Systemic lupus erythematosus (SLE) is a generalized autoimmune disease affecting several organ systems, characterized by the presence of a vast array of autoantibodies, characteristically directed to nuclear antigens (ANA). The heterogeneity of clinical manifestations and the disease's unpredictable course characterized by flares and remissions are very likely a reflection of heterogeneity at the origin of disease, with a final common pathway leading to loss of tolerance to nuclear antigens. Impaired clearance of immune complexes and apoptotic material and production of autoantibodies have long been recognized as major pathogenic events Apoptotic defects underlie some models of autoimmune diseases, and they have been proposed in the pathogenesis of SLE) a prototypic autoimmune disorder Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by the production of high-titer IgG autoantibodies directed against nuclear autoantigens. Type I interferon (IFN-I) has been shown to play a pathogenic role in this disease. Cell death as driving force for autoantibodies production phagocytes engulf dead cells, which are recognized as dead by virtue of a characteristic "eat me" signal exposed on their surface. Inefficient engulfment of dead cells activates the immune system, causing disease such as systemic lupus erythematosus, The molecular details of these processes has been recently superbly reviewed in Cell, 2010. During apoptosis, the asymmetric distribution of phospholipids (PS) of the plasma membrane gets lost and PS is translocated to the outer leaflet of the plasma membrane. There, PS acts as one major "eat me" signal that ensures efficient recognition and uptake of apoptotic cells by phagocytes. PS recognition of activated phagocytes induces the secretion of anti-inflammatory cytokines like interleukin-10 Accumulation of dead cells containing nuclear autoantigens in sites of immune selection may provide survival signals for autoreactive B-cells. The production of antibodies against nuclear structures determines the initiation of chronic autoimmunity in systemic lupus erythematosus. Various soluble molecules and biophysical properties of the surface of apoptotic cells play significant roles in the appropriate recognition and further processing of dying and dead cells. We exemplarily discuss how Milk fat globule epidermal growth factor 8 (MFG-E8), biophysical membrane alterations, High mobility group box 1 (HMGB1), C-reactive protein (CRP), and anti-nuclear autoantibodies may contribute to the etiopathogenesis of the disease. Over 50 years ago, the identification of antibodies to double-stranded (ds) DNA (?). Whilst widely regarded as synonymous with patients who have systemic lupus erythematosus (SLE), doubts have been raised about their significance whether they are merely part of the spectrum of anti-nucleosome antibodies. There is increasing evidence that in systemic lupus erythematosus, nucleosomes, the basic chromatin component, represent both a driving immunogen and a major in vivo target for antibodies. Either a disturbed apoptosis or a reduced clearance of apoptotic cells by phagocytes may lead to an increased exposure of apoptotic nucleosomes to the immune system. These nucleosomes, which have been cleaved and modified during the process of apoptosis, escape normal clearance. Immune complexes containing DNA and RNA are responsible for disease manifestations found in patients with systemic lupus erythematosus (SLE). B cells contribute to SLE pathology through BCR recognition of endogenous DNA- and RNA- associated autoantigens to production of class-switched DNA- and RNA-reactive autoantibodies, contributing to an inflammatory amplification loop characteristic of the disease. Intriguingly, self-DNA and RNA are typically non-stimulatory for TLR9/7 - engagement of the type I IFN receptor promotes B cell activation by weakly stimulatory DNA and RNA TLR ligands. Anti-nucleosome antibodies were positive in 40 (97.6%) patients with active SLE, had a stronger correlation than anti-dsDNA antibodies with SLEDAI score. Anti-nucleosome antibodies test is highly sensitive and specific for the diagnosis of SLE, There mouse models of autoimmune disorders where mutations of the lpr and gld genes lead to defective expression of Fas and respectively, FasL, resulting in the persistence of autoreactive immune cells due to deficiency of their elimination through apoptotic mechanisms The Fas/FasL pathway of apoptosis in SLE Fas is a 43 kDa glycoprotein molecule which is involved in inducing apoptosis in both B and T lymphocytes. In the murine MRL/Ipr-Ipr model of systemic lupus erythematosus (SLE), the lymphoproliferation (lpr) mutation results in defective transcription of the gene that codes for the Fas protein. MRL mice which carry the homozygous recessive Ipr mutation develop a severe early-onset genetically predetermined autoimmune syndrome. Susceptibility to SLE is found to be associated with many genes, one of which is APO-1/Fas gene, which is present on chromosome 10 in humans. The APO-1/Fas promoter contains consensus sequences for binding of several transcription factors that affect the intensity of Fas expression in cells. The mutations in the APO-1/Fas promoter are associated with risk and severity in various autoimmune diseases. A decreased rate of apoptosis, possibly related to elevated levels of soluble Fas (sFas) which can inhibit Fas mediated apoptosis of lymphocytes. In overwhelming majority of situations alterations in Fas and FasL expression are viewed in frames of Fas-mediated apoptosis. In the present work we tested a possible involvement of Fas-ligand-mediated "reverse signaling" in pathogenesis of autoimmune diseases such as rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). We show that high level of sFas in RA patient blood correlates with a high activity of disease; in SLE patients with elevated sFas level there was a correlation between sFas concentration and leucopenia, and tissue and organ damage. We showed for the first time that at high concentrations in serum sFas is present in oligomeric form. Oligomeric sFas demonstrated cytotoxicity in lymphocyte primary culture and in transformed cells, while non-toxic recombinant Fas-ligand partially blocked this effect. Levels of sFas correlated with the percentages of activated B cells defined as CD20(+)CD38(+) cells. Serum levels of sFas correlate with percentages of activated B cells but not with that of activated T cells. There was a significant correlation between serum concentrations of sFAS and IL-18 in SLE patients sFas and alfa-TNF serum levels are increased in SLE patients. sFas levels seems to be secondary to alfa-TNF action, which is enhanced in inflammatory conditions such as SLE. Bcl-2 antigen expression and IL-10 serum levels are related to the maintenance of SLE activity. These alterations may interfere with the apoptotic process Fas ligand (FasL), an apoptosis-inducing member of the TNF cytokine family, and its receptor Fas are critical for the shutdown of chronic immune responses and prevention of autoimmunity. Accordingly, mutations in their genes cause severe lymphadenopathy and autoimmune disease in mice and humans. FasL function is regulated by deposition in the plasma membrane and metalloprotease-mediated shedding. mFasL is essential for cytotoxic activity and constitutes the guardian against lymphadenopathy, autoimmunity and cancer, whereas excess sFasL appears to promote autoimmunity Lymphocytes from aged autoimmune MRL/lpr mice overexpress Fas ligand (FasL), and are cytotoxic against Fas+ target cells. This cytotoxic potential is only partly due to FasL, as wild-type MRL+/+ lymphocytes are not able to kill Fas+ targets after induction of FasL. Type I Interferons and apoptosis Type I IFN (IFN-I) was firstly described in 1957 as a soluble factor responsible for viral resistance in vitro. IFN-I can be considered a "director" of protective immune responses. The recent finding of the so-called interferon signature in patients suffering from different autoimmune diseases has underlined its possible role in the pathogenesis of these diseases. Plasmacytoid dendritic cells (pDCs) are specialized type I IFN producers significantly enhance autoreactive B cell proliferation, autoantibody production, and survival in response to TLR and BCR stimulation. . IFNAR2-/- B cells failed to upregulate nucleic acid-sensing Toll-like receptors TLR7 as well as TLR9 expression in response to IFN-I, and effector responses to TLR7 and TLR9 agonists were significantly decreased as compared to B cells from WT mice following treatment with IFN-alpha. In addition, serum levels of interferon-alpha (IFN-alpha) increase in parallel with the Fas-dependent cytotoxic potential of lymphocytes from MRL/lpr mice as they age. To understand the mechanisms underlying these observations, combined suppression subtractive hybridization (SSH) and RT-PCR were used to study differential gene expression in splenocytes from MRL/lpr mice compared with splenocytes from MRL+/+ mice. Twenty-two genes were upregulated transcriptionally in MRL/lpr splenocytes compared with their MRL+/+ counterparts. Furthermore, 9 of these genes were also upregulated after treatment of MRL/lpr splenocytes with IFN-alpha, and 4 were strongly downregulated. MRL/lpr lymphocytes were also found to be hyperresponsive to IFN-alpha. Nagafuchi H, Wakisaka S, Takeba Y, Takeno M, Sakane T, Suzuki N. Aberrant expression of Fas ligand on anti-DNA autoantibody secreting B lymphocytes in patients with systemic lupus erythematosus: "immune privilege"-like state of the autoreactive B cells. Suzuki N, Ichino M, Mihara S, Kaneko S, Sakane T. Inhibition of Fas/Fas ligand-mediated apoptotic cell death of lymphocytes in vitro by circulating anti-Fas ligand autoantibodies in patients with systemic lupus erythematosus.Arthritis Rheum. 1998 A novel subset of memory B cells is enriched in autoreactivity and correlates with adverse outcomes in SLE.Nicholas MW,2008. CD19(hi) B cells have elevated CXCR3 levels and chemotax in response to its ligand CXCL9. Thus, CD19(hi) B cells are precursors to anti-self PCs, and identify an SLE patient subset likely to experience poor clinical outcomes. Quantitative genetic variation in CD19 expression correlates with autoimmunity.[J Immunol. B Lymphocyte signaling established by the CD19/CD22 loop regulates autoimmunity Warnatz K, Expansion of CD19(hi)CD21(lo/neg) B cells in common variable immunodeficiency (CVID) patients with autoimmune cytopenia Although IFN-α was reported to promote the survival of peripheral B-lymphocytes via the PI3-kinase-Akt pathway, the triggered signalling pathways involved in the protection of B cell from apoptosis need to be clarified. Using flow cytometry and western blot analysis, we have found that type 1 IFNs (IFN-α/β) protect human B cells in culture from spontaneous apoptosis and from apoptosis mediated by anti-CD95 agonist, in a dose- and time-dependant manner. IFN-α/β-mediated anti-apoptotic effect on human B cells was totally abrogated by blockade of IFNR1 chain. Our data indicate that PI3Kδ, Rho-A, NFκB and Bcl-2/BclXL are active downstream of IFN receptors and are the major effectors of IFN-α/β-rescued B cells from apoptosis. Furthermore, immunohistochemical results show marked reduction in numbers of CD20 positive B cell in both spleen and Peyer’s patches from mice treated with anti-IFNR1 blocking antibody compared with control group. Moreover, ultrastructural observations of these organs show an obvious increase in apoptotic cells from mice treated with anti-IFNR1 blocking antibody. Our results provide more details about the triggered signalling pathways and the phosphorylation cascade which are involved in the protection of B cell from apoptosis after treatment with IFN-α/β. at high concentrations in serum sFas is present in oligomeric form. Oligomeric sFas demonstrated cytotoxicity in lymphocyte primary culture and in transformed cells, while non-toxic recombinant Fas-ligand partially blocked this effect - a possible involvement of Fas-ligand-mediated “reverse signaling” in pathogenesis of autoimmune diseases In healthy controls, more memory than naive T lymphocytes underwent apoptosis. By contrast, in patients with SLE, more naive T cells underwent apoptosis with TNFalpha (p<0.01). Enhanced apoptosis of T cells in SLE was independent of disease activity or medication. Finally, inhibition experiments showed that apoptosis in the presence of TNFalpha was only partly blocked with anti-Fas ligand (FasL) antibody mFas expression levels were significantly higher (P < 0.01) among SLE patients than those in healthy controls, the expression levels had a positive (r = 0.381, P < 0.01) correlation with the early apoptosis rate of PBLs in SLE patients SLE serum induce classical caspase-dependent apoptosis, and this was independent of death receptor pathways. results demonstrate increasing serum concentrations of the soluble molecules sFas and sFasL during the first days after birth, indicating possibly a gradual decrease of apoptosis in early neonatal life. Neutrophil apoptosis was significantly increased in patients with juvenile-onset SLE as compared with the noninflammatory controls Concentrations of TRAIL and FasL were significantly increased in sera from patients with juvenile-onset SLE, Lymphocytes from aged autoimmune MRL/lpr mice overexpress Fas ligand (FasL), and are cytotoxic against Fas+ target cells. This cytotoxic potential is only partly due to FasL, as wild-type MRL+/+ lymphocytes are not able to kill Fas+ targets after induction of FasL. In addition, serum levels of interferon-alpha (IFN-alpha) increase in parallel with the Fas-dependent cytotoxic potential of lymphocytes from MRL/lpr mice as they age MRL/lpr lymphocytes overexpressed mRNA for the IFN-alpha receptor (IFNAR-1 and IFNAR-2) chains of the IFN-alpha/beta receptor and exhibited high endogenous levels of both Stat1 and phosphorylated Stat1 proteins. Lymphocytes from young MRL/lpr mice, with low Fas-dependent cytotoxic activity, were found to become highly cytotoxic against Fas+ targets after treatment with IFN-alpha. These data suggest that IFN-alpha plays an important role in the physiopathology of the systemic lupus erythematosus (SLE)-like syndrome that occurs in MRL/lpr mice. B lymphocytes mediate Fas-dependent cytotoxicity in MRL/lpr mice. A novel subset of memory B cells is enriched in autoreactivity and correlates with adverse outcomes in SLE. of circulating memory B cells with >2-fold higher levels of CD19. We show here that the presence of CD19(hi) B cells correlates with long-term adverse outcomes. These B cells do not appear anergic, as they exhibit high basal levels of phosphorylated Syk and ERK1/2, signal transduce in response to BCR crosslinking, and can become plasma cells (PCs) in vitro. Autoreactive anti-Smith (Sm) B cells are enriched B cell functions are under the regulation of B cell antigen receptor (BCR)-induced signals and by specialized cell surface coreceptors, or "response regulators", which inform B cells of their microenvironment. These response regulators include CD19 and CD22. Importantly, this "CD19/CD22 loop" is significantly related to an autoimmune phenotype in mice. Thus, the CD19/CD22 loop may be a potential therapeutic target B cell phenotypes in SLE Regulatory B cells that produce IL-10 are now recognized as an important component of the immune system . B10 progenitor (B10pro) cells have also been identified within the spleen CD1d(hi)CD5(+)CD19(hi) B-cell subset that B cells exert their regulatory role through the production of interleukin-10 (IL-10) by either B-1, marginal zone (MZ), or transitional 2-MZ precursor B-cell subsets. We have recently found that IL-10-producing regulatory B cells predominantly localize within a rare CD1d(hi)CD5(+) B-cell subset that shares cell surface markers with both B-1 and MZ B cells. We have labeled this specific subset of regulatory B cells as B10 cells deficient for CD19 (CD19(-/-) NZB/W mice), an important protective role for regulatory B10 cells in this systemic autoimmune disease B cell depletion initiated in 4-wk-old mice hastened disease onset, which paralleled depletion of the IL-10-producing regulatory B cell subset called B10 cells SLE as the result of defects both in apoptosis control and B cell regulation
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