A role for IL-25 and IL-33–driven type-2 innate lymphoid cells in atopic dermatitis

Type 2 innate lymphoid cells (ILC2s, nuocytes, NHC) require RORA and GATA3 for their development. We show that human ILC2s express skin homing receptors and infiltrate the skin after allergen challenge, where they produce the type 2 cytokines IL-5 and IL-13. Skin-derived ILC2s express the IL-33 receptor ST2, which is up-regulated during activation, and are enriched in lesional skin biopsies from atopic patients. Signaling via IL-33 induces type 2 cytokine and amphiregulin expression, and increases ILC2 migration. Furthermore, we demonstrate that E-cadherin ligation on human ILC2 dramatically inhibits IL-5 and IL-13 production. Interestingly, down-regulation of E-cadherin is characteristic of filaggrin insufficiency, a cardinal feature of atopic dermatitis (AD). ILC2 may contribute to increases in type 2 cytokine production in the absence of the suppressive E-cadherin ligation through this novel mechanism of barrier sensing. Using Rag1^−/− and RORα-deficient mice, we confirm that ILC2s are present in mouse skin and promote AD-like inflammation. IL-25 and IL-33 are the predominant ILC2-inducing cytokines in this model. The presence of ILC2s in skin, and their production of type 2 cytokines in response to IL-33, identifies a role for ILC2s in the pathogenesis of cutaneous atopic disease.Atopic dermatitis (AD) is a common pruritic inflammatory skin disease that is associated with barrier dysfunction and Th2 cell adaptive immune responses to common environmental allergens. It is a disease with complex genetic and environmental susceptibility factors. Although it is likely that many genetic loci are involved, the association of filaggrin-null mutations with AD has provided a major step forward in our understanding of disease pathogenesis (Palmer et al., 2006). Filaggrin is expressed in keratinocytes and is thought to have a role in skin barrier function, cutaneous pH, and hydration (Presland et al., 2001; Sandilands et al., 2009). However, little is known as to how an inherited epidermal abnormality leads to a compromised skin barrier, skin inflammation, and related atopic disorders, although high levels of IL-13 and IL-4 are known to be expressed in lesions of AD (Leung et al., 2004; Kim et al., 2013).Although Th2 cells have been characterized as producers of the cardinal cytokines IL-4, IL-5, and IL-13 in AD (Leung et al., 2004), the recent discovery of innate lymphoid cells (ILCs) raises the question of their potential involvement as innate sources of type 2 cytokines in this disease. Several recent studies have identified a family of CD45-expressing hematopoietic effector ILCs that link the innate and adaptive arms of the immune system (Mjösberg et al., 2011; Spits and Cupedo, 2012; Walker et al., 2013). Such ILCs are found in the blood, spleen, intestine, liver, lung, FALCs (fat-associated lymphoid clusters), and LNs of mice (Moro et al., 2010; Neill et al., 2010; Price et al., 2010; Saenz et al., 2010; Mjösberg et al., 2011). An ILC subset that produces type 2 cytokines (IL-5, IL-9, and IL-13), and which is independent of RORγt, has been designated as the type 2 ILC or ILC2 (Spits et al., 2013; Walker et al., 2013). ILC2s are negative for lineage markers of T and B cells, but in mice they express c-Kit (CD117), ST2, CD90, and the hematopoietic and lymphoid markers CD45 and IL-7Rα (CD127). Consistent with their expression of IL-17RB (IL-17BR and IL-25R) and ST2 (IL-33R) receptors, these cells respond to IL-25 and IL-33 by producing type 2 cytokines, and in mice ILC2s have been shown to induce goblet cell hyperplasia and eosinophilia, and contribute to protection against helminth infections (Moro et al., 2010; Neill et al., 2010; Price et al., 2010; Spits and Cupedo, 2012).In mice, lung-resident ILC2s have also been demonstrated to contribute to airway hyper-reactivity, induced by viral or allergen challenge (Moro et al., 2010; Mjösberg et al., 2011; Monticelli et al., 2011; Barlow et al., 2012; Klein Wolterink et al., 2012). However, ILC2s also serve to restore epithelial integrity and lung function after infection with the H1N1 influenza virus, predominantly by producing amphiregulin, a regulator of wound healing (Monticelli et al., 2011). The human counterparts of ILC2 were recently reported in human lung parenchyma and bronchoalveolar lavage fluid, and defined as lineage-negative cells that express IL-7Rα and the ST2 subunit of the IL-33 receptor (Monticelli et al., 2011). More comprehensively, Spits et al. (2013) reported CD45^hi, CD127⁺, and CD117⁺ cells in peripheral blood, fetal gut, and the inflamed nasal polyps of patients with rhinosinusitis. The cells also expressed CRTH2 and CD161 and, in response to epithelial cytokines, produced large amounts of IL-13 and IL-5, but not IL-17A or IL-22 (Mjösberg et al., 2011).Recently, ILC2-like cells have been reported within mouse and human atopic lesional skin and, at least in mice, recruitment of ILC2-like cells to sites of inflammation was demonstrated to be dependent on TSLP and independent of IL-33 (Kim et al., 2013). However, transgenic mice with IL-33 expressed under the keratin 14 promoter developed a spontaneous AD-like inflammation of the skin which associated with ILC2 infiltration (Imai et al., 2013). A further murine study identified ILC2s in the skin which were present at a 30% frequency of T cells and were IL-7 and IL-2 dependent. Using intravital microscopy, it was shown that these ILC2s interacted with mast cells and produced IL-13 (Roediger et al., 2013). It is therefore unclear to what extent human and murine skin-derived ILC2s are dependent on IL-33. This is an important question for understanding disease and for directing future therapeutic activity. Herein, we define a lineage-negative, IL-7Rα⁺CRTH2⁺c-kit⁺ICOS⁺CD161⁺CD25⁺CCR4⁺CCR10⁺NKp46⁻CD56⁻, RORα⁺GATA3⁺ ILC2 in human skin that is elevated in biopsies from AD patients and shows elevated ST2, IL-17BR, TSLPR, and KLRG1 expression. These cells respond potently to IL-33 by releasing type 2 cytokines and amphiregulin. Furthermore, human ILC2 can be inhibited by their ligation of E-cadherin, suggesting a novel mechanism for barrier sensing. Investigation of ILC2s in a BALB/c mouse model of dermatitis demonstrated their contribution to skin inflammation, and further identified primary roles for IL-25 and IL-33 in their regulation, with a lesser role for TSLP in this model. Thus, the ILC2-initiating cytokines IL-25, IL-33, and TSLP all play a role in the regulation of skin inflammation and represent potential therapeutic pathways in AD.     

Impaired Plasma Membrane Targeting of Grb2–Murine Son of Sevenless (mSOS) Complex and Differential Activation of the Fyn–T Cell Receptor (TCR)-ζ–Cbl Pathway Mediate T Cell Hyporesponsiveness in Autoimmune Nonobese Diabetic Mice

Nonobese diabetic (NOD) mouse thymocytes are hyporesponsive to T cell antigen receptor (TCR)-mediated stimulation of proliferation, and this T cell hyporesponsiveness may be causal to the onset of autoimmune diabetes in NOD mice. We previously showed that TCR-induced NOD T cell hyporesponsiveness is associated with a block in Ras activation and defective signaling along the PKC/Ras/MAPK pathway. Here, we report that several sequential changes in TCR-proximal signaling events may mediate this block in Ras activation. We demonstrate that NOD T cell hyporesponsiveness is associated with the (a) enhanced TCR-β–associated Fyn kinase activity and the differential activation of the Fyn–TCR-ζ–Cbl pathway, which may account for the impaired recruitment of ZAP70 to membrane-bound TCR-ζ; (b) relative inability of the murine son of sevenless (mSOS) Ras GDP releasing factor activity to translocate from the cytoplasm to the plasma membrane; and (c) exclusion of mSOS and PLC-γ1 from the TCR-ζ–associated Grb2/pp36–38/ZAP70 signaling complex. Our data suggest that altered tyrosine phosphorylation and targeting of the Grb2/pp36–38/ZAP70 complex to the plasma membrane and cytoskeleton and the deficient association of mSOS with this Grb2-containing complex may block the downstream activation of Ras and Ras-mediated amplification of TCR/CD3-mediated signals in hyporesponsive NOD T cells. These findings implicate mSOS as an important mediator of downregulation of Ras signaling in hyporesponsive NOD T cells.     

Group 2 innate lymphoid cells support hematopoietic recovery under stress conditions

The cell-cycle status of hematopoietic stem and progenitor cells (HSPCs) becomes activated following chemotherapy-induced stress, promoting bone marrow (BM) regeneration; however, the underlying molecular mechanism remains elusive. Here we show that BM-resident group 2 innate lymphoid cells (ILC2s) support the recovery of HSPCs from 5-fluorouracil (5-FU)–induced stress by secreting granulocyte-macrophage colony-stimulating factor (GM-CSF). Mechanistically, IL-33 released from chemo-sensitive B cell progenitors activates MyD88-mediated secretion of GM-CSF in ILC2, suggesting the existence of a B cell–ILC2 axis for maintaining hematopoietic homeostasis. GM-CSF knockout mice treated with 5-FU showed severe loss of myeloid lineage cells, causing lethality, which was rescued by transferring BM ILC2s from wild-type mice. Further, the adoptive transfer of ILC2s to 5-FU–treated mice accelerates hematopoietic recovery, while the reduction of ILC2s results in the opposite effect. Thus, ILC2s may function by “sensing” the damaged BM spaces and subsequently support hematopoietic recovery under stress conditions.     

α/β–T Cell Receptor (TCR)+CD4−CD8− (NKT) Thymocytes Prevent Insulin-dependent Diabetes Mellitus in Nonobese Diabetic (NOD)/Lt Mice by the Influence of Interleukin (IL)-4 and/or IL-10

We have previously shown that nonobese diabetic (NOD) mice are selectively deficient in α/β-T cell receptor (TCR)⁺CD4⁻CD8⁻ NKT cells, a defect that may contribute to their susceptibility to the spontaneous development of insulin-dependent diabetes mellitus (IDDM). The role of NKT cells in protection from IDDM in NOD mice was studied by the infusion of thymocyte subsets into young female NOD mice. A single intravenous injection of 10⁶ CD4^−/lowCD8⁻ or CD4⁻CD8⁻ thymocytes from female (BALB/c × NOD)F1 donors protected intact NOD mice from the spontaneous onset of clinical IDDM. Insulitis was still present in some recipient mice, although the cell infiltrates were principally periductal and periislet, rather than the intraislet pattern characteristic of insulitis in unmanipulated NOD mice. Protection was not associated with the induction of “allogenic tolerance” or systemic autoimmunity. Accelerated IDDM occurs after injection of splenocytes from NOD donors into irradiated adult NOD recipients. When α/β-TCR⁺ and α/β-TCR⁻ subsets of CD4⁻CD8⁻ thymocytes were transferred with diabetogenic splenocytes and compared for their ability to prevent the development of IDDM in irradiated adult recipients, only the α/β-TCR⁺ population was protective, confirming that NKT cells were responsible for this activity. The protective effect in the induced model of IDDM was neutralized by anti–IL-4 and anti–IL-10 monoclonal antibodies in vivo, indicating a role for at least one of these cytokines in NKT cell-mediated protection. These results have significant implications for the pathogenesis and potential prevention of IDDM in humans.     

Plasmacytoid dendritic cells promote HIV-1–induced group 3 innate lymphoid cell depletion

Group 3 innate lymphoid cells (ILC3s) have demonstrated roles in promoting antibacterial immunity, maintaining epithelial barrier function, and supporting tissue repair. ILC3 alterations are associated with chronic inflammation and inflammatory disease; however, the characteristics and relevant regulatory mechanisms of this cell population in HIV-1 infection are poorly understood due in part to a lack of a robust model. Here, we determined that functional human ILC3s develop in lymphoid organs of humanized mice and that persistent HIV-1 infection in this model depletes ILC3s, as observed in chronic HIV-1–infected patients. In HIV-1–infected mice, effective antiretroviral therapy reversed the loss of ILC3s. HIV-1–dependent reduction of ILC3s required plasmacytoid dendritic cells (pDCs), IFN-I, and the CD95/FasL pathway, as targeted depletion or blockade of these prevented HIV-1–induced ILC3 depletion in vivo and in vitro, respectively. Finally, we determined that HIV-1 infection induces CD95 expression on ILC3s via a pDC- and IFN-I–dependent mechanism that sensitizes ILC3s to undergo CD95/FasL-mediated apoptosis. We conclude that chronic HIV-1 infection depletes ILC3s through pDC activation, induction of IFN-I, and CD95-mediated apoptosis.     

Interferon γ–independent Rejection of Interleukin 12–transduced Carcinoma Cells Requires CD4+ T Cells and Granulocyte/Macrophage Colony–stimulating Factor

We analyzed the ability of interferon (IFN)-γ knockout mice (GKO) to reject a colon carcinoma transduced with interleukin (IL)-12 genes (C26/IL-12). Although the absence of IFN-γ impaired the early response and reduced the time to tumor onset in GKO mice, the overall tumor take rate was similar to that of BALB/c mice. In GKO mice, C26/IL-12 tumors had a reduced number of infiltrating leukocytes, especially CD8 and natural killer cells. Analysis of the tumor site, draining nodes, and spleens of GKO mice revealed reduced expression of IFN- inducible protein 10 and monokine induced by γ-IFN. Despite these defects, GKO mice that rejected C26/IL-12 tumor, and mice that were primed in vivo with irradiated C26/IL-12 cells, showed the same cytotoxic T lymphocyte activity but higher production of granulocyte/macrophage colony–stimulating factor (GM-CSF) as compared with control BALB/c mice. Treatment with monoclonal antibodies against GM-CSF abrogated tumor regression in GKO but not in BALB/c mice. CD4 T lymphocytes, which proved unnecessary or suppressive during rejection of C26/IL-12 cells in BALB/c mice, were required for tumor rejection in GKO mice. CD4 T cell depletion was coupled with a decline in GM-CSF expression by lymphocytes infiltrating the tumors or in the draining nodes, and with the reduction and disappearance of granulocytes and CD8 T cells, respectively, in tumor nodules. These results suggest that GM-CSF can substitute for IFN-γ in maintaining the CD8–polymorphonuclear leukocyte cross-talk that is a hallmark of tumor rejection.     

IL-1β–driven osteoclastogenic Tregs accelerate bone erosion in arthritis

IL-1β is a proinflammatory mediator with roles in innate and adaptive immunity. Here we show that IL-1β contributes to autoimmune arthritis by inducing osteoclastogenic capacity in Tregs. Using mice with joint inflammation arising through deficiency of the IL-1 receptor antagonist (Il1rn^–/–), we observed that IL-1β blockade attenuated disease more effectively in early arthritis than in established arthritis, especially with respect to bone erosion. Protection was accompanied by a reduction in synovial CD4⁺Foxp3⁺ Tregs that displayed preserved suppressive capacity and aerobic metabolism but aberrant expression of RANKL and a striking capacity to drive RANKL-dependent osteoclast differentiation. Both Il1rn^–/– Tregs and wild-type Tregs differentiated with IL-1β accelerated bone erosion upon adoptive transfer. Human Tregs exhibited analogous differentiation, and corresponding RANKL^hiFoxp3⁺ T cells could be identified in rheumatoid arthritis synovial tissue. Together, these findings identify IL-1β–induced osteoclastogenic Tregs as a contributor to bone erosion in arthritis.     

Selective Expression of a Stable Cell Surface Molecule on Type 2 but Not Type 1 Helper T Cells

T helper cell type 1 (Th1) and 2 (Th2) are central to immune regulation. However, no stable cell surface marker capable of distinguishing and separating these two subsets of CD4⁺ cells has yet been found. Using differential display PCR, we have identified a gene encoding a cell membrane bound molecule, originally designated ST2L, T1, DER4, or Fit, expressed constitutively and stably on the surface of murine Th2s, but not Th1s even after stimulation with a range of immunological stimuli. Antibody against a peptide derived from ST2L strongly and stably labeled the surface of cloned Th2s but not Th1s, and Th2s but not Th1s derived from naive T cells of ovalbumin T cell receptor–α/β transgenic mice. Three-color single cell flow cytometric analysis shows that cell surface ST2L coexpressed with intracellular interleukin (IL)-4, but not with interferon (IFN)-γ. The antibody selectively lysed Th2s in vitro in a complement-dependent manner. In vivo, it enhanced Th1 responses by increasing IFN-γ production and decreasing IL-4 and IL-5 synthesis. It induced resistance to Leishmania major infection in BALB/c mice and exacerbated collagen-induced arthritis in DBA/1 mice. Thus, ST2L is a stable marker distinguishing Th2s from Th1s and is also associated with Th2 functions. Hence, it may be a target for therapeutic intervention.     

The V–J Recombination of T Cell Receptor-γ Genes Is Blocked in Interleukin-7 Receptor–deficient Mice

IL-7R-deficient mice have severely impaired expansion of early lymphocytes and lack γδ T cells. To elucidate the role of IL-7R on γδ T cell development, we analyzed the rearrangements of TCR-α, β, γ, and δ genes in the thymus of the IL-7R-deficient mice. Southern blot analysis with a Jγ1 probe revealed that more than 70% of Jγ1 and Jγ2 alleles are recombined to form distinct Vγ1.2–Jγ2 and Vγ2–Jγ1 fragments in control mice. On the contrary, no such recombination was detected in the mutant mice. The rearrangements in the TCR-α, β, and δ loci were comparably observed in control and mutant mice. PCR analysis indicated that the V–J recombination of all the Vγ genes is severely hampered in the mutant mice. The mRNA of RAG-1, RAG-2, Ku-80, and terminal deoxynucleotidyl transferase (TdT) genes was equally detected between control and mutant thymi, suggesting that the expression of common recombination machinery is not affected. These data demonstrated that the V–J recombination of the TCR γ genes is specifically blocked in the IL-7R-deficient mice and suggested the presence of highly specific regulation for TCR γ gene rearrangement.     

IL-33/ST2信号与Treg在免疫性疾病中的研究进展

白细胞介素-33(interleukin-33,IL-33)作为白细胞介素-1(interleukin-1,IL-1)家族的成员,是由受损或坏死的屏障细胞(内皮细胞和上皮细胞)释放的内源性细胞因子。IL-33信号转导依赖于特异性受体生长刺激表达基因2蛋白(growth stimulation expressed gene 2,ST2)的识别和相互作用,ST2主要表达于免疫细胞。IL-33通过靶向T H2细胞、肥大细胞、嗜酸性粒细胞、2型先天性淋巴细胞(2 innate lymphoid cells,ILC2)调控2型免疫反应,也可以通过CD8+T细胞、天然杀伤细胞(natural killer cell,NK)和树突状细胞调控1型免疫反应。最近研究发现,IL-33/ST2信号转导影响调节性T细胞(regulatory T cell,Treg)在外周的动态平衡、表型多样性和功能。Treg是建立和维持免疫自身耐受所必需的,因此,研究IL-33/ST2信号在Treg生物学中的作用对免疫性疾病治疗具有重要意义。该文讨论IL-33/ST2信号对Treg的不同影响,以期为肿瘤、炎症和自身免疫病的诊疗提供参考。     

Biliary repair and carcinogenesis are mediated by IL-33–dependent cholangiocyte proliferation

Injury to the biliary epithelium triggers inflammation and fibrosis, which can result in severe liver diseases and may progress to malignancy. Development of a type 1 immune response has been linked to biliary injury pathogenesis; however, a subset of patients with biliary atresia, the most common childhood cholangiopathy, exhibit increased levels of Th2-promoting cytokines. The relationship among different inflammatory drivers, epithelial repair, and carcinogenesis remains unclear. Here, we determined that the Th2-activating cytokine IL-33 is elevated in biliary atresia patient serum and in the livers and bile ducts of mice with experimental biliary atresia. Administration of IL-33 to WT mice markedly increased cholangiocyte proliferation and promoted sustained cell growth, resulting in dramatic and rapid enlargement of extrahepatic bile ducts. The IL-33–dependent proliferative response was mediated by an increase in the number of type 2 innate lymphoid cells (ILC2s), which released high levels of IL-13 that in turn promoted cholangiocyte hyperplasia. Induction of the IL-33/ILC2/IL-13 circuit in a murine biliary injury model promoted epithelial repair; however, induction of this circuit in mice with constitutive activation of AKT and YAP in bile ducts induced cholangiocarcinoma with liver metastases. These findings reveal that IL-33 mediates epithelial proliferation and suggest that activation of IL-33/ILC2/IL-13 may improve biliary repair and disruption of the circuit may block progression of carcinogenesis.     

1,25二羟维生素D3对哮喘小鼠的Rac1-IL33-ILC2通路的作用

目的观察1,25二羟维生素D31,25-(OH)2-D3对哮喘小鼠Ras相关的C3肉毒素底物1(Ras-related C3 botulinum toxin substrate 1,Rac1)、白细胞介素-33(IL-33)和2型固有淋巴细胞(type 2 innate lymphocytes,ILC2)的影响。方法将30只7周龄BALB/c雌性小鼠随机分为对照组、哮喘组、干预组,每组各10只小鼠,卵清蛋白混合液致敏并雾化吸入建立哮喘小鼠模型,干预组每次激发前腹腔注射1,25(OH)2-D3混合液0.08 ml,对照组和哮喘组以生理盐水代替。末次激发24 h后对小鼠肺组织中IL-33、Rac1、ILC2进行检测并比较。结果与对照组比较,哮喘组Rac1下降,IL-33水平增高,ILC2数目升高。且Rac1与IL-33、ILC2呈明显的负相关性(r=-0.954、r=-0.957,P<0.05)。干预组IL-33及ILC2数目较哮喘组显著下降,Rac1较哮喘组显著上升,差异有统计学意义(P<0.05)。结论哮喘小鼠存在Rac1下降,IL-33水平增高,ILC2数目升高的免疫变化;1,25-(OH)2-D3可能通过上调哮喘小鼠Rac1的表达,导致IL-33等细胞因子水平产生减少,进而抑制ILC2的活化、减轻哮喘的免疫炎症。