(A) Proliferation rate of effector CD8 T cells at early contraction phase. Wnt signaling also resulted in larger numbers of antigen-specific memory CD4 T cells, their functional attributes and expansion after the secondary contamination were not improved. Thus, constitutive activation of the canonical Wnt pathway favors memory CD8 T cell formation during initial immunization, resulting in enhanced immunity upon second encounter with the same pathogen. Protective cellular immunity relies on antigen-specific CD4 and CD8 T cells, which exist at very low frequencies in nave hosts (1-3). After infection or immunization, nave T cells undergo massive clonal expansion, generating large numbers of antigen-specific effector T cells equipped with cytokines and/or cytolytic molecules to combat pathogens. The proliferative expansion phase is followed by a rapid decline of antigen-specific T cells, and such contraction of the effector T cells does not seem to be correlated with clearance of the pathogens (4). A fraction of antigen-specific T cells (approximately 5-10%) survive the contraction phase and form a pool of memory T cells, which will respond with accelerated expansion rate upon re-encounter with the same antigen. This immunological memory is the basis for vaccination, and much effort has been devoted to improve vaccine design through manipulating T cell responses to maximize memory T cell formation (1,5-7). Three major classes of signals are known to be critical for T cell activation and transition to memory T cells, i.e., signal 1 from antigen stimulation of TCR, signal 2 derived from co-stimulatory molecules such as CD28, and signal 3 from pro-inflammatory cytokines including IL-12 and type I interferons (1,2). Recent studies exhibited that the effect of inflammatory cytokines such as IL-12 on effector and memory CD8+T cells may be at least partly mediated by differential expression of the T-box transcription factor, T-bet (8,9). It is not known whether additional signals such as morphogenic Wnt signaling and its downstream transcriptional programs have a role in modulating Diclofenac diethylamine T cell responses. Wnt proteins are secreted, lipid-modified glycoproteins that activate multiple signal transduction pathways to regulate a variety of cellular Diclofenac diethylamine activities, including cell fate determination, proliferation, and gene expression (10,11). The canonical Wnt pathway transduces signals via the intracellular mediator -catenin. In the Diclofenac diethylamine absence of conversation between Wnt and its Frizzled receptors, -catenin is usually kept at a low level by a multi-molecular destruction complex made up of casein kinase Diclofenac diethylamine I and glycogen synthase kinase 3. These two kinases sequentially phosphorylate a set of conserved serine and threonine residues in the N-terminus of -catenin, and the resulting phosphorylated footprint marks -catenin for Diclofenac diethylamine constant degradation by the proteosome. Under this condition, the Wnt effector transcription factors T cell factor-1 (TCF-1) and lymphoid enhancer-binding factor 1 (LEF-1) are associated with Groucho/transducin-like enhancer of split (TLE) corepressor proteins and act as transcriptional repressors. When Wnt ligand binds to Frizzled receptors and co-receptors, glycogen synthase kinase 3 activity is usually inhibited and the destruction complex is usually inactivated, resulting in accumulation of -catenin in the cytoplasm. Upon entering the nucleus, -catenin replaces Groucho/TLE, forms complexes with TCF-1/LEF-1, and activates the transcription of Wnt target genes. Although LEF-1-null mice did not display abnormalities in T cell development, inactivation of TCF-1 resulted in incomplete blocks at multiple early T cell developmental stages (12). TCF-1 and LEF-1 Rabbit Polyclonal to POLE4 double deficiency completely arrested T cell development at the immature.