Briefly, reporter DNA constructs resident in each plate well were resuspended with 50 l Opti-MEM and then mixed with 50 l diluted SureFECT transfection reagent. B cells and PHA-activated rhesus monkey lymphocytes. Accordingly, the high levels of TAAR1 that we observed on lymphocytes are inducible and fully functional, capable of transmitting a signal likely via PKA and PKC activation following ligand binding. More importantly, an increase in TAAR1 receptor expression is concomitant with lymphocyte immune activation, suggesting a possible role for TAAR1 in the generation or regulation of an immune response. TAAR1 is emerging as a potential therapeutic target, with regard to its ability to modulate brain monoamines. The current MC-Val-Cit-PAB-vinblastine data raises the possibility that TAAR1-targeted drugs may also alter immune function. Introduction Trace Amine Associated Receptor 1 (TAAR1) is a G protein coupled receptor (GPCR) that responds to a wide spectrum of agonists, including endogenous trace amines, common biogenic amines and thyronamines, as well as exogenous psychostimulant drugs of the amphetamine class, including methamphetamine. Whereas endogenous common biogenic amines bind to a variety of receptors, trace amines and amphetamines show a greater specificity for TAAR1 and have served as useful probes for characterizing TAAR1 pharmacology and functionality. These TAAR1 agonists are also monoamine transporter substrates. Accordingly, much of the research on TAAR1 has focused on its role as a modulator of monoaminergic function and mediator of psychostimulant action in the brain. Stemming from this work is a conceptualization that TAAR1 may be a potential target for novel therapeutics aimed at treating drug addiction and other neuropsychiatric conditions which are hallmarked by aberrations in brain monoaminergic systems, but highly selective drugs that target TAAR1 have been slow in coming. In addition to its expression in brain, TAAR1 is also expressed in a number of peripheral tissues, including liver, kidney, spleen, pancreas, heart and gastrointestinal tract tissues (Borowsky et al., 2001), but functionality of TAAR1 in non-neurological tissue has been less examined. Also, TAAR1 expression has been reported in cells of the immune system (Nelson et al., 2007). Our previous work has shown that methamphetamine produces MC-Val-Cit-PAB-vinblastine a TAAR1-dependent increase in cyclic AMP (cAMP) activation, as indicated using a CRE-luciferase assay, as well as phosphorylation-dependent downstream effects on monoamine transporter kinetic function that are attenuated with PKA or PKC inhibitors, suggesting that both the PKA and PKC pathways are activated by methamphetamine binding to TAAR1 (Miller et al., 2005, Xie and Miller, 2007, 2009). The present study CD109 was initiated to more formally investigate which signaling pathways are activated by TAAR1. We first determined which signal transduction pathways are activated by methamphetamine in the presence and absence of TAAR1 in transfected HEK293 cells. In doing so, we identified two pathways that are upregulated in a TAAR-1 dependent manner, CREB and NFAT, along with concurrent changes in the phosphorylation status of PKA and PKC. As both of these pathways are known to be induced traditionally following lymphocyte receptor-activation, these data led us to investigate the expression of TAAR1 by lymphocytes following lymphocyte immune activation. We next verified TAAR1 expression and then determined MC-Val-Cit-PAB-vinblastine whether the TAAR1-mediated signal transduction pathways get activated by methamphetamine in rhesus monkey PHA-activated PBMC and immortalized B lymphocytes. We then MC-Val-Cit-PAB-vinblastine used a newly-identified TAAR1 antagonist, N-(3-Ethoxy-phenyl)-4-pyrrolidin-1-yl-3-trifluoro-methyl-benzamide [EPPTB] (Bradaia et al., 2009), to selectively inhibit TAAR1 signal transduction. Finally, we used the newly established methamphetamine/EPPTB system as a tool to demonstrate the functional capability of TAAR1 that is MC-Val-Cit-PAB-vinblastine upregulated on lymphocytes following immune activation to transduce a signal and activate downstream pathways. Materials and Methods Chemicals,.