IL-12- and IL-23-induced T helper cell subsets: birds of the same feather flock together

Preliminary Investigation and Therapeutic Efficacy Determination of a Novel Anti-IL-17A Antibody, Indikizumab

Purpose

The study aimed to develop and characterize Indikizumab, a novel humanized anti-IL-17A monoclonal antibody (mAb), for potential therapeutic use in inflammatory indications such as psoriasis, psoriatic arthritis, rheumatoid arthritis, and ankylosing spondylitis.

Methods

The research involved the purification of IL-17 isoforms, epitope mapping, affinity ranking, and comparative binding assessment of anti-IL-17 antibodies. The study also included cell-based neutralization assays and in vivo studies using mouse models to evaluate the efficacy of Indikizumab.

Results

Indikizumab demonstrated a high binding affinity (KD=27.2 pM) and specificity for IL-17A, with comparable potency to Secukinumab. In cell-based neutralization assays, Indikizumab effectively neutralized the effects of IL-17A and demonstrated a statistically significant reduction in plasma KC (Keratinocyte) levels in a mouse model. In imiquimod-induced psoriasis mouse model, Indikizumab showed potential in reducing the psoriasis index.

Conclusion

Indikizumab represents a promising therapeutic option for inflammatory indications with its high binding affinity, specificity for IL-17A, and effectiveness in neutralizing IL-17A effects in vivo.

An intestinal TH17 cell-derived subset can initiate cancer

Approximately 25% of cancers are preceded by chronic inflammation that occurs at the site of tumor development. However, whether this multifactorial oncogenic process, which commonly occurs in the intestines, can be initiated by a specific immune cell population is unclear. Here, we show that an intestinal T cell subset, derived from interleukin-17 (IL-17)-producing helper T (TH17) cells, induces the spontaneous transformation of the intestinal epithelium. This subset produces inflammatory cytokines, and its tumorigenic potential is not dependent on IL-17 production but on the transcription factors KLF6 and T-BET and interferon-γ. The development of this cell type is inhibited by transforming growth factor-β1 (TGFβ1) produced by intestinal epithelial cells. TGFβ signaling acts on the pretumorigenic TH17 cell subset, preventing its progression to the tumorigenic stage by inhibiting KLF6-dependent T-BET expression. This study therefore identifies an intestinal T cell subset initiating cancer.

Th17 Cells, Glucocorticoid Resistance, and Depression

Depression is a severe mental disorder that disrupts mood and social behavior and is one of the most common neuropsychological symptoms of other somatic diseases. During the study of the disease, a number of theories were put forward (monoamine, inflammatory, vascular theories, etc.), but none of those theories fully explain the pathogenesis of the disease. Steroid resistance is a characteristic feature of depression and can affect not only brain cells but also immune cells. T-helper cells 17 type (Th17) are known for their resistance to the inhibitory effects of glucocorticoids. Unlike the inhibitory effect on other subpopulations of T-helper cells, glucocorticoids can enhance the differentiation of Th17 lymphocytes, their migration to the inflammation, and the production of IL-17A, IL-21, and IL-23 in GC-resistant disease. According to the latest data, in depression, especially the treatment-resistant type, the number of Th17 cells in the blood and the production of IL-17A is increased, which correlates with the severity of the disease. However, there is still a significant gap in knowledge regarding the exact mechanisms by which Th17 cells can influence neuroinflammation in depression. In this review, we discuss the mutual effect of glucocorticoid resistance and Th17 lymphocytes on the pathogenesis of depression.

Cutaneous manifestations of inflammatory bowel disease: basic characteristics, therapy, and potential pathophysiological associations

Inflammatory bowel disease (IBD) is a chronic inflammatory disease typically involving the gastrointestinal tract but not limited to it. IBD can be subdivided into Crohn's disease (CD) and ulcerative colitis (UC). Extraintestinal manifestations (EIMs) are observed in up to 47% of patients with IBD, with the most frequent reports of cutaneous manifestations. Among these, pyoderma gangrenosum (PG) and erythema nodosum (EN) are the two most common skin manifestations in IBD, and both are immune-related inflammatory skin diseases. The presence of cutaneous EIMs may either be concordant with intestinal disease activity or have an independent course. Despite some progress in research on EIMs, for instance, ectopic expression of gut-specific mucosal address cell adhesion molecule-1 (MAdCAM-1) and chemokine CCL25 on the vascular endothelium of the portal tract have been demonstrated in IBD-related primary sclerosing cholangitis (PSC), little is understood about the potential pathophysiological associations between IBD and cutaneous EIMs. Whether cutaneous EIMs are inflammatory events with a commonly shared genetic background or environmental risk factors with IBD but independent of IBD or are the result of an extraintestinal extension of intestinal inflammation, remains unclear. The review aims to provide an overview of the two most representative cutaneous manifestations of IBD, describe IBD's epidemiology, clinical characteristics, and histology, and discuss the immunopathophysiology and existing treatment strategies with biologic agents, with a focus on the potential pathophysiological associations between IBD and cutaneous EIMs.

Molecular Mechanisms of T Helper Cell Differentiation and Functional Specialization

Th cells, which orchestrate immune responses to various pathogens, differentiate from naïve CD4 T cells into several subsets that stimulate and regulate immune responses against various types of pathogens, as well as a variety of immune-related diseases. Decades of research have revealed that the fate decision processes are controlled by cytokines, cytokine receptor signaling, and master transcription factors that drive the differentiation programs. Since the Th1 and Th2 paradigm was proposed, many subsets have been added to the list. In this review, I will summarize these events, including the fate decision processes, subset functions, transcriptional regulation, metabolic regulation, and plasticity and heterogeneity. I will also introduce current topics of interest.

TH17 cell heterogeneity and its role in tissue inflammation

Since their discovery almost two decades ago, interleukin-17-producing CD4+ T cells (TH17 cells) have been implicated in the pathogenesis of multiple autoimmune and inflammatory disorders. In addition, TH17 cells have been found to play an important role in tissue homeostasis, especially in the intestinal mucosa. Recently, the use of single-cell technologies, along with fate mapping and various mutant mouse models, has led to substantial progress in the understanding of TH17 cell heterogeneity in tissues and of TH17 cell plasticity leading to alternative T cell states and differing functions. In this Review, we discuss the heterogeneity of TH17 cells and the role of this heterogeneity in diverse functions of TH17 cells from homeostasis to tissue inflammation. In addition, we discuss TH17 cell plasticity and its incorporation into the current understanding of T cell subsets and alternative views on the role of TH17 cells in autoimmune and inflammatory diseases.

Th17 Cells: Orchestrators of Mucosal Inflammation and Potential Therapeutic Targets

T helper 17 (Th17) cells represent a specialized subgroup of effector CD4+ T cells known for their role in provoking neutrophil-driven tissue inflammation, particularly within mucosal tissues. Although they are pivotal for defending the host against extracellular bacteria and fungi, they have also been associated with development of various T cell-mediated inflammatory conditions, autoimmune diseases, and even cancer. Notably, Th17 cells exhibit a dual nature, with different Th17 cell subtypes showcasing distinct effector functions and varying capacities to incite autoimmune tissue inflammation. Furthermore, Th17 cells exhibit significant plasticity, which carries important functional implications, both in terms of their expression of cytokines typically associated with other effector T cell subsets and in their interactions with regulatory CD4+ T cells. The intricate balance of Th17 cytokines can also be a double-edged sword in inflammation, autoimmunity, and cancer. Within this article, we delve into the mechanisms that govern the differentiation, function, and adaptability of Th17 cells. We culminate with an exploration of therapeutic potentials in harnessing the power of Th17 cells and their cytokines. Targeted interventions to modulate Th17 responses are emerging as promising strategies for autoimmunity, inflammation, and cancer treatment. By precisely fine-tuning Th17-related pathways, we may unlock new avenues for personalized therapeutic approaches, aiming to restore immune balance, alleviate the challenges of these disorders, and ultimately enhance the quality of life for individuals affected by them.

Divergent functions of IL-17-family cytokines in DSS colitis: Insights from a naturally-occurring human mutation in IL-17F

The IL-17 family is structurally distinct from other cytokine subclasses. IL-17A and IL-17F, the most closely related of this family, form homodimers and an IL-17AF heterodimer. While IL-17A and IL-17F exhibit similar activities in many settings, in others their functions are divergent. To better understand the function of IL-17F in vivo, we created mice harboring a mutation in Il17f originally described in humans with unexplained chronic mucosal candidiasis (Ser-65-Leu). We evaluated Il17fS65L/S65L mice in DSS-colitis, as this is one of the few settings where IL-17A and IL-17F exhibit opposing activities. Specifically, IL-17A is protective of the gut epithelium, a finding that was revealed when trials of anti-IL-17A biologics in Crohn's disease failed and recapitulated in many mouse models of colitis. In contrast, mice lacking IL-17F are resistant to DSS-colitis, partly attributable to alterations in intestinal microbiota that mobilize Tregs. Here we report that Il17fS65L/S65L mice do not phenocopy Il17f-/- mice in DSS colitis, but rather exhibited a worsening disease phenotype much like Il17a-/- mice. Gut inflammation in Il17fS65L/S65L mice correlated with reduced Treg accumulation and lowered intestinal levels of Clostridium cluster XIV. Unexpectedly, the protective DSS-colitis phenotype in Il17f-/- mice could be reversed upon co-housing with Il17fS65L/S65L mice, also correlating with Clostridium cluster XIV levels in gut. Thus, the Il17fS65L/S65L phenotype resembles an IL-17A deficiency more closely than IL-17F deficiency in the setting of DSS colitis.

Celastrol Regulates the Secretion of Interleukin-17 in Patients with Sympathetic Ophthalmia Through Signal Transducer and Activator of Transcription 3

Purpose: The excessive secretion of interleukin (IL)-17 contributes to the pathological process of sympathetic ophthalmia (SO). Celastrol is a naturally active product and exhibits an immunosuppressive effect. However, whether the supplementation of celastrol relieves SO remains unclear. Methods: The peripheral blood mononuclear cells (PBMCs) were extracted from the venous blood samples of 20 SO patients and 20 healthy controls, followed by stimulating with various concentrations of celastrol. The levels of IL-23 and IL-17 were measured by enzyme-linked immunosorbent assay and real-time polymerase chain reaction assay. The activation of the signal transducer and activator of transcription 3 (STAT3) in PBMCs of SO patients was detected by Western blot. Results: The levels of IL-23 and IL-17 in PBMCs isolated from SO patients were significantly increased compared with those in PBMCs isolated from healthy controls. Celastrol treatment inhibited the production of both IL-23 and IL-17 in PBMCs of SO patients in a dose-dependent manner. In PBMCs isolated from SO patients and healthy controls, the administration of recombinant human IL-23 (rIL-23) enhanced the production of IL-17, which was then suppressed by co-stimulation with celastrol. Also, celastrol treatment reduced rIL-23-induced phosphorylation of STAT3 in PBMCs isolated from SO patients. Conclusions: Celastrol can reduce the production of IL-17 in PBMCs of SO patients. The mechanism may be related to the reduction of IL-23 secretion, which in turn inhibits the phosphorylation of STAT3.

Role of cytokines produced by T helper immune-modulators in dengue pathogenesis: A systematic review and meta-analysis

BACKGROUND AND OBJECTIVES

Modulation of the immune reaction is essential in the development of various diseases, including dengue's "Cytokine Tsunami", an increase in vascular permeability with concomitant severe vascular leakage. We aim to identify the role of T-helper (Th) cells, Th2 and Th7, with their related cytokines in dengue pathogenesis.

MATERIAL AND METHODS

Nine electronic databases and manual search were applied to detect available publications. A meta-analysis using a fixed- or random-effect model was performed to measure standardized mean difference (SMD) with 95% confidence interval (CI). The National Institute of Health (NIH) tools for observational cohort, cross-sectional, and case-control studies were used to examine the risk of bias. The protocol was recorded in PROSPERO with CRD42017060230.

RESULTS

A total of 38 articles were found including 19 case-control, 11 cross-sectional and 8 prospective cohort studies. We indicated that Th2 cytokines (IL-4, IL-6, IL-8) and Th17 cytokine (IL-17) in dengue patients were notably higher than in a healthy control group in acute phase (SMD = 1.59, 95% CI [0.68, 2.51], p = 0.001; SMD = 1.24, 95% CI [0.41, 2.06], p = 0.003; SMD = 1.13, 95% CI [0.61, 1.66], p<0.0001; SMD = 1.74, 95% CI [0.87, 2.61], p<0.0001), respectively.

CONCLUSIONS

This study provides evidence of the significant roles of IL-4, IL-6, IL-8, IL-10 and IL-17 in the pathogenesis of developing a severe reaction in dengue fever. However, to fully determine the association of Th cytokines with dengue, it is necessary to perform further studies to assess kinetic levels during the duration of the illness.

A Two-Step Process of Effector Programming Governs CD4+ T Cell Fate Determination Induced by Antigenic Activation in the Steady State

Various processes induce and maintain immune tolerance, but effector T cells still arise under minimal perturbations of homeostasis through unclear mechanisms. We report that, contrary to the model postulating primarily tolerogenic mechanisms initiated under homeostatic conditions, effector programming is an integral part of T cell fate determination induced by antigenic activation in the steady state. This effector programming depends on a two-step process starting with induction of effector precursors that express Hopx and are imprinted with multiple instructions for their subsequent terminal effector differentiation. Such molecular circuits advancing specific terminal effector differentiation upon re-stimulation include programmed expression of interferon-γ, whose production then promotes expression of T-bet in the precursors. We further show that effector programming coincides with regulatory conversion among T cells sharing the same antigen specificity. However, conventional type 2 dendritic cells (cDC2) and T cell functions of mammalian target of rapamycin complex 1 (mTORC1) increase effector precursor induction while decreasing the proportion of T cells that can become peripheral Foxp3⁺ regulatory T (pTreg) cells.

The mechanisms in the steady state that govern the formation of effector T cells with potentially autoimmune functions remain unclear. Opejin et al. reveal a two-step process starting with induction of effector precursors that express Hopx and are imprinted with multiple instructions for their subsequent terminal effector differentiation.

Cytokines and transcription factors in the differentiation of CD4+ T helper cell subsets and induction of tissue inflammation and autoimmunity

CD4⁺T helper (Th) cells are critical in homeostasis and host defense but are also central to the development of various autoimmune diseases if they become dysregulated. Specifically, pathogenic Th1 and Th17 cells contribute to autoimmune inflammation whereas Treg and Tr1 cells are important for maintaining immune tolerance and resolution of inflammation, respectively. Cytokines trigger signaling pathways in naive T cells that induce lineage-defining transcription factors that direct their differentiation into the distinct T helper cell subsets. It has become clear that the differentiation of T helper cells is not only influenced by the cytokine milieu but also by their metabolic state, cues from the microbiota and the tissue they reside in. A comprehensive understanding how these various stimuli contribute to T helper cell differentiation and phenotype could potentially provide novel ways for therapeutic intervention in autoimmunity and tissue inflammation.

Transcriptomic profiling of bovine blood dendritic cells and monocytes following TLR stimulation

Dendritic cells (DC) and monocytes are vital for the initiation of innate and adaptive immune responses. Recently, we identified bona fide DC subsets in blood of cattle, revealing subset- and species-specific transcription of toll-like receptors (TLR). In the present study, we analyzed phenotypic and transcriptional responses of bovine DC subsets and monocytes to in vitro stimulation with four to six different TLR ligands. Bovine DC subsets, especially plasmacytoid DC (pDC), showed a clear increase of CCR7, CD25, CD40, CD80, CD86, and MHC-II expression both on mRNA and protein level. Flow cytometric detection of p38 MAPK phosphorylation 15 min after stimulation confirmed activation of DC subsets and monocytes in accordance with TLR gene expression. Whole-transcriptome sequencing of sorted and TLR-stimulated subsets revealed potential ligand- and subset-specific regulation of genes associated with inflammation, T-cell co-stimulation, migration, metabolic reprogramming, and antiviral activity. Gardiquimod was found to evoke strong responses both in DC subsets and monocytes, while Poly(I:C) and CpG preferentially triggered responses in cDC1 and pDC, respectively. This in-depth analysis of ligand responsiveness is essential for the rational design of vaccine adjuvants in cattle, and provides a solid basis for comparative studies on DC and monocyte biology across species.

Intermediate Monocytes and Cytokine Production Associated With Severe Forms of Chagas Disease

Monocytes are classified according to their CD14 and CD16 expression into classical (reparative), intermediate (inflammatory), and non-classical. This study assessed the frequency of monocyte and the relationship between monocyte subset percentages and the levels of blood cytokines in Colombian chagasic patients with different clinical forms. This study included chagasic patients in different clinical stages: indeterminate (IND) n = 14, chronic chagasic cardiomyopathy (CCC) n = 14, and heart transplant chagasic (HTCC) n = 9; controls with non-chagasic cardiopathy (NCC) n = 15, and healthy individuals (HI) n = 15. Peripheral blood mononuclear cells (PBMCs) were isolated, labeled for CD14, CD16, and HLA-DR, and analyzed by flow cytometry. Cytokines were measured with a bead-based immunoassay. Percentages of total CD14+ CD16+ and CD14+ HLA-DR+ monocytes were higher in patients with heart involvement (CCC, HTCC, and NCC) than controls. Percentages of intermediate monocytes increased in symptomatic chagasic patients (CCC and HTCC) compared to asymptomatic chagasic patients (IND) and controls (HI). Asymptomatic chagasic patients (IND) had higher percentages of classical monocytes, an increased production of CCL17 chemokine compared to chagasic symptomatic patients (CCC), and their levels of CCL17 was positively correlated with the percentage of classical monocyte subset. In CCC, the percentages of intermediate and classical monocytes were positively correlated with IL-6 levels, which were higher in this group compared to HI, and negatively with IL-12p40 concentration, respectively. Remarkably, there also was an important increased of classical monocytes frequency in three chronic chagasic patients who underwent cardiac transplant, of which one received anti-parasitic treatment. Our findings suggest that cardiac chagasic patients have an increased percentage of inflammatory monocytes and produce more IL-6, a biomarker of heart failure and left ventricular dysfunction, whereas asymptomatic chagasic individuals present a higher percentage of reparative monocytes and CCL17.

Interleukin-12 and -23 blockade mitigates elastase-induced abdominal aortic aneurysm

Macrophages play an important role in the inflammatory process that contributes to the development of abdominal aortic aneurysm (AAA). Studies of human and mouse AAA tissue reveal expanded populations of macrophages producing an abundance of pro-inflammatory cytokines, including TNF-α, IL-12p40 and high level of metalloprotease 9 (MMP-9) at the late stages of disease. Herein, we show that blockade of IL-12p40 in the early phase of aneurysm development suppresses macrophage expansion, inflammatory cytokine and MMP-9 production and mitigates AAA development. Since IL-12 and IL-23 are related cytokines that share the common p40 subunit, we also evaluate the effect of direct IL-23 blockade on the development of AAA. Specific IL-23p19 blockade prevents AAA progression with the same efficiency as IL-12p40 antagonism, suggesting that the efficacy of anti-IL-12p40 treatment may reflect IL-23 blockade. IL-12p40 and IL-23p19 are also abundantly expressed in human AAA tissue. Our findings have potential translational value since IL-12p40 and IL-23p19 antagonists already exist as FDA-approved therapeutics for various chronic inflammatory conditions.

The IL-23/IL-17 pathway in human chronic inflammatory diseases-new insight from genetics and targeted therapies

Chronic inflammatory diseases such as rheumatoid arthritis, inflammatory bowel disease, spondyloarthritis, and psoriasis cause significant morbidity and are a considerable burden for the patients in terms of pain, impaired function, and diminished quality of life, as well as for society, because of the associated high health-care costs and loss of productivity. Our limited understanding of the pathogenic mechanisms involved in these diseases currently hinders early diagnosis and the development of more specific and effective therapies. The past years have been marked by considerable progress in our insight of the genetic basis of many diseases. In particular, genome-wide association studies (GWAS) performed with thousands of patients have provided detailed information about the genetic variants associated with a large number of chronic inflammatory diseases. These studies have brought to the forefront many genes linked to signaling pathways that were not previously known to be involved in pathogenesis, pointing to new directions in the study of disease mechanisms. GWAS also provided fundamental evidence for a key role of the immune system in the pathogenesis of these diseases, because many of the identified loci map to genes involved in different immune processes. However, the mechanisms by which disease-associated genetic variants act on disease development and the targeted cell populations remain poorly understood. The challenge of the post-GWAS era is to understand how these variants affect pathogenesis, to allow translation of genetic data into better diagnostics and innovative treatment strategies. Here, we review recent results that document the importance of the IL-23/IL-17 pathway for the pathogenesis of several chronic inflammatory diseases and summarize data that demonstrate how therapeutic targeting of this pathway can benefit affected patients.

Association of TNF, IL12, and IL23 gene polymorphisms and psoriatic arthritis: meta-analysis

BACKGROUND

Psoriatic arthritis (PsA) is a chronic skin and joint condition that considerably affects patient quality of life. Several studies have demonstrated different associations of genetic polymorphisms in the pathogenic process of PsA. Therefore, we conducted a meta-analysis to estimate the effect of polymorphisms in the cytokines TNF, IL12B, IL23A, and IL23R on PsA risk.

METHODS

We screened 1,097 abstracts and identified 14 relevant studies published between January 2007 and December 2017. A systematic search was conducted in PubMed, Web of Knowledge and Scopus databases. Meta-analyses were performed for the comparisons of alleles and multiple genetic models.

RESULTS

Among the cytokines studied, we found 17 polymorphisms that were the most investigated. The association to PsA was observed in the presence of polymorphisms: TNF-238 G > A (rs361525), -308 G > A (rs1800629), and -857 C > T (rs1799724); IL12B C > G (rs6887695) and A > C (rs3212227); IL23A A > G (rs2066808) and IL23R G > A (rs11209026).

CONCLUSION

Our findings suggest that these variant cytokine genes may strongly influence the immunological response of PsA.

Multilayer regulation of CD4 T cell subset differentiation in the era of single cell genomics

CD4 T cells are major immune cell types that mediate effector responses appropriate for diverse incoming threats. These cells have been categorized into different subsets based on how they are induced, expression of specific master transcription factors, and the resulting effector cell phenotypes as defined by expression of signature cytokines. However, recent studies assessing the expression of gene modules in single CD4 T cells, rather than expression of one or a few signature genes, have provided a more complex picture in which the canonical model does not fit as cleanly as proposed. Here, we review the concepts of lineage commitment, plasticity and functional heterogeneity in the context of this greater complexity. We then apply our current understanding of CD4 T cell subsets to discuss outstanding questions regarding follicular helper T cells and follicular regulatory T cells with respect to their shared features with other known CD4 T cell subsets.

Androgen receptor moonlighting in the prostate cancer microenvironment

Androgen receptor (AR) signaling is vital for the normal development of the prostate and is critically involved in prostate cancer (PCa). AR is not only found in epithelial prostate cells but is also expressed in various cells in the PCa-associated stroma, which constitute the tumor microenvironment (TME). In the TME, AR is expressed in fibroblasts, macrophages, lymphocytes and neutrophils. AR expression in the TME was shown to be decreased in higher-grade and metastatic PCa, suggesting that stromal AR plays a protective role against PCa progression. With that, the functionality of AR in stromal cells appears to deviate from the receptor's classical function as described in PCa cells. However, the biological action of AR in these cells and its effect on cancer progression remains to be fully understood. Here, we systematically review the pathological, genomic and biological literature on AR actions in various subsets of prostate stromal cells and aim to better understand the consequences of AR signaling in the TME in relation to PCa development and progression.

Enrichment of IL-17A+ IFN-γ+ and IL-22+ IFN-γ+ T cell subsets is associated with reduction of NKp44+ ILC3s in the terminal ileum of Crohn's disease patients

Crohn's disease (CD) is a chronic inflammatory condition of the human gastrointestinal tract whose aetiology remains largely unknown. Dysregulated adaptive immune responses and defective innate immunity both contribute to this process. In this study, we demonstrated that the interleukin (IL)-17A+ interferon (IFN)-γ+ and IL-22+ IFN-γ+ T cell subsets accumulated specifically in the inflamed terminal ileum of CD patients. These cells had higher expression of Ki-67 and were active cytokine producers. In addition, their proportions within both the IL-17A-producer and IL-22-producer populations were increased significantly. These data suggest that IL-17A+ IFN-γ+ and IL-22+ IFN-γ+ T cell subsets might represent the pathogenic T helper type 17 (Th17) population in the context of intestinal inflammation for CD patients. In the innate immunity compartment we detected a dramatic alteration of both phenotype and function of the intestinal innate lymphoid cells (ILCs), that play an important role in the maintenance of mucosal homeostasis. In the inflamed gut the frequency of the NKp44- CD117- ILC1s subset was increased significantly, while the frequency of NKp44+ ILC3s was reduced. Furthermore, the frequency of human leucocyte antigen D-related (HLA-DR)-expressing-NKp44+ ILC3s was also reduced significantly. Interestingly, the decrease in the NKp44+ ILC3s population was associated with an increase of pathogenic IL-17A+ IFN-γ+ and IL-22+ IFN-γ+ T cell subsets in the adaptive compartment. This might suggest a potential link between NKp44+ ILC3s and the IL-17A+ IFN-γ+ and IL-22+ IFN-γ+ T cell subsets in the terminal ileum of CD patients.

Estradiol enhances capacity of TLR-matured splenic dendritic cells to polarize CD4+ lymphocytes into IL-17/GM-CSF-producing cells in vitro

There are little data on modulatory effects of estrogens on rat dendritic cell (DC) responses to inflammatory stimuli, and consequently their ability to activate and polarize CD4+ T lymphocyte-mediated immune responses. Splenic conventional DCs from young female Albino Oxford rats were activated in vitro with LPS (TLR4 agonist) or R848 (TLR7/8 agonist) in the presence and absence of 17β-estradiol (E2), and their allostimulatory and CD4+ lymphocyte polarizing ability in mixed leukocyte culture (MLC) were studied. Irrespective of the E2 presence, LPS and R848 up-regulated the expression of MHC II on DCs, so they exhibited enhanced allostimulatory capacity in co-culture with CD4+ lymphocytes. On the other hand, E2 promoted stimulatory action of both TLRs on OX62+ DC IL-23 production, augmented their stimulatory effects on IL-6 and IL-1β production, but diminished their enhancing effects on the expression IL-10 and IL-27 by DCs. Consequently, in MLC, OX62+ DCs activated/matured in the co-presence of E2 and either LPS or R848 increased the levels of IL-17, the signature Th17 cell cytokine, when compared with those activated/matured in the absence of E2. GM-CSF levels were also increased in these MLC. Given that the expression of IL-7 mRNA was diminished in DCs activated/matured in the co-presence of E2 and TLR, this increase most likely did not reflect enhanced differentiation of Th cells producing GM-CSF only (Th-GM).

CONCLUSIONS

E2 augments capacity of LPS- and R848-activated/matured DCs from young rat spleen to induce differentiation of IL-17- and GM-CSF-producing cells.

Protective effect of antigen delivery using monoolein-based liposomes in experimental hematogenously disseminated candidiasis

We evaluated the potential of a liposomal antigen delivery system (ADS) containing Candida albicans cell wall surface proteins (CWSP) in mediating protection against systemic candidiasis. Treatment of bone-marrow-derived dendritic cells with CWSP-loaded dioctadecyldimethylammonium bromide:monoolein (DODAB:MO) liposomes enhanced and prolonged their activation comparatively to free antigen, indicating that liposome-entrapped CWSP were released more sustainable. Therefore, we immunized mice with CWSP either in a free form or loaded into two different DODAB:MO liposome formulations, respectively designated as ADS1 and ADS2, prior to intravenous C. albicans infection. Immunization with ADS1, but not with ADS2, conferred significant protection to infected mice, comparatively to immunization with CWSP or empty liposomes as control. ADS1-immunized mice presented significantly higher serum levels of C. albicans-specific antibodies that enhanced phagocytosis of this fungus. In these mice, a mixed cytokine production profile was observed encompassing IFN-γ, IL-4, IL-17A and IL-10. Nevertheless, only production of IL-4, IL-17 and IL-10 was higher than in controls. In this study we demonstrated that DODAB:MO liposomes enhance the immunogenicity of C. albicans antigens and host protection in a murine model of systemic candidiasis. Therefore, this liposomal adjuvant could be a promising candidate to assess in vaccination against this pathogenic fungus.

STATEMENT OF SIGNIFICANCE

This work describes the immunomodulation capacity of the previously validated antigen delivery system (ADS) composed by dioctadecyldimethylammonium bromide (DODAB) and monoolein (MO) lipids incorporating the cell wall surface proteins (CWSP) from C. albicans. Here, we not only present the ability of this system in facilitating antigen uptake by DCs in vitro, but also that this system induces higher levels of pro-inflammatory cytokines and opsonizing specific IgG antibodies in serum of mice immunized subcutaneously. We show that the ADS are efficient nanocarrier and modulate the immune response against intravenous C. albicans infection favoring mouse protection. In sum, we show that the incorporation of C. albicans antigens in DODAB:MO nanocarries are a promising vaccine strategy against C. albicans fungal infection.

RBPJ Controls Development of Pathogenic Th17 Cells by Regulating IL-23 Receptor Expression

Interleukin-17 (IL-17)-producing helper T cells (Th17 cells) play an important role in autoimmune diseases. However, not all Th17 cells induce tissue inflammation or autoimmunity. Th17 cells require IL-23 receptor (IL-23R) signaling to become pathogenic. The transcriptional mechanisms controlling the pathogenicity of Th17 cells and IL-23R expression are unknown. Here, we demonstrate that the canonical Notch signaling mediator RBPJ is a key driver of IL-23R expression. In the absence of RBPJ, Th17 cells fail to upregulate IL-23R, lack stability, and do not induce autoimmune tissue inflammation in vivo, whereas overexpression of IL-23R rescues this defect and promotes pathogenicity of RBPJ-deficient Th17 cells. RBPJ binds and trans-activates the Il23r promoter and induces IL-23R expression and represses anti-inflammatory IL-10 production in Th17 cells. We thus find that Notch signaling influences the development of pathogenic and non-pathogenic Th17 cells by reciprocally regulating IL-23R and IL-10 expression.

(p40)2-Fc reduces immune-inflammatory response through the activation of T cells in collagen induced arthritis mice

IL-12p40 homodimer, a natural antagonist of IL-12 and IL-23, performs an important role in the expression of proinflammatory cytokines that is essential for Th1 and Th17 immune responses. Here, we reveal the therapeutic and immunosuppressive effect of the IL-12p40 subunit ((p40)2-Fc) in an experimental autoimmune arthritis model. We hypothesized that (p40)2-Fc may reduce the inflammatory response and the activation of T cells. In this study, we intraperitoneally injected (p40)2-Fc into collagen induced arthritis (CIA) mice to identify whether (p40)2-Fc attenuates CIA severity. (p40)2-Fc reduced the development of CIA, joint inflammation and cartilage destruction. (p40)2-Fc also significantly decreased the concentration of serum immunoglobulin as well as the number of T cells and C II specific T cells. In addition, osteoclastogenesis in (p40)2-Fc treated mice was down-regulated compared to the mice treated with (p40)2-Fc control. We observed that (p40)2-Fc treatment alleviates arthritis in mice with CIA, reducing inflammation and osteoclast differentiation. These findings suggest that (p40)2-Fc can be a potential therapeutic approach for autoimmune arthritis.

Antigenic Stimulation of Kv1.3-Deficient Th Cells Gives Rise to a Population of Foxp3-Independent T Cells with Suppressive Properties

Multiple sclerosis (MS) is an immune-mediated demyelinating disease of the CNS that has been linked with defects in regulatory T cell function. Therefore, strategies to selectively target pathogenic cells via enhanced regulatory T cell activity may provide therapeutic benefit. Kv1.3 is a voltage-gated potassium channel expressed on myelin-reactive T cells from MS patients. Kv1.3-knockout (KO) mice are protected from experimental autoimmune encephalomyelitis, an animal model of MS, and Kv1.3-KO Th cells display suppressive capacity associated with increased IL-10. In this article, we demonstrate that myelin oligodendrocyte glycoprotein-specific Kv1.3-KO Th cells exhibit a unique regulatory phenotype characterized by high CD25, CTLA4, pSTAT5, FoxO1, and GATA1 expression without a corresponding increase in Foxp3. These phenotypic changes result from increased signaling through IL-2R. Moreover, myelin oligodendrocyte glycoprotein-specific Kv1.3-KO Th cells can ameliorate experimental autoimmune encephalomyelitis following transfer to wild-type recipients in a manner that is partially dependent on IL-2R and STAT5 signaling. The present study identifies a population of Foxp3(-) T cells with suppressive properties that arises in the absence of Kv1.3 and enhances the understanding of the molecular mechanism by which these cells are generated. This increased understanding could contribute to the development of novel therapies for MS patients that promote heightened immune regulation.

CXCL11-dependent induction of FOXP3-negative regulatory T cells suppresses autoimmune encephalomyelitis

A single G protein-coupled receptor (GPCR) can activate multiple signaling cascades based on the binding of different ligands. The biological relevance of this feature in immune regulation has not been evaluated. The chemokine-binding GPCR CXCR3 is preferentially expressed on CD4+ T cells, and canonically binds 3 structurally related chemokines: CXCL9, CXCL10, and CXCL11. Here we have shown that CXCL10/CXCR3 interactions drive effector Th1 polarization via STAT1, STAT4, and STAT5 phosphorylation, while CXCL11/CXCR3 binding induces an immunotolerizing state that is characterized by IL-10(hi) (Tr1) and IL-4(hi) (Th2) cells, mediated via p70 kinase/mTOR in STAT3- and STAT6-dependent pathways. CXCL11 binds CXCR3 with a higher affinity than CXCL10, suggesting that CXCL11 has the potential to restrain inflammatory autoimmunity. We generated a CXCL11-Ig fusion molecule and evaluated its use in the EAE model of inflammatory autoimmune disease. Administration of CXCL11-Ig during the first episode of relapsing EAE in SJL/J mice not only led to rapid remission, but also prevented subsequent relapse. Using GFP-expressing effector CD4+ T cells, we observed that successful therapy was associated with reduced accumulation of these cells at the autoimmune site. Finally, we showed that very low doses of CXCL11 rapidly suppress signs of EAE in C57BL/6 mice lacking functional CXCL11.

Measurement of IL-12 (p40, p35), IL-23p19, and IFN-γ mRNA in duodenal biopsies of cats with inflammatory enteropathy

Background

Dietary hypersensitivity and inflammatory bowel disease (IBD) are important causes of chronic vomiting and diarrhea in cats. IL‐23 has been recently found to be a key factor in the immunopathogenesis of IBD in humans but the involvement in IBD has not been investigated in cats.

Hypothesis/Objectives

Expression of genes encoding Il‐12p35 and p40, IL‐23p19, and IFN‐γ may be up‐regulated in duodenal biopsy specimens taken from cats with histologic evidence of inflammation.

Animals and Methods

Duodenal biopsy specimens were collected from control cats (n = 21) and cats with inflammatory enteropathy (n = 13). Routine histopathology, immunohistochemistry (IHC), and qRT‐PCR were used to assess expression of MHC class II and to measure gene transcripts encoding the p35, p40, and p19 subunits of the IL‐12 family of cytokines and IFN‐γ.

Results

There were significant differences in expression of mRNA encoding IL‐12p35 and IL‐23p19 between healthy cats and cats with inflammatory enteropathy. IL‐12p35 mRNA was lower in the duodenal mucosa of cats with inflammatory enteropathy compared with the mucosa of healthy cats (P = .001). In contrast, IL‐23p19 mRNA expression was higher in duodenal biopsy specimens from cats with inflammatory enteropathy than in those from healthy controls (P = .001). There was no difference in expression of IL‐12p40 and IFN‐γ mRNA (P > .05). The majority of cats with inflammatory enteropathy had histologic evidence of moderate to severe colitis (score 2).

Conclusions and Clinical Importance

The results of this preliminary study suggest that IL‐23 plays a role in the pathogenesis of feline inflammatory enteropathy.

Recent advances in understanding the molecular mechanisms of the development and function of Th17 cells

IL-17-producing T helper (Th17) cells comprise a distinct Th subset involved in epithelial cell- and neutrophil-mediated immune responses against extracellular microbes. At the same time, Th17 cells play significant roles in the development of autoimmune diseases including rheumatoid arthritis and multiple sclerosis. Since the identification of Th17 cells approximately a decade ago, the molecular mechanisms of their differentiation have been intensively studied and a number of signaling cascades and transcription factors have been shown to be involved. Here, we review the current knowledge regarding the function of Th17 cells in vivo as well as several key concepts for the molecular mechanisms of Th17 differentiation. We also discuss the emerging roles of phosphoinositide 3-kinase (PI3K), mammalian target of rapamycin complex 1 (mTORC1) and hypoxia-inducible factor 1 (HIF-1) in the differentiation of Th17 cells.

Vibrio cholerae O395 outer membrane vesicles modulate intestinal epithelial cells in a NOD1 protein-dependent manner and induce dendritic cell-mediated Th2/Th17 cell responses

Like other Gram-negative pathogens, Vibrio cholerae, the causative agent of the diarrheal disease cholera, secretes outer membrane vesicles (OMVs). OMVs are complex entities composed of a subset of envelope lipid and protein components and play a role in the delivery of effector molecules to host cells. We previously showed that V. cholerae O395 cells secrete OMVs that are internalized by host cells, but their role in pathogenesis has not been well elucidated. In the present study, we evaluated the interaction of OMVs with intestinal epithelial cells. These vesicles induced expression of proinflammatory cytokines such as IL-8 and GM-CSF and chemokines such as CCL2, CCL20, and thymic stromal lymphopoietin in epithelial cells through activation of MAPK and NF-κB pathways in NOD1-dependent manner. Epithelial cells stimulated with OMVs activated dendritic cells (DCs) in a direct co-culture system. Activated DCs expressed high levels of co-stimulatory molecules; released inflammatory cytokines IL-1β, IL-6, TNF-α, and IL-23 and chemokines CCL22 and CCL17; and subsequently primed CD4(+) T cells leading to IL-4, IL-13, and IL-17 expression. These results suggest that V. cholerae O395 OMVs modulate the epithelial proinflammatory response and activate DCs, which promote T cell polarization toward an inflammatory Th2/Th17 response.

Expression of Th17 cells in breast cancer tissue and its association with clinical parameters

Th17 cells are newly identified effector CD4(+) T cells, which play an active role in inflammation and autoimmune diseases and may be relevant for anti-tumor defenses. In the present study, we examined expression of Th17 cells in specimens of breast cancer tissue and its association with clinical, pathology, and immunological parameters. Expression rates of Th17 and T regulatory (Treg) cells in breast cancer and normal (i.e. non-cancerous) tissue were evaluated using flow cytometry in 30 patients with breast carcinoma. Further, expression of interleukin-17 (IL-17), interleukin-1β (IL-1β), and interleukin-6 (IL-6) in breast cancer tissue was evaluated by immunohistochemical staining. Associations between Th17 expression and other parameters were analyzed by multiple linear regression analysis. We observed that expression of Th17 cells was significantly higher in breast cancer compared to normal breast tissue. Further, expressions of IL-17, IL-1β, and IL-6 in cancer tissue positively correlated with expression of Th17 cells. In addition, there was a negative association between the numbers of Th17 cells and TNM stage, blood vessel invasion, and increased numbers of metastatic lymph nodes. Finally, expression of Th17 was not associated with expression of Treg. In conclusion, Th17 cells appear to be involved in anti-tumor immune responses and are associated with a more favorable prognosis.

Coronin 1A is an essential regulator of the TGFβ receptor/SMAD3 signaling pathway in Th17 CD4(+) T cells

Transforming growth factor β (TGFβ) plays a central role in maintaining immune homeostasis by regulating the initiation and termination of immune responses and thus preventing the development of autoimmune diseases. In this study, we describe an essential mechanism by which the actin regulatory protein Coronin 1A (Coro1A) ensures the proper response of Th17 CD4(+) T cells to TGFβ. Coro1A has been established as a key player in T cell survival, migration, activation, and Ca(2+) regulation in naive T cells. We show that mice lacking Coro1a developed less severe experimental autoimmune encephalomyelitis (EAE). Unexpectedly, upon the re-induction of EAE, Coro1a(-/-) mice exhibited enhanced EAE signs that correlated with increased numbers of IL-17 producing CD4(+) cells in the central nervous system (CNS) compared to wild-type mice. In vitro differentiated Coro1a(-/-) Th17 CD4(+) T cells consistently produced more IL-17 than wild-type cells and displayed a Th17/Th1-like phenotype in regard to the expression of the Th1 markers T-bet and IFNγ. Mechanistically, the Coro1a(-/-) Th17 cell phenotype correlated with a severe defect in TGFβR-mediated SMAD3 activation. Taken together, these data provide experimental evidence of a non-redundant role of Coro1A in the regulation of Th17 CD4(+) cell effector functions and, subsequently, in the development of autoimmunity.

Interleukin-23 as a potential therapeutic target for rheumatoid arthritis

Cytokine-mediated immunity plays a crucial role in the pathogenesis of various autoimmune diseases, including rheumatoid arthritis (RA). Increasing evidence has revealed the importance of IL-23, which closely resembles IL-12 structurally and immunologically, in linking innate and adaptive immunity. IL-23, a newly identified heterodimeric pro-inflammatory cytokine, is composed of a p40 subunit in common with IL-12 and a unique p19 subunit. Recent evidence suggests that IL-23, rather than IL-12, is the crucial factor in the pathogenesis of various immune-mediated disorders. In addition, recent studies have explored the role of IL-23 in patients with RA. An elevated expression of IL-23 has been demonstrated in the synovial fibroblasts and plasma of patients with RA. Moreover, an association between IL-23 and IL-23R polymorphisms with susceptibility to RA has been reported. Therefore, the targeting of IL-23 or the IL-23 receptor has been proposed as a potential therapeutic approach for RA. In this review we will discuss the biological features of IL-23, and summarize recent advances in our understanding of the role of IL-23 in the pathogenesis and treatment of RA.

Transcription factor IRF8 directs a silencing programme for TH17 cell differentiation

T_H17 cells are recognized as a unique subset of T helper cells that have critical roles in the pathogenesis of autoimmunity and tissue inflammation. Although RORγt is necessary for the generation of T_H17 cells, the molecular mechanisms underlying the functional diversity of T_H17 cells are not fully understood. Here we show that a member of interferon regulatory factor (IRF) family of transcription factors, IRF8, has a critical role in silencing T_H17-cell differentiation. Mice with a conventional knockout, as well as a T cell-specific deletion, of the Irf8 gene exhibited more efficient T_H17 cells. Indeed, studies of an experimental model of colitis showed that IRF8 deficiency resulted in more severe inflammation with an enhanced T_H17 phenotype. IRF8 was induced steadily and inhibited T_H17-cell differentiation during T_H17 lineage commitment at least in part through its physical interaction with RORγt. These findings define IRF8 as a novel intrinsic transcriptional inhibitor of T_H17-cell differentiation.

The molecular mechanisms that regulate T_H17 cell diversity are poorly understood. Ouyang et al. show that the transcription factor interferon regulatory factor-8 is required for T_H17-cell differentiation and that its absence increases the severity of an experimental model of colitis.

Expression of IL-23/Th17 pathway in a murine model of Coxsackie virus B3-induced viral myocarditis

Background

The IL-23/Th17 pathway is implicated in the pathogenesis of a number of chronic inflammatory and autoimmune diseases. Whether it regulates the viral myocarditis (VMC) is unknown.

Results

To examine the pathogenesis role of IL-23/Th17 axis in VMC, we used male BALB/c mice to induced VMC by Coxsackie virus B3 (CVB3) peritoneal injection. IL-23, IL-17, and signal transducer and activator of transcription 3 (STAT3) mRNA in the myocardium of VMC mice were assessed by semi-quantitative RT-PCR. IL-23 and IL-17 protein from blood serum were evaluated by ELISA. Phosphorylated-STAT3 (p-STAT3) protein expression in the myocardium was evaluated by immunohistochemical staining. Flow cytometric analysis was used to evaluate the frequencies of Th17 subsets. Isolated CD4⁺ T cells from VMC mice were cultured with recombinant IL-23(rIL-23) in vitro. In addition, a STAT3-specific inhibitor (S3I-201) was used to test whether regulation of STAT3 could be partly responsible for Th17 diminution. Results showed that expression of IL-23, IL-17, STAT3 mRNA and protein increased in VMC mice. When purified CD4⁺ T cells derived from VMC mice were cultured in vitro with rIL-23, the frequency of Th17 cells was dramatically increased, accompanied by significantly enhanced production of IL-17 in the supernatants of cultured CD4⁺ T cells. S3I-201 significantly restrained Th17 cell proliferation.

Conclusions

The IL-23/Th17 pathway axis is strongly expressed in murine VMC, identifying a novel pathway of potential significance in viral myocarditis.

Fate mapping of IL-17-producing T cells in inflammatory responses

Here we describe a reporter mouse strain designed to map the fate of cells that have activated interleukin 17A (IL-17A). We found that IL-17-producing helper T cells (T(H)17 cells) had distinct plasticity in different inflammatory settings. Chronic inflammatory conditions in experimental autoimmune encephalomyelitis (EAE) caused a switch to alternative cytokines in T(H)17 cells, whereas acute cutaneous infection with Candida albicans did not result in the deviation of T(H)17 cells to the production of alternative cytokines, although IL-17A production was shut off in the course of the infection. During the development of EAE, interferon-γ (IFN-γ) and other proinflammatory cytokines in the spinal cord were produced almost exclusively by cells that had produced IL-17 before their conversion by IL-23 ('ex-T(H)17 cells'). Thus, this model allows the actual functional fate of effector T cells to be related to T(H)17 developmental origin regardless of IL-17 expression.

Immunosuppressive effects of tacrolimus on macrophages ameliorate experimental colitis

BACKGROUND

Tacrolimus is a novel immunomodulator for inflammatory bowel diseases. Immunosuppressive effects of tacrolimus on T cells are well known; however, the effects of tacrolimus on macrophages remain unclear. The aim of this study was to investigate the effects of tacrolimus on activated macrophages and to examine its efficacy in murine colitis models.

METHODS

Proinflammatory cytokine production from lipopolysaccharide (LPS)-stimulated peritoneal macrophages of IL-10-knockout (KO) mice with and without tacrolimus was measured. We investigated the effects of tacrolimus on nuclear factor-κB (NF-κB), mitogen-activated protein kinase (MAPK), and caspase activation in macrophages and the induction of apoptosis in macrophages in vitro and examined the in vivo apoptotic effect of tacrolimus on colonic macrophages in IL-10-KO mice. We evaluated the effect of the rectal administration of tacrolimus on colonic inflammation in IL-10-KO mice and dextran sulfate sodium (DSS)-induced colitis in CB.17/SCID mice.

RESULTS

Proinflammatory cytokine production from tacrolimus-treated macrophages was significantly lower than that from untreated cells. Tacrolimus suppressed LPS-induced activation of both NF-κB and MAPK in macrophages and induced apoptosis of macrophages via activation of caspases 3 and 9. Rectal administration of tacrolimus evoked apoptosis of colonic macrophages in IL-10-KO mice. Moreover, the rectal administration of tacrolimus ameliorated colitis in IL-10-KO mice and DSS-induced colitis in CB.17/SCID mice. Gene expression of inflammatory cytokines in colonic mucosa was significantly lower in tacrolimus-treated mice than in untreated mice.

CONCLUSIONS

Tacrolimus suppresses the function of activated macrophages and promotes their apoptosis, which may lead to the amelioration of colonic inflammation.

Effector T cell plasticity: flexibility in the face of changing circumstances

As more states of CD4 T cell differentiation are uncovered, their flexibility is also beginning to be recognized. Components that control the plasticity of CD4 T cell populations include cellular conditions, clonality, transcriptional circuitry and chromatin modifications. Appearance of cellular flexibility may arise from truly flexible genetic programs or, alternatively, from heterogeneous populations. New tools will be needed to define the rules that allow or prohibit cellular transitions.

T regulatory cells control antigen-induced recruitment of mast cell progenitors to the lungs of C57BL/6 mice

In C57BL/6 mice, the recruitment of mast cell progenitors (MCps) to the lung is a feature of Ag-induced pulmonary inflammation that requires sensitization and challenge and is totally inhibited by the administration of anti-CD4 at the time of challenge. When mAb to TGFbeta1 or to IL-10R was administered at the time of challenge, the recruitment of MCp/10(6) mononuclear cells (MNCs) to the lung was inhibited by 56.3 and 69.6%, respectively, whereas mAb to IL-4, IFN-gamma, IL-6, IL-17A, and IL-17F had no effect. In sensitized and challenged C57BL/6 mice lacking TGFbetaRII on CD4(+) cells, the recruitment of MCp/10(6) MNCs was reduced by 67.8%. The requirement for TGFbeta1 and IL-10 suggested a role for CD4(+)CD25(+) T regulatory cells. Mice treated with anti-CD25 at the time of Ag-challenge showed a reduction in the recruitment of MCp/10(6) MNCs by 77.2% without any reduction in MNC influx. These results reveal an unexpected role for T regulatory cells in promoting the recruitment of MCps to the lungs of C57BL/6 mice with Ag-induced pulmonary inflammation.

The multiple faces of CXCL12 (SDF-1alpha) in the regulation of immunity during health and disease

Chemokines are a group of small, structurally related molecules that regulate the trafficking of various types of leukocytes through interactions with a subset of 7-transmembrane G-protein-coupled receptors. As key chemoattractants of inflammatory leukocytes, chemokines have been marked as potential targets for neutralization in autoimmune diseases. Cancer cells also express chemokines, where they function as survival/growth factors and/or angiogenic factors that promote tumor development and angiogenesis. Accordingly, these functions make them attractive targets for therapy of these diseases. Recently, we reported that one of these chemokines CXCL12 (SDF-1alpha) functions as an anti-inflammatory chemokine during autoimmune inflammatory responses and explored the mechanistic basis of this function. As a pleiotropic chemokine, CXCL12 participates in the regulation of tissue homeostasis, immune surveillance, autoimmunity, and cancer. This chemokine is constitutively expressed in the BM and various tissues, which enables it to regulate the trafficking and localization of immature and maturing leukocytes, including BM stem cells, neutrophils, T cells, and monocytic cells. We have shown recently that CXCL12 increases immunological tolerance in autoimmune diseases by polarizing Tregs and by doing so, restrains the progression of these diseases. This finding suggests a possible use of stabilized rCXCL12 as a potential drug for therapy of these diseases and targeted neutralization of CXCL12 for therapy of cancer diseases. The current review explores the different biological properties of CXCL12 and discusses the implications of CXCL12-based therapies for autoimmunity and cancer diseases.

Unifying roles for regulatory T cells and inflammation in cancer

Activities of CD4(+) regulatory (T(REG)) cells restore immune homeostasis during chronic inflammatory disorders. Roles for T(REG) cells in inflammation-associated cancers, however, are paradoxical. It is widely believed that T(REG) function in cancer mainly to suppress protective anticancer responses. However, we demonstrate here that T(REG) cells also function to reduce cancer risk throughout the body by efficiently downregulating inflammation arising from the gastrointestinal (GI) tract. Building on a "hygiene hypothesis" model in which GI infections lead to changes in T(REG) that reduce immune-mediated diseases, here we show that gut bacteria-triggered T(REG) may function to inhibit cancer even in extraintestinal sites. Ability of bacteria-stimulated T(REG) to suppress cancer depends on interleukin (IL)-10, which serves to maintain immune homeostasis within bowel and support a protective antiinflammatory T(REG) phenotype. However, under proinflammatory conditions, T(REG) may fail to provide antiinflammatory protection and instead contribute to a T helper (Th)-17-driven procarcinogenic process; a cancer state that is reversible by downregulation of inflammation. Consequently, hygienic individuals with a weakened IL-10 and T(REG)-mediated inhibitory loop are highly susceptible to the carcinogenic consequences of elevated IL-6 and IL-17 and show more frequent inflammation-associated cancers. Taken together, these data unify seemingly divergent disease processes such as autoimmunity and cancer and help explain the paradox of T(REG) and inflammation in cancer. Enhancing protective T(REG) functions may promote healthful longevity and significantly reduce risk of cancer.

Roles for inflammation and regulatory T cells in colon cancer

Risk for developing cancer rises substantially as a result of poorly regulated inflammatory responses to pathogenic bacterial infections. Anti-inflammatory CD4(+) regulatory cells (T(REG)) function to restore immune homeostasis during chronic inflammatory disorders. It seems logical that T(REG) cells would function to reduce risk of inflammation-associated cancer in the bowel by down-regulating inflammation. It is widely believed, however, that T(REG) function in cancer mainly to suppress protective anticancer inflammatory responses. Thus roles for inflammation, T(REG) cells, and gut bacteria in cancer are paradoxical and are the subject of controversy. Our accumulated data build upon the "hygiene hypothesis" model in which gastrointestinal (GI) infections lead to changes in T(REG) that reduce inflammation-associated diseases. Ability of T(REG) to inhibit or suppress cancer depends upon gut bacteria and IL-10, which serve to maintain immune balance and a protective anti-inflammatory T(REG) phenotype. However, under poorly regulated pro-inflammatory conditions, T(REG) fail to inhibit and may instead contribute to a T helper (Th)-17-driven procarcinogenic process, a cancer state that is reversible by down-regulation of inflammation and interleukin (IL)-6. Consequently, hygienic individuals with a weakened IL-10- and T(REG)-mediated inhibitory loop are highly susceptible to the carcinogenic consequences of elevated inflammation and show more frequent inflammation-associated cancers. Taken together, these data help explain the paradox of inflammation and T(REG) in cancer and indicate that targeted stimulation of T(REG) may promote health and significantly reduce risk of cancer.

Plasticity of T-cell phenotype and function: the T helper type 17 example

Mature T helper type 1 (Th1) and Th2 cells antagonize the development of the opposing subset to sustain lineage-specific responses. However, the recent identification of a third distinct subset of helper T cells - the Th17 lineage - collapses the established Th1/Th2 dichotomy and raises intriguing questions about T-cell fate. In this review, we discuss the Th17 subset in the context of the effector and regulatory T-cell lineages. Initial studies suggested reciprocal developmental pathways between Th17/Th1 subsets and between Th17/regulatory T-cell subsets, and identified multiple mechanisms by which Th1 and Th2 cells antagonize the generation of Th17 cells. However, recent observations reveal the susceptibility of differentiated Th17 cells to Th1 polarization and the enhancement of Th17 memory cells by the Th1 factors interferon-gamma and T-bet. In addition, new data indicate late-stage plasticity of a subpopulation of regulatory T cells, which can be selectively induced to adopt a Th17 phenotype. Elucidating the mechanisms that undermine cross-lineage suppression and facilitate these phenotype shifts will not only clarify the flexibility of T-cell differentiation, but may also shed insight into the pathogenesis of autoimmunity and cancer. Furthermore, understanding these phenomena will be critical for the design of immunotherapy that seeks to disrupt lineage-specific T-cell responses and may suggest ways to manipulate the balance between pathogenic and regulatory lymphocytes for the restoration of homeostasis.