Increased prevalence of IL-17-producing peripheral blood lymphocytes in pre-eclampsia

Citation
Toldi G, Rigó J Jr, Stenczer B, Vásárhelyi B, Molvarec A. Increased prevalence of IL‐17‐producing peripheral blood lymphocytes in pre‐eclampsia. Am J Reprod Immunol 2011; 66: 223–229 Problem Systemic inflammation is a dominant component in the pathogenesis of pre‐eclampsia. Besides the imbalance of Th1 and Th2 cells, alterations of the prevalence of Th17 and regulatory T cells have also been suggested to contribute to inflammation. We aimed to describe the prevalence of these four CD4 lymphocyte subtypes in pre‐eclampsia and normal pregnancy, along with that of IL‐17‐producing CD8 and NK cells. Method of study Twenty pre‐eclamptic and 22 normal pregnant women were enrolled in this study. Using flow cytometry, we determined the prevalence of IL‐17‐producing cells among the CD4, CD8 and NK cell subsets. Furthermore, we measured the prevalence of CD4+ Tregs, and Th1/Th2 cells were characterized using cell surface chemokine receptor markers. Results We demonstrated that there is a shift not only in the Th1/Th2 but also in the Th17/Treg balance favouring skewness towards a pro‐inflammatory status in pre‐eclampsia. The proportion of CD8 and NK cells that express IL‐17 was also higher in pre‐eclampsia. Conclusion The prevalence of IL‐17‐producing CD4, CD8 and NK cells is elevated in pre‐eclampsia, indicating that both the innate and adaptive arms of the immune system are involved in the development of the exaggerated maternal systemic inflammation observed in this pregnancy‐specific disorder.     

Induction, function and regulation of IL-17-producing T cells

Recent reports have provided convincing evidence that IL‐17‐producing T cells play a key role in the pathogenesis of organ‐specific autoimmune diseases, a function previously attributed exclusively to IFN‐γ‐secreting Th1 cells. Furthermore, it appears that IL‐17‐producing T cells can also function with Th1 cells to mediate protective immunity to pathogens. Although much of the focus has been on IL‐17‐secreting CD4⁺ T cells, termed Th17 cells, CD8⁺ T cells, γδ T cells and NKT cells are also capable of secreting IL‐17. The differentiation of Th17 cells from naïve T cells appears to involve signals from TGF‐β, IL‐6, IL‐21, IL‐1β and IL‐23. Furthermore, IL‐1α or IL‐1β in synergy with IL‐23 can promote IL‐17 secretion from memory T cells. The induction or function of Th17 cells is regulated by cytokines secreted by the other major subtypes of T cells, including IFN‐γ, IL‐4, IL‐10 and at high concentrations, TGF‐β. The main function of IL‐17‐secreting T cells is to mediate inflammation, by stimulating production of inflammatory cytokines, such as TNF‐α, IL‐1β and IL‐6, and inflammatory chemokines that promote the recruitment of neutrophils and macrophages.     

Role of CD4 T cell helper subsets in immune response and deviation of CD8 T cells in mice*

The ability of different CD4⁺ T cell subsets to help CD8⁺ T‐cell response is not fully understood. Here, we found using the murine system that Th17 cells induced by IL‐1β, unlike Th1, were not effective helpers for antiviral CD8 responses as measured by IFNγ‐producing cells or protection against virus infection. However, they skewed CD8 responses to a Tc17 phenotype. Thus, the apparent lack of help was actually immune deviation. This skewing depended on both IL‐21 and IL‐23. To overcome this effect, we inhibited Th17 induction by blocking TGF‐β. Anti‐TGF‐β allowed the IL‐1β adjuvant to enhance CD8⁺ T‐cell responses without skewing the phenotype to Tc17, thereby providing an approach to harness the benefit of common IL‐1‐inducing adjuvants like alum without immune deviation.     

Interleukin-17 in inflammatory skin disorders

PURPOSE OF REVIEW: Recently, a novel and unique subset of interleukin (IL)-17-producing CD4+ T helper (Th17) cells, distinct from Th1 and Th2 cells, was discovered. The question is addressed as to what extent inflammatory skin diseases are associated with the actions of this newly discovered Th17 cell subset. RECENT FINDINGS: Th17 cells are involved in protection against bacterial pathogens. In addition, it is now clear that Th17 cells may also be crucial in the pathogenesis of various chronic inflammatory diseases that were formerly categorized as Th1-mediated disorders. SUMMARY: In this review, we summarize the current knowledge of IL-17 and Th17 cells and discuss the possible role of IL-17 in the pathology of psoriasis, contact hypersensitivity and atopic dermatitis. Whereas IL-17 may play an important role in the pathogenesis of psoriasis and contact hypersensitivity, its role in atopic dermatitis is still unclear.     

Tim‐3 regulates inflammatory cytokine expression and Th17 cell response induced by monocytes from patients with chronic hepatitis B

Tim‐3 is expressed on monocytes/macrophages and is involved in the regulation of inflammatory responses. The aim of this study was to determine the effect of Tim‐3 on inflammatory response triggered by peripheral monocytes from patients with chronic hepatitis B (CHB). Tim‐3 expression on peripheral monocytes and frequency of Th17 cells in peripheral blood mononuclear cells (PBMCs) derived from CHB patients were detected. Followed by lipopolysaccharides (LPS) activation of circulating monocytes from CHB patients, expression of inflammatory cytokines including TNF‐α，IL‐1β and IL‐6 were examined in the presence and absence of Galectin‐9 which is the ligand for Tim‐3. Subsequently, after purified CD4+T cells were cocultured with LPS‐activated monocytes from CHB patients in the presence of anti‐Tim‐3 antibody, percentage of Th17 cells and production of IL‐17 were measured. Tim‐3 expression was significantly upregulated and closely correlated to the frequency of Th17 cells in patients with CHB. Expression of TNF‐α，IL‐1β and IL‐6 increased significantly in monocytes stimulated with LPS and Galectin‐9, compared to LPS stimulation alone. LPS‐activated monocytes from CHB patients could drive differentiation of memory CD4+T cells to Th17 cells. However, under the blockade of Tim‐3 signalling by anti‐Tim‐3 antibody, percentage of Th17 cells and production of IL‐17 decreased significantly. Our results demonstrate that upregulated expression of Tim‐3 on circulating monocytes accelerates inflammatory response by promoting production of inflammatory cytokines and Th17 responses in CHB.     

Characterization of Th17 and FoxP3+ Treg Cells in Paediatric Psoriasis Patients

Psoriasis is one of the most common inflammatory skin conditions affecting both children and adults. Growing evidence indicates that T‐helper 17 (Th17) cells and CD4⁺CD25⁺ regulatory T (Treg) cells play an important role in the pathogenesis of psoriasis. However, the relationship between Th17 and Treg cells and their dynamic variations in paediatric psoriasis remain unclear. In this study, we found that both Th17 and FoxP3⁺ Treg cells and the ratio of Th17 to Treg cell frequency in the peripheral circulation were increased in patients with paediatric psoriasis and were positively correlated with the disease severity. The function of Treg to suppress CD4⁺CD25^? T cell proliferation and IFN‐γ secretion was impaired during the onset of psoriasis. After disease remission, both the Th17 and Treg cell frequencies were decreased, and the suppressive function of the Treg cells was obviously restored. However, neither Treg cells from the disease onset nor those after remission can regulate IL‐17 secretion by CD4⁺ T cells. These findings will further our understanding of the associations between Th17 and Treg cells in paediatric psoriasis and their influence on disease severity.     

Th17 cells confer long-term adaptive immunity to oral mucosal Candida albicans infections

Oropharyngeal candidiasis (OPC) is an opportunistic infection caused by Candida albicans. Despite its prevalence, little is known about C. albicans-specific immunity in the oral mucosa. Vaccines against Candida generate both T helper type 1 (Th1) and Th17 responses, and considerable evidence implicates interleukin (IL)-17 in immunity to OPC. However, IL-17 is also produced by innate immune cells that are remarkably similar to Th17 cells, expressing the same markers and localizing to similar mucosal sites. To date, the relative contribution(s) of Th1, Th17, and innate IL-17-producing cells in OPC have not been clearly defined. Here, we sought to determine the nature and function of adaptive T-cell responses to OPC, using a new recall infection model. Mice subjected to infection and re-challenge with Candida mounted a robust and stable antigen-specific IL-17 response in CD4+ but not CD8+ T cells. There was little evidence for Th1 or Th1/Th17 responses. The Th17 response promoted accelerated fungal clearance, and Th17 cells could confer protection in Rag1−/− mice upon adoptive transfer. Surprisingly, CD4 deficiency did not cause OPC but was instead associated with compensatory IL-17 production by Tc17 and CD3+CD4−CD8− cells. Therefore, classic CD4+Th17 cells protect from OPC but can be compensated by other IL-17-producing cells in CD4-deficient hosts.     

IL‐15‐dependent CD8+CD122+ T cells ameliorate experimental autoimmune encephalomyelitis by modulating IL‐17 production by CD4+ T cells

Interleukin‐15 (IL‐15) is an inflammatory cytokine whose role in autoimmune diseases has not been fully elucidated. Th17 cells have been shown to play critical roles in experimental autoimmune encephalomyelitis (EAE) models. In this study, we demonstrate that blockade of IL‐15 signaling by TMβ‐1 mAb treatment aggravated EAE severity. The key mechanism was not NK‐cell depletion but depletion of CD8⁺CD122⁺ T cells. Adoptive transfer of exogenous CD8⁺CD122⁺ T cells to TMβ‐1‐treated mice rescued animals from severe disease. Moreover, transfer of preactivated CD8⁺CD122⁺ T cells prevented EAE development and significantly reduced IL‐17 secretion. Naïve effector CD4⁺CD25^? T cells cultured with either CD8⁺CD122⁺ T cells from wild‐type mice or IL‐15 transgenic mice displayed lower frequencies of IL‐17A production with lower amounts of IL‐17 in the supernatants when compared with production by effector CD4⁺CD25^? T cells cultured alone. Addition of a neutralizing antibody to IL‐10 led to recovery of IL‐17A production in Th17 cultures. Furthermore, coculture of CD8⁺CD122⁺ T cells with effector CD4⁺ T cells inhibited their proliferation significantly, suggesting a regulatory function for IL‐15 dependent CD8⁺CD122⁺ T cells. Taken together, these observations suggest that IL‐15, acting through CD8⁺CD122⁺ T cells, has a negative regulatory role in reducing IL‐17 production and Th17‐mediated EAE inflammation.     

CTLA‐4 (CD152) enhances the Tc17 differentiation program

Although CD8⁺ T cells that produce IL‐17 (Tc17 cells) have been linked to host defense, Tc17 cells show reduced cytotoxic activity, which is the characteristic function of CD8⁺ T cells. Here, we show that CTLA‐4 enhances the frequency of IL‐17 in CD8⁺ T cells, indicating that CTLA‐4 (CD152) specifically promotes Tc17 differentiation. Simultaneous stimulation of CTLA‐4^+/+ and CTLA‐4^?/? T cells in cocultures and agonistic CTLA‐4 stimulation unambiguously revealed a cell‐intrinsic mechanism for IL‐17 control by CTLA‐4. The quality of CTLA‐4‐induced Tc17 cells was tested in vivo, utilizing infection with the facultative intracellular bacterium Listeria monocytogenes (LM). Unlike CTLA‐4^+/+ Tc17 cells, CTLA‐4^?/? were nearly as efficient as Tc1 CTLA‐4^+/+ cells in LM clearance. Additionally, adoptively transferred CTLA‐4^?/? Tc17 cells expressed granzyme B after rechallenge, and produced Tc1 cytokines such as IFN‐γ and TNF‐α, which strongly correlate with bacterial clearance. CTLA‐4^+/+ Tc17 cells demonstrated a high‐quality Tc17 differentiation program ex vivo, which was also evident in isolated IL‐17‐secreting Tc17 cells, with CTLA‐4‐mediated enhanced upregulation of Tc17‐related molecules such as IL‐17A, RORγt, and IRF‐4. Our results show that CTLA‐4 promotes Tc17 differentiation that results in robust Tc17 responses. Its inactivation might therefore represent a central therapeutic target to enhance clearance of infection.     

Redox imbalance and IL‐17 responses in memory CD4+ T cells from patients with psoriasis

All stages of the inflammatory process involved in T cell‐mediated chronic skin disorders like psoriasis are affected by redox imbalance. On the other hand, Th17 cells have a critical role in the pathogenesis of psoriasis. In this study, we evaluated redox status in memory CD4 + T cells and plasma of patients with psoriasis and its correlation with IL‐17 response. To this end, memory T cells were isolated from 10 patients with psoriasis and 10 controls. Intracellular Glutathione (GSH), reactive oxygen species (ROS) and superoxide as well as IL‐17 were measured using flow cytometry. Plasma total anti‐oxidant capacity (TAC) was quantified by ferric reducing ability of plasma (FRAP) assay. The expression of catalase (CAT), superoxide dismutase 1(SOD1), superoxide dismutase 2 (SOD2), nuclear factor, erythroid 2 like 2 (NFE2L2) and cytochrome b‐245 beta chain (CYBB) genes were analysed using real‐time PCR. Our results showed an increased intracellular ROS production in memory CD4 + T cells of patients compared to controls, (P = 0.04). Furthermore, a significant decrease in expression of catalase gene was found in patients, (P = 0.02). However, no significant differences were observed for intracellular GSH, IL‐17 and TAC levels between patients and controls. Also, no correlation was seen between the intracellular IL‐17 level and intracellular ROS, GSH and catalase gene expression levels. Collectively, we found an increased ROS production in stimulated memory T cells of patients that could be due to reduced expression of catalase gene. However, it seems that these redox abnormalities have no relationship with IL‐17 response in memory T cells.     

Psoriasis in humans is associated with down-regulation of galectins in dendritic cells

We have investigated the expression and role of galectin‐1 and other galectins in psoriasis and in the Th1/Th17 effector and dendritic cell responses associated with this chronic inflammatory skin condition. To determine differences between psoriasis patients and healthy donors, expression of galectins was analysed by RT‐PCR in skin samples and on epidermal and peripheral blood dendritic cells by immunofluorescence and flow cytometry. In the skin of healthy donors, galectin‐1, ‐3 and ‐9 were expressed in a high proportion of Langerhans cells. Also, galectins were differentially expressed in peripheral blood dendritic cell subsets; galectin‐1 and galectin‐9 were highly expressed in peripheral myeloid dendritic cells compared with plasmacytoid dendritic cells. We found that non‐lesional as well as lesional skin samples from psoriasis patients had low levels of galectin‐1 at the mRNA and protein levels, in parallel with low levels of IL‐10 mRNA compared with skin from healthy patients. However, only lesional skin samples expressed high levels of Th1/Th17 cytokines. The analysis of galectin‐1 expression showed that this protein was down‐regulated in Langerhans cells and dermal dendritic cells as well as in peripheral blood CD11c⁺ DCs from psoriasis patients. Expression of galectin‐1 correlated with IL‐17 and IL‐10 expression and with the psoriasis area and index activity. Addition of galectin‐1 to co‐cultures of human monocyte‐derived dendritic cells with autologous T lymphocytes from psoriasis patients attenuated the Th1 response. Conversely, blockade of galectin binding increased IFNγ production and inhibited IL‐10 secretion in co‐cultures of monocyte‐derived dendritic cells with CD4⁺ T cells. Our results suggest a model in which galectin‐1 down‐regulation contributes to the exacerbation of the Th1/Th17 effector response in psoriasis patients. Copyright © 2012 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Fetal BM‐derived mesenchymal stem cells promote the expansion of human Th17 cells,but inhibit the production of Th1 cells

Th type 17 (Th17) cells have been identified as a proinflammatory T‐cell subset. Here, we investigated the regulation of human Th17 cells by fetal BM‐derived mesenchymal stem cells (FBM‐MSC). We cocultured FBM‐MSC with human PBMC or CD4⁺ T cells from healthy donors. FBM‐MSC significantly suppressed the proliferation of CD4⁺ T cells stimulated by PHA and recombinant IL‐2. Significantly higher levels of IL‐17 were observed in FBM‐MSC cocultured with either PBMC or CD4⁺ T cells than that in PBMC cultured alone or CD4⁺ T cells cultured alone. Flow cytometry analysis showed that the percentage of Th17 cells in coculture of FBM‐MSC and CD4⁺ T cells was significantly higher than that in CD4⁺ T‐cell cultured alone. FBM‐MSC did not express IL‐17 protein. Consistent with the augmentation of Th17 cells, significantly higher levels of IL‐6 and IL‐1 were observed in coculture of FBM‐MSC and CD4⁺ T cells than that in CD4⁺ T‐cell culture, while the levels of IL‐23 were similar between FBM‐MSC + PBMC coculture and PBMC alone, or FBM‐MSC + CD4⁺ T‐cell and CD4⁺ T‐cell alone. The presence of FBM‐MSC decreased the percentage of Th1 cells, but minimally affected the expansion of CD4⁺CD25⁺ T cells. In conclusion, our data demonstrate for the first time that FBM‐MSC promote the expansion of Th17 cells and decrease IFN‐γ‐producing Th1 cells. These data suggest that IL‐6 and IL‐1, instead of IL‐23, may be partly involved in the expansion of Th17 cells.     

Role of podoplanin in the high interleukin‐17A secretion resulting from interactions between activated lymphocytes and psoriatic skin‐derived mesenchymal cells

In the context of psoriasis, T helper type 17 (Th17) cells infiltrate the inflammatory site and interact with local mesenchymal cells, including skin fibroblasts. The aim of this work was to study the interactions of skin‐derived fibroblasts with peripheral blood mononuclear cells (PBMC) with a focus on the Th17 pathway and to identify a mechanism which leads to a high interleukin (IL)?17 secretion. A co‐culture system between PBMC and skin fibroblasts was developed. Healthy and patient PBMC were added to non‐lesional or lesional skin fibroblasts at a 5:1 ratio for 48 h in the presence or not of activation with phytohaemagglutinin (PHA). Monocytes were removed or not by adherence before the co‐culture. An anti‐podoplanin antibody was also used during the co‐culture. Cytokine production (IL‐8, IL‐6, IL‐1β and IL‐17) was measured by enzyme‐linked immunosorbent assay (ELISA) and cell staining (CD3, CD4, IL‐17 and podoplanin) by flow cytometry. Without T cell receptor (TCR) activation, IL‐8, IL‐6 and IL‐1β production increased in PBMC‐fibroblast co‐culture compared to PBMC alone. No additional effect was observed with TCR activation, with no difference in the Th17 cell percentage in activated‐PBMC alone or co‐cultured. Conversely, IL‐17 production was increased highly only in co‐cultures between control and patient activated‐PBMC and skin fibroblasts. Removal of monocytes decreased cytokine production, notably that of IL‐17. Addition of an anti‐podoplanin antibody decreased IL‐17 secretion by 60%. Interactions between resting PBMC and fibroblasts induce the IL‐8, IL‐6 and IL‐1β production. PBMC activation and cell interactions are critical for a high IL‐17 secretion. Podoplanin contributes largely to this massive IL‐17 secretion.     

Distinctive features of classic and nonclassic (Th17 derived) human Th1 cells

T helper17 (Th17) lymphocytes represent a third arm of the CD4⁺ T‐cell effector responses, in addition to Th1 and Th2 cells. Th17 cells have been found to exhibit high plasticity because they rapidly shift into the Th1 phenotype in inflammatory sites. In humans, Th1 cells derived from Th17 cells express CD161, whereas classic Th1 cells do not; these Th17‐derived Th1 cells have been termed nonclassic Th1 cells. In this study, we examined similarities and differences between classic and nonclassic human Th1 cells by assessing a panel of T‐cell clones, as well as CD161⁺ or CD161^? CD4⁺ T cells derived ex vivo from the circulation of healthy subjects or the synovial fluid of patients with juvenile idiopathic arthritis. The results show that nonclassic Th1 cells can be identified based on CD161 expression, as well as the consistent expression of retinoic acid orphan receptor C, IL‐17 receptor E, CCR6, and IL‐4‐induced gene 1, which are all virtually absent in classic Th1 cells. The possibility to distinguish these two‐cell subsets by using such a panel of markers may allow the opportunity to better establish the respective pathogenic roles of classic and nonclassic (Th17 derived) Th1 cells in different chronic inflammatory disorders.     

Committed Tc17 cells are phenotypically and functionally resistant to the effects of IL‐27

IL‐17‐secreting CD8⁺ T cells (Tc17 cells) have been implicated in immunity to infections, cancer, and autoimmune diseases. Thus far, studies on Tc17 cells have primarily investigated their development from naïve precursors, while the biology of committed Tc17 cells has been less characterized, in particular during the effector phase of immune responses. IL‐27 is an important regulator of inflammation through the induction of regulatory Tr1 cells, as well as a suppressor of Th17‐cell development. IL‐27 suppresses the development of Tc17 cells, but its effects on committed Tc17 cells are unknown. Here we demonstrate that even though IL‐27 completely inhibited the development of C57BL/6 mouse Tc17 cells, it had little effect on previously committed Tc17 cells. Although committed Tc17 cells were capable of responding to IL‐27, it had no effect on expression of RORγt and RORα, or production of various cytokines. Committed Tc17 cells did not express granzyme B and lacked cytotoxicity in vitro, features that remained unaltered by IL‐27 treatment. Nonetheless, they efficiently induced diabetes, irrespective of treatment with IL‐27 prior to transfer into RIP‐mOVA mice. These findings suggest that use of IL‐27 to modulate autoimmune diseases might have limited therapeutic efficacy if autoaggressive Tc17 cells have already developed.     

Predominance of activated,clonally expanded T helper type 17 cells within the CD4+ T cell population in psoriatic lesions

Recent evidence points to the T helper type 17 (Th17) subset as key in the pathogenesis of psoriasis, but cells of this type in lesions remain to be fully characterized. Here we isolated, enumerated, functionally tested and clonotyped the CD4⁺ Th cell population ex vivo from lesional biopsies and paired peripheral blood samples from psoriasis patients. Th17 cells were over‐represented dramatically in lesions from all patients, representing 49–93% of CD4⁺ Th cells compared with 3–18% in blood. Most lesional Th17 cells produced interleukin (IL)‐17A ex vivo without further stimulation and expressed the CD45RO⁺ phenotype characteristic of activated or memory cells. There was no increase in ‘natural’ [CD25^hiforkhead box protein 3 (FoxP3⁺)] regulatory T cells in lesions versus peripheral blood, but there was enrichment of ‘induced’ IL‐10⁺ regulatory T cell numbers in biopsies from some patients. The lesional Th17 cells exhibited a bias in T cell receptor Vβ chain usage, suggestive of specific expansion by antigen. The therapeutic challenge is to overcome the dominance of overwhelming numbers of such antigen‐specific Th17 cells in psoriatic lesions.