TLR8 deletion accelerates autoimmunity in a mouse model of lupus through a TLR7-dependent mechanism (original) (raw)
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Immunity, 2006
Antibodies (Abs) to RNA-and DNA-containing autoantigens are characteristic of systemic lupus erythematosus (SLE). We showed previously that Toll-like receptor (TLR) 9, recognizing DNA, is required for the spontaneous generation of DNA autoantibodies, but not for the development of lupus nephritis in susceptible mice. We report that lupus-prone mice deficient in TLR7, a receptor for ssRNA, failed to generate Abs to RNA-containing antigens (Ags) such as Smith (Sm) Ag. TLR9 and TLR7 also had dramatic effects on clinical disease in lupus-prone mice. In the absence of TLR9, autoimmune disease was exacerbated, lymphocytes and plasmacytoid DCs were more activated, and serum IgG and IFN-a were increased. In contrast, TLR7-deficient mice had ameliorated disease, decreased lymphocyte activation, and decreased serum IgG. These findings reveal opposing inflammatory and regulatory roles for TLR7 and TLR9, despite similar tissue expression and signaling pathways. These results have important implications for TLR-directed therapy of autoimmune disease.
Proceedings of the National Academy of Sciences, 2014
Systemic lupus erythematosus (SLE) is a complex autoimmune disease with diverse clinical presentations characterized by the presence of autoantibodies to nuclear components. Toll-like receptor (TLR)7, TLR8, and TLR9 sense microbial or endogenous nucleic acids and are implicated in the development of SLE. In mice TLR7deficiency ameliorates SLE, but TLR8-or TLR9-deficiency exacerbates the disease because of increased TLR7 response. Thus, both TLR8 and TLR9 control TLR7 function, but whether TLR8 and TLR9 act in parallel or in series in the same or different cell types in controlling TLR7-mediated lupus remains unknown. Here, we reveal that double TLR8/9-deficient (TLR8/9 −/−) mice on the C57BL/6 background showed increased abnormalities characteristic of SLE, including splenomegaly, autoantibody production, frequencies of marginal zone and B1 B cells, and renal pathology compared with single TLR8 −/− or TLR9 −/− mice. On the cellular level, TLR8 −/− and TLR8/ 9 −/− dendritic cells were hyperesponsive to TLR7 ligand R848, but TLR9 −/− cells responded normally. Moreover, B cells from TLR9 −/− and TLR8/9 −/− mice were hyperesponsive to R848, but TLR8 −/− B cells were not. These results reveal that TLR8 and TLR9 have an additive effect on controlling TLR7 function and TLR7-mediated lupus; however, they act on different cell types. TLR8 controls TLR7 function on dendritic cells, and TLR9 restrains TLR7 response on B cells. knockout mice | innate immunity | endosomal TLRs S ystemic lupus erythematosus (SLE) is a complex chronic autoimmune disease that arises spontaneously and is characterized by production of autoantibodies against self-nucleic acids and associated proteins (1). These autoantibodies bind selfnucleic acids released by dying cells and form immune complexes that accumulate in different parts of the body, leading to inflammation and tissue damage. The kidneys, skin, joints, lungs, serous membranes, as well as, the cardiovascular, nervous and musculoskeletal system become targets of inflammation at onset or during the course of the disease (2). The etiology of SLE is unknown, yet genetics, sex, infectious agents, environmental factors, and certain medications may play a role in the initiation of the disease by causing alterations in lymphoid signaling, antigen presentation, apoptosis, and clearance of immune complexes (3, 4). Toll-like receptors (TLRs) detect specific microbial components widely expressed by bacteria, fungi, protozoa, and viruses, and initiate signaling pathways critical for induction of immune responses to infection (5). In contrast to the cell surface TLRs that detect bacterial cell wall components and viral particles, nucleic acid-sensing TLRs are localized mainly within endosomal compartments (6). Human endosomal TLRs consist of TLR3, which senses viral double-stranded RNA (dsRNA) (7), TLR7 and TLR8, which recognize viral single-stranded RNA (8-10), and TLR9, which detects bacterial and viral unmethylated CpGcontaining DNA motifs (11). Interestingly, these endosomal TLRs are also able to detect self-nucleic acids (12-14). Although the
A Tlr7 translocation accelerates systemic autoimmunity in murine lupus
Proceedings of the National Academy of Sciences, 2006
The y-linked autoimmune accelerating ( yaa ) locus is a potent autoimmune disease allele. Transcription profiling of yaa -bearing B cells revealed the overexpression of a cluster of X-linked genes that included Tlr7 . FISH analysis demonstrated the translocation of this segment onto the yaa chromosome. The resulting overexpression of Tlr7 increased in vitro responses to Toll-like receptor (TLR) 7 signaling in all yaa -bearing males. B6. yaa mice are not overtly autoimmune, but the addition of Sle1 , which contains the autoimmune-predisposing Slam/Cd2 haplotype, causes the development of fatal lupus with numerous immunological aberrations. B6. Sle1yaa CD4 T cells develop the molecular signature for T FH cells and also show expression changes in numerous cytokines and chemokines. Disease development and all component autoimmune phenotypes were inhibited by Sles1 , a potent suppressor locus. Sles1 had no effect on yaa -enhanced TLR7 signaling in vitro , and these data place Sles1 downs...
TLR8 deficiency leads to autoimmunity in mice
Journal of Clinical Investigation, 2010
TLRs play an essential role in the induction of immune responses by detecting conserved molecular products of microorganisms. However, the function of TLR8 is largely unknown. In the current study, we investigated the role of TLR8 signaling in immunity in mice. We found that Tlr8 -/-DCs overexpressed TLR7, were hyperresponsive to various TLR7 ligands, and showed stronger and faster NF-κB activation upon stimulation with the TLR7 ligand R848. Tlr8 -/mice showed splenomegaly, defective development of marginal zone (MZ) and B1 B cells, and increased serum levels of IgM and IgG2a. Furthermore, Tlr8 -/mice exhibited increased serum levels of autoantibodies against small nuclear ribonucleoproteins, ribonucleoprotein, and dsDNA and developed glomerulonephritis, whereas neither Tlr7 -/nor Tlr8 -/-Tlr7 -/mice showed any of the phenotypes observed in Tlr8 -/mice. These data provide evidence for a pivotal role for mouse TLR8 in the regulation of mouse TLR7 expression and prevention of spontaneous autoimmunity.
Proceedings of the National Academy of Sciences, 2009
Using the Unc93b1 3d mutation that selectively abolishes nucleic acid-binding Toll-like receptor (TLR) (TLR3, -7, -9) signaling, we show these endosomal TLRs are required for optimal production of IgG autoAbs, IgM rheumatoid factor, and other clinical parameters of disease in 2 lupus strains, B6-Fas lpr and BXSB. Strikingly, treatment with lipid A, an autoAb-inducing TLR4 agonist, could not overcome this requirement. The 3d mutation slightly reduced complete Freund's adjuvant (CFA)-mediated antigen presentation, but did not affect T-independent type 1 or alum-mediated T-dependent humoral responses or TLR-independent IFN production induced by cytoplasmic nucleic acids. These findings suggest that nucleic acid-sensing TLRs might act as an Achilles' heel in susceptible individuals by providing a critical pathway by which relative tolerance for nucleic acid-containing antigens is breached and systemic autoimmunity ensues. Importantly, this helps provide an explanation for the high frequency of anti-nucleic acid Abs in lupus-like systemic autoimmunity.
TLR7 drives accumulation of ABCs and autoantibody production in autoimmune-prone mice
Immunologic Research, 2013
Although autoantibodies are the hallmarks of most autoimmune diseases, the mechanisms by which autoreactive B cells are generated and accumulate are still poorly understood. Overexpression of Toll-like receptor 7 (TLR7) that recognizes single-stranded RNAs has been implicated in systemic lupus erythematosus (SLE), although the cellular mechanism by which this receptor drives the disease is unknown. We recently identified a population of CD11c ? ageassociated B cells (ABCs) which is driven by TLR7 signaling, secretes autoantibodies and appears in autoimmune-prone mice by the time of onset of autoimmunity. Mice lacking the Mer receptor develop autoantibodies and splenomegaly similar to other mouse models of SLE. Here, we show that Mer -/mice that lack TLR7 fail to develop anti-chromatin IgG antibodies, perhaps because they also fail to develop ABCs. Moreover, depletion of CD11c ? ABCs from Mer -/mice leads to rapid reduction in autoantibodies. Together, these data strongly suggest that ABCs and/or their descendants are the primary source of autoantibodies in Mer -/mice and that TLR7 signaling is crucial for accumulation of ABCs and development of autoantibodies. These data demonstrate for the first time that TLR7, and not TLR9, is responsible for generation of anti-chromatin IgG antibodies in Mer -/mice.
Arthritis & rheumatology (Hoboken, N.J.), 2018
Toll-like receptors (TLRs) 7 and 9 are important innate signaling molecules with opposing roles in the development and progression of Systemic Lupus Erythematosus (SLE). While multiple studies support a dependency on TLR7 for disease development, genetic ablation of TLR9 results in severe disease with glomerulonephritis (GN) by a largely unknown mechanism. The present study was designed to examine the suppressive role of TLR9 in the development of severe lupus. We crossed Sle1 lupus-prone mice with TLR9-deficient mice to generate Sle1TLR9 . These mice were aged and evaluated for severe autoimmunity by assessing splenomegaly, GN, immune cell populations, autoantibody and total immunoglobulin profiles, kidney dendritic cell (DC) function and TLR7 protein expression. Young mice were used for functional B cell studies, immunoglobulin profiling and TLR7 expression. Sle1TLR9 mice developed severe disease similar to TLR9-deficient MRL and Nba2 models. Sle1TLR9 B cells produced more class-s...
The Journal of Immunology, 2006
Systemic lupus erythematosus is characterized by the production of autoantibodies directed against nuclear Ags, including nucleosome and DNA. TLR9 is thought to play a role in the production of these autoantibodies through the capacity of nuclear immunogenic particles to interact both with BCR and TLR9. To determine the role of TLR9 in SLE, C57BL/6-lpr/lpr-TLR9 ؊/؊ and TLR9 ؉/؉ mice were analyzed. The abrogation of TLR9 totally impaired the production of anti-nucleosome Abs, whereas no difference was observed in the frequency of anti-dsDNA autoantibodies whose titer was strikingly higher in TLR9 ؊/؊ mice. In addition a higher rate of mesangial proliferation was observed in the kidney of TLR9-deficient animals. These results indicate that in C57BL/6-lpr/lpr mice, TLR9 is absolutely required for the anti-nucleosome Ab response but not for anti-dsDNA Ab production which is involved in mesangial proliferation.