S2, available athttp://www.jem.org/cgi/content/full/jem.20080462/DC1), suggesting that accelerated uptake of ligands is also unlikely to explain our findings. Reeves. 2007.Arthritis Rheum.56:37703783). We display that TMPD elicits IFN-I production, monocyte recruitment, and autoantibody production specifically through a Toll-like receptor (TLR) 7 and myeloid differentiation element 88 (MyD88)dependent pathway. In vitro studies exposed that TMPD augments the effect of TLR7 ligands but does not directly activate TLR7 itself. The effects of TMPD were amplified from the Y-linked autoimmune acceleration cluster, which carries a duplication of theTLR7gene. In contrast, deficiency of Fc receptors (FcRs) did not affect the production of IFN-I. Collectively, the data demonstrate that TMPD-stimulated IFN-I production requires TLR7/MyD88 signaling and is self-employed of autoantibody-mediated uptake of ribonucleoproteins by FcRs. Systemic lupus erythematosus (SLE) is definitely a chronic autoimmune disease characterized by the production of antibodies against an array of self-antigens such as double-stranded (ds) DNA and Sulfabromomethazine components of small nuclear ribonucleoproteins (snRNPs), including the Sm/RNP antigens (U1, U2, U4-6, and U5 snRNPs), Ro/SS-A antigens (Y RNAs), and additional antigens (1). Recent evidence strongly suggests that type I IFNs (IFN-Is), a family of antiviral cytokines, are integral to the pathogenesis of SLE. Elevated serum levels of IFN-I and overexpression of IFN-stimulated genes DDR1 Sulfabromomethazine (ISGs) in the peripheral blood of SLE individuals have been shown by several organizations (24). This IFN signature is associated with more active disease and the presence of autoantibodies against dsDNA and the Sm/RNP and Ro/SS-A antigens (5,6). The etiology of excessive IFN-I in SLE is definitely incompletely recognized. Study on innate immunity offers led to the recognition of several pathways mediating IFN-I production in mammalian cells. Toll-like receptor (TLR) 3, a sensor for viral dsRNA, and TLR4, the receptor for LPS, both stimulate IFN-I secretion through Toll/IL-1 receptor domaincontaining adaptor inducing IFN- (TRIF) (7). In contrast, TLR7/8 and TLR9 mediate IFN-I production via myeloid differentiation element 88 (MyD88) in response to single-stranded (ss) RNA and unmethylated CpG DNA, respectively (810). In addition, cytoplasmic receptors that identify intracellular nucleic acids and induce IFN-I have been described recently. Retinoic acidinducible gene I (RIG-I) and melanoma differentiation-associated gene 5 (MDA5) identify cytoplasmic RNA and result in IFN-I by activating IFN- promoter stimulator 1 (IPS-1; also known as MAVS, VISA, and CARDIF) and IFN regulatory element (IRF) 3 (1114). Cytoplasmic DNA binds to a newly explained cytoplasmic sensor and causes IFN-I production via a pathway requiring TANK-binding kinase 1 (TBK-1) and IRF3 (15,16). It has been hypothesized that nucleic acids from dying cells may act as ligands for TLR7/8 and TLR9 to result in IFN-I production in SLE. Immune complexes (ICs) created by autoantibodies to DNA and snRNPs help to transport these endogenous ligands to endosomes where TLR7, 8, and 9 are normally found (17). Activation of these TLRs then induces the production of IFN-I by plasmacytoid DCs (PDCs). This hypothesis is definitely supported by several in vitro studies (18,19). However, restorative administration of recombinant IFN- can directly trigger the production of anti-dsDNA antibodies (20), and in several mouse model of lupus, IFN-I production is required for the induction of Sulfabromomethazine autoantibodies (2123), suggesting that IFN-I dysregulation may occur upstream of autoantibody development. Therefore, it remains controversial whether nucleic acidcontaining ICs in SLE initiate IFN-I production or take action to perpetuate a positive opinions loop of IFN production initiated by another element, such as Sulfabromomethazine a viral illness. Experimental lupus induced from the hydrocarbon oil 2,6,10,14-tetramethylpentadecane (TMPD; also known as pristane) displays many key immunological and medical features of Sulfabromomethazine human being SLE, including the presence of the IFN signature and lupus autoantibodies such as anti-dsDNA, -Sm, and -RNP (2426). Importantly, IFN-I play an essential role with this model, as the development of glomerulonephritis and production of autoantibodies (anti-Sm/RNP, -dsDNA, and -Su) are abolished in IFN-I receptordeficient (IFNAR/) mice (22). Unexpectedly, a human population of Ly6Chiimmature monocytes that accumulates in the peritoneal cavity after TMPD treatment, rather than DCs, is the major source of the excess IFN-I seen in this model (27). The prolonged influx of.