti-DNA autoreactive B cells, consistent with a lack of increased IgM anti-DNA production in nontransgenic C57BL/6 Yaa mice. Our results suggest that Yaa can activate autoreactive B cells in a BCR-dependent manner, related to differences in the form and nature of autoantigens.

IL-18 cDNA vaccination protects mice from spontaneous lupus-like autoimmune disease.

The lupus-like autoimmune syndrome of MRL/Mp-Tnfrsf6lpr (lpr) mice is characterized by progressive lymphadenopathy and autoantibody production, leading to early death from renal failure. Activation of T helper lymphocytes is one of the events in the pathogenesis of the disease in these mice and likely in human systemic lupus erythematosus. Among T helper lymphocyte-dependent cytokines, IFN-gamma plays a pivotal role in the abnormal cell activation and the fatal development of the lpr disease. IL-18, an inducer of IFN-gamma in T lymphocytes and natural killer cells, may contribute to the disease because cells from lpr mice are hypersensitive to IL-18 and express high levels of IL-18. To assess the contribution of IL-18 to the pathogenesis in the animal model, in vivo inhibition of IL-18 was attempted. Young lpr mice were vaccinated against autologous IL-18 by repeated administration of a cDNA coding for the murine IL-18 precursor. Vaccinated mice produced autoantibodies to murine IL-18 and exhibited a significant reduction in spontaneous lymphoproliferation and IFN-gamma production as well as less glomerulonephritis and renal damage. Moreover, mortality was significantly delayed in anti-IL-18-vaccinated mice. These studies support the concept that IL-18 plays a major role in the pathogenesis of the autoimmune syndrome of lpr mice and that a reduction in IL-18 activity could be a therapeutic strategy in autoimmune diseases.

Linkage of a major quantitative trait locus to Yaa gene-induced lupus-like nephritis in (NZW x C57BL/6)F1 mice.

In the present study, we mapped the major quantitative trait loci (QTL) differing between the NZW and C57BL/6 inbred strains of mice by making use of (NZW x C57BL/6.Yaa)F1 mice, a model in which the lupus-like autoimmune syndrome observed in male mice is associated with the presence of an as yet unidentified Y chromosome-linked autoimmune acceleration gene, Yaa. Linkage analysis of 126 C57BL/6 x (NZW x C57BL/6.Yaa)F1 backcross males provided evidence for a major QTL on chromosome 7 controlling both the severity of glomerulonephritis and the production of IgG anti-DNA autoantibody and retroviral gp70-anti-gp70 immune complexes. Two additional QTL of C57BL/6 origin on chromosome 17 had no apparent individual effects, but showed strong epistatic interaction with chromosome 7 QTL for disease severity and anti-DNA autoantibody production. Our data also identified on chromosome 13 a QTL of NZW origin with a major effect on the level of gp70, and showing an additive effect with the chromosome 7 QTL on the level of gp70 immune complexes. Our study thus provides a model to dissect the complex genetic interactions that result in manifestations of murine lupus-like disease.

Interleukin-4 protects against a genetically linked lupus-like autoimmune syndrome.

Interleukin-4 (IL-4) provides support for humoral immune responses through upregulation of T helper (Th) type 2 cell differentiation, but it is not known whether IL-4 promotes antibody-mediated autoimmune diseases such as systemic lupus erythematosus (SLE). Here, we show that the constitutive expression of an IL-4 transgene by B cells completely prevents the development of lethal lupus-like glomerulonephritis in the (NZW x C57BL/6.Yaa)F1 murine model of SLE. This was associated with marked changes in the serum levels of IgG subclasses, rather than in the total levels of anti-DNA antibodies, with a lack of IgG3, a decrease of IgG2a, and an increase in IgG1 subclasses, and by a strong reduction in the serum levels of gp70-anti-gp70 immune complexes. This effect of the transgene appears to result from a modulation of the Th1 versus Th2 autoimmune response, since the protected mice displayed comparably modified IgG2a and IgG3 antibody response against exogenous T cell-dependent antigen, but not against T cell-independent antigens. Thus, IL-4 prevents the development of this lupus-like autoimmune disease, most likely by downregulating the appearance of Th1-mediated IgG subclasses of autoantibodies such as the IgG3 autoantibodies which have been shown to be especially nephritogenic.