5B). Dynamics of the Cell Fate Decision The observation that removal of the antigen at T6 resulted in eleven different possible outcomes gave us the opportunity to analyze in detail the factors that affect cell fate selection. Ag removal recognized three unique populations based on CD25 large quantity and Akt/mTOR activation that correlated with these T cell fates. Further analysis of related simulation trajectories implicated a negative feedback loop including Foxp3, PTEN, and Akt/mTOR. Taken together, these results suggest that there is a essential period following TCR activation during which heterogeneity in the differentiating human population 5(6)-FAM SE leads to improved plasticity of cell fate. Introduction CD4+ T cells can be grouped into two main sub-types: those which exert an activating effect on the immune response (helper T cells, Th), and those which suppress immune reactions (regulatory T cells, Treg). Treg cells perform an important part in suppressing T cell mediated immunity, limiting damage caused by the immune response and avoiding autoimmune diseases (1). However, Treg cells may play a detrimental role in malignancy by acting as an effector of immune suppression by tumors. In several recent studies of human being Treg cells in individuals with malignancy, the number of Treg cells within tumors and their suppressive activity were found to be elevated and to forecast poor survival (2). Understanding the factors that control the induction of Treg cells has the potential to advance therapies including either removal of antigen-specific Treg cells in the context of malignancy (3), or enhancement of Treg-mediated suppression in the context of autoimmune reactions (4). Treg cells are characterized by the transcription element forkhead package P3 (Foxp3), a specific pattern of cytokine production, and immunosuppressive function (5C7). Treg cells suppress additional effector T cells through several mechanisms (8), including deletion of effector cells via granzyme B (9), secretion of immunosuppressive cytokines such as transforming growth element (TGF-), interleukin (IL-)10 and IL-35 (10), metabolic disruption through the production of adenosine (11) or competition for IL-2 (12, 13) and finally, inhibition of dendritic cell maturation(8, 14).Two main groups of Treg cells are currently known: organic and adaptive (induced) Treg cells. Natural regulatory T (nTreg) cells become committed to a regulatory fate while still in the thymus (14), whereas induced Treg (iTreg) cells, arise from na?ve T cells in the periphery under stimulation by specific factors including IL-10 (15), TGF- (16), low antigen (Ag) dose (17, 18), 5(6)-FAM SE and particular dendritic cell (DC) subsets (19C21). iTreg and Th both develop in the periphery from common, na?ve, uncommitted T cell precursors, which differentiate upon encountering cognate peptide:major histocompatibility complex (pMHC) on the surface of antigen-presenting cells (APC). Earlier studies possess indicated that both Ag dose and the duration of Ag activation strongly influence the choice between regulatory and helper cells in the T cell response specific for a particular Ag, such that high dose favors Th and low dose favors Treg (17, 18, 22). Understanding the molecular determinants of this process has major implications for the development of targeted immunomodulation treatments (23). For example, it is important in a malignancy vaccination strategy to deliver a high enough dose to induce tumor-specific Th1 cells. A more delicate balance must be accomplished in the context of autoimmunity, because many individuals have increased numbers of auto-reactive T cells, which any therapy must avoid activating. Thus, a strategy designed to induce Ag-specific Treg must deliver a dose that will favor the induction of self-Ag-specific Treg without activating or inducing autoreactive Th1/Th17 cells. Few vaccination strategies in malignancy or autoimmunity consider the 5(6)-FAM SE dose of the Ag and this may be one reason for the limited success of these attempts to day (24, 25). Treg differentiation is definitely affected by multiple signaling pathways including those stimulated by engagement of T cell receptor (TCR), the co-stimulatory molecule CD28, IL-2 receptor (IL-2R) and TGF- receptor (TGF-R). We recently reported the culture of CD4+ T cells with DC showing low dose Ag resulted Wnt1 in both the development of preexisting nTreg and the conversion of na?ve T cells into iTreg (18), and the induction of Treg was inversely correlated with the strength of the TCR signal as measured by phosphorylation of the S6 ribosomal protein (pS6). pS6 is definitely downstream of the phosphoinositide 3-kinase/protein kinase B/mammalian target of.