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

Regulation of T helper cell subsets by cyclooxygenases and their metabolites

Cyclooxygenases and their metabolites are important regulators of inflammatory responses and play critical roles in regulating the differentiation of T helper cell subsets in inflammatory diseases. In this review, we highlight new information on regulation of T helper cell subsets by cyclooxygenases and their metabolites. Prostanoids influence cytokine production by both antigen presenting cells and T cells to regulate the differentiation of naïve CD4(+) T cells to Th1, Th2 and Th17 cell phenotypes. Cyclooxygenases and PGE2 generally exacerbate Th2 and Th17 phenotypes, while suppressing Th1 differentiation. Thus, cycloxygenases may play a critical role in diseases that involve immune cell dysfunction. Targeting of cyclooxygenases and their eicosanoid products may represent a new approach for treatment of inflammatory diseases, tumors and autoimmune disorders.

A novel role of IGFBP7 in mouse uterus: regulating uterine receptivity through Th1/Th2 lymphocyte balance and decidualization

Previously we have screened out Insulin-like Growth Factor Binding Protein 7 (IGFBP7) as a differentially expressed gene in post-implantation uterus versus pre-implantation uterus by suppressive subtractive hybridation. However its function in uterus was not clearly identified. In this research, the expression and function of IGFBP7 during post-implantation were studied. We found that IGFBP7 was mainly located in the glandular epithelium and the stroma, and was upregulated after embryo implantation. The vector pCR3.1-IGFBP7-t expressing partial IGFBP7 was constructed. Inhibition of IGFBP7 by specific DNA immunization induced significant reduction of implanted embryos and pregnancy rate. The number of implanted embryos (5.68±0.46) was significantly reduced after immunization with pCR3.1-IGFBP7-t, as compared with that of the mice immunized with the control vector (12.29±0.36) or saline (14.58±0.40) (p<0.01). After specific inhibition of IGFBP7, the T helper type 1 (Th1) cytokine IFNγ, was significantly elevated (p<0.05) and the Th2 cytokines IL-4 and IL-10, were reduced in uteri (p<0.05). The increase of Tbet and the decrease of Gata3 were found in mice peripheral lymphocytes by flow cytometry. The expression of decidualization marker IGFBP1 and angiogenesis regulator VEGF were declined in uteri (p<0.05). The expression of apoptosis-associated proteins, caspase3 and Bcl-2, were also declined (p<0.05). These results showed that inhibition of IGFBP7 induced pregnancy failure by shifting uterine cytokines to Th1 type dominance and repressing uterine decidualization.

Size and dynamics of mucosal and peripheral IL-17A+ T-cell pools in pediatric age, and their disturbance in celiac disease

Mucosal interleukin (IL)-17A-producing T cells contribute to protective antimicrobial responses and to epithelial barrier integrity; their role in celiac disease (CD) is debated. We analyzed the frequency and developmental dynamics of mucosal (intraepithelial lymphocytes (IEL)) and circulating (peripheral blood (PB)) IL-17A (T17) and/or interferon (IFN)-γ-producing (T1, T1/T17) T-cell populations in 86 pediatric controls and 116 age-matched CD patients upon phorbol myristate acetate/ionomycin or CD3/CD28 stimulation. T17 and T1/17 are physiologically present among IEL and PB populations, and their frequency is selectively and significantly reduced in CD IEL. The physiological age-dependent increase of Th17 IEL is also absent in CD, while IFN-γ-producing PB-T cells significantly accumulate with patient's age. Finally, the amplitude of IL-17A+ and IFN-γ+ T-cell pools are significantly correlated in different individuals; this relationship only applies to CD4+ T cells in controls, while it involves also the CD4- counterpart in CD patients. In conclusion, both size and dynamics of mucosa-associated and circulating IL-17A+ T-cell pools are finely regulated in human pediatric subjects, and severely disturbed in CD. The impaired IL-17A+ IEL-T pool may negatively impact on epithelial barrier efficiency, and contribute to CD mucosa damage; the disturbed dynamics of circulating IL-17A+ and IFN-γ+ T-cell pools may be involved in the extraintestinal autoimmune manifestations associated with CD.

Efficacy of topical blockade of interleukin-1 in experimental dry eye disease

PURPOSE

To evaluate the therapeutic efficacy of topical interleukin-1 receptor antagonist (IL-1Ra) in the treatment of dry eye disease.

DESIGN

Laboratory investigation.

METHODS

Dry eye disease was induced in C57BL/6 female mice through exposure to a desiccating environment within a controlled environment chamber. Topical formulations containing 5% IL-1Ra, 1% methylprednisolone, 0.05% cyclosporin A, and a vehicle control containing carboxymethylcellulose sodium were applied after the induction of dry eye. Corneal fluorescein staining was performed by a masked observer in the different treatment groups. Immunohistochemical studies were undertaken to enumerate corneal CD11b+ cells, as well as to evaluate corneal lymphangiogenesis. Real-time polymerase reaction was used to quantify the expression of interleukin-1β in the cornea.

RESULTS

A significant decrease in corneal fluorescein staining was observed after topical treatment with 5% IL-1Ra (P < .01), 1% methylprednisolone (P < .01), and 0.05% cyclosporin A (P < .03). Additionally, a significant decrease in the numbers of central corneal CD11b+ cells (P < .05), corneal lymphatic growth (P < .05), and corneal interleukin-1β expression (P < .003), compared with vehicle treated, were demonstrated only after treatment with 5% IL-1Ra and 1% methylprednisolone, and were absent after cyclosporin A treatment.

CONCLUSIONS

Topical treatment with IL-1Ra is effective in ameliorating the clinical signs of the dry eye disease, as well as in reducing underlying inflammation. These effects are comparable with those resulting from treatment with topical methylprednisolone. Topical IL-1Ra may hold promise as a novel therapeutic strategy in the treatment of dry eye.

Study of the uterine local immune response in a murine model of embryonic death due to Tritrichomonas foetus

PROBLEM

Bovine tritrichomonosis is a sexually transmitted disease caused by Tritrichomonas foetus, characterized by conceptus loss. We developed a mouse model of tritrichomonosis to study the mechanisms involved in the embryonic death. We hypothesized that embryonic death may be due to an exacerbated maternal response to the pathogen that then affects embryo development.

METHOD OF STUDY

We infected BALB/c mice with Tritrichomonas foetus and paired them after confirming active infection. We studied the expression of pro- and anti-inflammatory cytokines, markers for T regulatory and T helper 17 cells as well as haem-oxygenase-1 expression in uterine tissue by real-time RT-PCR.

RESULTS

As expected, TNF-α was augmented in infected animals. IL-10 and IL-4 were also up-regulated. Treg-associated genes were higher expressed in uteri of infected group. In mice that have lost their conceptus after the infection, haem-oxygenase-1 (HO-1) mRNA levels were strongly decreased, while RORγt mRNA, a reliable marker for Th17, was augmented in uterus.

CONCLUSION

A T effector response of type 1 and 17 may be involved in tritrichomonosis-related embryonic death. This alters protective mechanisms as HO-1. Increased regulatory T cells may facilitate embryonic death by promoting the persistence of infection.

Interleukin 10 and tumor necrosis factor-alpha in pregnancy: aspects of interest in clinical obstetrics

The purpose of this study was to review the literature regarding the action of the cytokines interleukin 10 (IL-10) and tumor necrosis factor-alpha (TNF-α) in pregnancy and to emphasize the factors that are of interest to clinical obstetrics. The literature highlights several actions of IL-10 and TNF-α during pregnancy. The actions of these cytokines seem to be antagonistic and dependent on the balance between them, which is orchestrated by the specific immunosuppressive action of IL-10. TNF-α has a characteristic inflammatory action, and it is an additional diabetogenic factor in pregnancy. The loss of the control of the production of these cytokines, with increase of TNF-α, is related to the risk for developing obstetric complications, particularly recurrent fetal loss, gestational diabetes mellitus, hypertensive syndromes, and fetal growth restriction. However, study results are controversial and are not clearly defined. These issues are attributed to the heterogeneity of the studies, particularly regarding their sample sizes and sources, the evaluation methods, and the multiplicity of factors and conditions that influence cytokine production. These questions are fundamental and should be addressed in future investigations to obtain more consistent results that can be applied to obstetric practice.

T helper 17 cells and regulatory T-cell imbalance in paediatric patients with asthma

Asthma is a chronic inflammatory disorder of the lung, which is thought to be determined by the balance between the T helper (Th)2 and Th1 responses. This study evaluated whether the balance between Th17 cells and regulatory T cells (T(reg)) was impaired in asthma patients. The proportion of peripheral blood Th17 cells of the total CD4(+) cell population in asthma patients was significantly higher than in controls (mean ± SD 0.72 ± 0.5% versus 0.31 ± 0.4%, respectively). The proportion of peripheral T(reg) cells in asthma patients was significantly lower than in controls (mean ± SD 12.1 ± 4.6% versus 27.2 ± 7.5%, respectively). Analysis of mRNA generally confirmed the flow cytometry data, suggesting that the changes in cytokine levels were mediated at the transcription level. In paediatric asthma patients, the CD4(+) T-cell phenotype was skewed toward the Th17 phenotype, suggesting that a Th17/T(reg) functional imbalance plays a role in asthma.

Effects of 1,25(OH)2 vitamin D3 on cytokine production by endometrial cells of women with recurrent spontaneous abortion

OBJECTIVE

To investigate immunomodulatory effect of 1,25(OH)2 vitamin D3 (1,25(OH)2D3) on cytokine production by endometrial cells of women with unexplained recurrent spontaneous abortion (URSA).

DESIGN

In vitro study.

SETTING

Academic research center.

PATIENT(S)

Patients with URSA and healthy controls.

INTERVENTION(S)

Treatment with 1,25(OH)2D3.

MAIN OUTCOME MEASURE(S)

Production of interferon γ (IFN-γ), interleukin-10 (IL-10), transforming growth factor β (TGF-β), IL-17, IL-6, and IL-8 by whole endometrial cells (WECs) and endometrial stromal cells in the presence and absence of 1,25(OH)2D3 and 1α-hydroxylase activity of these cell populations were measured in patients with URSA and healthy controls.

RESULT(S)

1,25(OH)2D3 interfered with production of cytokines by WECs of the control and URSA groups, except IL-8 which was increased in URSA group. In endometrial stromal cells, 1,25(OH)2D3 down-regulated cytokine production as well with stimulatory effect on the production of TGF-β in patients with URSA. Cytokine profile of WECs from patients with URSA skewed toward TH2 phenotype after treatment with 1,25(OH)2D3. Endometrial cells of both groups had comparable capacity to produce 1,25(OH)2D3.

CONCLUSION(S)

Considering the complex network of immunoregulation at the fetomaternal interface, potential beneficial effects of vitamin D3 in patients with URSA need to be investigated in clinical practice. Comparable levels of 1,25(OH)2D3 production and similar trend of cytokine expression by WECs of URSA and control groups after vitamin D3 treatment reflect the same local metabolic machinery of this hormone.

Cytokines in autoimmunity: role in induction, regulation, and treatment

Cytokines play a pivotal role in the pathogenesis of autoimmune diseases. The precise triggers for the breakdown of self-tolerance and the subsequent events leading to the induction of pathogenic autoimmune responses remain to be defined for most of the naturally occurring autoimmune diseases. Studies conducted in experimental models of human autoimmune diseases and observations in patients have revealed a general scheme in which proinflammatory cytokines contribute to the initiation and propagation of autoimmune inflammation, whereas anti-inflammatory cytokines facilitate the regression of inflammation and recovery from acute phase of the disease. This idea is embodied in the T helper (Th) 1/Th2 paradigm, which over the past two decades has had a major influence on our thinking about the role of cytokines in autoimmunity. Interestingly, over the past decade, the interleukin (IL)-17/IL-23 axis has rapidly emerged as the new paradigm that has compelled us to critically re-examine the cytokine-driven immune events in the pathogenesis and treatment of autoimmunity. In this 2-volume special issue of the journal, leading experts have presented their research findings and viewpoints on the role of cytokines in the context of specific autoimmune diseases.

Robust antigen specific th17 T cell response to group A Streptococcus is dependent on IL-6 and intranasal route of infection

Group A streptococcus (GAS, Streptococcus pyogenes) is the cause of a variety of clinical conditions, ranging from pharyngitis to autoimmune disease. Peptide-major histocompatibility complex class II (pMHCII) tetramers have recently emerged as a highly sensitive means to quantify pMHCII-specific CD4⁺ helper T cells and evaluate their contribution to both protective immunity and autoimmune complications induced by specific bacterial pathogens. In lieu of identifying an immunodominant peptide expressed by GAS, a surrogate peptide (2W) was fused to the highly expressed M1 protein on the surface of GAS to allow in-depth analysis of the CD4⁺ helper T cell response in C57BL/6 mice that express the I-A^b MHCII molecule. Following intranasal inoculation with GAS-2W, antigen-experienced 2W:I-A^b-specific CD4⁺ T cells were identified in the nasal-associated lymphoid tissue (NALT) that produced IL-17A or IL-17A and IFN-γ if infection was recurrent. The dominant Th17 response was also dependent on the intranasal route of inoculation; intravenous or subcutaneous inoculations produced primarily IFN-γ⁺ 2W:I-A^b+ CD4⁺ T cells. The acquisition of IL-17A production by 2W:I-A^b-specific T cells and the capacity of mice to survive infection depended on the innate cytokine IL-6. IL-6-deficient mice that survived infection became long-term carriers despite the presence of abundant IFN-γ-producing 2W:I-A^b-specific CD4⁺ T cells. Our results suggest that an imbalance between IL-17- and IFN-γ-producing CD4⁺ T cells could contribute to GAS carriage in humans.

Group A streptococcus (GAS) causes many different conditions, ranging from strep throat, flesh eating disease to post infectious complications involving the heart. Here, we used a novel technique to study the CD4⁺ T cell immune response against GAS infection in a mouse model. We first generated a recombinant GAS strain that expresses a specific epitope (2W) - M protein fusion and used this to intranasally inoculate mice. Peptide specific CD4⁺ T cells were concentrated and analyzed using 2W-MHC-II tetramers. This technology allowed us to probe the antigen specific CD4⁺ T cell response to new depths and certainty. Infection induced a robust 2W-specific Th17 cell response, which was dependent on the route of infection, IL-6, and was independent of superantigens. IL-6^-/- mice were exquisitely susceptible to intranasal infection. However, those that survived became immune carriers, unable to clear streptococci from NALT. Further, multiple infections generated an IL-17⁺ IFN-γ⁺ double positive population of CD4⁺ T cells that are known to be associated with autoimmune disease in humans and directly responsible for autoimmune pathology in rodent models. Our results provide a new direction for understanding two important consequences of streptococcal pharyngitis, the very common immune carrier state, and the rarer state involving autoimmune complications.

Low level of regulatory T cells and maintenance of balance between regulatory T cells and TH17 cells in HIV-1-infected elite controllers

BACKGROUND

A subgroup of HIV-1-infected individuals, elite controllers, have spontaneous viral control and offer an exceptional opportunity to study virological and immunolocigal factors of possible involvement in control of HIV-1 infection.

METHODS

The frequencies of Tregs and TH17 cells was evaluated and correlated to markers of disease progression in peripheral blood mononuclear cells from 3 different groups of individuals infected with HIV-1: treatment-naive viremic individuals, individuals on successful highly active antiretroviral therapy, and elite controllers. In addition, a group of HIV-1-negative individuals were included.

RESULTS

We demonstrate that elite controllers have lower levels of Tregs compared with HIV-1-infected viremic individuals, but that the low Treg level does not differ between individuals with HIV-1 control, whether natural or therapy induced. We also show that T-cell activation and proliferation both correlate to the level of Tregs. Finally, the TH17/Treg ratio was similar in Elite Controllers and uninfected controls, whereas in viremic and treated HIV-1-infected individuals, the TH17/Treg ratio was lower compared with uninfected controls.

CONCLUSIONS

We show that one feature of spontaneous HIV-1 control is a maintained balance between regulatory T cells and TH17 cells.

Optimization of human Th17 cell differentiation in vitro: evaluating different polarizing factors

Regarding discrepancies that exist among different studies which have tried to clarify critical factors in human Th17 cell differentiation, the aim of this study was to identify the best condition for human Th17 differentiation and to clarify the possible role of TGF-β in differentiation of these cells. Naïve CD4(+) T cells were isolated from cord blood samples and cultured either in X-VIVO 15 serum-free medium or RPMI 1640 containing 10% FBS. Purified cells were treated with different combinations of polarizing cytokines (TGF-β, IL-1β, IL-6, IL-23 and IL-21) followed by analysis of the expression of characteristic genes and their relevant cytokines by real-time quantitative RT-PCR and ELISA method, respectively. Our data indicate that a combination of TGF-β plus IL-6 and IL-23 cytokines in X-VIVO 15 serum-free medium could be applied as the best condition for developing human Th17 cells in compare with other studied cytokine treatments. It is shown that TGF-β could be considered as a positive regulator for human Th17 cell differentiation only if applied in average concentrations. Interestingly, polarizing treatments in absence of TGF-β, induced double-secreting Th17 cells which co-express IL-17 and IFN-γ whereas polarization in presence of TGF-β-induced single-secreting (only IL-17 expressing) Th17 cells.

Immune modulation by chemotherapy or immunotherapy to enhance cancer vaccines

Chemotherapy has been a mainstay in cancer treatment for many years. Despite some success, the cure rate with chemotherapy remains unsatisfactory in some types of cancers, and severe side effects from these treatments are a concern. Recently, understanding of the dynamic interplay between the tumor and immune system has led to the development of novel immunotherapies, including cancer vaccines. Cancer vaccines have many advantageous features, but their use has been hampered by poor immunogenicity. Many developments have increased their potency in pre-clinical models, but cancer vaccines continue to have a poor clinical track record. In part, this could be due to an inability to effectively overcome tumor-induced immune suppression. It had been generally assumed that immune-stimulatory cancer vaccines could not be used in combination with immunosuppressive chemotherapies, but recent evidence has challenged this dogma. Chemotherapies could be used to condition the immune system and tumor to create an environment where cancer vaccines have a better chance of success. Other types of immunotherapies could also be used to modulate the immune system. This review will discuss how immune modulation by chemotherapy or immunotherapy could be used to bolster the effects of cancer vaccines and discuss the advantages and disadvantages of these treatments.

A distinct role of CD4+ Th17- and Th17-stimulated CD8+ CTL in the pathogenesis of type 1 diabetes and experimental autoimmune encephalomyelitis

Both CD4(+) Th17-cells and CD8(+) cytotoxic T lymphocytes (CTLs) are involved in type 1 diabetes and experimental autoimmune encephalomyelitis (EAE). However, their relationship in pathogenesis of these autoimmune diseases is still elusive. We generated ovalbumin (OVA)- or myelin oligodendrocyte glycoprotein (MOG)-specific Th17 cells expressing RORγt and IL-17 by in vitro co-culturing OVA-pulsed and MOG(35-55) peptide-pulsed dendritic cells (DC(OVA) and DC(MOG)) with CD4(+) T cells derived from transgenic OTII and MOG-T cell receptor mice, respectively. We found that these Th17 cells when transferred into C57BL/6 mice stimulated OVA- and MOG-specific CTL responses, respectively. To assess the above question, we adoptively transferred OVA-specific Th17 cells into transgenic rat insulin promoter (RIP)-mOVA mice or RIP-mOVA mice treated with anti-CD8 antibody to deplete Th17-stimulated CD8(+) T cells. We demonstrated that OVA-specific Th17-stimulated CTLs, but not Th17 cells themselves, induced diabetes in RIP-mOVA. We also transferred MOG-specific Th17 cells into C57BL/6 mice and H-2K(b-/-) mice lacking of the ability to generate Th17-stimulated CTLs. We further found that MOG-specific Th17 cells, but not Th17-activated CTLs induced EAE in C57BL/6 mice. Taken together, our data indicate a distinct role of Th17 cells and Th17-stimulated CTLs in the pathogenesis of TID and EAE, which may have great impact on the overall understanding of Th17 cells in the pathogenesis of autoimmune diseases.

Dual function of polycomb group proteins in differentiated murine T helper (CD4+) cells

BACKGROUND

Following antigen recognition, naive T helper (Th; CD4+) cells can differentiate toward one of several effector lineages such as Th1 and Th2; each expressing distinctive transcriptional profiles of cytokine genes. These cytokines eventually instruct the strategy of the immune response. In our search for factors that propagate the transcriptional programs of differentiated Th cells, we previously found that Polycomb group (PcG) proteins, which are known as epigenetic regulators that maintain repressive chromatin states, bind differentially the signature cytokine genes. Unexpectedly, their binding to the Ifng (Interferon-g) in Th1 cells and Il4 (Interleukin-4) in Th2 cells, was correlated with transcriptional activation. Therefore, in this study we aimed to determine the functional role of PcG proteins in the regulation of the expression of the signature cytokine genes.

METHODS

PcG proteins were knocked down in primary and established murine Th cells using transduction of lentiviruses encoding short hairpin RNAs (shRNAs) directed to Mel-18, Ezh2, Eed and Ring1A, representative of two different PcG complexes. The chromatin structure and the binding activity of PcG proteins and transcription factors at the Ifng promoter were assessed by chromatin immunoprecipitation (ChIP) assays.

RESULTS

Downregulation of PcG proteins was consistent with their function as positive regulators of the signature cytokine genes in primary and established Th1 and Th2 cells. Moreover, the PcG protein Mel-18 was necessary to recruit the Th1-lineage specifying transcription factor T-bet, and the T cell receptor (TCR)-inducible transcription factor NFAT1 to the Ifng promoter in Th1 cells. Nevertheless, our results suggest that PcG proteins can function also as conventional transcriptional repressors in Th cells of their known target the Hoxa7 gene.

CONCLUSIONS

Our data support a model whereby the non-differentially expressed PcG proteins are recruited in a Th-lineage specific manner to their target genes to enforce the maintenance of specific transcriptional programs as transcriptional repressors or activators. Although our results suggest a direct effect of PcG proteins in the regulation of cytokine gene expression, indirect functions cannot be excluded.

Circulating inflammation markers and risk of epithelial ovarian cancer

BACKGROUND

Factors contributing to chronic inflammation appear to be associated with increased risk of ovarian cancer. The purpose of this study was to assess the association between circulating levels of inflammation mediators and subsequent risk of ovarian cancer.

METHODS

We conducted a case-control study of 230 cases and 432 individually matched controls nested within three prospective cohorts to evaluate the association of prediagnostic circulating levels of inflammation-related biomarkers (IL-1β, IL-2, IL-4, IL-5, IL-6, IL-10, IL-12p40, IL-12p70, IL-13, TNFα, IL-1Ra, sIL-1RII, sIL-2Ra, sIL-4R, sIL-6R, sTNF-R1, and sTNF-R2) measured using Luminex xMap technology with risk of ovarian cancer.

RESULTS

We observed a trend across quartiles for IL-2 (OR(Q4 vs. Q1): 1.57, 95% CI: 0.98-2.52, P = 0.07), IL-4 (OR(Q4 vs. Q1): 1.50, 95% CI: 0.95-2.38, P = 0.06), IL-6 (OR(Q4 vs. Q1): 1.63, 95% CI: 1.03-2.58, P = 0.03), IL-12p40 (OR(Q4 vs. Q1): 1.60, 95% CI: 1.02-2.51, P = 0.06), and IL-13 (OR(Q4 vs. Q1): 1.42, 95% CI: 0.90-2.26, P = 0.11). Trends were also observed when cytokines were modeled on the continuous scale for IL-4 (P trend = 0.01), IL-6 (P trend = 0.01), IL-12p40 (P trend = 0.01), and IL-13 (P trend = 0.04). ORs were not materially different after excluding cases diagnosed less than 5 years after blood donation or when limited to serous tumors.

CONCLUSIONS AND IMPACT

This study provides the first direct evidence that multiple inflammation markers, specifically IL-2, IL-4, IL-6, IL-12, and IL-13, may be associated with risk of epithelial ovarian cancer, and adds to the evidence that inflammation is involved in the development of this disease.

Joining the immunological dots in recurrent miscarriage

While raised cellular immunity mediated by T helper (Th) 1 type cells may be harmful for the developing embryo/foetus, it is likely that Th2 type immunity may be helpful. The role of natural killer (NK) cells is presently underestimated, although they are clearly important in angiogenesis and the coordinated invasion of the decidua by the trophoblast. Deficient T regulatory cell (Treg) function is evident in women with recurrent miscarriage particularly when this occurs in early pregnancy. The role of the pro-inflammatory Th17 cells is presently unclear. However, early evidence suggests that excessive Th17 activity may promote miscarriage and preterm delivery. This may relate to the ability of these cells to produce those cytokines that encourage Th1 and NK cell activity. As such recurrent miscarriage may be caused not only by chromosomal abnormalities, autoimmunity and uterine abnormalities but also by subclinical uterine infection and inflammation which by stimulating interleukin 6 favours Th17 development over Tregs. This review examines the role of these different cells in early pregnancy and suggests a schema that may join the dots of the immunological puzzle called pregnancy. Finally, suggestions are made as to how inappropriate immunity in recurrent miscarriage may be down-regulated using currently available therapies.

Cytokines in recurrent pregnancy loss

BACKGROUND

Recurrent pregnancy loss (RPL) is defined as the occurrence of three or more consecutive miscarriages prior to 20 weeks gestation. Exaggerated maternal immune response to fetal antigens has been proposed to be one of the mechanisms underlying recurrent pregnancy loss.

METHOD

A comprehensive literature search was conducted from the websites of the National Library of Medicine (http://www.ncbl.nlm.nih.gov) and Pubmed Central, the US National Library of Medicine's digital archive of life sciences literature (http://www.pubmedcentral.nih.gov/). The data was assessed from books and journals that published relevant articles in this field.

RESULT

In normal pregnancy, tolerance of the genetically incompatible fetus by the maternal immune system depends on the interactions of an array of cytokines secreted by maternal and fetal cells at the site of implantation. Earlier research indicated that altered immunity in RPL is dominated by the Th1/Th2 hypothesis, which proposed that the fetus escapes maternal-derived T-cell responses through skewing the Th0 differentiation toward Th2 pathway which dampens pro-inflammatory Th1-type immunity. Recent studies indicate the role of proinflammatory Th17 cells and immunoregulatory Treg cells in RPL in addition to Th1/Th2 interactions.

CONCLUSION

Cytokines form a complex regulatory network which maintains homeostasis between the fetal unit and the maternal immune system. If this delicate balance is adversely affected, immunoregulatory mechanisms may be insufficient to restore homeostasis and this may lead to pregnancy failure.

Cytokine reporter mice in immunological research: perspectives and lessons learned

Cytokines are soluble messenger molecules with important regulatory functions throughout the immune system. 'Cytokine reporter' strains express marker molecules under control of elements from cytokine genes allowing for easy identification of their cellular sources. Such systems are well-accepted tools for research of cytokine function. The value of these strains lies in the ability to perform experiments relying on identification and isolation of live cytokine-expressing cells, provided that the reporter faithfully reflects the proper cytokine mRNA and protein production. As more diverse cell subsets are defined by their cytokine expression, the field has adapted with the generation of more sophisticated strains. In this review we summarize the evolution of cytokine detection methods and give examples of knowledge gained using cytokine reporter mice for cell types expressing interferon-γ and interleukin-4, -10 and -17. We also discuss current options for generating such reporter strains and their potential pitfalls.

A live Leishmania major vaccine containing CpG motifs induces the de novo generation of Th17 cells in C57BL/6 mice

Cutaneous leishmaniasis produces open sores that lead to scarring and disfiguration. We have reported that vaccination of C57BL/6 mice with live Leishmania major plus CpG DNA (Lm/CpG) prevents lesion development and provides long-term immunity. Our current study aims to characterize the components of the adaptive immune response that are unique to Lm/CpG. We find that this vaccine enhances the proliferation of CD4(+) Th17 cells, which contrasts with the highly polarized Th1 response caused by L. major alone; the Th17 response is dependent upon release of vaccine-induced IL-6. Neutralization of IFN-gamma and, in particular, IL-17 caused increased parasite burdens in Lm/CpG-vaccinated mice. IL-17R-deficient Lm/CpG-vaccinated mice develop lesions, and display decreased IL-17 and IFN-gamma, despite normal IL-12, production. Neutrophil accumulation is also decreased in the IL-17R-deficient Lm/CpG-vaccinated mice but Treg numbers are augmented. Our data demonstrate that activation of immune cells through CpG DNA, in the presence of live L. major, causes the specific induction of Th17 cells, which enhances the development of a protective cellular immunity against the parasite. Our study also demonstrates that vaccines combining live pathogens with immunomodulatory molecules may strikingly modify the natural immune response to infection in an alternative manner to that induced by killed or subunit vaccines.

Th1/Th2/Th17 and regulatory T-cell paradigm in pregnancy

T-helper (Th) cells play a central role in modulating immune responses. The Th1/Th2 paradigm has now developed into the new Th1/Th2/Th17 paradigm. In addition to effector cells, Th cells are regulated by regulatory T (Treg) cells. Their capacity to produce cytokines is suppressed by immunoregulatory cytokines such as transforming growth factor (TGF)-beta and interleukin (IL)-10 or by cell-to-cell interaction. Here, we will review the immunological environment in normal pregnancy and complicated pregnancy, such as implantation failure, abortion, preterm labor, and preeclampsia from the viewpoint of the new Th1/Th2/Th17 and Treg paradigms.

Neutrophils and macrophages work in concert as inducers and effectors of adaptive immunity against extracellular and intracellular microbial pathogens

Emerging data suggest new facets of the concerted participation of neutrophils and macrophages in antimicrobial immunity. The classical view is that DCs and macrophages are the inducers of adaptive antimicrobial immunity, but there is evidence for neutrophil participation in this task as cytokine and chemokine producers and APCs. On the other hand, the concept that the T(H)1 response is only associated with control of infections by intracellular pathogens through activation of macrophages by IFN-gamma, and the T(H)17/IL-17 axis is only involved in protection against extracellular pathogens through mobilization and activation of neutrophils is simplistic: There is evidence suggesting that T(H)1 and T(H)17 responses, separately or in parallel, may use macrophages and neutrophils against infections by extracellular and intracellular microbial pathogens. Opsonization by pathogen-specific Igs enhances the antimicrobial capabilities of neutrophils and macrophages in infections by extracellular and intracellular microbes. The functional partnership between macrophages and neutrophils as inducers and effectors of adaptive antimicrobial immunity conforms to their affiliation with the myeloid phagocyte system and reveals a strategy based on the concurrent use of the two professional phagocytes in the adaptive defense mechanisms. Starting from a common myeloid precursor in the bone marrow, macrophages and neutrophils split during differentiation but come together at the infectious foci for a cooperative strategy that uses modulator and effector activities to attack invading microbial pathogens.

High throughput sequencing reveals a complex pattern of dynamic interrelationships among human T cell subsets

Developing T cells face a series of cell fate choices in the thymus and in the periphery. The role of the individual T cell receptor (TCR) in determining decisions of cell fate remains unresolved. The stochastic/selection model postulates that the initial fate of the cell is independent of TCR specificity, with survival dependent on additional TCR/coreceptor "rescue" signals. The "instructive" model holds that cell fate is initiated by the interaction of the TCR with a cognate peptide-MHC complex. T cells are then segregated on the basis of TCR specificity with the aid of critical coreceptors and signal modulators [Chan S, Correia-Neves M, Benoist C, Mathis (1998) Immunol Rev 165: 195-207]. The former would predict a random representation of individual TCR across divergent T cell lineages whereas the latter would predict minimal overlap between divergent T cell subsets. To address this issue, we have used high-throughput sequencing to evaluate the TCR distribution among key T cell developmental and effector subsets from a single donor. We found numerous examples of individual subsets sharing identical TCR sequence, supporting a model of a stochastic process of cell fate determination coupled with dynamic patterns of clonal expansion of T cells bearing the same TCR sequence among both CD4(+) and CD8+ populations.