Acid Receptor-related Orphan Receptor Γt Research Articles

Cutting Edge: Crucial Role of IL-1 and IL-23 in the Innate IL-17 Response of Peripheral Lymph Node NK1.1− Invariant NKT Cells to Bacteria

We have shown previously that peripheral lymph node-resident retinoic acid receptor-related orphan receptor γt(+) NK1.1(-) invariant NKT (iNKT) cells produce IL-17A independently of IL-6. In this study, we show that the concomitant presence of IL-1 and IL-23 is crucial to induce a rapid and sustained IL-17A/F and IL-22 response by these cells that requires TCR-CD1d interaction and partly relies on IL-23-mediated upregulation of IL-23R and IL-1R1 expression. We further show that IL-1 and IL-23 produced by pathogen-associated molecular pattern-stimulated dendritic cells induce this response from NK1.1(-) iNKT cells in vitro, involving mainly TLR2/4-signaling pathways. Finally, we found that IL-17A production by these cells occurs very early and transiently in vivo in response to heat-killed bacteria. Overall, our study indicates that peripheral lymph node NK1.1(-) iNKT cells could be a source of innate Th17-related cytokines during bacterial infections and supports the hypothesis that they are able to provide an efficient first line of defense against bacterial invasion.

Critical role of Th17 cells in inflammation and neovascularization after ischaemia

Increasing evidence suggests that CD4(+) T cells contribute to neovascularization in ischaemic tissue. However, the T cell subset responsible for neovascularization after ischaemia remains to be determined. Here, we investigated the role of Th17 cells secreting interleukin (IL)-17, a newly identified subset of CD4(+) T cells, in the neovascularization after murine hindlimb ischaemia. Unilateral hindlimb ischaemia was produced in wild-type (WT) C57BL/6 mice. Depletion of CD4(+) T cells resulted in significantly reduced blood flow perfusion in the ischaemic limbs. The expression of IL-17 and retinoic acid receptor-related orphan receptor γt (RORγt) was up-regulated in the ischaemic limbs. IL-17-deficient mice showed a significant reduction in blood flow perfusion, inflammatory cell infiltration, and production of angiogenic cytokines in the ischaemic limbs compared with WT mice. In bone marrow transplantation experiments, the absence of IL-17 specifically in bone marrow cells diminished the neovascularization after ischaemia. Furthermore, IL-17-deficient CD4(+) T cells transferred into the ischaemic limbs of T cell-deficient athymic nude mice evoked a significantly limited neovascularization compared with WT CD4(+) T cells. These findings identify Th17 cells as a new angiogenic T cell subset and provide new insight into the mechanism by which T cells promote neovascularization after ischaemia.

Distribution of Th17 cells and Th1 cells in peripheral blood and cerebrospinal fluid in chronic inflammatory demyelinating polyradiculoneuropathy

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is an immune-mediated demyelinating disease of the peripheral nervous system. Th17 and Th1 cells contribute to the pathogenesis of most autoimmune diseases, but little is known about their distribution and reciprocal relationship in CIDP. In this study, we analyzed the distribution of Th17, Th1, and Th17/Th1 cells in the peripheral blood and cerebrospinal fluid (CSF). The results showed that the frequency of Th17 cells was significantly higher in the peripheral blood mononuclear cell (PBMCs) and CSF of active CIDP in comparison with remitting CIDP or to other non-inflammatory neurological diseases (ONDs), accompanied by similar findings for Th17/Th1 cells. Both active and remitting CIDP have higher percentage of Th1 cells in the CSF than OND. CSF protein levels positively correlated with the frequencies of Th17 cells either in the PBMCs or CSF of active CIDP, while there was no significant correlation with Th1 cells. In line with these observations, the levels of interleukin-17 (IL-17) in plasma and transcript factors retinoic acid receptor-related orphan receptor (ROR)γt expressed by PBMCs were significantly higher in the active CIDP than remitting CIDP or OND. In summary, our preliminary findings suggest that elevated numbers of inflammatory T cells, especially for Th17 cells, might be an important determinant in the evolution of CIDP.

Smad2 Positively Regulates the Generation of Th17 Cells*[S

Development of Foxp3(+) regulatory T cells and pro-inflammatory Th17 cells from naive CD4(+) T cells requires transforming growth factor-β (TGF-β) signaling. Although Smad4 and Smad3 have been previously shown to regulate Treg cell induction by TGF-β, they are not required in the development of Th17 cells. Thus, how TGF-β regulates Th17 cell differentiation remains unclear. In this study, we found that TGF-β-induced Foxp3 expression was significantly reduced in the absence of Smad2. More importantly, Smad2 deficiency led to reduced Th17 differentiation in vitro and in vivo. In the experimental autoimmune encephalomyelitis model, Smad2 deficiency in T cells significantly ameliorated disease severity and reduced generation of Th17 cells. Furthermore, we found that Smad2 associated with retinoid acid receptor-related orphan receptor-γt (RORγt) and enhanced RORγt-induced Th17 cell generation. These results demonstrate that Smad2 positively regulates the generation of inflammatory Th17 cells.

Altered response of CD4+ T cells to TGF-β and IL-6 in the absence of the vitamin D receptor (88.9)

Abstract Th17 cells play critical roles in autoimmunity. The active form of vitamin D, 1,25(OH)2D3, has been shown to directly regulate T cell function, but the role of vitamin D and vitamin D receptor (VDR) in the differentiation of Th17 cells is not very clear. Induction of Th17 cells using TGF-β and IL-6 resulted in twice as many Th17 cells in VDR KO cultures as WT. The increased frequency of Th17 cells in VDRKO cultures was not a result of higher expression of retinoic acid receptor-related orphan receptor-γT (ROR-γT). 1,25(OH)2D3 deficient CD4+ T cells also overproduced IL-17. Treatment of WT CD4+ T cells with 1,25(OH)2D3 significantly inhibited the generation of Th17 cells. The number of Treg cells in Th0 cultures of CD4+ cells from VDR KO mice was higher, compared to WT. TGF-β addition to the cultures induced Tregs in both the VDR KO and WT cultures, but there were significantly more Tregs in WT than VDR KO cultures. Addition of both TGF-β and IL-6 to WT CD4 cultures caused a 4-fold reduction in Treg cells. The reduction of Tregs by TGF-β and IL-6 in VDR KO cultures was only 2-fold. VDR KO T cells cultured with TGF-β and IL-6 produced significantly more IL-10 than their WT counterparts. Our data suggest the 1,25(OH)2D3 and signaling through the VDR are important regulators of Th17 differentiation. Furthermore, VDR KO T cells have altered responses to TGF-β and IL-6 that resulted in increased numbers of both Th17 and Treg cells.

Smad3 Differentially Regulates the Induction of Regulatory and Inflammatory T Cell Differentiation

Transforming growth factor beta (TGF-beta) is a crucial cytokine with pleiotropic functions on immune cells. In CD4(+) T cells, TGF-beta is required for induction of both regulatory T and Th17 cells. However, the molecular mechanism underlying this differential T cell fate decision remains unclear. In this study, we have evaluated the role of Smad3 in the development of Th17 and regulatory T cells. Smad3 was found to be dispensable for natural regulatory T cell function. However, induction of Foxp3 expression by TGF-beta in naive T cells was significantly reduced in the absence of this molecule. On the contrary, Smad3 deficiency led to enhanced Th17 differentiation in vitro and in vivo. Moreover, Smad3 was found to interact with retinoid acid receptor-related orphan receptor gammat (RORgammat) and decrease its transcriptional activity. These results demonstrate that Smad3 is differentially involved in the reciprocal regulatory and inflammatory T cell generation.

Skin and Peripheral Lymph Node Invariant NKT Cells Are Mainly Retinoic Acid Receptor-Related Orphan Receptor γt+ and Respond Preferentially under Inflammatory Conditions

Lymph nodes (LNs) have been long considered as comprising few invariant NKT (iNKT) cells, and these cells have not been studied extensively. In this study, we unravel the existence of stable rather than transitional LN-resident NK1.1(-) iNKT cell populations. We found the one resident in peripheral LNs (PLNs) to comprise a major IL-17-producing population and to express the retinoic acid receptor-related orphan receptor (gamma)t (ROR(gamma)t). These cells respond to their ligand alpha-galactosylceramide (alpha-GalCer) in vivo by expanding dramatically in the presence of LPS, providing insight into how this rare population could have an impact in immune responses to infection. PLN-resident ROR(gamma)t(+) NK1.1(-) iNKT cells express concomitantly CCR6, the integrin alpha-chain alpha(E) (CD103), and IL-1R type I (CD121a), indicating that they might play a role in inflamed epithelia. Accordingly, skin epithelia comprise a major ROR(gamma)t(+) CCR6(+)CD103(+)CD121a(+) NK1.1(-) cell population, reflecting iNKT cell composition in PLNs. Importantly, both skin and draining PLN ROR(gamma)t(+) iNKT cells respond preferentially to inflammatory signals and independently of IL-6, indicating that they could play a nonredundant role during inflammation. Overall, our study indicates that ROR(gamma)t(+) iNKT cells could play a major role in the skin during immune responses to infection and autoimmunity.