The transcription factor BATF modulates cytokine-mediated responses in T cells

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Cytokine & Growth Factor Reviews xxx (2015) xxx–xxx

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Mini review

The transcription factor BATF modulates cytokine-mediated responses in T cells Nina Sopel, Anna Graser, Stephanie Mousset, Susetta Finotto* Department of Molecular Pneumology, Friedrich-Alexander University Erlangen-Nürnberg, 91052 Erlangen, Germany

A R T I C L E I N F O

A B S T R A C T

Article history: Available online xxx

The transcription factor BATF (basic leucine zipper transcription factor, ATF-like), belongs to the AP-1 family of transcription factors and has been shown to be predominantly expressed in cells of haematopoietic origin, especially in B and T cells. In studies using Batf-deficient mice, a profound defect in the differentiation of T helper cells type 17 (Th17) and follicular T helper cells (Tfh) was described, as well as an impairment of antibody production with switched isotypes. More recently BATF has been described to influence also Th2 and Th9 responses in models of murine experimental asthma. In CD8+ T cells BATF has been found associated with anti-viral responses. This review summarizes the role of BATF in CD4+ T cell subsets and in CD8+ T cells, with particular focus on this transcription factor in the setting of allergic asthma. ã 2016 Elsevier Ltd. All rights reserved.

Keywords: AP-1 BATF T cells Asthma

1. Introduction The family of basic leucine zipper transcription factors, ATF-like (BATF) comprises three members (BATF, BATF2 and BATF3) and belongs to the group of AP-1 transcription factors. These factors are homo- or heterodimers composed of Jun, Fos or ATF/CREB proteins. They possess a DNA-binding domain (DBD) and a leucine zipper motif (bZIP), interestingly, all BATF isoforms lack the transactivation domain other AP-1 factors, such as Jun or Fos, have [1,2]. Dependent on the composition of this dimer, the environment surrounding the cell and on other transcription factors or upstream kinases, AP-1 complexes are able to activate or inhibit target genes. The effects of AP-1 gene modulation involve i. a. proliferation, differentiation and survival of the cell [1–4]. BATF and BATF3 are mainly expressed in haematopoietic cells, with high BATF expression in T and B cells and BATF3 being especially important for the development of CD8a+ dendritic cells (DC). BATF2 was also found in non-haematopoietic cells, while there seems to be no expression in T cells. Recent data from knockout models suggests that the lack of one BATF type can be partly cross-compensated by other BATF family members [2,5,6].

Abbreviations: AHR, airway hyperresponsiveness; AP-1, activator protein 1; BALF, bronchoalveolar lavage fluid; BATF, basic leucine zipper transcription factor; OVA, Ovalbumin; STAT, signal transducer and activator of transcription. * Corresponding author at: Department of Molecular, Pneumology FriedrichAlexander University, Erlangen Nürnberg Hartmannstrasse 14, Room 0.011, 91052 Erlangen, Germany. E-mail address: susetta.fi[email protected] (S. Finotto).

Mice deficient for BATF have firstly been described to lack T helper cells type 17 (Th17) and follicular T helper cells (Tfh). Furthermore, it was found that these mice are incapable to produce antibodies with switched isotypes. Recently it has been shown that BATF also influences Th2, Th9 and Th1 responses in models of allergic airway diseases. Finally, anti-viral CD8+ T cell responses are altered in the absence of BATF [7–14]. Therefore, in this review we want to focus on the role of BATF in CD4+ and CD8+ T cells and its impact on effector functions in disease states, especially in murine experimental asthma. 2. Expression and regulation of BATF BATF was first described in 1995 by Dorsey et al. as a modulator of the AP-1 transcription complex in specific human tissues, after being identified in a cDNA library from human B cells infected with Epstein-Barr virus (EBV). By analysing poly-adenylated mRNA from different human tissues and established cell lines with northern blot analysis, they showed a strong hybridization in Raji Burkitt’s lymphoma and in the lung [15]. Only a few months later Hasegawa et al. published the finding of a new bZIP transcription factor, which they called SFA-2 (SF-HT-activated gene-2). This protein was also described to be highly expressed in T and B cells, especially after transformation with human T cell leukaemia virus type I (HTLV-I) [16]. Already in these first descriptions it was noted that BATF is unable to form homodimers and it prefers Jun-family members as dimer partners, which then bind to AP-1 binding sites on the DNA [15,16].

http://dx.doi.org/10.1016/j.cytogfr.2016.03.004 1359-6101/ ã 2016 Elsevier Ltd. All rights reserved.

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Further studies in human tissues verified BATF expression in haematopoietic cells and revealed that BATF is not expressed in embryonic cells and that it is differentially expressed throughout the development of thymocytes. While CD4 and CD8 doublenegative and CD4 or CD8 single-positive thymocytes express BATF, CD4 and CD8 double-positive cells do not express this factor [17,18]. In addition to its expression in T and B cells, there is evidence that BATF also plays a role in hematopoietic stem cells (HSC), as it is involved in limiting self-renewal and promoting lymphoid differentiation after DNA-damage in these cells [19]. 2.1. Inducing BATF expression BATF expression is described to mainly occur in hematopoietic tissues, e. g. spleen, thymus and lymph nodes [18], but also in hematopoietic stem cells [19]. BATF expression has been observed in the myeloid lineage in murine M1 myeloid leukaemia cells and in primary hematopoietic cells, isolated from murine bone marrow, rested for 4 h and then stimulated for 2 h with either Interleukin 6 (IL-6) or leukaemia inhibiting factor (LIF) [20,21]. In these cells, BATF expression has been shown to be induced by IL6 in a signal transducer and activator of transcription 3 (STAT3)dependent manner [21]. Furthermore, it has been described that BATF expression is necessary for a subset of IL-6-induced genes [10]. In naïve murine wild-type lung CD4+ T cells, addition of IL6 did not induce Batf mRNA expression in the context of antiCD3 and anti-CD28 antibody stimulation, however, if the transcription factor T-bet (T-box 21) is deleted, then IL-6 could induce Batf mRNA expression [22]. In the absence of IL-6, Ikeda and co-workers have demonstrated that in naïve CD4+ T cells Batf mRNA expression is induced by the cytokine IL-1. [23] Recently it has been discovered that under Th9-favoring conditions (IL4 + TGF-b) Batf expression is induced dependent on STAT6 [9]. In CD8+ T cells stimulated with IL-12 plus anti-CD3/antiCD28 antibodies and in B cells stimulated with IL-4 and lipopolysaccharide (LPS), Batf expression was found upregulated [7,24]. Furthermore, Batf expression in HSCs was observed to be induced by granulocyte-colony stimulating factor (G-CSF) via STAT3 [19]. 2.2. Post-translational modifications of BATF The activity and intracellular location of proteins can be influenced by post-translational modifications such as phosphorylation, ubiquitination, sumoylation or O-glycosylation. It has been shown that BATF can be phosphorylated on serine, threonine and tyrosine residues in vivo and in vitro. By mutating the serine residue on position 43 (S43) within the DBD, to mimic the phosphorylated (S43D) or the unphosphorylated (S43A) state respectively, it has been observed that both mutants formed heterodimers with Jun and were detectable in the nucleus. Furthermore, both mutants were able to inhibit the activity of a simple AP-1 reporter gene construct, even though the phosphorylated form (S43D) could not bind to DNA. These results led to the conclusion that phosphorylation of BATF has an impact on DNA binding, but not on its intracellular localization. It has been assumed that, due to its small size, BATF can freely diffuse into the nucleus or that it is actively transported when bound to a dimer partner [25]. 3. BATF expression in lymphocytes To determine the effects of a transcription factor and to estimate its impact on the phenotype of cells, it is possible to either overexpress or delete the protein of interest. In case of BATF, several approaches have been made: to date there are two models which overexpress a hemagglutinin-tagged form of BATF (HA-

BATF) under either the murine thymus-specific p56lck promoter [26] or the human CD2 promoter, to achieve an overexpression of BATF in T cells [27]. Furthermore, three independently generated Batf knockout models have been described so far. The first model to be published was the Batf / mouse, where the exons I and II were deleted by homologous recombination [10]. In the literature, the second Batf-deficient mouse strain is referred to as BatfDZ/DZ mouse, here exon III was removed [7]. In the third model, the coding sequence of exon I was replaced with the sequence for green fluorescent protein (GFP, Batfgfp/gfp) [24]. All of the currently available Batf-deficient models are global knockouts, with no detectable BATF expression in every cell type. 3.1. BATF expression in B cells After overexpression of BATF-HA under the CD2 promoter, a reduction of the total cellularity of the spleen was observed, with lower numbers of both T and B cells [28]. However, deletion of BATF, in both the Batf / and the BatfDZ/DZ model, did not alter the development of B cells [7,10]. Interestingly, while the concentration of IgM antibodies in the serum of BatfDZ/DZ mice was comparable to that of wild-type mice, none of the other antibody classes were detected, independently of confrontation with antigen. This was accompanied by a lack of germinal centre formation in the spleen, but B cell proliferation was not altered. Further analysis identified that the expression of the Aicda gene, which encodes for activation-induced cytidine deaminase (AID) is barely detectable in purified B cells, indicating a role for BATF in the signalling pathway between B cell activation and Aicda expression [7]. Studies using the Batf / model confirmed the normal B cell proliferation and plasma cell differentiation, as well as the lack of AID expression. Furthermore, it has been shown that the expression of other proteins, which influence the class-switch recombination (CSR) in B cells, e. g. Bach-2, Bcl-6 and Blimp-1, were not altered in the absence of BATF. While it has been observed that BATF probably directly regulates Aicda gene expression, retroviral AID expression in Batf-deficient cells did not restore CSR. Assuming further contribution of BATF to CSR, germline transcripts (GLT) of I-region promoters upstream of the switch regions were analysed and found decreased for every isotype, except the m-chain. Retroviral overexpression of BATF, in contrast, enhanced GLTs from all I-region promoters. These data indicate an intrinsic role for BATF for the isotype-switching of antibodies [8]. 3.2. Thymic BATF expression As noted above, it was discovered that during T cell development in the thymus the expression of BATF varies in different stages [18]. This was also observed when BATF was overexpressed (p56lck promoter model), however the proliferation of those cells was diminished after different stimuli in both overexpression models (p56lck and CD2 promoter) [26,27]. Furthermore, the in vitro secretion of several cytokines, e. g. IL-2, IL-4, IL-10, was strongly decreased in p56lck-HA-BATF thymocytes as compared to wildtype cells. Analysing natural killer T (NKT) cells in the thymus revealed a defect in their development [26], which was attributed to both an impaired expansion and maturation of these cells when BATF is overexpressed [29]. Interestingly, deletion of BATF did not seem to impair NKT cell development [7,10]. 3.3. BATF in CD4+ T cells To define the role of BATF in different T cell subsets, in vitro differentiation studies were conducted with wild-type and Batfdeficient naïve CD4+ T cells. While no difference was observed in

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the capacity of Batf / cells to differentiate into Th1, Th2 or Treg cells, a profound defect was discovered in Th17 development. Also in a murine in vivo model of multiple sclerosis (experimental autoimmune encephalomyelitis, EAE), which relies on Th17 cells, Batf-deficient mice were protected from the disease. Further studies revealed that important genes for Th17 development, namely Rorc,Rora, Il17 and Il21, are dependent on BATF, while the signalling pathway of the Th17-inducing cytokines IL-6 and TGF-b is not altered. It was shown that BATF directly binds to several promoter- and intergenic regions of the Il17a-Il17f gene locus. Additionally, more BATF binding sites were identified in the promoter regions of Il21 and Il22 [10]. A study carried out by Li et al. also showed that the BATF-Jun dimer together with interferon regulatory factor 4 (IRF4) influences the expression of IL-10 in Th17 cells [30]. In the BatfDZ/DZ model, in vitro differentiation experiments verified the findings on normal Th1 and Treg development, as well as impaired Th17 cell differentiation, as observed in the Batf / model. However, in the BatfDZ/DZ model, the Th2 differentiation was reduced, as shown by decreased Gata3 and Il4 mRNA levels in the absence of BATF. This might be due to the genetic background, as the BatfDZ/DZ cells used were isolated

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from mice with a C57/Bl6 genetic background and the reduced Gata3 and IL-4 levels were not detected when cells were isolated from Batf-deficient Balb/c mice [7,8]. Beside the impaired Th17 differentiation, Batf-deficient mice also lack CXCR5+ follicular T helper cells. In Tfh cells, Bcl-6 and cmaf expression was identified to be directly regulated by BATF [7,8]. Recently it has been shown that also expression of IL-4 is dependent on BATF in these cells [14]. Tfh cells are found in germinal centres and by giving T cell help to B cells influence antibody CSR. As there is no germinal centre formation and no antibody CSR in the absence of BATF, probably both T and B cellintrinsic effects are involved [7,8,31]. Regarding the Th9 subset, Jabeen et al. have shown that naïve CD4+ T cells lacking BATF hardly differentiate into Th9 cells under Th9-favoring conditions [9]. 3.4. BATF in CD8+ T cells Reports on the expression of BATF in CD8+ T cells are mainly associated with chronic viral infections. In a first study analysing murine and human CD8+ memory T cell development, it was

Fig. 1. The role of BATF on T cell responses in allergic asthma. Upon allergen contact in the lung, epithelial cells are stimulated to release TGF-b and IL-6. Other sources of IL6 are dendritic cells (DC). TGF-b and IL-6 together stimulate CD4+ T cells to differentiate into Th17 cells and TGF-b alone favours the development of regulatory T cells (Treg). IL-6 and IFNg, which is secreted from Th1 cells, inhibit Treg differentiation. Th2 and Th17 cells are contributing to the pathogenicity of allergic asthma, while Treg and Th1 cells are thought to play an inhibitory role. (a) In wild-type mice in a murine model of allergic asthma, BATF is crucial for Th17 development, influences Th2 differentiation and its expression is up-regulated in asthma. (b) In the absence of BATF in experimental allergic asthma, Th17 cells fail to develop and Th2 cells are diminished. IFNg secreting CD4+ Th1 cells are increased in this setting, influencing the number of Treg cells.

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shown that BATF expression is induced in those cells [32]. Later, BATF expression was found increased in HIV-gag-protein-specific CD8+ T cells, but not in naïve CD8+ T cells [33]. Comparing acute and chronic infections with lymphocytic choriomeningitis virus (LCMV) in mice revealed that during chronic infection BATF expression is rapidly induced and expressed over a long period of time, which lead to the conclusion that high and persistent levels of BATF could be used as a marker of exhausted CD8+ T cells. This was supported by the finding that T cell effector function was improved by siRNA-mediated knockdown of BATF in HIV-gagprotein-specific CD4+ and CD8+ T cells [33]. Analysing the Batfgfp/gfp reporter mouse and the model antigen Ovalbumin (OVA), Kuroda et al. observed that in these mice antigen-specific CD8+ T effector cell differentiation in the spleen is decreased after five days and this decrease is maintained until after 30 days. Additionally, in this model, BATF seemed to add to the IL12-mediated acetylation of histone H3 and the induction of oxidative phosphorylation in the metabolism of the cell. Further in vivo studies using LCMV infection demonstrated reduced numbers of virus-specific CD8+ T cells in the absence of BATF, which secreted lower amounts of Interferon gamma (IFNg) and showed a higher rate of apoptosis [24]. In accordance with these findings, LCMV infected Batf-deficient mice display increased viral replication in the lung, liver and spleen. These results lead to the conclusion that BATF is a necessary factor to control LCMV infections and that the observed defects in the absence of BATF are dependent on CD8+ T cells [12]. Further studies confirmed these findings and extended them by the observation that not only primary responses are influenced by BATF, but also secondary effector immune responses are diminished when BATF is lacking, hinting a function in memory formation. Using ChIP-Seq techniques it has been found that BATF is able to bind to regulatory regions of many genes, including genes for CD8+ effector function (e.g. Prdm1, Id2), molecules involved in TCR signalling (e.g. Cd28, Csk) or coding for effector molecules (e.g. Il2, Ifng). In this study evidence was provided for a role of BATF during the transition from naïve to effector CD8+ T cells. [13] This has been further investigated by Godec et al., where BATF was identified to be essential for the early phase of CD8+ T cell effector differentiation. Using an acute LCMV infection model and an inducible shRNA-dependent knockdown of Batf, it has been shown that more cells undergo apoptosis by day five after infection when Batf expression was reduced from the beginning, while inhibition of Batf 72 h after infection had no influence on CD8+ effector cell differentiation [34]. 4. Contribution of BATF expression to allergic diseases All data on BATF that has been obtained so far, implies that this transcription factor could be a key player in orchestrating multiple aspects of allergic and inflammatory diseases or cancer. T helper cell subtypes and/or antibodies contribute to the pathophysiology of many diseases, e.g. asthma, EAE or inflammatory bowel disease (IBD) [35–37]. As the major interest of our group focuses on asthma, we want to discuss in the following paragraphs the current knowledge of BATF in the setting of allergic asthma. 4.1. The allergic immune response In allergic asthma, in addition to cells of the innate immune system e. g. eosinophils and mast cells, several T helper cell subsets contribute to the pathogenicity of the disease. Th2 cells and their signature cytokines IL-4, IL-5 and IL-13 are described to cause classical symptoms observed in asthma, such as airway hyperresponsiveness (AHR), eosinophilia in the lung and tissue

remodelling [35]. IL-17 producing Th17 cells are also thought to drive AHR and additionally to promote neutrophilia in the lung, contributing to a more untreatable and severe form of this disease [35,38]. Additionally, Th9 cells are involved in asthma pathogenesis. In a house dust mite (HDM) induced model of allergic asthma it has been observed that Th9 cells develop even earlier than Th2 cells. In human atopic patients higher numbers of Th9 cells correlated with elevated IgE levels. [39] IgE is released from B cells and binds to the Fc epsilon receptor I (FceRI) expressed on the mast cell membrane. When cell surface-bound IgE antibodies are crosslinked with antigen, mast cells rapidly release broncho-constrictive substances, such as histamine and prostaglandin, which further enhance the inflammatory response [40,41]. While all of the above mentioned cell types are supposed to have proinflammatory properties in asthma development, Th1 and Treg cells are thought to play a protective role [42,43]. Fig. 1a depicts molecular processes during asthmatic inflammation. All these facts together with the knowledge that BATF is a crucial factor for the development of Th9, Th17 and Tfh cells, as well as antibody CSR suggest BATF as a key transcription factor orchestrating the multiple aspects of allergic asthma. 4.2. BATF and the allergic phenotype In the past years we have been investigating the role of BATF in asthma by using Batf-deficient and transgenic mice, which overexpress BATF under the CD2 promoter, in different models of allergic asthma [10,11]. Compared to wild-type mice, we observed that lack of BATF protects the mice from acquiring an asthmatic phenotype. The cardinal features of allergic asthma, AHR, eosinophilia, neutrophilia, lung inflammation and mucus hyperproduction were markedly decreased in the absence of BATF [11]. Using different models of adoptive transfer with Batf-deficient and -sufficient cells and allergen challenge, other groups confirmed these findings [9,14]. For example, in the study by Jabeen et al., where they used a Th9-dependent model of OVA-induced asthma (OVA plus thymic stromal lymphopoietin, TSLP) and then transferred CD4+ T cells from wild-type and BatfDZ/DZ mice into RAG-deficient hosts, mice that received Batf-deficient T cells displayed an ameliorated asthmatic phenotype as compared to those mice that received wild-type T cells [9]. So far BATF expression has been described in hematopoietic tissues [18], hematopoietic stem cells [19], murine M1 myeloid leukaemia cells and in primary hematopoietic cells, isolated from murine bone marrow [20,21]. In our study on Batf-deficient mice in a murine model of allergic asthma, we observed that, beside the expected lack of IgE antibodies, also mast cells, which derive from common myeloid progenitors [44] and are important players in asthma [41], are markedly decreased in the lungs of OVA sensitized and challenged mice in the absence of BATF [11]. The cytokine IL-3, released by Th2 cells, is an important growth and developmental factor for mucosal mast cells [45]. When we measured IL-3 levels in the supernatants of total lung cells, we saw that in asthmatic mice lacking BATF, IL-3 levels were barely detectable, while wildtype cells secreted high amounts of it [11]. Therefore, to determine if Batf / mice had a defect in mast cell development, we generated bone marrow derived mast cells (BMMC) from wildtype and Batf / mice. For evaluation, we assessed the cell membrane expression of classical mast cell markers c-kit, the receptor for stem cell factor (SCF), IL-3 receptor alpha chain (CD123) and the high affinity receptor for IgE, FceRI, by flow cytometry. As in the lung, we observed a decrease of ckit+FceRI+CD123+ BMMC when BATF was lacking, indicating a yet unknown role of BATF in mast cell development, which needs further investigation [11].

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4.3. Impaired Th2 and Th17 responses in the absence of BATF The first in vitro differentiation experiments revealed that depending on the model used, Th2 differentiation was not altered [10] or slightly diminished [7], while Batf-deficient cells had a profound defect in Th17 development, independent of the mouse strain analysed [7,10]. In our, as well as in other experimental models of asthma, a decreased secretion of Th2-related cytokines (IL-4, IL-5, IL-13) was observed after OVA treatment in the absence of BATF [9,11,14]. Furthermore, we found that Gata3 mRNA expression, which is vitally important for the Th2 program, was reduced in Batf / lung CD4+ T cells after OVA treatment [11,46]. These data indicate a role for BATF in Th2 cells (Fig. 1b). This notion is supported by more recent studies using again a Th2 in vitro differentiation approach, where expression of the cytokines IL-4, IL-5 and IL-13, as well as GATA3 expression were decreased. Moreover, it was shown by ChIP analysis that BATF can bind to the promoter region of Gata3 [9,14]. As demonstrated by several groups, IL-17 secretion is barely detectable in the absence of BATF, independent of treatment with OVA. Also the described defects in RORgt (encoded by Rorc) expression and IL-10 and IL-21 secretion in Batf-deficiency were confirmed in our model of experimental murine asthma (Fig. 1b) [7,9–11,30]. 4.4. Differential effects of BATF on CD4+ Th1 and CD8+ Tc1 effector function Previous publications have found no influence of BATF on Th1 differentiation [7,10], however in our model of allergic lung inflammation we saw markedly increased levels of IFNg in the BALF of OVA treated Batf / mice [11]. Th1 responses are thought to have a protective role in allergic asthma [47] and further experiments revealed that in the lungs of Batf-deficient mice higher numbers of IFNg+ T cells can be found in both the CD4+ and the CD8+ compartment, but not in other cell types, e.g. CD11c+ cells, independently of being treated with OVA or not (Fig. 1b) [11]. In contrast, in CD8+ T cells from Batfgfp/gfp mice, that were stimulated with IL-12 plus anti-CD3/anti-CD28 antibodies, BATF seemed to be involved in acetylation of the Tbx21 (coding for T-bet) promoter, as it was shown that both Tbx21 and Ifng mRNA levels were reduced in the absence of BATF [24]. Diminished IFNg expression in Batfdeficiency was also observed in antigen specific CD8+ T cells after LCMV infection [12]. Another study using LCMV infection discovered that the transcription factor Eomesodermin (Eomes) was less expressed in Batf-deficient CD8+ T cells, while T-bet expression was unaltered or also decreased. Interestingly, the same study found that IFNg and Eomes expression is enhanced in in vitro stimulated versus naïve CD8+ T cells lacking BATF, while Tbx21 expression is not induced or inhibited. The authors argue that in CD8+ T cells BATF might mediate the transition from naïve to effector cells, with TCR-signalling-dependent activation of BATF as a first step and subsequent induced expression of T effector cell transcription factors and cytokine receptors, with concurrent inhibition of effector molecule synthesis [13]. Taken together, the actions of BATF in Th1 and Tc1 cells are so far unresolved and seem to differ according to the organs analysed, the stimuli used and the time point of analysis. Therefore further studies are needed to define a clear role of BATF in Th1 and Tc1 cells.

found a decreased number of CD4+CD25+FoxP3+ lung Treg cells in the absence of BATF in untreated as well as in OVA treated mice. Consistent with the role of STAT5 in Treg cells and the absence of these cells in STAT5 deficient mice [51], we found a decrease of phosphorylated STAT5 (pSTAT5) in Batf / asthmatic mice (Fig. 1b) [11]. Intranasal application of an anti-IFNg antibody during the challenge phase of the OVA model increased the amount of CD4+CD25+FoxP3+ Treg cells, as compared to IgG control antibody treatment. Interestingly, anti-IFNg treatment did enhance Treg cell numbers, but there were still fewer of them than in the wild-type controls, indicating that the increased amounts of IFNg in the absence of BATF affect peripheral Treg cell development, but also suggesting that other factors are involved [11]. Thus the role of BATF in Treg cells is far from being resolved: our data imply an influence of BATF on Treg cell development, probably by regulation of IFNg expression and/or by a yet unknown mechanism [11]. Betz et al. also observed a decrease in splenic Treg cells isolated from naïve mice, but in their in vitro differentiation approach mentioned above, they did not observe a difference in Treg cell development in the absence of BATF [7]. In a model of EAE, Schraml et al. also showed diminished numbers of splenic FoxP3+ Treg cells in Batf / mice, independently of immunization with MOG(35–55) peptide [10]. They further analysed FoxP3 induction after stimulating naïve CD4+ T cells with TGF-b1 and found no difference between the wild-type and BATF knockout. Interestingly, when these cells were stimulated with both TGF-b and IL-6, the amount of FoxP3+ cells was even elevated in the absence of BATF [10]. A microarray analysis of in vitro differentiated Treg cells showed that BATF is expressed in these cells, but in qRT-PCR studies the mRNA expression levels of Batf are relatively low as compared to e.g. Th9 and Th17 cells [9]. 5. Potential use of BATF inhibition as a therapeutic approach The transcription factor BATF has been shown to influence the cytokine responses of several T helper cell subsets [7,9–11,14]. As the immune response of allergic asthma is complex and involves different sets of T helper cells [35,43], the inhibition of BATF in CD4+ T cells locally in the lung might be a possible therapeutic strategy. In asthma, most of the previous therapeutic approaches focused on the neutralization of effector molecules, e.g. IL-5 and IgE, or the blockade of receptors (e.g. IL-4R) but with limited success [52]. Targeting BATF could reduce many of these effector molecules at the same time. Inhibition of BATF expression could be accomplished by either RNA interference (RNAi) or a small molecule specifically targeting BATF. A further challenge might be to only suppress BATF expression in CD4+ T cells, as CD8+ T cell responses, especially against viruses, might be detrimental with decreased BATF levels. 6. Conclusions The transcription factor BATF plays a key role in the differentiation of T helper cell subsets and Ig class-switching [7– 10]. Apart from that we suggest an important function in mast cell development and in murine models of allergic asthma it was observed that mice deficient for Batf are protected from the disease [9,11,14]. Taken together, the previous findings on BATF make it an interesting target for the treatment of allergic asthma, as well as other T helper cell-derived-cytokine-driven diseases.

4.5. BATF in regulatory T cells Beside Th1 cells, regulatory T cells are also described to be beneficial in asthma [48,49], but IFNg suppresses peripheral Treg cell development [50]. In accordance with this, in our study we

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Conflict of interest The authors declare no conflicts of interest.

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Acknowledgements This work was funded by the Department of Molecular Pneumology, Friedrich-Alexander University Erlangen-Nürnberg and the SFB643 “Strategies of cellular immune intervention”, Friedrich-Alexander University Erlangen-Nürnberg.

[25]

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Please cite this article in press as: N. Sopel, et al., The transcription factor BATF modulates cytokine-mediated responses in T cells, Cytokine Growth Factor Rev (2016), http://dx.doi.org/10.1016/j.cytogfr.2016.03.004

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Nina Sopel is a PhD student in the laboratory of Prof. Dr. Dr. Susetta Finotto at the Department of Molecular Pneumology of the Friedrich-Alexander University Erlangen-Nürnberg. She obtained her Master of Science Degree in Biology in 2011 from the Technical University in Munich. Her research filed is the immunologic response in Asthma bronchiale, with a focus on T cell immunology in murine models of allergic asthma

Anna Graser graduated from the University of Regensburg as a pharmacist in 2010. She obtained her PhD in 2015 at the Department of Molecular Pneumology of the Friedrich-Alexander University Erlangen-Nürnberg. Her studies involved the role of Rhinovirus on Th17 cells as well as the role of IL-17A in asthma.

Stephanie Mousset graduated in Molecular Life Sciences in 2011 at the Friedrich-Alexander University ErlangenNürnberg. During her time as a PhD student in the laboratory of Prof. Dr. Dr. Susetta Finotto she analysed the role of nuocytes in allergic asthma, as well as immunotherapeutic strategies in different mouse strains.

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Susetta Finotto graduated at the University of Padua, Italy. After her PhD studies in the Division of Clinical Immunology and Allergy, Department of Medicine under the supervision of Profs J .A. Denburg, J. Dolovic and J. S. Marshall, she continued a post-doc training at the Molecular Medicine, McMaster Immunology Research Centre in Prof. J. Gauldie’s laboratory. She then performed studies on the role of Stem Cell Factor in mast cells and in allergic asthma under the supervision of Prof. Dean D. Metcalfe at the National Institute of Allergy and Infectious Diseases in the laboratory of Allergic Diseases, in Bethesda, MD. She then did Post-doctoral training at the Institute of Cellular Biology at the University of Heidelberg. She habilitated at the University of Mainz, after a Post-doctoral training on the role of T cells in asthma. In Mainz, she was the Head of the laboratories of Lung Immunology and Chief of the asthma core facility. In 2000, she did a Sabbatical year at Prof J. M. Drazen’s laboratory at the Pulmonary Medicine at Brigham and Women’s Hospital, Harvard Medical School in Boston, MA. In 2009 she was appointed Head of the Department of Molecular Pneumology at the University Hospital in Erlangen. Prof. Finotto’s research interest is focused on immunologic mechanisms underlying Asthma bronchiale and lung tumours.

Please cite this article in press as: N. Sopel, et al., The transcription factor BATF modulates cytokine-mediated responses in T cells, Cytokine Growth Factor Rev (2016), http://dx.doi.org/10.1016/j.cytogfr.2016.03.004