Regulatory T cells in cancer: where are we now?

There have been substantial strides forward in our understanding of the contribution of regulatory T (Treg) cells to cancer immunosuppression. In this issue, we present a series of papers highlighting emerging themes on this topic relevant not only to our understanding of the fundamental biology of tumour immunosuppression but also to the design of new immunotherapeutic approaches. The substantially shared biology of CD4⁺ conventional T (Tconv) and Treg cells necessitates a detailed understanding of the potentially opposing functional consequences that immunotherapies will have on Treg and Tconv cells, a prominent example being the potential for Treg-mediated hyperprogressive disease following anti-PD-1 therapy. Such understanding will aid patient stratification and the rational design of combination therapies. It is also becoming clear, however, that Treg cells within tumours exhibit distinct biological features to both Tconv cells and Treg cells in other tissues. These distinct features provide the opportunity for development of targeted immunotherapies with greater efficacy and reduced potential for inducing systemic toxicity.     

A three-cell model for activation of naïve T helper cells

It is generally assumed that the activation of naïve T helper (Th) cells is the result of a two‐cell interaction between the Th cell and a dendritic cell (DC) and that three signals are required. Signal one or stimulation is the recognition by the T‐cell receptor (TCR) of antigenic peptides presented by major histocompatibility complex (MHC) class II molecules. Signal two or co‐stimulation is mainly provided by the triggering of CD28 on the T cell by CD80 and CD86 molecules on the DC. Signal three or polarization directs T‐cell differentiation into various effector phenotypes such as Th1 and Th2. Both signals, two and three, are often assumed to result from the binding of microbial products or endogenous molecular danger signals to germline‐encoded receptors such as toll‐like receptors (TLR) on the DC. However, recent data challenge this two‐cell model by revealing that Th1 polarization requires the presence of interferon‐γ (IFN‐γ) provided by a third cell. I propose here a three‐cell model for naïve Th‐cell activation. In this model, delivery of signal three by the DC is dependent on help provided by other innate immune cells such as NK cells, NK T cells, γδ T cells, mast cells, eosinophils and basophils. The rationale behind this model is that the innate immune system has been designed by evolution to select an appropriate class of immune response to protect the host.     

Stability of regulatory T cells in T helper 2–biased allergic airway diseases

Regulatory T (Treg) cells potentially suppress the deleterious activities of effector T cells and maintain a state of tolerance against antigens in the airway mucosa. A decrease in the number and function of Treg cells is observed in T helper 2 (Th2)–biased allergic airway diseases. However, adoptive transfer of naturally occurring Treg (tTreg) cells or peripherally derived Treg (pTreg) cells in asthmatic mouse models did not yield satisfactory results in any previous studies. Here, we review the recent progress in the identification and plasticity of tTreg and pTreg cells in Th2–biased airway diseases and summarize the factors affecting the stability and function of Treg cells. This review may serve as foundation for understanding the molecular mechanisms underlying the stability of tTreg and pTreg cells and development of effective strategies for treating allergic airway diseases.     

γδT cells but not αβT cells contribute to sepsis-induced white matter injury and motor abnormalities in mice

Background

Infection and sepsis are associated with brain white matter injury in preterm infants and the subsequent development of cerebral palsy.

Methods

In the present study, we used a neonatal mouse sepsis-induced white matter injury model to determine the contribution of different T cell subsets (αβT cells and γδT cells) to white matter injury and consequent behavioral changes. C57BL/6J wild-type (WT), T cell receptor (TCR) δ-deficient (Tcrd ^?/?, lacking γδT cells), and TCRα-deficient (Tcra ^?/?, lacking αβT cells) mice were administered with lipopolysaccharide (LPS) at postnatal day (PND) 2. Brain myelination was examined at PNDs 12, 26, and 60. Motor function and anxiety-like behavior were evaluated at PND 26 or 30 using DigiGait analysis and an elevated plus maze.

Results

White matter development was normal in Tcrd ^?/? and Tcrα ^?/? compared to WT mice. LPS exposure induced reductions in white matter tissue volume in WT and Tcrα ^?/? mice, but not in the Tcrd ^?/? mice, compared with the saline-treated groups. Neither LPS administration nor the T cell deficiency affected anxiety behavior in these mice as determined with the elevated plus maze. DigiGait analysis revealed motor function deficiency after LPS-induced sepsis in both WT and Tcrα ^?/? mice, but no such effect was observed in Tcrd ^?/? mice.

Conclusions

Our results suggest that γδT cells but not αβT cells contribute to sepsis-induced white matter injury and subsequent motor function abnormalities in early life. Modulating the activity of γδT cells in the early stages of preterm white matter injury might represent a novel therapeutic strategy for the treatment of perinatal brain injury.

     

CD8+ cells regulate the T helper-17 response in an experimental murine model of Sjögren syndrome

This study investigated the regulatory function of CD8⁺ cells in T helper-17 (Th17) cell-mediated corneal epithelial barrier disruption that develops in a murine desiccating stress (DS) model that resembles Sjögren syndrome. CD8⁺ cell depletion promoted generation of interleukin-17A (IL-17A)-producing CD4⁺ T cells via activation of dendritic cells in both the ocular surface and draining cervical lymph nodes in C57BL/6 mice subjected to DS. T-cell-deficient nude recipient mice receiving adoptively transferred CD4⁺ T cells from CD8⁺ cell-depleted donors exposed to DS displayed increased CD4⁺ T-cell infiltration and elevated IL-17A and CC-chemokine attractant ligand 20 levels in the ocular surface, which was associated with greater corneal barrier disruption. Enhanced DS-specific corneal barrier disruption in CD8-depleted donor mice correlated with a Th17-mediated expression of matrix metalloproteinases (MMP-3 and MMP-9) in the recipient corneal epithelium. Co-transfer of CD8⁺CD103⁺ regulatory T cells did not affect the ability of DS-specific pathogenic CD4⁺ T cells to infiltrate and cause ocular surface disease in the nude recipients, showing that CD8⁺ cells regulate the efferent arm of DS-induced immune response. In summary, CD8⁺ regulatory cells suppress generation of a pathogenic Th17 response that has a pivotal role in DS-induced disruption of corneal barrier function.     

Regulatory T cells in HIV infection: Who’s suppressing what?

The role of regulatory T cells (Treg) in HIV pathogenesis is not fully elucidated. Persistent antigens, such as HIV, are believed to promote the expansion and activation of antigen-specific Treg, and several reports have described beneficial and detrimental roles for Treg in HIV pathogenesis. These apparently contradictory observations may arise from imprecision in enumerating Treg and the lack of definition of Treg subsets. New markers allowing more precise identification and purification of Treg for functional studies have been described recently, and these may open avenues for efficient isolation of pure, homogenous populations of human Treg.     

Translational Mini-Review Series on Th17 Cells: Are T helper 17 cells really pathogenic in autoimmunity?

OTHER ARTICLES PUBLISHED IN THIS MINI‐REVIEW SERIES ON Th17 CELLS
Function and regulation of human T helper 17 cells in health and disease. Clin Exp Immunol 2009; doi:10.1111/j.1365‐2249.2009.04037.x
Induction of interleukin‐17 production by regulatory T cells. Clin Exp Immunol 2009; doi:10.1111/j.1365‐2249.2009.04038.x
CD4⁺ T helper cells: functional plasticity and differential sensitivity to regulatory T cell‐mediated regulation. Clin Exp Immunol 2009; doi:10.1111/j.1365‐2249.2009.04040.x
Development of mouse and human T helper 17 cells. Clin Exp Immunol 2009; doi:10.1111/j.1365‐2249.2009.04041.x

Summary

In this review the authors discuss the evidence for T helper type 17 (Th17) cells as pathogenic T cells in autoimmunity. Studies with cytokine‐deficient mice or blocking of interleukin (IL)‐17, IL‐21 and IL‐22 have resulted in a conflicting data set. Although in the experimental autoimmune encephalomyelitis model the role of Th17 cells remains a point of debate, this IL‐17‐producing T cell in experimental arthritis is clearly contributing to inflammation and destruction.     

Differentiation of follicular helper T cells by salivary gland epithelial cells in primary Sjögren's syndrome

Follicular helper T cells (Tfh), which play a pivotal role in B cell activation and differentiation in lymphoid structures, secrete IL-21 whose augmented secretion is a hallmark of several autoimmune diseases. To decipher the cellular and molecular interactions occurring in salivary glands of patients suffering from primary Sjögren's syndrome (pSS), we investigated whether salivary gland epithelial cells (SGECs) were capable to induce Tfh differentiation. Co-cultures of naïve CD4⁺ T cells and SGECs from both patients with pSS and controls were performed. Here, we report that IL-6 and ICOSL expression by SGECs contributes to naïve CD4⁺ T differentiation into Tfh cells, as evidenced by their acquisition of a specific phenotype, characterized by Bcl-6, ICOS and CXCR5 expression and IL-21 secretion, but also but by their main functional feature: the capacity to enhance B lymphocytes survival. We demonstrated an increase of serum IL-21 with systemic activity. Finally, we analyzed the potential occurrence of a genetic association between IL-21 or IL-21R gene polymorphisms and pSS or elevated IL-21 secretion. This study, which demonstrates a direct induction of Tfh differentiation by SGECs, emphasizes a yet unknown pathogenic role of SGECs and suggests that Tfh and IL-21 might be relevant biomarkers and/or therapeutic targets in primary Sjögren's syndrome.     

Thymic but not splenic CD8⁺ DCs can efficiently cross-prime T cells in the absence of licensing factors

Cross‐presentation is an important mechanism to elicit both immune defenses and tolerance. Although only a few DC subsets possess the machinery required for cross‐presentation, little is known about differences in cross‐presenting capabilities of DCs belonging to the same subpopulation but localized in different lymphoid organs. In this study, we demonstrate that steady‐state thymic CD8⁺ DCs can efficiently cross‐prime naïve CD8⁺ T cells in the absence of costimulation. Surprisingly, cross‐priming by splenic CD8⁺ DCs was dependent on licensing factors such as GM‐CSF. In the absence of GM‐CSF, antigen–MHC‐class‐I complexes were detected on thymic but not on splenic CD8⁺ DCs, indicating that the cross‐presentation capacity of the thymic subpopulation was higher. The observed cross‐priming differences between thymic and splenic CD8⁺ DCs did not correlate with differential antigen capture or costimulatory molecules found on the surface of DCs. Moreover, we did not detect overall impairment of antigen presentation, as peptide‐loaded splenic CD8⁺ DCs were able to induce CD8⁺ T‐cell proliferation. The observation that thymic CD8⁺ DCs are more efficient than splenic CD8⁺ DCs in T‐cell cross‐priming in the absence of licensing factors indicates that the requirements for efficient antigen presentation differ between these cells.     

Intranasal but not intravenous delivery of the adjuvant α-galactosylceramide permits repeated stimulation of natural killer T cells in the lung

Efficient induction of antigen-specific immunity is achieved by delivering multiple doses of vaccine formulated with appropriate adjuvants that can harness the benefits of innate immune mediators. The synthetic glycolipid α-galactosylceramide (α-GalCer) is a potent activator of NKT cells, a major innate immune mediator cell type effective in inducing maturation of DCs for efficient presentation of co-administered antigens. However, systemic administration of α-GalCer results in NKT cell anergy in which the cells are unresponsive to subsequent doses of α-GalCer. We show here that α-GalCer delivered as an adjuvant by the intranasal route, as opposed to the intravenous route, enables repeated activation of NKT cells and DCs, resulting in efficient induction of cellular immune responses to co-administered antigens. We show evidence that after intranasal delivery,α-GalCer is selectively presented by DCs for the activation of NKT cells, not B cells. Furthermore, higher levels of PD-1 expression, a potential marker for functional exhaustion of the NKT cells when α-GalCer is delivered by the intravenous route, are not observed after intranasal delivery. These results support a mucosal route of delivery for the utility of α-GalCer as an adjuvant for vaccines, which often requires repeated dosing to achieve durable protective immunity.     

Neurodegenerative phenotypes in an A53T α-synuclein transgenic mouse model are independent of LRRK2

Mutations in the genes encoding LRRK2 and α-synuclein cause autosomal dominant forms of familial Parkinson's disease (PD). Fibrillar forms of α-synuclein are a major component of Lewy bodies, the intracytoplasmic proteinaceous inclusions that are a pathological hallmark of idiopathic and certain familial forms of PD. LRRK2 mutations cause late-onset familial PD with a clinical, neurochemical and, for the most part, neuropathological phenotype that is indistinguishable from idiopathic PD. Importantly, α-synuclein-positive Lewy bodies are the most common pathology identified in the brains of PD subjects harboring LRRK2 mutations. These observations may suggest that LRRK2 functions in a common pathway with α-synuclein to regulate its aggregation. To explore the potential pathophysiological interaction between LRRK2 and α-synuclein in vivo, we modulated LRRK2 expression in a well-established human A53T α-synuclein transgenic mouse model with transgene expression driven by the hindbrain-selective prion protein promoter. Deletion of LRRK2 or overexpression of human G2019S-LRRK2 has minimal impact on the lethal neurodegenerative phenotype that develops in A53T α-synuclein transgenic mice, including premature lethality, pre-symptomatic behavioral deficits and human α-synuclein or glial neuropathology. We also find that endogenous or human LRRK2 and A53T α-synuclein do not interact together to influence the number of nigrostriatal dopaminergic neurons. Taken together, our data suggest that α-synuclein-related pathology, which occurs predominantly in the hindbrain of this A53T α-synuclein mouse model, occurs largely independently from LRRK2 expression. These observations fail to provide support for a pathophysiological interaction of LRRK2 and α-synuclein in vivo, at least within neurons of the mouse hindbrain.     

CD4+ T helper cells and regulatory T cells in active lupus nephritis: an imbalance towards a predominant Th1 response?

The objective of this study was to evaluate the frequency of CD4⁺ T cell subsets in peripheral blood mononuclear cells (PBMC), urine and renal tissue from patients with lupus nephritis (LN). PBMC and urinary cells were collected from 17 patients with active LN, 20 disease controls (DC) with primary glomerulonephritis and 10 healthy controls (HC) and were analysed by flow cytometry with markers for T helper type 1 (Th1), Th2, Th17 and regulatory T cells (T_reg) cells. T cell subsets were assessed by immunohistochemistry from LN biopsy specimens from 12 LN patients. T cell subtypes in PBMC were re‐evaluated at 6 months of therapy. CD4⁺ T cells were decreased in PBMC in LN compared with DC and HC (P = 0·0001). No differences were observed in urinary CD4⁺ T cell subsets between LN and DC. The frequency of urinary Th17 cells was higher in patients with non‐proliferative than in proliferative LN (P = 0·041). CD3⁺ and T‐box 21 ( ) cells were found in glomeruli and interstitium of LN patients, while forkhead box protein 3 (FoxP3), retinoid‐related orphan receptor gamma (ROR‐γ) and GATA binding protein 3 (GATA‐3) were present only in glomeruli. Th1 cells in PBMC were correlated negatively with urinary Th1 cells (Rho = –0·531; P = 0·028) and with T_bet in renal interstitium (Rho = –0·782; P = 0·004). At 6 months, LN patients showed an increase in Th17 cells in PBMC. In conclusion, the inverse association between Th1 cells from PBMC and urinary/renal tissue indicate a role for Th1 in LN pathophysiology. Urinary Th17 cells were associated with less severe LN, and Th17 increased in PBMC during therapy. Urinary CD4⁺ T cells were not different between LN and DC.     

Establishment of an animal model of open tibial fractures with infection in New Zealand rabbits北大核心

BACKGROUND: Open facture is easy to induce infection, which is an urgent problem in clinic. Establishing a reliable animal model of open fracture with infection is of great significance for drug and instrument development and application. OBEJCTIVE: To develop an open fracture with infection model in New Zealand white rabbits, and to identify the available number of bacteria that can cause infection. METHODS: The amount of bacteria was determined by establishing open fracture structure and verifying the concentration of bacterial colonies. Thirty New Zealand white rabbits were randomly divided into control group and four experimental groups, and a transverse fracture at the middle part of tibia was established in all rabbits, followed by the injection of 1 mL of normal saline or 1mL of Staphylococcus aureus suspension at the concentrations of 1×105, 1×106, 5×106, and 1×107 CFU/mL. Afterwards, the optimal concentration of 1 mL of bacteria liquid causing infection was determined by gross observation, body temperature analysis and body mass measurement, white blood cell and C-reactive protein detection, bacterial culture and pathological observation. RESULTS AND CONCLUSION: Rabbits in the 5×106 CFU/mL group were all infected and had higher survival rate. In the 1×105 and 1×106 CFU/mL groups, some rabbits showed no infection. One rabbit died due to infection in the 1×107 CFU/mL group. In summary, the reliable infection model of open fracture can be induced by injected with 1 mL of Staphylococcus aureus at the concentration of 5×106 CFU/mL in New Zealand white rabbits, which can be used as an effective model to guide drugs and instruments related anti-infective research. © 2018, Journal of Clinical Rehabilitative Tissue Engineering Research. All rights reserved.