Dendritic‐cell expression of Ship1 regulates Th2 immunity to helminth infection in mice

In mouse models of infection with the gastrointestinal parasite Trichuris muris, appropriate dendritic‐cell (DC) Ag sampling, migration, and presentation to T cells are necessary to mount a protective Th2‐polarized adaptive immune response, which is needed to clear infection. SH2‐containing inositol 5′‐phosphatase 1 (SHIP‐1) has been shown to be an important regulator of DC function in vitro through the negative regulation of the phosphoinositide 3‐kinase (PI3K) pathway, but its role in vivo is relatively unexplored. In the current work, mice with a specific deletion of SHIP‐1 in DCs (Ship1^ΔDC) were infected with the parasite T. muris. Ship1^ΔDC mice were susceptible to infection due to ineffective priming of Th2‐polarized responses. This is likely due to an increased production of interleukin (IL) 12p40 by SHIP‐1‐deficient DCs, as in vivo antibody blockade of IL‐12p40 was able to facilitate the clearing of infection in Ship1^ΔDC mice. Our results describe a critical role for SHIP‐1 in regulating the ability of DCs to efficiently prime Th2‐type responses.     

Deletional and regulatory mechanisms coalesce to drive transplantation tolerance through mixed chimerism

Establishing donor‐specific immunological tolerance could improve long‐term outcome by obviating the need for immunosuppressive drug therapy, which is currently required to control alloreactivity after organ transplantation. Mixed chimerism is defined as the engraftment of donor hematopoietic stem cells in the recipient, leading to viable coexistence of both donor and recipient leukocytes. In numerous experimental models, cotransplantation of donor bone marrow (BM) into preconditioned (e.g., through irradiation or cytotoxic drugs) recipients leads to transplantation tolerance through (mixed) chimerism. Mixed chimerism offers immunological advantages for clinical translation; pilot trials have established proof of concept by deliberately inducing tolerance in humans. Widespread clinical application is prevented, however, by the harsh preconditioning currently necessary for permitting BM engraftment. Recently, the immunological mechanisms inducing and maintaining tolerance in experimental mixed chimerism have been defined, revealing a more prominent role for regulation than historically assumed. The evidence from murine models suggests that both deletional and regulatory mechanisms are critical in promoting complete tolerance, encompassing also the minor histocompatibility antigens. Here, we review the current understanding of tolerance through mixed chimerism and provide an outlook on how to realize widespread clinical translation based on mechanistic insights gained from chimerism protocols, including cell therapy with polyclonal regulatory T cells.     

Type I IFN‐mediated synergistic activation of mouse and human DC subsets by TLR agonists

Novel approaches of dendritic cell (DC) based cancer immunotherapy aim at harnessing the unique attributes of different DC subsets. Classical monocyte‐derived DC vaccines are currently being replaced by either applying primary DCs or specifically targeting antigens and adjuvants to these subsets in vivo. Appropriate DC activation in both strategies is essential for optimal effect. For this purpose TLR agonists are favorable adjuvant choices, with TLR7 triggering being essential for inducing strong Th1 responses. However, mouse CD8α⁺ DCs, considered to be the major cross‐presenting subset, lack TLR7 expression. Interestingly, this DC subset can respond to TLR7 ligand upon concurrent TLR3 triggering. Nevertheless, the mechanism underlying this synergy remains obscure. We now show that TLR3 ligation results in the production of IFN‐α, which rapidly induces the expression of TLR7, resulting in synergistic activation. Moreover, we demonstrate that this mechanism conversely holds for plasmacytoid DCs that respond to TLR3 ligation when TLR7 pathway is mobilized. We further demonstrate that this mechanism of sharpening DC senses is also conserved in human BDCA1⁺ DCs and plasmacytoid DCs. These findings have important implications for future clinical trials as it suggests that combinations of TLR ligands should be applied irrespective of initial TLR expression profiles on natural DC subsets for optimal stimulation.     

Granulocyte‐augmented chemokine production induced by type II collagen containing immune complexes is mediated via TLR4 in rheumatoid arthritis patients

Rheumatoid arthritis (RA) patients with early elevations of antibodies against collagen type II (CII) have a distinct acute onset phenotype, associated with cytokine induction by surface‐bound anti‐CII‐containing immune complexes (ICs) and high C‐reactive protein (CRP) and erythrocyte sedimentation rate (ESR). Polymorphonuclear granulocytes (PMNs) and peripheral blood mononuclear cells (PBMCs) are abundant in the vicinity of CII in RA joints, and both PMN and PBMC reactivity against anti‐CII IC individually relate to early joint destruction and early elevation of CRP and ESR in RA. We searched for CII‐dependent mechanisms that might attract PMNs and PBMCs to RA joints. Human PBMCs and PMNs were stimulated with anti‐CII ICs and control ICs, either individually or in cocultures. Cocultured PMNs and PBMCs stimulated with anti‐CII ICs synergistically augmented production of the chemokines CXCL8, RANTES and MCP‐1, whereas downregulation was seen with control IC. This upregulation was unique to chemokines, as TNF‐α, IL‐1β, and GM‐CSF were downregulated in anti‐CII IC‐stimulated cocultures. The coculture‐associated chemokine upregulation depended on endogenous TLR4 ligand(s) and functionally active PMN enzymes, and was partially mediated by GM‐CSF. As anti‐CII levels peak around the time of RA diagnosis, this mechanism can attract inflammatory cells to joints in early RA and intensify the anti‐CII‐associated acute onset RA phenotype.     

Coincident diabetes mellitus modulates Th1‐, Th2‐, and Th17‐cell responses in latent tuberculosis in an IL‐10‐ and TGF‐β‐dependent manner

Type 2 diabetes mellitus (DM) is a risk factor for the development of active tuberculosis (TB), although its role in the TB‐induced responses in latent TB (LTB) is not well understood. Since Th1, Th2, and Th17 responses are important in immunity to LTB, we postulated that coincident DM could alter the function of these CD4⁺ T‐cell subsets. To this end, we examined mycobacteria‐induced immune responses in the whole blood of individuals with LTB‐DM and compared them with responses of individuals without DM (LTB‐NDM). T‐cell responses from LTB‐DM are characterized by diminished frequencies of mono‐ and dual‐functional CD4⁺ Th1, Th2, and Th17 cells at baseline and following stimulation with mycobacterial antigens‐purified protein derivative, early secreted antigen‐6, and culture filtrate protein‐10. This modulation was at least partially dependent on IL‐10 and TGF‐β, since neutralization of either cytokine resulted in significantly increased frequencies of Th1 and Th2 cells but not Th17 cells in LTB‐DM but not LTB individuals. LTB‐DM is therefore characterized by diminished frequencies of Th1, Th2, and Th17 cells, indicating that DM alters the immune response in latent TB leading to a suboptimal induction of protective CD4⁺ T‐cell responses, thereby providing a potential mechanism for increased susceptibility to active disease.     

Coordinated expansion of both memory T cells and NK cells in response to CMV infection in humans

NK cells are key players in the fight against persistent viruses. Human cytomegalovirus (HCMV) infection is associated with the presence of a population of CD16⁺ CD56^dim NKG2C⁺ NK cells in both acutely and latently infected individuals. Here, we studied the nature of these terminally differentiated NK cells in different human populations infected with HCMV: healthy donors stratified by age, thymectomized individuals, pregnant women suffering from primary CMV infection, and lung transplant patients. Both CD16⁺ CD56^dim NK‐ and CD8 T‐cell phenotypes as well as functional capacities were determined and stratified according to age and/or CMV event. Similarly to T‐cell responsiveness, we observe an accumulation over time of NKG2C⁺ NK cells, which preferentially expressed CD57. This accumulation is particularly prominent in elderly and amplified further by CMV infection. Latent HCMV infection (without replication) is sufficient for NKG2C⁺ CD57⁺ NK cells to persist in healthy individuals but is not necessarily required in old age. Collectively, the present work supports the emerging concept that CMV shapes both innate and adaptive immunity in humans.     

母胎界面树突状细胞CCL17和CCL22表达在母胎免疫耐受中的作用

目的: 检测非孕期子宫内膜和正常妊娠早期及复发性自然流产患者蜕膜中树突状细胞(DC)CCL17和CCL22的表达差异,探讨母胎界面DC在CD4⁺CD25⁺调节性T细胞(Treg)的募集及母胎免疫耐受微环境形成中的作用。方法: 正常早孕组人工流产时、复发性流产组清宫时取其蜕膜,正常未孕组行子宫切除时取其内膜组织。分离蜕膜或子宫内膜单个核细胞,体外诱导培养DC,用real-time PCR法分析3组DC CCL17和CCL22 mRNA的表达水平,ELISA法检测3组DC培养上清液中CCL17和CCL22蛋白的表达。结果: 正常早孕组蜕膜DC CCL17和CCL22 mRNA的表达分别为3.04±0.40和1.83±0.24,均高于正常未孕组(0.85±0.24和0.31±0.08,P<0.01)和复发性流产组(1.65±0.14和0.96±0.09,P<0.01)。正常早孕组蜕膜DC能够持续旺盛分泌趋化因子CCL17和CCL22,在培养的12~96 h内CCL17和CCL22的分泌量逐渐增多。同一时点早孕组DC分泌的CCL17和CCL22均明显高于未孕组和复发性流产组DC分泌的CCL17和CCL22(P<0.01)。结论: 正常妊娠后蜕膜DC表达CCL17和CCL22增强,DC可能通过高表达CCL17和CCL22而增强对CD4⁺CD25⁺Treg的趋化作用,从而在母胎界面的免疫耐受中发挥重要作用,蜕膜DC表达CCL17和CCL22下降可能与复发性自然流产的发病有关。     

Metabolism of murine TH17 cells: Impact on cell fate and function

An effective adaptive immune response relies on the ability of lymphocytes to rapidly act upon a variety of insults. In T lymphocytes, this response includes cell growth, clonal expansion, differentiation, and cytokine production, all of which place a significant energy burden on the cell. Recent evidence shows that T‐cell metabolic reprogramming is an essential component of the adaptive immune response and specific metabolic pathways dictate T‐cell fate decisions, including the development of T_H17 versus T regulatory (Treg) cells. T_H17 cells have garnered significant attention due to their roles in the pathology of immune‐mediated inflammatory diseases. Attempts to characterize T_H17 cells have demonstrated that they are highly dynamic, adjusting their function to environmental cues, which dictate their metabolic program. In this review, we highlight recent data demonstrating the impact of cellular metabolism on the T_H17/Treg balance and present factors that mediate T_H17‐cell metabolism. Some examples of these include the differential impact of the mTOR signaling complexes on T‐helper‐cell differentiation, hypoxia inducible factor 1 alpha (HIF1α) promotion of glycolysis to favor T_H17‐cell development, and ACC1‐dependent de novo fatty acid synthesis favoring T_H17‐cell development over Treg cells. Finally, we discuss the potential therapeutic options and the implications of modulating T_H17‐cell metabolism for the treatment of T_H17‐mediated diseases.     

Deciphering CD137 (4‐1BB) signaling in T‐cell costimulation for translation into successful cancer immunotherapy

CD137 (4‐1BB, TNF‐receptor superfamily 9) is a surface glycoprotein of the TNFR family which can be induced on a variety of leukocyte subsets. On T and NK cells, CD137 is expressed following activation and, if ligated by its natural ligand (CD137L), conveys polyubiquitination‐mediated signals via TNF receptor associated factor 2 that inhibit apoptosis, while enhancing proliferation and effector functions. CD137 thus behaves as a bona fide inducible costimulatory molecule. These functional properties of CD137 can be exploited in cancer immunotherapy by systemic administration of agonist monoclonal antibodies, which increase anticancer CTLs and enhance NK‐cell‐mediated antibody‐dependent cell‐mediated cytotoxicity. Reportedly, anti‐CD137 mAb and adoptive T‐cell therapy strongly synergize, since (i) CD137 expression can be used to select the T cells endowed with the best activities against the tumor, (ii) costimulation of the lymphocyte cultures to be used in adoptive T‐cell therapy can be done with CD137 agonist antibodies or CD137L, and (iii) synergistic effects upon coadministration of T cells and antibodies are readily observed in mouse models. Furthermore, the signaling cytoplasmic tail of CD137 is a key component of anti‐CD19 chimeric antigen receptors that are used to redirect T cells against leukemia and lymphoma in the clinic. Ongoing phase II clinical trials with agonist antibodies and the presence of CD137 sequence in these successful chimeric antigen receptors highlight the importance of CD137 in oncoimmunology.     

Circular RNA circZbtb20 maintains ILC3 homeostasis and function via Alkbh5-dependent m6A demethylation of Nr4a1 mRNA

Group 3 innate lymphoid cells (ILC3s) play critical roles in innate immunity and gut homeostasis. However, how ILC3 homeostasis is regulated remains elusive. Here, we identified a novel circular RNA, circZbtb20, that is highly expressed in ILC3s and required for their maintenance and function. CircZbtb20 deletion causes reduced ILC3 numbers, increasing susceptibility to C. rodentium infection. Mechanistically, circZbtb20 enhances the interaction of Alkbh5 with Nr4a1 mRNA, leading to ablation of the m⁶A modification of Nr4a1 mRNA to promote its stability. Nr4a1 initiates Notch2 signaling activation, which contributes to the maintenance of ILC3 homeostasis. Deletion of Alkbh5 or Nr4a1 also impairs ILC3 homeostasis and increases susceptibilities to bacterial infection. Thus, our findings reveal an important role of circular RNA in the regulation of innate lymphoid cell homeostasis.     

TGF‐β induces the differentiation of human CXCL13‐producing CD4+ T cells

In the ectopic lymphoid‐like structures present in chronic inflammatory conditions such as rheumatoid arthritis, a subset of human effector memory CD4⁺ T cells that lacks features of follicular helper T (Tfh) cells produces CXCL13. Here, we report that TGF‐β induces the differentiation of human CXCL13‐producing CD4⁺ T cells from naïve CD4⁺ T cells. The TGF‐β‐induced CXCL13‐producing CD4⁺ T cells do not express CXCR5, B‐cell lymphoma 6 (BCL6), and other Tfh‐cell markers. Furthermore, expression levels of CD25 (IL‐2Rα) in CXCL13‐producing CD4⁺ T cells are significantly lower than those in FoxP3⁺ in vitro induced Treg cells. Consistent with this, neutralization of IL‐2 and knockdown of STAT5 clearly upregulate CXCL13 production by CD4⁺ T cells, while downregulating the expression of FoxP3. Furthermore, overexpression of FoxP3 in naïve CD4⁺ T cells downregulates CXCL13 production, and knockdown of FoxP3 fails to inhibit the differentiation of CXCL13‐producing CD4⁺ T cells. As reported in rheumatoid arthritis, proinflammatory cytokines enhance secondary CXCL13 production from reactivated CXCL13‐producing CD4⁺ T cells. Our findings demonstrate that CXCL13‐producing CD4⁺ T cells lacking Tfh‐cell features differentiate via TGF‐β signaling but not via FoxP3, and exert their function in IL‐2‐limited but TGF‐β‐rich and proinflammatory cytokine‐rich inflammatory conditions.     

Interleukin‐2 critically regulates bone marrow erythropoiesis and prevents anemia development

Mice deficient in IL‐2 signaling develop severe anemia indicating a defect in erythropoiesis. However, why deficiency in IL‐2, an essential growth factor for lymphocytes, or in IL‐2 signaling components should result in defective erythropoiesis is unclear. Here, we have analyzed the mechanism of IL‐2 signaling deficiency induced anemia in mice and show that IL‐2 plays an indispensable role in bone marrow (BM) erythropoiesis via maintenance of regulatory T (Treg) cells. In absence of IL‐2 signaling, IFN‐γ produced by the activated T cells suppressed klf1 expression, resulting in an early block in erythrocyte differentiation. Anemia, in IL‐2 or IL‐2 signaling deficient mice always developed prior to the manifestation of other autoimmune complications such as colitis, suggesting that anemia in these mice might be a contributing factor in inducing other pathological complications in later stages. Our study shows, how essential cytokines of lymphoid cells could exert critical influence on the development of erythrocytes and thus expanding our understanding of the complex regulation of hematopoiesis in the BM. Besides, our findings might facilitate the use of IL‐2 and anti‐IFN‐γ as a clinical remedy against anemia that arise in cancer patients following radiotherapy or chemotherapy, a context which simulates the situation of IL‐2 deficiency.     

A regulatory cross‐talk between Vγ9Vδ2 T lymphocytes and mesenchymal stem cells

The physiological functions of human TCRVγ9Vδ2⁺ γδ lymphocytes reactive to non‐peptide phosphoantigens contribute to cancer immunosurveillance and immunotherapy. However, their regulation by mesenchymal stem cells (MSC), multipotent and immunomodulatory progenitor cells able to infiltrate tumors, has not been investigated so far. By analyzing freshly isolated TCRVγ9Vδ2⁺ lymphocytes and primary cell lines stimulated with synthetic phosphoantigen or B‐cell lymphoma cell lines in the presence of MSC, we demonstrated that MSC were potent suppressors of γδ‐cell proliferation, cytokine production and cytolytic responses in vitro. This inhibition was mediated by the COX‐2‐dependent production of prostaglandin E2 (PGE₂) and by MSC through EP2 and EP4 inhibitory receptors expressed by Vγ9Vδ2 T lymphocytes. COX‐2 expression and PGE₂ production by MSC were not constitutive, but were induced by IFN‐γ and TNF‐α secreted by activated Vγ9Vδ2 T cells. This regulatory cross‐talk between MSC and Vγ9Vδ2 T lymphocytes involving PGE₂ could be of importance for the antitumor and antimicrobial activities of γδ T cells.     

Relationship between expression of toll-like receptors 2/4 in dendritic cells and chronic hepatitis B virus infection

Objective: This study is to explore the relationship between the chronic hepatitis B virus (HBV) infection and the expressions of toll-like receptor 2/4 (TLR2/4) in peripheral blood dendritic cells (DCs), to find out the immunological significance of TLR2/4 in HBV progression. Methods: Patients had been divided into the HBV, HBV-related liver cirrhosis (HBV-LC), and HBV-related hepatocellular carcinoma (HBV-HCC) groups. Healthy individuals served as normal controls (NC). Flow cytometry was used to determine the percentage of DCs in peripheral blood, and the expression of TLR2/4 in DCs as well as the expression of HBeAg. Real-time quantitative PCR was performed to measure the content of HBV-DNA. Results: The percentages of DCs in peripheral blood exhibited a slightly decreasing trend, without statistical significances, along with the disease severity in HBV patients (9.40 ± 2.05%, 7.11 ± 3.82%, 6.51 ± 4.38% and 6.00 ± 4.73% for the groups of NC, HBV, HBV-LC, and HBV-HCC, respectively). The expression of TLR2 was significantly increased in the disease progression, with the TLR2 expression rates of 2.60 ± 1.70%, 2.67 ± 2.89%, 3.53 ± 3.41% and 5.11 ± 4.93 for NC, HBV, HBV-LC, HBV-HCC, respectively. Similar results were found for TLR4 (expression rates: 45.34 ± 4.46%, 53.94 ± 5.21%, 65.16 ± 5.92% and 75.54 ± 6.12%), which was positively correlated with TLR2. Furthermore, the HBeAg level was increased, while the amount of HBV-DNA exhibited a declining trend, along with the disease severity. Correlation analysis revealed that the expression of HBeAg was positively correlated with TLR2. Conclusions: The elevated expressions of TLR2/4 on DC cell surfaces in peripheral blood may synergistically promote the disease progression of chronic HBV infection.     

Cytotoxic T lymphocyte antigen 4 immunoglobulin modified dendritic cells attenuate allergic airway inflammation and hyperresponsiveness by regulating the development of T helper type 1 (Th1)/Th2 and Th2/regulatory T cell subsets in a murine model of asthma

T helper type 2 (Th2) and regulatory T cells (T(reg) ) have been postulated to have critical roles in the pathogenesis of allergic asthma. Cytotoxic T lymphocyte antigen 4 immunoglobulin (CTLA4Ig) gene-modified dendritic cells (DC-CTLA4Ig) have the potential to reduce Th2 cells and induce T(reg) cells. In the present study, we evaluated the therapeutic effects and potential mechanisms of the adoptive transfer of DC-CTLA4Ig into mice in an experimental model of asthma. BALB/c mice were sensitized with ovalbumin (OVA) and challenged with aerosolized OVA for 7 days. Just prior to the first challenge, DC-CTLA4Ig, DCs or DCs infected with DC-green fluorescent protein (GFP) were injected intravenously into mice. The administration of DC-CTLA4Ig reduced airway hyperresponsiveness, relieved asthmatic airway inflammation and decreased the numbers of esosinophils in the BALF in OVA-sensitized/challenged mice. In addition, DC-CTLA4Ig altered the balance of Th1/Th2 cytokine production in the lungs with increased interferon (IFN)-γ levels and decreased interleukin (IL)-4 levels, decreased the percentage of Th2 and increased both the percentage of Th1 and T(reg) cells in the lungs of OVA-sensitized/challenged mice. This research demonstrates that DC-CTL4Ig reduces airway hyperresponsiveness effectively and prevents airway inflammation in OVA-sensitized/challenged mice, which is due most probably to attenuated secretion of Th2 cytokines and increased secretion of Th1 cytokines in the local airway, and the correction of the pulmonary imbalance between Th1/Th2 cells and Th2/T(reg) cells.     

FcepsilonRI cross-linking activates a type II phosphatidylinositol 4-kinase in RBL 2H3 cells

Crosslinking of FcepsilonRI on rat basophilic leukemia (RBL 2H3) cells leads to an increase in Phosphatidylinositol 4-kinase activity. This increase in Ptdlns 4-kinase activity is strongly correlated with its tyrosyl phosphorylation state. Characterization of the enzyme activity in anti phosphotyrosine immunoprecipitates suggests it as a type II Ptdlns 4-kinase. Membrane cholesterol depletion studies showed a reduction in type II Ptdlns 4-kinase activity suggesting that lipid rafts play an important role in activation of the enzyme. The enzyme activity was inhibited by resveratrol. In situ inhibition of type II Ptdlns 4-kinase activity showed a reduction in beta-hexosaminidase release upon FcepsilonRI cross-linking. These studies suggest that a type II Ptdlns 4-kinase is an integral component of FcepsilonRI mediated signal transduction mechanisms.