Other pattern-recognition receptor signaling pathways, for example RIG-I and NOD1, can also activate IRF3 and IRF5 thus ensuring robust type I IFN production in response to both viral and bacterial infections [112]. IRF7 levels are increased after type I IFN signaling, thus further amplifying type I IFN responses [113, 114]. Interestingly, IRF5 is also https://www.selleckchem.com/products/VX-770.html involved in the expression of genes important for Th17 responses, such as IL-6 and p40

(a subunit of IL-23 and IL-12), suggesting that IRF5 plays an important role both in type I IFN- and Th17-dependent diseases [111]. Notably, polymorphisms in the IRF5 gene have been repeatedly shown to associate with both SLE and SS [115-117], and an enhanced transcription of an alternatively spliced variant of IRF5 as well as increased IRF5 protein expression was demonstrated for an SLE-associated IRF5 gene haplotype [115, 116, 118, 119].

Furthermore, increased levels of IL-6, p40, and IFN-β, the genes of which are transcriptionally regulated by IRF5, are found in patients with SLE and SS (reviewed in [67, 120]), indicating that dysregulation through TLR/IRF pathways are central in systemic autoimmunity and may affect both type I interferon and Th17 responses. Additional imbalances in the TLR/IRF pathways in systemic autoimmunity arise from the circulating DNA- or RNA-containing immune complexes that activate TLR7 and TLR9 signaling after endocytosis Tipifarnib clinical trial via Fc receptors, inducing the simultaneous production of type I IFNs and cytokines important for the generation of Th17 cells (such as IL-23 and IL-6) [121]. These effects are potentially additive with those driven by the genetic polymorphisms of the factors downstream of the TLRs. Supporting evidence for a role of IRFs in systemic autoimmune disease have further been derived from mouse models; Irf5−/− mice develop less-severe disease [122] and mice lacking the IRF-specific E3 ligase TRIM21 (Trim21−/−)

develop lupus-like features such as circulating antinuclear antibodies and glomerulonephritis through an IL-23/Th17-dependent pathway [48]. Both type I IFN and IL-17 have pleiotropic effects on immune Parvulin responses, such as activation and recruitment of myeloid cells or promotion of adaptive immunity and B-cell responses, and both can prove beneficial or detrimental to the host depending on the context. Type I IFNs and IL-17 are thus crucial to the host’s innate defense mechanisms against viruses and against extracellular bacteria and fungi. However, type I IFNs and IL-17 are also implicated in the pathogenesis of several inflammatory and autoimmune diseases. Although type I IFNs have been shown to antagonize Th17 responses, it is also evident from the observations made in diseases such as psoriasis or SLE that type I IFN and Th17 responses can coexist to drive inflammation and disease [123, 124].