Programmed death ligand 1 regulates a critical checkpoint for autoimmune myocarditis and pneumonitis in MRL mice

MRL/MpJ-Fas(lpr) (MRL-Fas(lpr)) mice develop a spontaneous T cell and macrophage-dependent autoimmune disease that shares features with human lupus. Interactions via the programmed death 1/programmed death ligand 1 (PD-1/PD-L1) pathway down-regulate immune responses and provide a negative regulatory checkpoint in mediating tolerance and autoimmune disease. Therefore, we tested the hypothesis that the PD-1/PD-L1 pathway suppresses lupus nephritis and the systemic illness in MRL-Fas(lpr) mice. For this purpose, we compared kidney and systemic illness (lymph nodes, spleen, skin, lung, glands) in PD-L1 null (-/-) and PD-L1 intact (wild type, WT) MRL-Fas(lpr) mice. Unexpectedly, PD-L1(-/-);MRL-Fas(lpr) mice died as a result of autoimmune myocarditis and pneumonitis before developing renal disease or the systemic illness. Dense infiltrates, consisting of macrophage and T cells (CD8(+) > CD4(+)), were prominent throughout the heart (atria and ventricles) and localized specifically around vessels in the lung. In addition, once disease was evident, we detected heart specific autoantibodies in PD-L1(-/-);MRL-Fas(lpr) mice. This unique phenotype is dependent on MRL-specific background genes as PD-L1(-/-);MRL(+/+) mice lacking the Fas(lpr) mutation developed autoimmune myocarditis and pneumonitis. Notably, the transfer of PD-L1(-/-);MRL(+/+) bone marrow cells induced myocarditis and pneumonitis in WT;MRL(+/+) mice, despite a dramatic up-regulation of PD-L1 expression on endothelial cells in the heart and lung of WT;MRL(+/+) mice. Taken together, we suggest that PD-L1 expression is central to autoimmune heart and lung disease in lupus-susceptible (MRL) mice.     

A proinflammatory role of IL-18 in the development of spontaneous autoimmune disease.

Serum from patients with systemic lupus erythematosus (SLE) contained significantly higher concentrations of IL-18 than normal individuals. MRL/lpr mice, which develop spontaneous lupus-like autoimmune disease, also had higher serum levels of IL-18 than wild-type MRL/++ mice. Daily injections of IL-18 or IL-18 plus IL-12 resulted in accelerated proteinuria, glomerulonephritis, vasculitis, and raised levels of proinflammatory cytokines in MRL/lpr mice. IL-18-treated MRL/lpr mice also developed a "butterfly" facial rash resembling clinical SLE. In contrast, MRL/lpr mice treated with IL-18 plus IL-12 did not develop a facial rash. The facial lesion in the IL-18-treated mice showed epidermal thickening with intense chronic inflammation accompanied by increased apoptosis, Ig deposition, and early systemic Th2 response compared with control or IL-12 plus IL-18-treated mice. These data therefore show that IL-18 is an important mediator of lupus-like disease and may thus be a novel target for therapeutic intervention of spontaneous autoimmune diseases.     

Analysis of C4 and the C4 binding protein in the MRL/lpr mouse

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.     

Decreased expression of the Ets family transcription factor Fli-1 markedly prolongs survival and significantly reduces renal disease in MRL/lpr mice

Increased Fli-1 mRNA is present in PBLs from systemic lupus erythematosus patients, and transgenic overexpression of Fli-1 in normal mice leads to a lupus-like disease. We report in this study that MRL/lpr mice, an animal model of systemic lupus erythematosus, have increased splenic expression of Fli-1 protein compared with BALB/c mice. Using mice with targeted gene disruption, we examined the effect of reduced Fli-1 expression on disease development in MRL/lpr mice. Complete knockout of Fli-1 is lethal in utero. Fli-1 protein expression in heterozygous MRL/lpr (Fli-1(+/-)) mice was reduced by 50% compared with wild-type MRL/lpr (Fli-1(+/+)) mice. Fli-1(+/-) MRL/lpr mice had significantly decreased serum levels of total IgG and anti-dsDNA Abs as disease progressed. Fli-1(+/-) MRL/lpr mice had significantly increased splenic CD8(+) and naive T cells compared with Fli-1(+/+) MRL/lpr mice. Both in vivo and in vitro production of MCP-1 were significantly decreased in Fli-1(+/-) MRL/lpr mice. The Fli-1(+/-) mice had markedly decreased proteinuria and significantly lower pathologic renal scores. At 48 wk of age, survival was significantly increased in the Fli-1(+/-) MRL/lpr mice, as 100% of Fli-1(+/-) MRL/lpr mice were alive, in contrast to only 27% of Fli-1(+/+) mice. These findings indicate that Fli-1 expression is important in lupus-like disease development, and that modulation of Fli-1 expression profoundly decreases renal disease and improves survival in MRL/lpr mice.     

Leukocyte-endothelial cell interactions are enhanced in dermal postcapillary venules of MRL/fas(lpr) (lupus-prone) mice: roles of P- and E-selectin

MRL/fas(lpr) mice are affected by a systemic autoimmune disease that results in widespread leukocytic infiltration of the vasculature, including in the skin. The molecular pathways responsible for this leukocyte recruitment are poorly understood. Therefore, the aim of these experiments was to examine the mechanisms of leukocyte trafficking in the dermal microvasculature of MRL/fas(lpr) mice. Intravital microscopy was used to examine leukocyte rolling and adhesion in dermal postcapillary venules of MRL/fas(lpr) mice at 8, 12, and 16 wk of age. When compared with age-matched BALB/c and MRL(+/+) (nondiseased) mice, leukocyte rolling and adhesion in MRL/fas(lpr) mice were significantly enhanced at 12 wk of age, and remained elevated at 16 wk of age. At 8 and 12 wk, leukocyte rolling in all three strains was almost entirely inhibited by an anti-P-selectin mAb. In contrast, at 16 wk some (approximately 10%) leukocyte rolling persisted following P-selectin blockade. This residual rolling was predominantly inhibitable with an anti-E-selectin mAb; however, treatment with anti-E-selectin mAb alone had a minimal effect. P-selectin-deficient MRL/fas(lpr) mice also displayed leukocyte rolling that was significantly lower than in wild-type MRL/fas(lpr) mice. However, in these mice, leukocyte adhesion remained at the elevated levels observed in wild-type MRL/fas(lpr) mice. This adhesion was eliminated by chronic treatment with anti-E-selectin mAb. These findings indicate that leukocyte-endothelial cell interactions are enhanced in the dermal microvasculature of MRL/fas(lpr) mice above the age of 12 wk. Furthermore, the data suggest that the endothelial selectins share overlapping roles in mediating this enhanced leukocyte recruitment.     

CTLA4IgG gene delivery prevents autoantibody production and lupus nephritis in MRL/lpr mice

MRL/MP-lpr/lpr (MRL/lpr) mice spontaneously develop an autoimmune syndrome closely resembling systemic lupus erythematosus (SLE) in humans, characterized by hypergammaglobulinemia, various autoantibody production, and the development of fatal glomerulonephritis. We have previously demonstrated that systemic administration of soluble form of CTLA4IgG prevented autoantibody-related diseases in MRL/lpr mice. To test the potential protective effects of CTLA4IgG gene delivery on the development of lupus nephritis, we injected MRL/lpr mice with a recombinant adenovirus vector containing CTLA4IgG gene, Adex1CACTLA4IgG (AdCTLA4IgG). It was demonstrated that a single administration of intravenous injection of AdCTLA4IgG into MRL/lpr mice resulted in almost complete amelioration of lupus nephritis.     

Deficiency in beta(2)-microglobulin, but not CD1, accelerates spontaneous lupus skin disease while inhibiting nephritis in MRL-Fas(lpr) nice: an example of disease regulation at the organ level

When mutations that inactivate molecules that function in the immune system have been crossed to murine lupus strains, the result has generally been a uniform up-regulation or down-regulation of autoimmune disease in the end organs. In the current work we report an interesting dissociation of target organ disease in beta(2)-microglobulin (beta(2)m)-deficient MRL-Fas(lpr) (MRL/lpr) mice: lupus skin lesions are accelerated, whereas nephritis is ameliorated. beta(2)m deficiency affects the expression of classical and nonclassical MHC molecules and thus prevents the normal development of CD8- as well as CD1-dependent NK1(+) T cells. To further define the mechanism by which beta(2)m deficiency accelerates skin disease, we studied CD1-deficient MRL/lpr mice. These mice do not have accelerated skin disease, excluding a CD1 or NK1(+) T cell-dependent mechanism of beta(2)m deficiency. The data indicate that the regulation of systemic disease is not solely governed by regulation of initial activation of autoreactive lymphocytes in secondary lymphoid tissue, as this is equally relevant to renal and skin diseases. Rather, regulation of autoimmunity can also occur at the target organ level, explaining the divergence of disease in skin and kidney in beta(2)m-deficient mice.     

Depletion of autoreactive plasma cells and treatment of lupus nephritis in mice using CEP-33779, a novel, orally active, selective inhibitor of JAK2

Accumulating evidence suggests that autoreactive plasma cells play an important role in systemic lupus erythematosus (SLE). In addition, several proinflammatory cytokines promote autoreactive B cell maturation and autoantibody production. Hence, therapeutic targeting of such cytokine pathways using a selective JAK2 inhibitor, CEP-33779 (JAK2 enzyme IC(50) = 1.3 nM; JAK3 enzyme IC(50)/JAK2 enzyme IC(50) = 65-fold), was tested in two mouse models of SLE. Age-matched, MRL/lpr or BWF1 mice with established SLE or lupus nephritis, respectively, were treated orally with CEP-33779 at 30 mg/kg (MRL/lpr), 55 mg/kg or 100 mg/kg (MRL/lpr and BWF1). Studies included reference standard, dexamethasone (1.5 mg/kg; MRL/lpr), and cyclophosphamide (50 mg/kg; MRL/lpr and BWF1). Treatment with CEP-33779 extended survival and reduced splenomegaly/lymphomegaly. Several serum cytokines were significantly decreased upon treatment including IL-12, IL-17A, IFN-α, IL-1β, and TNF-α. Anti-nuclear Abs and frequencies of autoantigen-specific, Ab-secreting cells declined upon CEP-33779 treatment. Increased serum complement levels were associated with reduced renal JAK2 activity, histopathology, and spleen CD138(+) plasma cells. The selective JAK2 inhibitor CEP-33779 was able to mitigate several immune parameters associated with SLE advancement, including the protection and treatment of mice with lupus nephritis. These data support the possibility of using potent, orally active, small-molecule inhibitors of JAK2 to treat the debilitative disease SLE.     

Modulation of renal disease in MRL/lpr mice genetically deficient in the alternative complement pathway factor B

In systemic lupus erythematosus, the renal deposition of complement-containing immune complexes initiates an inflammatory cascade resulting in glomerulonephritis. Activation of the classical complement pathway with deposition of C3 is pathogenic in lupus nephritis. Although the alternative complement pathway is activated in lupus nephritis, its role in disease pathogenesis is unknown. To determine the role of the alternative pathway in lupus nephritis, complement factor B-deficient mice were backcrossed to MRL/lpr mice. MRL/lpr mice develop a spontaneous lupus-like disease characterized by immune complex glomerulonephritis. We derived complement factor B wild-type (B+/+), homozygous knockout (B-/-), and heterozygous (B+/-) MRL/lpr mice. Compared with B+/- or B+/+ mice, MRL/lpr B-/- mice developed significantly less proteinuria, less glomerular IgG deposition, and decreased renal scores as well as lower IgG3 cryoglobulin production and vasculitis. Serum C3 levels were normal in the B-/- mice compared with significantly decreased levels in the other two groups. These results suggest that: 1) factor B plays an important role in the pathogenesis of glomerulonephritis and vasculitis in MRL/lpr mice; and 2) activation of the alternative pathway, either by the amplification loop or by IgA immune complexes, has a prominent effect on serum C3 levels in this lupus model.     

Differential oxidative modification of proteins in MRL+/+ and MRL/lpr mice: Increased formation of lipid peroxidation-derived aldehyde-protein adducts may contribute to accelerated onset of autoimmune response

Even though reactive oxygen species (ROS) have been implicated in SLE pathogenesis, the contributory role of ROS, especially the consequences of oxidative modification of proteins by lipid peroxidation-derived aldehydes (LPDAs) such as malondialdehyde (MDA) and 4-hydroxynonenal (HNE) in eliciting an autoimmune response and disease pathogenesis remains largely unexplored. MRL/lpr mice, a widely used model for SLE, spontaneously develop a condition similar to human SLE, whereas MRL+/+ mice with the same MRL background, show much slower onset of SLE. To assess if the differences in the onset of SLE in the two substrains could partly be due to differential expression of LPDAs and to provide evidence for the role of LPDA-modified proteins in SLE pathogenesis, we determined the serum levels of MDA-/HNE-protein adducts, anti-MDA-/HNE-protein adduct antibodies, MDA-/HNE-protein adduct specific immune complexes, and various autoantibodies in 6-, 12- and 18-week old mice of both substrains. The results show age-related increases in the formation of MDA-/HNE-protein adducts, their corresponding antibodies and MDA-/HNE-specific immune complexes, but MRL/lpr mice showed greater and more accelerated response. Interestingly, a highly positive correlation between increased anti-MDA-/HNE-protein adduct antibodies and autoantibodies was observed. More importantly, we further observed that HNE-MSA caused significant inhibition in antinuclear antibodies (ANA) binding to nuclear antigens. These findings suggest that LPDA-modified proteins could be important sources of autoantibodies and CICs in these mice, and thus contribute to autoimmune disease pathogenesis. The observed differential responses to LPDAs in MRL/lpr and MRL+/+ mice may, in part, be responsible for accelerated and delayed onset of the disease, respectively.     

Treatment of autoimmune MRL/Ipr mice with monoclonal antibody to Thy-1.2: a single injection has sustained effects on lymphoproliferation and renal disease

MRL/Mp-lpr/lpr (MRL/lpr) mice spontaneously develop an autoimmune disease characterized by anti-DNA antibodies, immune-complex glomerulonephritis, and massive proliferation of a distinct population of T cells. The proliferating T cells have the phenotype Thy-1.2+, T200+, Lyt-1+,2-,3-, but Thy-1.2 and Lyt-1 are expressed in abnormally low density. These cells appear to function as helper cells, and neonatal thymectomy prevents both lymphoproliferation and autoimmunity, which suggests that autoimmunity in MRL/lpr mice is secondary to T cell proliferation. We therefore attempted to reduce lymphoproliferation by treating MRL/lpr mice with a single injection of rat monoclonal antibody (MAb) to Thy-1.2 (30-H12, IgG2b). Mice were treated at 8 wk, before the onset of overt disease. We found that MRL/lpr mice were resistant to depletion of circulating T cells (CTC) by anti-Thy-1.2; 0.6 mg of antibody totally depleted CTC from normal mice, but had little or no effect on CTC in MRL/lpr mice. However, treatment with 6 mg of MAb against Thy-1.2 reduced CTC in MRL/lpr mice by over 70%. Moreover, this single treatment markedly reduced the proliferation of CTC over the ensuing 3 mo, despite clearance of the anti-Thy-1.2 from the circulation within 3 wk. Treated mice maintained better renal function than untreated controls, as assessed by levels of blood urea nitrogen (BUN), although anti-DNA antibodies were not significantly reduced. The effect of anti-Thy-1.2 was specific; treatment with rat MAb to the common leukocyte antigen T200 produced only a transient effect on circulating lymphocytes and did not reduce renal disease. The prolonged effects of a single injection of anti-Thy-1.2 suggest that the MAb produces a sustained alteration in immune regulation. The improvement in renal disease is in accord with evidence that autoimmune disease in MRL/lpr mice is T cell dependent. Monoclonal anti-lymphocyte antibodies may be useful in the treatment of autoimmunity.     

Ophiopogonin D attenuates the progression of murine systemic lupus erythematosus by reducing B cell numbers

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by immune abnormalities leading to multi-organ damage. The activation of autoreactive B cell differentiation will lead to the production of pathogenic autoantibodies, contributing to the development of SLE. However, the effects of Ophiopogonin D (OP-D) on B cell activation and autoantibody production as well as renal injury in the pathogenesis of SLE remain unclear. MRL/lpr mice, one of the most commonly used animal models of SLE, were intragastrically administered with 5 mg/kg/d OP-D at 17 weeks of age for 3 weeks. The survival rates of mice in each group were monitored for 6 weeks until 23 weeks of age. Proteinuria and serum creatinine levels were measured. Serum levels of immunoglobulin (Ig)G, IgM, and anti-dsDNA autoantibodies were detected by enzyme-linked immunosorbent assay. Numbers of CD19⁺ B cells in the blood, spleen and bone marrow and numbers of splenic germinal center (GC) B cells were calculated by using flow cytometry. OP-D treatment prolonged survival in MRL/lpr mice. OP-D treatment reduced proteinuria and serum creatinine levels as well as mitigated renal pathological alternation in MRL/lpr mice. Furthermore, serum levels of IgG, IgM, and anti-dsDNA autoantibodies were reduced by OP-D treatment. OP-D lessened not only CD19⁺ B cells in the spleen and bone marrow but also plasma cells that secreted anti-dsDNA autoantibodies, IgG and IgM in the spleen and bone marrow. OP-D ameliorated the progression of SLE by inhibiting the secretion of autoantibodies though reducing B cell numbers.     

Critical role of the alpha 4 integrin/VCAM-1 pathway in cerebral leukocyte trafficking in lupus-prone MRL/fas(lpr) mice

MRL/fas(lpr) mice are affected by a systemic autoimmune disease that results in leukocyte recruitment to a wide range of vascular beds, including the cerebral microvasculature. The mechanisms responsible for the leukocyte trafficking to the brain in these animals are not known. Therefore, the aim of this study was to directly examine the cerebral microvasculature in MRL/fas(lpr) mice and determine the molecular mechanisms responsible for this leukocyte recruitment. Intravital microscopy was used to assess leukocyte-endothelial cell interactions (rolling, adhesion) in the pial microcirculation of MRL(+/+) (control) and MRL/fas(lpr) mice at 8, 12, and 16 wk of age. Leukocyte rolling and adhesion were rarely observed in MRL(+/+) mice of any age. MRL/fas(lpr) mice displayed similar results at 8 and 12 wk. However, at 16 wk, significant increases in leukocyte rolling and adhesion were observed in these mice. Histological analysis revealed that the interacting cells were exclusively mononuclear. Leukocyte rolling was reduced, but not eliminated in P-selectin(-/-)-MRL/fas(lpr) mice. However, leukocyte adhesion was not reduced in these mice, indicating that P-selectin-dependent rolling was not required for leukocyte recruitment to the cerebral vasculature in this model of systemic inflammation. E-selectin blockade also had no effect on leukocyte rolling. In contrast, blockade of either the alpha4 integrin or VCAM-1 eliminated P-selectin-independent leukocyte rolling. alpha4 Integrin blockade also significantly inhibited leukocyte adhesion. These studies demonstrate that the systemic inflammatory response that affects MRL/fas(lpr) mice results in leukocyte rolling and adhesion in the cerebral microcirculation, and that the alpha4 integrin/VCAM-1 pathway plays a central role in mediating these interactions.     

Type I IFN protects against murine lupus

Both the type I (IFN-alpha beta) and type II (IFN-gamma) IFNs have been heavily implicated in the pathogenesis of systemic lupus erythematosus. To test the relative roles of these systems, congenic lupus-prone MRL/CD95(lpr/lpr) (MRL/lpr) mice lacking the type I IFN receptor (IFN-RI), type II IFN receptor (IFN-RII), or both, were derived. As expected, deficiency for IFN-RII protected MRL/lpr mice from the development of significant autoimmune-associated lymphadenopathy, autoantibodies, and renal disease. However, deficiency for the IFN-RI surprisingly worsened lymphoproliferation, autoantibody production, and end organ disease; animals doubly deficient for IFN-RI and IFN-RII developed an autoimmune phenotype intermediate between wild-type and IFN-RII-deficient animals, all correlating with an ability of type I IFN to suppress MRL B cell activation. Thus, type I IFNs protect against both the humoral and end organ autoimmune syndrome of MRL/lpr mice, independent of IFN-gamma. These findings warrant caution in the use of type I IFN antagonists in the treatment of autoimmune diseases and suggest further investigation into the interplay between the types I and II IFNs during the ontogeny of pathogenic autoantibodies.     

Anti-CD4 monoclonal antibody therapy suppresses autoimmune disease in MRL/Mp-lpr/lpr mice.

MRL/Mp-lpr/lpr (MRL/lpr) mice spontaneously develop systemic autoimmune disease, characterized by vasculitis, lymphadenopathy, glomerulonephritis, and autoantibody formation. The target organ inflammatory lesions are composed largely of CD4+ "helper" T cells, while the massively enlarged lymph nodes are composed primarily of CD3+ CD4- CD8- TCR alpha/beta + "double-negative" T cells. In this study we investigated the effect of treatment of MRL/lpr mice with anti-CD4 monoclonal antibody (mAb); control groups consisted of animals treated with normal saline or rat immunoglobulin (Ig). Anti-CD4 mAb treatment, which was started at 4 weeks and continued through 20 weeks of age, resulted in a dramatic reduction of both the frequency and severity of the autoimmune disease, as demonstrated histologically and serologically. Anti-CD4 mAb therapy markedly reduced the frequency of glomerulonephritis and eliminated vasculitis of the major renal arterial branches. Glomerulonephritis was detected in 9 of 9 saline-treated, 9 of 9 rat Ig-treated, but in only 1 of 9 anti-CD4 mAb-treated mice; vasculitis was detected in 6 of 9 saline-treated, 7 of 9 rat Ig-treated, but in none of 9 anti-CD4 mAb-treated mice. The frequency of antinuclear antibodies, titer of anti-dsDNA antibodies, and total Ig levels were all significantly reduced by anti-CD4 mAb therapy. These data support the hypothesis that CD4+ T cells play a central role in the disease process in this autoimmune strain.     

Membranous glomerulonephritis development with Th2-type immune deviations in MRL/lpr mice deficient for IL-27 receptor (WSX-1)

MRL/lpr mice develop spontaneous glomerulonephritis that is essentially identical with diffuse proliferative glomerulonephritis (World Health Organization class IV) in human lupus nephritis. Lupus nephritis is one of the most serious complications of systemic lupus erythematosus. Diffuse proliferative glomerulonephritis is associated with autoimmune responses dominated by Th1 cells producing high levels of IFN-gamma. The initial mounting of Th1 responses depends on the function of the WSX-1 gene, which encodes a subunit of the IL-27R with homology to IL-12R. In mice deficient for the WSX-1 gene, proper Th1 differentiation was impaired and abnormal Th2 skewing was observed during infection with some intracellular pathogens. Disruption of the WSX-1 gene dramatically changed the pathophysiology of glomerulonephritis developing in MRL/lpr mice. WSX-1-/- MRL/lpr mice developed disease resembling human membranous glomerulonephritis (World Health Organization class V) with a predominance of IgG1 in glomerular deposits, accompanied by increased IgG1 and IgE in the sera. T cells in WSX-1-/- MRL/lpr mice displayed significantly reduced IFN-gamma production along with elevated IL-4 expression. Loss of WSX-1 thus favors Th2-type autoimmune responses, suggesting that the Th1/Th2 balance may be a pivotal determinant of human lupus nephritis development.     

Effects of dietary omega3 and omega6 lipids and vitamin E on proliferative response, lymphoid cell subsets, production of cytokines by spleen cells, and splenic protein levels for cytokines and oncogenes in MRL/MpJ-lpr/lpr mice

omega3 Fatty acid rich fish oil (FO) and vitamin E may delay the progress of certain autoimmune diseases. The present study examined the mechanisms of action of omega3 lipids and vitamin E in autoimmune-prone MRL/lpr mice suffering from extensive lymphoproliferation, lupus-like symptoms, and accelerated aging. To determine whether the effects of omega3 lipids in autoimmune disease is linked to vitamin E levels, weanling female MRL/lpr and congenic control MRL/++ mice were fed diets containing 10% corn oil (CO) or 10% FO at two levels of vitamin E (75 IU or 500 IU/kg diet) for 4 months. The appearance of lymph nodes was delayed in the mice fed FO, and higher levels of FO offered further protection against the appearance of lymph nodes. Analysis of the spleen cells revealed that the cells positive for Thy.1 and Fas were significantly higher in the MRL/++ mice. The groups fed high levels of vitamin E generally exhibited higher levels of Fas. The proliferative response of splenocytes of MRL/++ mice to mitogens was significantly higher compared with MRL/lpr mice. Interleukin (IL)-10 production by spleen cells was significantly higher in FO-fed MRL/lpr mice than in CO-fed mice. In mice fed a high level of vitamin E, the production of IL-12 and tumor necrosis factor-alpha was significantly lower and IL-2 was significantly higher than in animals fed a low level of vitamin E. Proinflammatory cytokines were higher in the MRL/lpr mice and both FO and vitamin E lowered the levels of proinflammatory cytokines and lipid mediators. Western blots revealed that c-myc and c-ras were significantly lower and IL-2 and transforming growth factor (TGF)-beta1 levels were significantly higher in the spleens of MRL/++ mice. FO lowered c-myc and high levels of vitamin E in the diets normalized the levels of TGF-beta1 in MRL/lpr mice. The observations from this study suggest that both FO and vitamin E modulate the levels of specific cytokines, decrease the levels of proinflammatory cytokines, inflammatory lipid mediators, and c-myc, and increase TGF-beta1 levels in spleens of MRL/lpr mice and thus may delay the progress of autoimmune diseases.     

Accelerated ischemia/reperfusion-induced injury in autoimmunity-prone mice

Natural Abs have been implicated in initiating mesenteric ischemia/reperfusion (I/R)-induced tissue injury. Autoantibodies have affinity and self-Ag recognition patterns similar to natural Abs. We considered that autoimmunity-prone mice that express high titers of autoantibodies should have enhanced I/R-induced injury. Five-month-old B6.MRL/lpr mice displayed accelerated and enhanced intestinal I/R-induced damage compared with 2-mo-old B6.MRL/lpr and age-matched C57BL/6 mice. Similarly, older autoimmune mice had accelerated remote organ (lung) damage. Infusion of serum IgG derived from 5-mo-old but not 2-mo-old B6.MRL/lpr into I/R resistant Rag-1-/- mice rendered them susceptible to local and remote organ injury. Injection of monoclonal IgG anti-DNA and anti-histone Abs into Rag-1-/- mice effectively reconstituted tissue injury. These data show that like natural Abs, autoantibodies, such as anti-dsDNA and anti-histone Abs, can instigate I/R injury and suggest that they are involved in the development of tissue damage in patients with systemic lupus erythematosus.     

IL-21 receptor is required for the systemic accumulation of activated B and T lymphocytes in MRL/MpJ-Fas(lpr/lpr)/J mice

MRL/MpJ-Fas(lpr/lpr)/J (MRL(lpr)) mice develop lupus-like disease manifestations in an IL-21-dependent manner. IL-21 is a pleiotropic cytokine that can influence the activation, differentiation, and expansion of B and T cell effector subsets. Notably, autoreactive CD4(+) T and B cells spontaneously accumulate in MRL(lpr) 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 MRL(lpr) mice deficient in IL-21R (MRL(lpr).IL-21R(-/-)). Lymphadenopathy and splenomegaly, which are characteristic traits of the MRL(lpr) 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 MRL(lpr) mice. Correspondingly, we observed a significant reduction in autoantibody titers. Activated CD4(+) CD44(+) CD62L(lo) 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 MRL(lpr) 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 MRL(lpr) mice.