IntroductionT helper (Th) cells may differentiate into distinct functional subsets according to the circumstances in which naive precursors encounter the nominal antigen for which they are specific. In the presence of interleukin-12 (IL-12), Th precursor cells become Th1 and high producers of interferon-␥ (IFN-␥), whereas in the presence of IL-4 they become Th2 and high producers of IL-4 and IL-5. These subsets have fundamentally different effector functions, in particular for their capacity to induce monocytes activation. 1 Recently, a distinct Th subset has been characterized in mice 2-6 and humans [7][8][9][10][11] for its high production of IL-17, the use of retinoid-related orphan receptor ␥t (ROR␥t) as master transcription factor, 12 its role in protection against extracellular bacteria and fungi, and in the pathogenesis of several autoimmune conditions, such as collageninduced arthritis, experimental autoimmune encephalomyelitis, and an animal model of inflammatory bowel disease. 4,13,14 Of interest, the generation of Th17 from naive precursors may follow different requirements in mice and humans. In mice, commitment to the Th17 lineage is dependent on transforming growth factor- (TGF-), IL-1, and IL-6, whereas in humans IL-1 and IL-6 but not TGF- appear to be required. 10,[15][16][17][18] The role of IL-23 in Th17 differentiation and effector function is still debated. IL-23 is a member of the IL-6 family of cytokines that shares with IL-12 the p40 subunit and has a unique p19 subunit. 19 IL-23 promotes Th17 responses in vivo but may be more important for the survival and population expansion of Th17 cells than for Th17 lineage commitment. 3,5,16 However, in conjunction with IL-1, IL-23 is sufficient for inducing naive human T cells to produce IL-17A, IL-17F, IL-22, IL-26, IFN-␥, C-C chemokine ligand 20 (CCL20)/ macrophage inflammatory protein 3␣ (MIP-3␣), and the transcription factor ROR␥t. 10 Moreover, mice lacking IL-23 are fully resistant to experimental autoimmune encephalomyelitis, collageninduced arthritis, and inflammatory bowel disease.The pattern of chemokine receptors expressed varies according to the differentiation stage and effector function of T cells. 20 The preferential expression of C-C chemokine receptor 6 (CCR6) distinguishes human Th17 from other Th subsets. 7,8,21,22 It should be stressed, however, that expression of CXC chemokine receptor 3 (CXCR3) within CCR6 ϩ T cells identifies T cells with preferential IFN-␥ production in response to purified protein derivative, whereas IL-17 production in response to Candida albicans hyphae is restricted to CCR6 ϩ CCR4 ϩ cells. 7 IL-17, when overexpressed in murine knee joint, causes inflammation and bone erosion. 23 Likewise, erosion observed in streptococcal cell wall-induced arthritis is highly reduced in IL-17R Ϫ/Ϫ and is associated with impaired expression of matrix metalloproteinases (MMPs). 24 T-cell clones producing IL-17 were generated from the synovium and synovial fluid of rheumatoid arthritis patients, 25 and IL-17 was shown t...
Systemic sclerosis (SSc) is a chronic autoimmune disease characterized by fibrosis and vasculopathy. CXCL4 represents an early serum biomarker of severe SSc and likely contributes to inflammation via chemokine signaling pathways, but the exact role of CXCL4 in SSc pathogenesis is unclear. Here, we elucidate an unanticipated mechanism for CXCL4-mediated immune amplification in SSc, in which CXCL4 organizes “self” and microbial DNA into liquid crystalline immune complexes that amplify TLR9-mediated plasmacytoid dendritic cell (pDC)-hyperactivation and interferon-α production. Surprisingly, this activity does not require CXCR3, the CXCL4 receptor. Importantly, we find that CXCL4-DNA complexes are present in vivo and correlate with type I interferon (IFN-I) in SSc blood, and that CXCL4-positive skin pDCs coexpress IFN-I-related genes. Thus, we establish a direct link between CXCL4 overexpression and the IFN-I-gene signature in SSc and outline a paradigm in which chemokines can drastically modulate innate immune receptors without being direct agonists.
doi: medRxiv preprint NOTE: This preprint reports new research that has not been certified by peer review and should not be used to guide clinical practice.
ApoA-1 (apolipoprotein A-1) is the main component of HDL (high-density lipoprotein) and stabilizes PON-1 (paraoxonase-1), which prevents lipid peroxidation and oxLDL (oxidized low-density lipoprotein) formation. Autoantibodies against apoA-1 [anti-(apoA-1) IgG] have been found in antiphospholipid syndrome and systemic lupus erythematosous, two diseases with an increased risk of thrombotic events, as well as in ACS (acute coronary syndrome). OxLDL levels are also elevated in these diseases. Whether anti-(apoA-1) IgGs exist in other prothrombotic conditions, such as APE (acute pulmonary embolism) and stroke, has not been studied and their potential association with oxLDL and PON-1 activity is not known. In the present study, we determined prospectively the prevalence of anti-(apoA-1) IgG in patients with ACS (n=127), APE (n=58) and stroke (n=34), and, when present, we tested their association with oxLDL levels. The prevalance of anti-(apoA-1) IgG was 11% in the ACS group, 2% in the control group and 0% in the APE and stroke groups. The ACS group had significantly higher median anti-(apoA-1) IgG titres than the other groups of patients. Patients with ACS positive for anti-(apoA-1) IgG had significantly higher median oxLDL values than those who tested negative (226.5 compared with 47.7 units/l; P<0.00001) and controls. The Spearman ranked test revealed a significant correlation between anti-(apoA-1) IgG titres and serum oxLDL levels (r=0.28, P<0.05). No association was found between PON-1 activity and oxLDL or anti-(apoA-1) IgG levels. In conclusion, anti-(apoA-1) IgG levels are positive in ACS, but not in stroke or APE. In ACS, their presence is associated with higher levels of oxLDL and is directly proportional to the serum concentration of oxLDL. These results emphasize the role of humoral autoimmunity as a mediator of inflammation and coronary atherogenesis.
Functional cytokine networks have been poorly characterized in systemic sclerosis (SSc). While interleukin-17A (IL-17A) is increased in SSc skin and other organs, its role is still debated, particularly considering fibrogenesis. We uncover here a dual function of IL-17A in the presence of transforming growth factor-β 1 (TGF-β), the master pro-fibrotic cytokine. In the one hand, we report an unexpected synergic activity resulting in enhanced production of IL-6 by dermal fibroblasts; in the other hand, a substantial inhibition of type I collagen (col-I) production. IL-17A or TGF-β enhanced the production of IL-6 by 8- to 16-folds when compared to control in healthy donors (HD) and SSc cultures. However, the joint presence of IL-17A and TGF-β resulted in robustly exuberant responses with levels of IL-6 up to 100-folds higher than those observed in untreated cells. Inhibition of NFκB signaling pathway preferentially inhibited the production of IL-6 driven by IL-17A in HD fibroblasts, while inhibition of PI3K preferentially inhibited the production of IL-6 driven by TGF-β. Interestingly, when p38 MAPK was inhibited, substantial reduction of IL-6 production was observed for both IL-17A and TGF-β. Consistently with the inhibition experiments, the combined stimulation of fibroblasts by IL-17A and TGF-β resulted in 1.8-fold increase in p38 MAPK phosphorylation (P = 0.025), when compared to levels of phosphorylated p38 MAPK induced by IL-17A alone. Furthermore, the enhanced phosphorylation of p38 MAPK in the joint presence of IL-17A and TGF-β was unique among the signaling molecules we examined. As expected, TGF-β induced SMAD2 phosphorylation and col-I production. However, in fibroblasts cultured in the joint presence of TGF-β and IL-17A, SMAD2 phosphorylation was decreased by 0.6-folds (P = 0.022) when compared to that induced by TGF-β alone. Remarkably, in this condition, the production of col-I and fibronectin was significantly decreased in both HD and SSc. Thus, IL-17A and TGF-β reciprocally influence each other effector functions in fibroblasts. Intracellular molecular switches may favor synergic or antagonistic activities, which are revealed by specific readouts. The implications of these data in the context of SSc are far reaching, particularly in terms of therapeutic approaches since IL-6, IL-17A, and TGF-β are all putative targets of treatment.
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