Loading

Journal of Immunology and Clinical Research

Regulatory T Cell Development from the Top Down: the Role of T Cell Receptor-Generated Second Messengers in Thymic Regulatory T Cell Development

Review Article | Open Access

  • 1. Department of Pathology and Laboratory Medicine, Division of Transfusion Medicine and Therapeutic Pathology, Perelman School of Medicine at the University of Pennsylvania, USA
+ Show More - Show Less
Corresponding Authors
Taku Kambayashi, Department of Pathology and Laboratory Medicine, 288 John Morgan Building, 3620 Hamilton Walk, Philadelphia,
Abstract

Regulatory T cells (Treg)s are a subset of CD4+ T cells with suppressive properties. Their function and development relies on the expression of the lineage-determining transcription factor Foxp3. Mutations in Foxp3 result in the failure of Treg development, leading to widespread autoimmunity and death in mice and in humans. Although some Tregs acquire expression of Foxp3 in the periphery (inducible Tregs; iTregs), a larger proportion of Tregs called natural Tregs (nTregs) are generated in the thymus during T cell development. Thymic Treg development is dependent on intracellular signal transduction events transduced by the T cell receptor (TCR), co-stimulatory molecules, and cytokines. Here we review the proximal signals emanating from the TCR that are essential for proper thymic Treg development, with particular emphasis on the PLCγ pathway

Keywords


•    Regulatory T cells
•    PLCγ pathway
•    TCR-mediated signals
 

Citation

Schmidt AM, Kambayashi T (2014) Regulatory T Cell Development from the Top Down: the Role of T Cell Receptor-Generated Second Messengers in Thymic Regulatory T Cell Development. J Immunol Clin Res 2(2): 1019.

REGULATORY T CELLS

Regulatory T cells (Tregs) are a subset of CD4+ T cells that are defined by expression of the transcription factor Foxp3, as well as their ability to suppress T cell-mediated immune responses [1,2]. Genetic mutations resulting in dysfunctional Foxp3 production lead to failed Treg generation and subsequently to fatal T cellmediated autoimmune inflammation in both mice and humans [3-7]. Tregs also prevent tissue damage resulting from excessive immune responses to foreign and commensal antigens [8-10]. Because of the importance of these cells in immune tolerance, the investigation of Treg development has been the focus of intense immunological research. A combination of T cell receptor (TCR), costimulatory receptor, and cytokine receptor ligation events are required for Foxp3 upregulation and entry of developing CD4+ T cells into the Treg repertoire [11]. Here, we review recent work elucidating the proximal signal transduction events downstream of the TCR that are required for formation of the Treg lineage.

High affinity TCR signals are required for natural Treg generation in the thymus

Like all T cells, naturally occurring (n)Tregs are generated through a tightly regulated development process occurring within the thymus, allowing for the production of a diverse population of Tregs with a wide array of TCR specificities [12]. Developing T cells perceive TCR-mediated survival signals generated from interactions with major histocompatibility complexes (MHC) bearing self peptides, allowing for positive selection, while overly strong signals lead instead to death by negative selection. Thus, the selection process acts both to impart T cells with the ability to respond to foreign peptides presented in the context of MHC, and to prevent overt T cell-mediated autoimmunity. While strong TCR-mediated signals can induce apoptosis in developing T cells, they can also instruct these cells toward Foxp3 upregulation and entry into the nTreg pool [13]. This phenomenon has been observed in multiple strains of TCR transgenic mice in which all T cells have been engineered to bear a TCR of a single specificity. In the absence of cognate peptide expression in the thymus, little to no Treg development is observed. However, when the cognate peptide is present during thymic development, an unusually high percentage of CD4+ T cells upregulate Foxp3 and obtain suppressive ability [14-18]. In addition, when the transgenically expressed self-antigen was altered such that the transgenic TCR bound to it with decreased affinity, Treg production was diminished in these models [15,19]. Such findings favor the notion that strong TCR-mediated signals are required to promote Treg development.

In addition to the TCR transgenic mouse models, the role of strong TCR signals for the selection of Tregs has been examined in the polyclonal setting using TCR-driven immediate early gene Nur77 expression as a surrogate for TCR signal strength. Nur77- driven GFP reporter-based studies demonstrate that both thymic and peripheral Tregs perceive TCR signals of higher magnitude than other CD4+ T cells [20,21]. Additionally, when the Nur77- GFP reporter mouse was bred to mice lacking the pro-apoptotic molecule Bim, CD4+ T cells that were rescued from clonal deletion had levels of Nur77-driven GFP similar to the levels normally found in Tregs [21]. This suggests that negative-selecting TCR signals are of similar strength to those that induce Treg generation. Together, these data suggest that strong TCR signals play a critical role in the generation of Tregs..

TCR-driven PLCγ1 activation is required at multiple stages of nTreg development

TCR ligation induces a cascade of TCR-mediated signal transduction events, emanating from the formation of multimolecular protein complexes beneath the surface of the cell [22]. One key event downstream of these proximal signaling complexes is the activation of phospholipase C γ1 (PLC-γ1). PLC-γ1 cleaves phosphatidylinositol-4,5-bisphosphate (PIP2 ) into a single molecule of inositol-1,4,5-triphosphate (IP3 ) and diacylglycerol (DAG) [23]. TCR-mediated PLC-γ1 activation is an absolute requirement for Treg development, as mice harboring a mutation disrupting PLC-γ1 recruitment post-TCR engagement fail to generate Tregs even though T cell positive selection is maintained [24]. This finding specifically implicates signal transduction events downstream of PLC-γ1 as the crucial components of TCR-mediated signaling that promote Treg development. Indeed, both IP3 and DAG generated by PLC-γ1 induce downstream activation of several transcription factors including NFAT, NF-κB, and AP-1; all of which have been shown to bind within promoter and/or enhancer regions of the Foxp3 genetic locus and augment Foxp3 expression in T cells [25-28].

Thymic Treg development is thought to occur in two sequential steps, one of which is TCR-dependent and another that is TCRindependent [29]. When developing CD4 single positive (SP) thymocytes encounter a strong TCR stimulus, they upregulate cell surface expression of the high-affinity interleukin-2 (IL-2) receptor subunit (CD25). This CD25+ CD4 SP population is highly enriched in Treg progenitors and is sensitive to IL-2 stimulation [29-31]. When the CD25+ CD4 SP Treg progenitors receive IL-2 signaling through CD25, Foxp3 expression is induced in a TCRindependent manner [29,30]. Thus, TCR-induced upregulation of CD25 in CD4 SP thymocytes represents an important step for nTreg generation, in addition to the induction of TCRdriven transcription factors necessary for Foxp3 expression. As is true for Foxp3 expression, multiple transcription factors induced downstream of IP3 and DAG production promote CD25 expression in T cells [25,32-35]. Thus, regulation of these TCRinduced second messengers is very likely to influence Treg development on a molecular level both for CD25 upregulation and for subsequent Foxp3 upregulation itself.

Role of TCR-mediated IP3 and Ca2+production in nTreg development

IP3 binds to receptor-gated Ca2+ channels (IP3 R) in the endoplasmic reticulum (ER) membrane, allowing Ca2+ ions to flow from the ER into the cytosol. The depletion of ER calcium stores causes activation of store-operated calcium channels (SOC) in the plasma membrane, allowing additional calcium to flow into the cell for maintenance of signaling and replenishment of ER stores. Calcium mobilization induces activation of the nuclear factor of activated T cells (NFAT) [36]. Multiple studies have shown that efficient calcium mobilization is required for Treg development, but how NFAT activation is ultimately involved in Foxp3 expression remains unclear [37]. While reporter-based assays have demonstrated that NFAT binding to the human Foxp3 promoter induces robust Foxp3 expression in human T cells, the relationship between NFAT and murine Treg development has been difficult to assess [27]. T cells express three different NFAT isoforms (NFAT1, NFAT2, and NFAT4), and several studies have shown that both single and doubleisoform knockout mice exhibit largely normal Treg development, likely because of redundancy among the NFAT isoforms [38,39]. A recent study found Treg development to be diminished when NFAT2 was deleted in early T cell development in mice additionally lacking NFAT1 (Nfat1−/−Nfat2fllflLck-Cre), suggesting NFAT2 may indeed drive Treg development at a specific stage of thymic maturation [40]. It is plausible that NFAT also promotes the formation of Treg progenitors, since NFAT binding is required at specific sites within the murine CD25 locus to achieve efficient CD25 expression [33,34]. Additionally, once Foxp3 expression occurs, NFAT/Foxp3 complexes can bind the IL-2 promoter to prevent IL-2 expression, as well as promote expression of the suppression-associated molecule Cytotoxic T-Lymphocyte Antigen 4 (CTLA-4); both of which are distinct traits of the Treg transcriptional program driven by Foxp3 [41]. Indeed, mutations of Foxp3 that disrupt the Foxp3/NFAT interface site abrogate Foxp3-driven suppressive function in transduced T cells [41].

Role of TCR-mediated DAG production in nTreg development

DAG initiates multiple signal transduction events relevant to both CD25 and Foxp3 expression. DAG activates protein kinase C (PKC), leading to downstream induction of nuclear factor κB (NF-κB) transcription factors. Additionally, DAG activates RAS guanyl nucleotide-releasing protein (Ras-GRP), which leads to extracellular signal-related kinase (ERK) activation and subsequent induction of the activator protein 1 (AP-1) transcription factor family members (22, 23). DAG signaling is terminated by enzymes known as DAG kinases (DGK)s, which convert DAG into phosphatidic acid [42]. The ζ isoform of DGK plays a major role in controlling DAG signals downstream of the TCR [42,43]. Hence, T cells lacking DGKζ demonstrate a selective enhancement of DAG-mediated signals upon TCR stimulation [44-46]. We recently reported that DGKζ-deficient mice exhibit a cell-intrinsic increase in both nTreg and CD25+ nTreg precursor development, supporting the role of DAG signaling in promoting Treg development [47]. This augmentation was partially dependent on activation of the NF-κB subunit c-Rel, which was enhanced downstream of TCR stimulation in DGKζ-deficient T cells [47]. The contribution of c-Rel was not surprising, as several groups have found c-Rel to drive Treg development in recent years [26,28,48-52]. c-Rel has been shown to promote opening of the Foxp3 locus by binding a conserved non-coding DNA sequence element (CNS3), and additionally forms a multi-transcription factor enhanceosome that drives gene expression from the Foxp3 promoter [26,28]. In support of these findings, mice expressing a constitutively active form of an upstream NF-κB/c-Rel pathway member, inhibitor of IκB kinase β (IKKβ), exhibit increased Treg frequencies; while mice lacking c-Rel develop very few Tregs at all [50, 51].

In addition to c-Rel, ERK activation also plays an important role in the enhanced generation of Tregs in DGKζ-deficient mice [47]. When ERK phosphorylation is pharmacologically inhibited, no Foxp3 upregulation is observed by in DGK-deficient immature thymocytes. Additionally, there is a linear correlation between the degree of ERK phosphorylation and the frequency of Foxp3 upregulation observed in vitro. Consistent with these findings, a transgenic mouse with selective enhancement of ERK signaling exhibits increased Treg development in vivo. While it remains unclear exactly how ERK might act to drive thymocytes toward the Treg lineage, AP-1 transcription factors that are activated downstream of ERK have been implicated in both CD25 and Foxp3 expression, several AP-1 binding sites exist in the promoter and enhancer regions of both the CD25 and Foxp3 genetic loci [25,34]. Thus, the activation of AP-1 transcription factors are likely important for Treg precursor generation (upregulation of CD25) as well as for the expression of Foxp3. Indeed, reporterbased assays show that AP-1 binding sites within the Foxp3 promoter is required for Foxp3 expression peripheral human T cells [25]. In addition to AP-1 activation, ERK phosphorylates the transcription factor Runx1, allowing Runx1 to interact with binding partners to augment its transcriptional activity [53-56]. Interestingly, Runx1 has been reported to bind the CNS2 region of the Foxp3 locus along with its transcriptional coactivator Cbf-β, and this binding is required for stable expression of Foxp3 in dividing nTregs [28,53,54]. It thus seems plausible that ERK activation could be working in a variety of ways to promote nTreg development downstream of TCR-mediated DAG production. The proximal signaling pathways from the TCR that contribute to Treg generation are summarized and depicted in (Figure 1).

 

CONCLUDING REMARKS

Many recent studies have investigated the factors required to drive developing thymocytes toward Foxp3 upregulation and Treg lineage choice. The answer to this question may uncover strategies for Treg enhancement in autoimmune and bone marrow transplantation settings, which could prove highly beneficial for human health. It is now clear that efficient Treg development requires TCR-driven signals of a certain magnitude and/or specificity, which are likely produced by interactions with self-antigen during Treg development within the thymus. Determining the relative contribution of specific signaling events downstream of the immunological synapse is more difficult, however, as several signaling pathways seem to be simultaneously required for efficient Foxp3 upregulation. Due to the complex nature of this process, an effective strategy to promote Treg development therapeutically might be to target signaling pathways proximal to TCR engagement. Such treatment would work to broadly enhance the magnitude of a given TCR signal from the top down. Inhibition of negative regulators of signal transduction, including DGKζ, could be an attractive approach, although proper targeting of such inhibitors could be complicated to put into practice. Additionally, whether increasing Treg population size would actually improve disease outcome remains unclear for many autoimmune disorders. Future studies will likely provide insights into this important question and hopefully transition our extensive knowledge of Treg development toward effective clinical practices.

FUNDING

This work was supported by grants from the National Blood Foundation, the University of Pennsylvania internal funds, and the National Institutes of Health (R01HL111501, R01HL107589)

REFERENCES

1. Josefowicz SZ, Lu LF, Rudensky AY. Regulatory T cells: mechanisms of differentiation and function. Annu Rev Immunol. 2012; 30: 531-564.

2. Sakaguchi S, Yamaguchi T, Nomura T, Ono M. Regulatory T cells and immune tolerance. Cell. 2008; 133: 775-787.

3. Bennett CL, Christie J, Ramsdell F, Brunkow ME, Ferguson PJ, Whitesell L, et al. The immune dysregulation, polyendocrinopathy, enteropathy, X-linked syndrome (IPEX) is caused by mutations of FOXP3. Nat Genet. 2001; 27: 20-21.

4. Brunkow ME, Jeffery EW, Hjerrild KA, Paeper B, Clark LB, Yasayko SA, et al. Disruption of a new forkhead/winged-helix protein, scurfin, results in the fatal lymphoproliferative disorder of the scurfy mouse. Nat Genet. 2001; 27: 68-73.

5. Kim JM, Rasmussen JP, Rudensky AY. Regulatory T cells prevent catastrophic autoimmunity throughout the lifespan of mice. Nat Immunol. 2007; 8: 191-197.

6. Lahl K, Loddenkemper C, Drouin C, Freyer J, Arnason J, Eberl G, et al. Selective depletion of Foxp3+ regulatory T cells induces a scurfy-like disease. J Exp Med. 2007; 204: 57-63.

7. Sakaguchi S, Sakaguchi N, Asano M, Itoh M, Toda M. Immunologic selftolerance maintained by activated T cells expressing IL-2 receptor alpha-chains (CD25). Breakdown of a single mechanism of selftolerance causes various autoimmune diseases. J Immunol. 1995; 155: 1151-1164.

8. Belkaid Y, Rouse BT. Natural regulatory T cells in infectious disease. Nat Immunol. 2005; 6: 353-360.

9. Cebula A, Seweryn M, Rempala GA, Pabla SS, McIndoe RA, Denning TL, et al. Thymus-derived regulatory T cells contribute to tolerance to commensal microbiota. Nature. 2013; 497: 258-262.

10. Rowe JH, Ertelt JM, Way SS. Foxp3(+) regulatory T cells, immune stimulation and host defence against infection. Immunology. 2012; 136: 1-10.

11. Lee HM, Bautista JL, Hsieh CS. Thymic and peripheral differentiation of regulatory T cells. Adv Immunol. 2011; 112: 25-71.

12. Lio CW, Hsieh CS. Becoming self-aware: the thymic education of regulatory T cells. Curr Opin Immunol. 2011; 23: 213-219.

13. Moran AE, Hogquist KA. T-cell receptor affinity in thymic development. Immunology. 2012; 135: 261-267.

14. Apostolou I, Sarukhan A, Klein L, von Boehmer H. Origin of regulatory T cells with known specificity for antigen. Nat Immunol. 2002; 3: 756- 763.

15. Jordan MS, Boesteanu A, Reed AJ, Petrone AL, Holenbeck AE, Lerman MA, et al. Thymic selection of CD4+CD25+ regulatory T cells induced by an agonist self-peptide. Nat Immunol. 2001; 2: 301-306.

16. Kawahata K, Misaki Y, Yamauchi M, Tsunekawa S, Setoguchi K, Miyazaki J, et al. Generation of CD4(+)CD25(+) regulatory T cells from autoreactive T cells simultaneously with their negative selection in the thymus and from nonautoreactive T cells by endogenous TCR expression. J Immunol. 2002; 168: 4399-4405.

17. Knoechel B, Lohr J, Kahn E, Bluestone JA, Abbas AK. Sequential development of interleukin 2-dependent effector and regulatory T cells in response to endogenous systemic antigen. J Exp Med. 2005; 202: 1375-1386.

18. Walker LS, Chodos A, Eggena M, Dooms H, Abbas AK. Antigendependent proliferation of CD4+ CD25+ regulatory T cells in vivo. J Exp Med. 2003; 198: 249-258.

19. Lee HM, Bautista JL, Scott-Browne J, Mohan JF, Hsieh CS. A broad range of self-reactivity drives thymic regulatory T cell selection to limit responses to self. Immunity. 2012; 37: 475-486.

20. Moran AE, Holzapfel KL, Xing Y, Cunningham NR, Maltzman JS, Punt J, et al. T cell receptor signal strength in Treg and iNKT cell development demonstrated by a novel fluorescent reporter mouse. J Exp Med. 2011; 208: 1279-1289.

21. Stritesky GL, Xing Y, Erickson JR, Kalekar LA, Wang X, Mueller DL, et al. Murine thymic selection quantified using a unique method to capture deleted T cells. Proc Natl Acad Sci U S A. 2013; 110: 4679-4684.

22. Kane LP, Lin J, Weiss A. Signal transduction by the TCR for antigen. Curr Opin Immunol. 2000; 12: 242-249.

23. Smith-Garvin JE, Koretzky GA, Jordan MS. T cell activation. Annu Rev Immunol. 2009; 27: 591-619.

24. Koonpaew S, Shen S, Flowers L, Zhang W. LAT-mediated signaling in CD4+CD25+ regulatory T cell development. J Exp Med. 2006; 203: 119-129.

25. Mantel PY, Ouaked N, Rückert B, Karagiannidis C, Welz R, Blaser K, et al. Molecular mechanisms underlying FOXP3 induction in human T cells. J Immunol. 2006; 176: 3593-3602.

26. Ruan Q, Kameswaran V, Tone Y, Li L, Liou HC, Greene MI, et al. Development of Foxp3(+) regulatory t cells is driven by the c-Rel enhanceosome. Immunity. 2009; 31: 932-940.

27. Tone Y, Furuuchi K, Kojima Y, Tykocinski ML, Greene MI, Tone M. Smad3 and NFAT cooperate to induce Foxp3 expression through its enhancer. Nat Immunol. 2008; 9: 194-202.

28. Zheng Y, Josefowicz S, Chaudhry A, Peng XP, Forbush K, Rudensky AY. Role of conserved non-coding DNA elements in the Foxp3 gene in regulatory T-cell fate. Nature. 2010; 463: 808-812.

29. Lio CW, Hsieh CS. A two-step process for thymic regulatory T cell development. Immunity. 2008; 28: 100-111.

30. Burchill MA, Yang J, Vang KB, Moon JJ, Chu HH, Lio CW, et al. Linked T cell receptor and cytokine signaling govern the development of the regulatory T cell repertoire. Immunity. 2008; 28: 112-121.

31. Fontenot JD, Dooley JL, Farr AG, Rudensky AY. Developmental regulation of Foxp3 expression during ontogeny. J Exp Med. 2005; 202: 901-906.

32. John S, Reeves RB, Lin JX, Child R, Leiden JM, Thompson CB, et al. Regulation of cell-type-specific interleukin-2 receptor alpha-chain gene expression: potential role of physical interactions between Elf-1, HMG-I(Y), and NF-kappa B family proteins. Mol Cell Biol. 1995; 15: 1786-1796.

33. Kim HP, Imbert J, Leonard WJ. Both integrated and differential regulation of components of the IL-2/IL-2 receptor system. Cytokine Growth Factor Rev. 2006; 17: 349-366. 

34. Kim HP, Leonard WJ. The basis for TCR-mediated regulation of the IL-2 receptor alpha chain gene: role of widely separated regulatory elements. EMBO J. 2002; 21: 3051-3059.

35. Tan TH, Huang GP, Sica A, Ghosh P, Young HA, Longo DL, et al. Kappa B site-dependent activation of the interleukin-2 receptor alpha-chain gene promoter by human c-Rel. Mol Cell Biol. 1992; 12: 4067-4075.

36. Oh-hora M. Calcium signaling in the development and function of T-lineage cells. Immunol Rev. 2009; 231: 210-224.

37. Oh-hora M, Rao A. The calcium/NFAT pathway: role in development and function of regulatory T cells. Microbes Infect. 2009; 11: 612-619.

38. Bopp T, Palmetshofer A, Serfling E, Heib V, Schmitt S, Richter C, et al. NFATc2 and NFATc3 transcription factors play a crucial role in suppression of CD4+ T lymphocytes by CD4+ CD25+ regulatory T cells. J Exp Med. 2005; 201: 181-187.

39. Vaeth M, Schliesser U, Müller G, Reissig S, Satoh K, Tuettenberg A, et al. Dependence on nuclear factor of activated T-cells (NFAT) levels discriminates conventional T cells from Foxp3+ regulatory T cells. Proc Natl Acad Sci U S A. 2012; 109: 16258-16263.

40. Oh-Hora M, Komatsu N, Pishyareh M, Feske S, Hori S, Taniguchi M, et al. Agonist-selected T cell development requires strong T cell receptor signaling and store-operated calcium entry. Immunity. 2013; 38: 881- 895.

41. Wu Y, Borde M, Heissmeyer V, Feuerer M, Lapan AD, Stroud JC, et al. FOXP3 controls regulatory T cell function through cooperation with NFAT. Cell. 2006; 126: 375-387.

42. Joshi RP, Koretzky GA. Diacylglycerol kinases: regulated controllers of T cell activation, function, and development. Int J Mol Sci. 2013; 14: 6649-6673.

43. Joshi RP, Schmidt AM, Das J, Pytel D, Riese MJ, Lester M, et al. The ζ isoform of diacylglycerol kinase plays a predominant role in regulatory T cell development and TCR-mediated ras signaling. Sci Signal. 2013; 6: ra102.

44. Olenchock BA, Guo R, Carpenter JH, Jordan M, Topham MK, Koretzky GA, et al. Disruption of diacylglycerol metabolism impairs the induction of T cell anergy. Nat Immunol. 2006; 7: 1174-1181.

45. Zhong XP, Hainey EA, Olenchock BA, Jordan MS, Maltzman JS, Nichols KE, et al. Enhanced T cell responses due to diacylglycerol kinase zeta deficiency. Nat Immunol. 2003; 4: 882-890.

46. Zhong XP, Hainey EA, Olenchock BA, Zhao H, Topham MK, Koretzky GA. Regulation of T cell receptor-induced activation of the Ras-ERK pathway by diacylglycerol kinase zeta. J Biol Chem. 2002; 277: 31089- 31098.

47. Schmidt AM, Zou T, Joshi RP, Leichner TM, Pimentel MA, Sommers CL, et al. Diacylglycerol kinase ζ limits the generation of natural regulatory T cells. Sci Signal. 2013; 6: ra101.

48. Deenick EK, Elford AR, Pellegrini M, Hall H, Mak TW, Ohashi PS. c-Rel but not NF-kappaB1 is important for T regulatory cell development. Eur J Immunol. 2010; 40: 677-681.

49. Grigoriadis G, Vasanthakumar A, Banerjee A, Grumont R, Overall S, Gleeson P, et al. c-Rel controls multiple discrete steps in the thymic development of Foxp3+ CD4 regulatory T cells. PLoS One. 2011; 6: e26851.

50. Isomura I, Palmer S, Grumont RJ, Bunting K, Hoyne G, Wilkinson N, et al. c-Rel is required for the development of thymic Foxp3+ CD4 regulatory T cells. J Exp Med. 2009; 206: 3001-3014.

51. Long M, Park SG, Strickland I, Hayden MS, Ghosh S. Nuclear factorkappaB modulates regulatory T cell development by directly regulating expression of Foxp3 transcription factor. Immunity. 2009; 31: 921-931.

52. Vang KB, Yang J, Pagán AJ, Li LX, Wang J, Green JM, et al. Cutting edge: CD28 and c-Rel-dependent pathways initiate regulatory T cell development. J Immunol. 2010; 184: 4074-4077.

53. Ono M, Yaguchi H, Ohkura N, Kitabayashi I, Nagamura Y, Nomura T, et al. Foxp3 controls regulatory T-cell function by interacting with AML1/Runx1. Nature. 2007; 446: 685-689.

54. Rudra D, Egawa T, Chong MM, Treuting P, Littman DR, Rudensky AY. Runx-CBFbeta complexes control expression of the transcription factor Foxp3 in regulatory T cells. Nat Immunol. 2009; 10: 1170-1177.

55. Tanaka T, Kurokawa M, Ueki K, Tanaka K, Imai Y, Mitani K, et al. The extracellular signal-regulated kinase pathway phosphorylates AML1, an acute myeloid leukemia gene product, and potentially regulates its transactivation ability. Mol Cell Biol. 1996; 16: 3967-3979.

56. Yoshimi M, Goyama S, Kawazu M, Nakagawa M, Ichikawa M, Imai Y, et al. Multiple phosphorylation sites are important for RUNX1 activity in early hematopoiesis and T-cell differentiation. Eur J Immunol. 2012; 42: 1044-1050

Received : 28 Jan 2014
Accepted : 25 Feb 2014
Published : 28 Feb 2014
Journals
Annals of Otolaryngology and Rhinology
ISSN : 2379-948X
Launched : 2014
JSM Schizophrenia
Launched : 2016
Journal of Nausea
Launched : 2020
JSM Internal Medicine
Launched : 2016
JSM Hepatitis
Launched : 2016
JSM Oro Facial Surgeries
ISSN : 2578-3211
Launched : 2016
Journal of Human Nutrition and Food Science
ISSN : 2333-6706
Launched : 2013
JSM Regenerative Medicine and Bioengineering
ISSN : 2379-0490
Launched : 2013
JSM Spine
ISSN : 2578-3181
Launched : 2016
Archives of Palliative Care
ISSN : 2573-1165
Launched : 2016
JSM Nutritional Disorders
ISSN : 2578-3203
Launched : 2017
Annals of Neurodegenerative Disorders
ISSN : 2476-2032
Launched : 2016
Journal of Fever
ISSN : 2641-7782
Launched : 2017
JSM Bone Marrow Research
ISSN : 2578-3351
Launched : 2016
JSM Mathematics and Statistics
ISSN : 2578-3173
Launched : 2014
Journal of Autoimmunity and Research
ISSN : 2573-1173
Launched : 2014
JSM Arthritis
ISSN : 2475-9155
Launched : 2016
JSM Head and Neck Cancer-Cases and Reviews
ISSN : 2573-1610
Launched : 2016
JSM General Surgery Cases and Images
ISSN : 2573-1564
Launched : 2016
JSM Anatomy and Physiology
ISSN : 2573-1262
Launched : 2016
JSM Dental Surgery
ISSN : 2573-1548
Launched : 2016
Annals of Emergency Surgery
ISSN : 2573-1017
Launched : 2016
Annals of Mens Health and Wellness
ISSN : 2641-7707
Launched : 2017
Journal of Preventive Medicine and Health Care
ISSN : 2576-0084
Launched : 2018
Journal of Chronic Diseases and Management
ISSN : 2573-1300
Launched : 2016
Annals of Vaccines and Immunization
ISSN : 2378-9379
Launched : 2014
JSM Heart Surgery Cases and Images
ISSN : 2578-3157
Launched : 2016
Annals of Reproductive Medicine and Treatment
ISSN : 2573-1092
Launched : 2016
JSM Brain Science
ISSN : 2573-1289
Launched : 2016
JSM Biomarkers
ISSN : 2578-3815
Launched : 2014
JSM Biology
ISSN : 2475-9392
Launched : 2016
Archives of Stem Cell and Research
ISSN : 2578-3580
Launched : 2014
Annals of Clinical and Medical Microbiology
ISSN : 2578-3629
Launched : 2014
JSM Pediatric Surgery
ISSN : 2578-3149
Launched : 2017
Journal of Memory Disorder and Rehabilitation
ISSN : 2578-319X
Launched : 2016
JSM Tropical Medicine and Research
ISSN : 2578-3165
Launched : 2016
JSM Head and Face Medicine
ISSN : 2578-3793
Launched : 2016
JSM Cardiothoracic Surgery
ISSN : 2573-1297
Launched : 2016
JSM Bone and Joint Diseases
ISSN : 2578-3351
Launched : 2017
JSM Bioavailability and Bioequivalence
ISSN : 2641-7812
Launched : 2017
JSM Atherosclerosis
ISSN : 2573-1270
Launched : 2016
Journal of Genitourinary Disorders
ISSN : 2641-7790
Launched : 2017
Journal of Fractures and Sprains
ISSN : 2578-3831
Launched : 2016
Journal of Autism and Epilepsy
ISSN : 2641-7774
Launched : 2016
Annals of Marine Biology and Research
ISSN : 2573-105X
Launched : 2014
JSM Health Education & Primary Health Care
ISSN : 2578-3777
Launched : 2016
JSM Communication Disorders
ISSN : 2578-3807
Launched : 2016
Annals of Musculoskeletal Disorders
ISSN : 2578-3599
Launched : 2016
Annals of Virology and Research
ISSN : 2573-1122
Launched : 2014
JSM Renal Medicine
ISSN : 2573-1637
Launched : 2016
Journal of Muscle Health
ISSN : 2578-3823
Launched : 2016
JSM Genetics and Genomics
ISSN : 2334-1823
Launched : 2013
JSM Anxiety and Depression
ISSN : 2475-9139
Launched : 2016
Clinical Journal of Heart Diseases
ISSN : 2641-7766
Launched : 2016
Annals of Medicinal Chemistry and Research
ISSN : 2378-9336
Launched : 2014
JSM Pain and Management
ISSN : 2578-3378
Launched : 2016
JSM Women's Health
ISSN : 2578-3696
Launched : 2016
Clinical Research in HIV or AIDS
ISSN : 2374-0094
Launched : 2013
Journal of Endocrinology, Diabetes and Obesity
ISSN : 2333-6692
Launched : 2013
Journal of Substance Abuse and Alcoholism
ISSN : 2373-9363
Launched : 2013
JSM Neurosurgery and Spine
ISSN : 2373-9479
Launched : 2013
Journal of Liver and Clinical Research
ISSN : 2379-0830
Launched : 2014
Journal of Drug Design and Research
ISSN : 2379-089X
Launched : 2014
JSM Clinical Oncology and Research
ISSN : 2373-938X
Launched : 2013
JSM Bioinformatics, Genomics and Proteomics
ISSN : 2576-1102
Launched : 2014
JSM Chemistry
ISSN : 2334-1831
Launched : 2013
Journal of Trauma and Care
ISSN : 2573-1246
Launched : 2014
JSM Surgical Oncology and Research
ISSN : 2578-3688
Launched : 2016
Annals of Food Processing and Preservation
ISSN : 2573-1033
Launched : 2016
Journal of Radiology and Radiation Therapy
ISSN : 2333-7095
Launched : 2013
JSM Physical Medicine and Rehabilitation
ISSN : 2578-3572
Launched : 2016
Annals of Clinical Pathology
ISSN : 2373-9282
Launched : 2013
Annals of Cardiovascular Diseases
ISSN : 2641-7731
Launched : 2016
Journal of Behavior
ISSN : 2576-0076
Launched : 2016
Annals of Clinical and Experimental Metabolism
ISSN : 2572-2492
Launched : 2016
Clinical Research in Infectious Diseases
ISSN : 2379-0636
Launched : 2013
JSM Microbiology
ISSN : 2333-6455
Launched : 2013
Journal of Urology and Research
ISSN : 2379-951X
Launched : 2014
Journal of Family Medicine and Community Health
ISSN : 2379-0547
Launched : 2013
Annals of Pregnancy and Care
ISSN : 2578-336X
Launched : 2017
JSM Cell and Developmental Biology
ISSN : 2379-061X
Launched : 2013
Annals of Aquaculture and Research
ISSN : 2379-0881
Launched : 2014
Clinical Research in Pulmonology
ISSN : 2333-6625
Launched : 2013
Annals of Forensic Research and Analysis
ISSN : 2378-9476
Launched : 2014
JSM Biochemistry and Molecular Biology
ISSN : 2333-7109
Launched : 2013
Annals of Breast Cancer Research
ISSN : 2641-7685
Launched : 2016
Annals of Gerontology and Geriatric Research
ISSN : 2378-9409
Launched : 2014
Journal of Sleep Medicine and Disorders
ISSN : 2379-0822
Launched : 2014
JSM Burns and Trauma
ISSN : 2475-9406
Launched : 2016
Chemical Engineering and Process Techniques
ISSN : 2333-6633
Launched : 2013
Annals of Clinical Cytology and Pathology
ISSN : 2475-9430
Launched : 2014
JSM Allergy and Asthma
ISSN : 2573-1254
Launched : 2016
Journal of Neurological Disorders and Stroke
ISSN : 2334-2307
Launched : 2013
Annals of Sports Medicine and Research
ISSN : 2379-0571
Launched : 2014
JSM Sexual Medicine
ISSN : 2578-3718
Launched : 2016
Annals of Vascular Medicine and Research
ISSN : 2378-9344
Launched : 2014
JSM Biotechnology and Biomedical Engineering
ISSN : 2333-7117
Launched : 2013
Journal of Hematology and Transfusion
ISSN : 2333-6684
Launched : 2013
JSM Environmental Science and Ecology
ISSN : 2333-7141
Launched : 2013
Journal of Cardiology and Clinical Research
ISSN : 2333-6676
Launched : 2013
JSM Nanotechnology and Nanomedicine
ISSN : 2334-1815
Launched : 2013
Journal of Ear, Nose and Throat Disorders
ISSN : 2475-9473
Launched : 2016
JSM Ophthalmology
ISSN : 2333-6447
Launched : 2013
Journal of Pharmacology and Clinical Toxicology
ISSN : 2333-7079
Launched : 2013
Annals of Psychiatry and Mental Health
ISSN : 2374-0124
Launched : 2013
Medical Journal of Obstetrics and Gynecology
ISSN : 2333-6439
Launched : 2013
Annals of Pediatrics and Child Health
ISSN : 2373-9312
Launched : 2013
JSM Clinical Pharmaceutics
ISSN : 2379-9498
Launched : 2014
JSM Foot and Ankle
ISSN : 2475-9112
Launched : 2016
JSM Alzheimer's Disease and Related Dementia
ISSN : 2378-9565
Launched : 2014
Journal of Addiction Medicine and Therapy
ISSN : 2333-665X
Launched : 2013
Journal of Veterinary Medicine and Research
ISSN : 2378-931X
Launched : 2013
Annals of Public Health and Research
ISSN : 2378-9328
Launched : 2014
Annals of Orthopedics and Rheumatology
ISSN : 2373-9290
Launched : 2013
Journal of Clinical Nephrology and Research
ISSN : 2379-0652
Launched : 2014
Annals of Community Medicine and Practice
ISSN : 2475-9465
Launched : 2014
Annals of Biometrics and Biostatistics
ISSN : 2374-0116
Launched : 2013
JSM Clinical Case Reports
ISSN : 2373-9819
Launched : 2013
Journal of Cancer Biology and Research
ISSN : 2373-9436
Launched : 2013
Journal of Surgery and Transplantation Science
ISSN : 2379-0911
Launched : 2013
Journal of Dermatology and Clinical Research
ISSN : 2373-9371
Launched : 2013
JSM Gastroenterology and Hepatology
ISSN : 2373-9487
Launched : 2013
Annals of Nursing and Practice
ISSN : 2379-9501
Launched : 2014
JSM Dentistry
ISSN : 2333-7133
Launched : 2013
Author Information X