T‐bet, a Th1 transcription factor regulates the expression of Tim‐3

Abstract

T-cell immunoglobulin, mucin domain-3 (Tim-3) is a membrane protein expressed at late stages of IFN-c secreting CD4 1 Th1 cell differentiation and constitutively on DC. Ligation of Tim-3 on Th1 cells terminates Th1 immune responses. In addition, Tim-3 plays a role in tolerance induction, although the mechanism by which this is accomplished has yet to be elucidated. While it is clear that Tim-3 plays an important role in the immune system, little is known regarding the molecular pathways that regulate Tim-3 expression. In the current study, we examine the role of Th1-associated transcription factors in regulating Tim-3 expression. Our experiments reveal that Tim-3 expression is regulated by the Th1-specific transcription factor T-bet. This introduces a novel paradigm into the generation of a Th1 response, whereby a transcription factor responsible for effector Th1 cell differentiation also increases the expression of a specific counter-regulatory molecule to ensure appropriate termination of pro-inflammatory Th1 immune responses.Key words: Autoimmunity . T cells . Transcription factors Supporting Information available online Introduction T-cell immunoglobulin, mucin domain-3 (Tim-3) is a type I transmembrane protein, originally identified as specifically and selectively induced upon the differentiation of naive CD4 1 Th cells into IFN-g-secreting Th1 effector cells [1], where it serves to promote termination of Th1 cells upon interaction with its ligand, galectin-9 [2]. Modulation of the Tim-3:galectin-9 pathway has potent effects in vivo as treatment with anti-Tim-3 antibody exacerbates the induction of EAE, an animal model of MS [1], and administration of Tim-3 fusion protein to immunized mice results in an uncontrolled Th1 response [3]. In addition, WT mice treated with Tim-3 fusion protein, as well as Tim-3-deficient mice, are refractory to tolerance induction [3,4]. Taken together, these data demonstrate the importance of the Tim-3:galectin-9 pathway in regulating inflammatory T-cell responses and states of immunological tolerance. Recently, Tim-3 expression has been demonstrated on DC and on cells of the innate immune system [5]. However, the factors that regulate Tim-3 expression in both T cells and innate immune cells have not been identified.Ã These authors contributed equally to this work. 859Recent evidence shows a correlation between mRNA expression levels of the Th1-specific transcription factor T-bet (Tbx21; T-box expressed in T cells), IFN-g and Tim-3 in T-cell clones from both patients with MS and healthy controls [6]. In this study, the linked expression of T-bet, IFN-g and Tim-3 could simply be due to the fact that T-bet is required for IFN-g transcription and IFN-gproducing Th1 cells predominantly express Tim-3 on their cell surface. Direct evidence that T-bet controls Tim-3 expression was lacking from this study. Interestingly, like Tim-3, T-bet is also expressed in DC where it controls IFN-g production [7] and is required for optimal TLR responsiveness [8]. Given that T-bet is crucial for in...

Antigen-Independent Induction of Tim-3 Expression on Human T Cells by the Common γ-Chain Cytokines IL-2, IL-7, IL-15, and IL-21 Is Associated with Proliferation and Is Dependent on the Phosphoinositide 3-Kinase Pathway

“…This suggests that in inflammatory states, where IL-2 and IL-15 are being produced, Tim-3 is upregulated, possibly to dampen the inflammatory process. Tim-3 was originally described as a Th1-related molecule and was recently shown to be upregulated on cells that have turned on the Th1 transcriptional protein T-bet (31). We find that Tim-3 is more easily induced on CD8 + T cells compared with CD4 + T cells in human samples, consistent with previous ex vivo studies (9).…”

“…For IL-2, this mechanism involves an increase in the levels of p-STAT5, which, in turn, induces expression of T-bet (48). Tim-3 expression is regulated directly by T-bet (31). Although IL-15 and IL-21 also increase IFN-g production (46), it is interesting to note that, through the induction of Tim-3 via T-bet, these cytokines can play a counter-regulatory role as well.…”

Activation of mitogen activated protein kinase-Erk kinase (MEK) increases T cell immunoglobulin mucin domain-3 (TIM-3) transcription in human T lymphocytes and a human mast cell line

“…However, these authors did not investigate the TIM-3 promoter activity in stimulated cells (Zhang et al, 2009). In murine TH1 cells, T-bet, a critical transcription factor for TH1 differentiation, binds directly to the Tim-3 promoter at approximately 400 bp upstream of the first ATG and up-regulates Tim-3 expression (Anderson et al, 2010). Although STAT-4 dose not bind to the Tim-3 promoter, its role is suggested in Tim-3 transcription since Tim-3 expression is reduced in STAT-4 knockout murine T cells (Anderson et al, 2010).…”

“…In murine TH1 cells, T-bet, a critical transcription factor for TH1 differentiation, binds directly to the Tim-3 promoter at approximately 400 bp upstream of the first ATG and up-regulates Tim-3 expression (Anderson et al, 2010). Although STAT-4 dose not bind to the Tim-3 promoter, its role is suggested in Tim-3 transcription since Tim-3 expression is reduced in STAT-4 knockout murine T cells (Anderson et al, 2010). Further study is required to reveal the element in TIM-3 promoter that is responsive to MEK activation.…”

“…In mast cells, TIM-3 expression is enhanced by treatment of tumor growth factor-␤ (TGF-␤) or by stimulation with antibody against Fc RI (Nakae et al, 2007;Wiener et al, 2007). Recently the involvement of T-box transcription factor T-bet and signal transducer and activator of transcription (STAT)-4 in TIM-3 transcription of murine T cells has been reported (Anderson et al, 2010). However, the regulatory mechanisms for TIM-3 expression remain to be explored.…”