Production Of Antinuclear Autoantibodies Research Articles

Persistence of pulmonary tertiary lymphoid tissues and anti-nuclear antibodies following cessation of cigarette smoke exposure.

Formation of pulmonary tertiary immune structures is a characteristic feature of advanced COPD. In the current study, we investigated the mechanisms of tertiary lymphoid tissue (TLT) formation in the lungs of cigarette smoke-exposed mice. We found that cigarette smoke exposure led to TLT formation that persisted following smoking cessation. TLTs consisted predominantly of IgM positive B cells, while plasma cells in close proximity to TLTs expressed IgM, IgG, and IgA. The presence of TLT formation was associated with anti-nuclear autoantibody (ANA) production that also persisted following smoking cessation. ANAs were observed in the lungs, but not the circulation of cigarette smoke-exposed mice. Similarly, we observed ANA in the sputum of COPD patients where levels correlated with disease severity and were refractory to steroid treatment. Both ANA production and TLT formation were dependent on interleukin-1 receptor 1 (IL-1R1) expression. Contrary to TLT and ANA, lung neutrophilia resolved following smoking cessation. These data suggest a differential regulation of innate and B cell-related immune inflammatory processes associated with cigarette smoke exposure. Moreover, our study further emphasizes the importance of interleukin-1 (IL-1) signaling pathways in cigarette smoke-related pulmonary pathogenesis.

Gr‐1highCD11b+ Cells Suppress B Cell Differentiation and Lupus‐like Disease in Lupus‐Prone Male Mice

Systemic lupus erythematosus (SLE) develops much more readily in females than in males. Previous research has focused primarily on identifying mechanisms pertinent to the pathology in females. The aim of the current study was to delineate active protective mechanisms in males. We present evidence of a new male-associated mechanism of protection against the development of lupus-like disease in lupus-prone (NZB × NZW)F1 mice. We identified previously uncharacterized cellular and functional differences in myeloid cells between male and female (NZB × NZW)F1 mice, with the use of flow cytometry, confocal imaging, in vivo antibody-mediated depletion, and in vitro cell coculture assays. A population of Gr-1(high) Ly-6G+CD11b+ myeloid cells was found to be constitutively increased in male (NZB × NZW)F1 mice as compared with female mice and was regulated by testosterone. The cells were located adjacent to spleen B cell follicles in vivo and were found to directly inhibit cytokine-induced differentiation of naive B cells into antibody-secreting cells in vitro. Most notably, treatment with anti-Gr-1-depleting antibodies increased the spontaneous production of antinuclear autoantibodies in male (NZB × NZW)F1 mice, while a similar approach in female mice had no effect on disease development. Male lupus-prone (NZB × NZW)F1 mice harbor elevated levels of a population of myeloid cells with pronounced immunosuppressive capacities that specifically target B cells and the production of antibodies in vivo. We suggest that these cells represent a male-driven inhibitory mechanism involved in the control of B cell pathogenesis, delaying (or preventing) lupus-like disease development in otherwise genetically predisposed male (NZB × NZW)F1 mice.

Autoreactive T cell activation is sufficient for breaking B cell tolerance in the setting of functional antigen-specific dominant tolerance (P4543)

Abstract Systemic lupus erythematosus is a multisystem autoimmune disease characterized by anti-nuclear autoantibody (ANA) production by activated autoreactive B cells and the persistence and activation of autoreactive T cells. Animal models of lupus provide evidence that T and B cells interact to drive autoimmunity. Whether a break in tolerance in the T cell or B cell compartment could lead to a break in tolerance in the other compartment is unclear. Several studies have addressed this issue using transgenic autoreactive B cells, but whether significant elaboration of autoreactive B cells in the normal repertoire can be driven by activated T cells has not been shown. To address this question, we developed a mouse model in which naïve or activated transgenic autoreactive CD4+ T cells are transferred into hosts expressing their cognate pseudo-autoantigen (autoAg) on B cells and other antigen presenting cells (APCs). Interestingly, autoAg-specific Th1 or Th2 cells, but not naïve cells, drive ANA production by endogenous autoreactive B cells. In bone marrow chimeras, autoAg expression by radioresistant APCs was crucial for sufficient suppression of B cell activation by activated T cells. Additonally, we found that radioresistant APCs most effectively activate autoAg-specific splenic Tregs. We have shown that T cell activation is an important checkpoint in the prevention of ANA production by autoreactive B cells and that antigen-specific Tregs most effectively control ANA production.

FLEx-autoAb transgenic mice, a novel mouse model for studying peripheral tolerance to B cells that acquire self-reactivity following somatic hypermutation. (P4034)

Abstract Uptake of nucleic acid-containing antigens by antigen receptors (BCRs) on B cells leading to endosomal TLR activation is thought to be critical for antinuclear autoantibody (ANA) production in lupus. However, it has been difficult to study this in peripheral B cells that acquire ANA specificity because current ANA BCR models are subjected to central tolerance mechanisms. To overcome this, we generated a FLEx-autoantibody (autoAb) transgenic model in which VH specificity can be changed from a non-self-reactive anti-nitrophenyl (NP) to anti-chromatin (3H9-56R) reactivity following Cre recombinase expression induced by tamoxifen (all B cells) or the activation induced cytidine deaminase promoter (during class-switch recombination/somatic hypermutation). In nonautoimmune C57BL/6 mice, B cells that acquire self-reactivity to chromatin were completely deleted after several days at all stages of development, although numbers of plasma cells were too low to analyze. Faslpr mutation enabled the development of only low levels of anti-id positive (56R+) plasma cells but did not rescue B cells at any other stages of development after tamoxifen. The provision of excess T cell help, through induction of chronic graft-versus-host disease in B6-Faslpr mice resulted in a marked increase in 56R+ plasma cells. These findings suggest that ANA-specificity and engagement of endogenous TLR is not sufficient to rescue autoreactive B cells even in mice with Fas deficiency.

Influence of cytokine auto antibodies on serum IFNα activity in SLE (P6287)

Abstract The type-I interferon (IFN-I) family consists of 12 IFN-α subtypes as well as IFN-β and IFN-ω. IFN-α subtypes are thought to play a pivotal role in the pathogenesis of autoimmune diseases such as lupus by enhancing the production of anti-nuclear autoantibodies and driving end organ damage in patients with lupus nephritis. Despite the putative role of IFN-αs in disease, serum IFN-α activity levels are often low or undetectable in lupus patients. Auto antibodies (AAbs) against a single IFNα subtype (IFNα4) have been detected in lupus patients suggesting they may alter serum IFNα activity and disease severity. To better understand this relationship, we have measured total IFNα and IFNα subtype-specific AAbs levels in lupus patient serum. Our results thus far reveal an excellent correlation between IFNα activity and AAb levels, suggesting AAbs may provide an indirect marker of cytokine activity in some patients. Toward this end, we have determined the AAb profile for eleven cytokines implicated in lupus to understand their relationship to IFNα levels and overall disease severity. The resulting cytokine profile will be presented towards the goal of determining the best targets for anti- cytokine therapy in lupus.

B Cell TLR7 Expression Drives Anti-RNA Autoantibody Production and Exacerbates Disease in Systemic Lupus Erythematosus–Prone Mice

Systemic lupus erythematosus (SLE) is a chronic systemic autoimmune disease characterized by the production of antinuclear autoantibodies. Antinuclear autoantibody development is recognized as one of the initial stages of disease that often results in systemic inflammation, kidney disease, and death. The etiology is complex, but it is clear that innate pathways may play an important role in disease progression. Recent data have highlighted an important role for the TLR family, particularly TLR7, in both human disease and murine models. In this study, we have presented a low copy conditional TLR7 transgenic (Tg7) mouse strain that does not develop spontaneous autoimmunity. When we combine Tg7 with the Sle1 lupus susceptibility locus, the mice develop severe disease. Using the CD19(Cre) recombinase system, we normalized expression of TLR7 solely within the B cells. Using this method we demonstrated that overexpression of TLR7 within the B cell compartment reduces the marginal zone B cell compartment and increases B and T cell activation but not T follicular helper cell development. Moreover, this enhanced B cell TLR7 expression permits the specific development of Abs to RNA/protein complexes and exacerbates SLE disease.

Lack of T cells in Act1-deficient mice results in elevated IgM-specific autoantibodies but reduced lupus-like disease

Act1 is a negative regulator of B-cell activation factor of the TNF family (BAFF) and CD40L-induced signaling. BALB/C mice lacking Act1 develop systemic autoimmunity resembling systemic lupus erythematosus (SLE) and Sjögren's syndrome (SjS). SLE and SjS are characterized by anti-nuclear IgG autoantibody (ANA-IgG) production and inflammation of peripheral tissues. As autoantibody production can occur in a T-cell dependent or T-cell independent manner, we investigated the role of T-cell help during Act1-mediated autoimmunity. Act1-deficiency was bred onto C57Bl/6 (B6.Act1(-/-) ) mice and B6.TCRβ(-/-) TCRδ(-/-) Act1(-/-) (TKO) mice were generated. While TCRβ/δ-sufficient B6.Act1(-/-) mice developed splenomegaly and lymphadenopathy, hypergammaglobulinemia, elevated levels of ANA-IgG, and kidney pathology, TKO mice failed to develop any such signs of disease. Neither B6.Act1(-/-) nor TKO mice developed SjS-like disease, suggesting that epigenetic interactions on the BALB/C background are responsible for this phenotype in BALB/C.Act1(-/-) mice. Interestingly, BAFF-driven transitional B-cell abnormalities, previously reported in BALB/C.Act1(-/-) mice, were intact in B6.Act1(-/-) mice and largely independent of T cells. In conclusion, T cells are necessary for the development of SLE-like disease in B6.Act1(-/-) mice, but not BAFF-driven transitional B-cell differentiation.

Pre-B Cell Leukemia Homeobox 1is a novel susceptibility gene that regulate T cell functions. (123.2)

Abstract Pre-leukemia homeobox (Pbx) 1 is a novel lupus susceptibility gene that regulates T cell activation and tolerance in both the NZM2410 lupus-prone mouse model and lupus patients. Lupus susceptibility is associated with the expression of a novel splice isoform Pbx1-d, which, when over expressed leads to an increased CD4+ T cell activation and a reduced induction of Tregs by retinoic acid. The exons encoding for the DNA binding domain and the Hox binding domain are deleted in Pbx-1d, predicting that this isoform functions as a dominant negative. To test this hypothesis, we used an osteogenesis model in which Pbx1 expression prevents differentiation. Pbx1-d expression in MC3T3 osteoblast progenitors mimicked the effect of shRNA Pbx1 in accelerating osteoblast differentiation. Furthermore, Pbx-1d binding to the SOX3 promoter was weaker than that of the full-length Pbx1-b isoform, and SOX3 expression was attenuated in Pbx1-d transfected cells. These results demonstrated that Pbx1-d functions as a dominant negative. C57BL/6 transgenic mice expressing Pbx1-d in their CD4+ T cells show an age-dependent increased in CD4+ T cell activation, with an expansion of CD44+ CD4+ memory cells, and the production of anti-nuclear autoantibodies. These results demonstrate that Pbx1 represents a novel regulator of T cell activation, whose impaired function leads to systemic autoimmunity.

Conditional deletion of tumor necrosis factor receptor-associated factor 6 (TRAF6) in medullary thymic epithelial cells leads to the development of classical autoimmune hepatitis in mice (123.40)

Abstract Autoimmune hepatitis (AIH) is an enigmatic disease in which loss of tolerance towards self-antigens is suspected among the causes; animal models are limited, however. TRAF6 is an important signaling adaptor protein that plays a critical role in T cell tolerance by regulating medullary thymic epithelial cell (mTEC) development. mTECs in turn regulate central tolerance by ectopically expressing self-antigens and eliminating autoreactive T cells during development. In this report, conditional knockout mice lacking TRAF6 expression in thymic epithelial cells (TRAF6ΔTEC) were generated using FoxN1-cre transgenic mice (FoxN1 expression is confined to mTECs). TRAF6 deletion inhibited mTEC development and the production of mature mTECs in the thymus. This correlated with spontaneous liver-specific autoimmunity and pathognomonic features of chronic autoimmune hepatitis including interphase and lobular hepatitis, T cell and plasma cell infiltration, elevated serum transaminases and IgG, and production of anti-nuclear autoantibodies against the livers of TRAF6ΔTEC animals. A significant increase in fibrosis was also detected in TRAF6ΔTEC mice compared to littermate controls. Our data indicate that mTECs play an intrinsic role in central tolerance, and their depletion leads to AIH. This model of spontaneous AIH represents an exciting new tool to investigate autoantigen-specific T and B cell responses and regulatory mechanisms underlying the disease.

Higher numbers of Gr1hiCD11b+ cells suppress B cell differentiation and autoantibody production in male BWF1 mice (72.7)

Abstract (NZBxNZW) F1 (BWF1) mice spontaneously develop a lupus-like disease characterized by elevated levels of anti-nuclear autoantibodies (ANA) and systemic inflammation and with a similar female bias as observed in humans. Bone marrow (BM) chimera studies have shown intrinsic disease-driving properties of female BM cells and subsequent flow-based analyses identified significantly less Gr1hiCd11b+ myeloid cells in BWF1 female mice as compared to males. As Gr1hiCD11b+ cells have been suggested to be immunosuppressive, we hypothesized that these cells suppress B cell activation and differentiation and protect against lupus-like disease in male BWF1 mice. We analyzed the effect of male and female Gr1hiCD11b + cells on 1) cytokine-driven B cell differentiation in vitro, 2) antibody responses to immunization, and 3) spontaneous autoantibody production. We found that Gr1hiCD11b+ cells from both male and female 4 wk old BWF1 mice significantly suppressed cytokine-driven plasma cell differentiation in vitro in a dose dependent manner. Likewise, treatment of male BWF1 mice with depleting anti-Gr1 antibody resulted in elevated antibody response to Np-CGG immunization. And finally, spontaneous production of ANA were significantly increased in male BWF1 mice during and after anti-Gr1 antibody treatment, with ANA levels comparable to those of unmanipulated BWF1 females. These data suggest a new and important role for immunosuppressive Gr1hiCD11b+ cells during antibody-mediated autoimmunity.

Btk levels set the threshold for B-cell activation and negative selection of autoreactive B cells in mice

AbstractOn antigen binding by the B-cell receptor (BCR), B cells up-regulate protein expression of the key downstream signaling molecule Bruton tyrosine kinase (Btk), but the effects of Btk up-regulation on B-cell function are unknown. Here, we show that transgenic mice overexpressing Btk specifically in B cells spontaneously formed germinal centers and manifested increased plasma cell numbers, leading to antinuclear autoantibody production and systemic lupus erythematosus (SLE)–like autoimmune pathology affecting kidneys, lungs, and salivary glands. Autoimmunity was fully dependent on Btk kinase activity, because Btk inhibitor treatment (PCI-32765) could normalize B-cell activation and differentiation, and because autoantibodies were absent in Btk transgenic mice overexpressing a kinase inactive Btk mutant. B cells overexpressing wild-type Btk were selectively hyperresponsive to BCR stimulation and showed enhanced Ca2+ influx, nuclear factor (NF)–κB activation, resistance to Fas-mediated apoptosis, and defective elimination of selfreactive B cells in vivo. These findings unravel a crucial role for Btk in setting the threshold for B-cell activation and counterselection of autoreactive B cells, making Btk an attractive therapeutic target in systemic autoimmune disease such as SLE. The finding of in vivo pathology associated with Btk overexpression may have important implications for the development of gene therapy strategies for X-linked agammaglobulinemia, the immunodeficiency associated with mutations in BTK.

Murine lupus strains differentially model unique facets of human lupus serology

Systemic lupus erythematosus (SLE) is a polygenic autoimmune disease characterized by the production of anti-nuclear autoantibodies that lead to subsequent end organ damage. Previous array-based studies in patients with SLE have shown that high immunoglobulin (Ig)G anti-nuclear autoantibody reactivity was associated with severe renal lupus, whereas IgM polyreactivity was associated with less severe disease. To ascertain how different murine lupus strains recapitulate these different autoantibody profiles seen in patients, serum from New Zealand black (NZB)/NZ white (W) F(1), Murphy Roths large (MRL)/lpr, NZ mixed (M)2410 and BXSB strains were compared using a comprehensive array-based screen. The array results were verified using enzyme-linked immunosorbent assays (ELISAs). Serum from MRL/lpr mice exhibited high levels of IgG anti-nuclear antibodies as well as anti-glomerular antibodies and variable levels of antibodies to myosin, Matrigel and thyroglobulin. Elevated anti-nuclear IgG antibodies were associated with severe nephritis in this strain. In contrast, NZM2410 mice exhibited lower IgG autoantibody levels with less severe nephritis but a significantly higher polyreactive IgM autoantibody profile. ELISA analysis confirmed these results. The NZB/NZW F(1) and BXSB strains exhibited an intermediate serological profile. Hence, just as in patients with SLE, whereas strong IgG reactivity to nuclear antigens is associated with severe renal disease, a polyreactive IgM seroprofile is also less ominous in murine lupus.

Requirement of myeloid cell–specific Fas expression for prevention of systemic autoimmunity in mice

The death receptor Fas is a critical mediator of the extrinsic apoptotic pathway, and its role in mediating lymphoproliferation has been extensively examined. The present study was undertaken to investigate the impact of myeloid cell-specific loss of Fas. Mice with Fas flanked by loxP sites (Fas(flox/flox) ) were crossed with mice expressing Cre under control of the murine lysozyme M gene promoter (Cre(LysM) ), which functions in mature lysozyme-expressing cells of the myelomonocytic lineage. The genotype for Cre(LysM) Fas(flox/flox) mice was verified by polymerase chain reaction and flow cytometric analysis. Flow cytometric analysis was also used to characterize myeloid, dendritic, and lymphoid cell distribution and activation in bone marrow, blood, and spleen. Luminex-based assays and enzyme-linked immunosorbent assays were used to measure serum cytokine/chemokine and immunoglobulin levels. Renal damage or dysfunction was examined by immunohistochemical and immunofluorescence analysis. Cre(LysM) Fas(flox/flox) mice exhibited a systemic lupus erythematosus (SLE)-like disease that included leukocytosis, splenomegaly, hypergammaglobulinemia, antinuclear autoantibody and proinflammatory cytokine production, and glomerulonephritis. Loss of Fas in myeloid cells increased levels of both Gr-1(low) and Gr-1(intermediate) blood monocytes and splenic macrophages and, in a paracrine manner, incited activation of conventional dendritic cells and lymphocytes in Cre(LysM) Fas(flox/flox) mice. Taken together, these results suggest that loss of Fas in myeloid cells is sufficient to induce inflammatory phenotypes in mice, reminiscent of an SLE-like disease. Thus, Fas in myeloid cells may be considered a suppressor of systemic autoimmunity.

The genetics of lupus: a functional perspective

Systemic lupus erythematosus (SLE) is an autoimmune disease with a strong genetic component and is characterized by chronic inflammation and the production of anti-nuclear auto-antibodies. In the era of genome-wide association studies (GWASs), elucidating the genetic factors present in SLE has been a very successful endeavor; 28 confirmed disease susceptibility loci have been mapped. In this review, we summarize the current understanding of the genetics of lupus and focus on the strongest associated risk loci found to date (P <1.0 × 10−8). Although these loci account for less than 10% of the genetic heritability and therefore do not account for the bulk of the disease heritability, they do implicate important pathways, which contribute to SLE pathogenesis. Consequently, the main focus of the review is to outline the genetic variants in the known associated loci and then to explore the potential functional consequences of the associated variants. We also highlight the genetic overlap of these loci with other autoimmune diseases, which indicates common pathogenic mechanisms. The importance of developing functional assays will be discussed and each of them will be instrumental in furthering our understanding of these associated variants and loci. Finally, we indicate that performing a larger SLE GWAS and applying a more targeted set of methods, such as the ImmunoChip and next generation sequencing methodology, are important for identifying additional loci and enhancing our understanding of the pathogenesis of SLE.

SLE: a Metabolic Disease of T Cells?

SLE is a multifactorial, heterogeneous group of disease which is potentially fatal and can be characterized by anti-nuclear autoantibody production and consequent organ, especially kidney failure [1]. Therapy is still restricted and limited to general immunosuppressants and cytotoxic drugs with many side effects. Therefore, the understanding of the fine molecular mechanisms of disease pathogenesis is crucial to develop new therapeutic approaches. The complex interaction of the innate dendritic cells and adaptive immune T and B cells significantly contribute to disease pathogenesis. Both T and B cells are hyperactive in SLE. T cells exhibit aberrant signaling profile upon antigen receptor activation and changes in proximal signaling molecules and adaptor proteins which together shape the pathogenic lupus T cell phenotype. Lupus T cells exhibit a metabolically dysregulated status, including persistent mitochondrial hyperpolarization (MHP) [2,3], increased mitochondrial mass, oxidative stress and depleted intracellular glutathione levels [4,5]. Lupus T cells also show increased cytoplasmic and mitochondrial calcium levels and signaling profile. A significant inducer of MHP is nitric oxide, which is produced mainly by monocytes in SLE. MHP leads to subsequent necrosis releasing necrotic material from T cells, which triggers dendritic cells and B cells. Closely related to MHP, T cells show altered metabolic gene expression signature, including the overexpression of the mitochondrial outer membrane protein VDAC (voltage dependent anion channel) and SOD2 (superoxide dismutase). Transaldolase, an enzyme of the pentose-phosphate pathway which is responsible for the production of nucleotides and maintenance of reducing environment [6] is also overexpressed in lupus T cells and it has been previously shown that overexpression of this enzyme results in MHP [7]. Consistent with altered metabolism, lupus T cells show enhanced activation of the mTOR (mammalian target of rapamycin) pathway.

Recent advances in the genetics of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease characterized by the production of antinuclear autoantibodies and the inflammatory infiltration of many organ systems. SLE is a complex disorder in which multiple genetic variants, together with environmental and hormonal factors, contribute to disease risk. In this article, we summarize our current understanding of the genetic contribution to SLE in light of recent genome-wide association studies, which have brought the total number of confirmed SLE susceptibility loci to 29. In the second section, we explore the functional implications of these risk loci and, in particular, highlight the role that many of these genes play in the Toll-like receptor and type I interferon signaling pathways. Finally, we discuss the genetic overlap between SLE and other autoimmune and inflammatory conditions as several risk loci are shared among multiple disorders, suggesting common underlying pathogenic mechanisms.

Lupus érythémateux systémique : de la physiopathologie au traitement

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease with multiorgan involvement characterized by an immune response against nuclear components. SLE patients experience a waxing and waning disease course and exhibit a wide array of clinical manifestations, reflecting the systemic nature of the disease. Environmental triggers such as viruses are likely to act in the context of susceptibility genes, including genes involved in antigen/immune complex clearance, lymphoid signalling, or apoptosis, among several others, explaining why the pathogenesis of this disease remains largely uncovered. The abnormal activation of the innate immunity is central to SLE physiopathology. Dendritic cells activation and unabated secretion of IFN-alpha are the key features of the disease through their involvement in the capture and the presentation of nuclear material to the autoreactive adaptive arm (T and B lymphocytes) leading to the subsequent production of anti-nuclear autoantibodies. In this line, numerous studies have demonstrated the prominent role of immune complexes deposition throughout the body which directly can induce inflammation and tissue damage. However, animal models and recent human studies support the concept that other effector pathways including cytotoxic T-lymphocytes could be involved in SLE pathogenesis through their ability to migrate and/or target specifically different tissues. The aim of this review is not to provide a comprehensive review of the SLE pathophysiology but rather to give an overview of the immunological abnormalities associated to SLE. The treatments that are currently used or that are in development to fight against abnormal immune response in SLE will be detailed. The genetics of SLE is not the scope of this review.

T-cell and B-cell signaling biomarkers and treatment targets in lupus

Systemic lupus erythematosus is characterized by the production of antinuclear autoantibodies and dysfunction of T-cells, B-cells, and dendritic cells. Here, we review newly recognized genetic factors and mechanisms that underlie abnormal intracellular signal processing and intercellular communication within the immune system in systemic lupus erythematosus. Activation of the mammalian target of rapamycin plays a pivotal role in abnormal activation of T and B-cells in systemic lupus erythematosus. In T-cells, increased production of nitric oxide and mitochondrial hyperpolarization were identified as metabolic checkpoints upstream of mammalian target of rapamycin activation. Mammalian target of rapamycin controls the expression T-cell receptor-associated signaling proteins CD4 and CD3zeta through increased expression of the endosome recycling regulator HRES-1/Rab4 gene, mediates enhanced Ca2+ fluxing and skews the expression of tyrosine kinases both in T and B-cells, and blocks the expression of Foxp3 and the expansion of regulatory T-cells. Mitochondrial hyperpolarization and the resultant ATP depletion predispose T-cells to necrosis, thus promoting the dendritic cell activation, antinuclear autoantibody production, and inflammation. Mitochondrial hyperpolarization, increased activity of mammalian target of rapamycin and Syk kinases, enhanced receptor recycling and Ca2+ flux have emerged as common T and B-cell biomarkers and targets for treatment in systemic lupus erythematosus.

A Defect in Marco Expression Contributes to Systemic Lupus Erythematosus Development via Failure to Clear Apoptotic Cells

Systemic lupus erythematosus is a multisystem autoimmune disease characterized by the production of numerous antinuclear autoantibodies and inflammatory mediators. The BXSB mouse strain is an excellent model of the disease. Previous work has determined a number of important disease susceptibility intervals that have been isolated in separate congenic strains. Here, we have combined expression data from those strains with functional analyses to demonstrate that reduced expression of the innate scavenger receptor Marco (macrophage receptor with collagenous structure) is a primary event in BXSB mice, that reduced mRNA expression is mirrored at the protein level, and that this results in a significant alteration in function. We have confirmed a role for Marco in the clearance of apoptotic cells and a generalized defect in both endocytosis and phagocytosis. The failure to clear apoptotic cells has previously been linked to the development of systemic lupus erythematosus. However, the use of congenic mice with limited phenotypes in this study has enabled us to propose that in the case of Marco at least, disease results from the production of anti-dsDNA Abs.

Dipeptidyl peptidase IV (DP IV) activity in serum and on lymphocytes of MRL/Mp-lpr/lpr mice correlates with disease onset.

DP IV (CD26), a serine protease expressed on activated T cells, participates in immune responses in vivo as well as in vitro. We measured cell surface and serum DP IV in mice of the autoimmune MRL/Mp-lpr/lpr (MRL/l) strain, which is characterized by massive T cell proliferation and production of anti-nuclear autoantibodies. The mass of inguinal lymph nodes correlated with serum DP IV activity. Furthermore, serum DP IV activity increased markedly in parallel with the acceleration of lymph node swelling and anti-nDNA antibody production. Serum DP IV activity in 16-week-old MRL/l mice reached levels up to three higher than those in age-matched MRL/Mp- +/+ mice or BALB/c mice. Immunohistochemical staining and flow cytometric analysis identified DV IV on surfaces of lymphocytes from the enlarged lymph nodes of MRL/l mice. Subcutaneous injection of the mechanism-based inhibitor, Pro-boroPro, reduced protease activity in serum and cell suspensions prepared from spleen and lymph nodes, confirming the identity of the enzyme as DP IV. These results indicate that the massively accumulating lymphocytes of MRL/l mice have a property characteristic of activated T cells, although they express little surface CD4 or CD8 and do not produce IL-2. DP IV may participate in the role these cells play in the pathogenesis of MRL/l autoimmune disease.