br Materials and methods br Results br Discussion In

Materials and methods
Results
Discussion In this report, we have analyzed the function of an orphan GPCR, and GPR84, using genetically-deficient mice. The expression of GPR84 in the T and myd88 inhibitor in the spleen prompted us to examine the functional responses of these cells under in vitro and in vivo stimulation conditions. Our studies indicate that although GPR84 is not necessary to modulate T and B cell proliferation, the absence of GPR84 selectively affects IL-4 production in CD4+ T cells. Increased production of IL-4 but not other cytokines, such as IFN-γ and IL-2, appears to be related to increased transcription of IL-4 within minutes of T cell activation. The signaling mechanisms that modulate early cytokine production in T cells are poorly understood. Several studies using mice genetically-deficient in expression of signaling molecules, such as MAPK family kinases (JNK-1 and JNK-2), itch E3 ubiquitin ligase, adaptor protein (DR-1) and transcription factors such as c-maf, and those belonging to the NFAT family of proteins (NFATc1, NFATc2 and NFATc3), have demonstrated that these proteins can either positively or negatively regulate production of Th2 cytokines such as IL-4, IL-5 and IL-13 [12], [13], [14], [15], [16], [17], [18], [19]. However, these studies do not address whether these signaling pathways directly modulate T cell receptor signaling within the first few minutes of naïve T cell activation. Mice deficient in NFATc2 were defective in early IL-4 production by NK1.1+ T cells [17]. On the other hand, stimulation of naive splenic NFATc2-deficient T cells resulted in the prolonged accumulation of IL-4 steady-state mRNA even after 24h of T cell activation, in contrast to a transient increase and rapid decline in IL-4 gene transcription observed in wild-type T cells [19]. There is also much evidence supporting the role of NFAT transcription factors in regulating IL-2 gene transcription. In this study, a selective increase in IL-4 but not IL-2 production was observed in GPR84-deficient mice. In addition, we are unable to demonstrate any differences in the nuclear translocation of either NFATc1 or NFATc2 in activated T cells in GPR84-deficient mice. These results suggest that a defect in NFAT activation does not likely explain hyper-IL-4 production by GPR84-deficient T cells in this study. The hyper-Th2 cytokine production in GPR84-deficient mice can at least be attributed to their ability to synthesize more IL-4 protein during primary stimulation. In contrast to the hyper-Th2 cytokine by GPR84−/− T cells under in vitro culture conditions, these effects could not be demonstrated in antigen-challenged mice. This suggested that threshold of signaling that is regulated by GPR84 in activated T cells can be compensated by additional signals during an active immune response in vivo. In spite of the lack of an in vivo phenotype, GPR84−/− deficient T cells could provide an excellent tool to dissect the similarities and differences in early T cell activation, which translate to the development of discrete cytokine-secreting effector populations.
Acknowledgement
Introduction Multiple sclerosis (MS) is a chronic demyelinating disease of the central nervous system (CNS) [1]. It is characterized by infiltration of inflammatory leukocytes to the CNS followed by oligodendrocyte cell death, myelin sheath destruction, and axonal injury. These effects lead to neurological deficits including visual and sensory disruption, tremor, motor weakness, bladder impairment, and clinical disability [2,3]. Patients with MS have enhanced cytokine production including interferon-γ (IFN-γ) and interleukin-17 (IL-17) via activation of Th1 and Th17 cells [4]. The increased secretion of IFN-γ and IL-17 has been associated with the abnormal generation of IL-12 and IL-23 by pro-inflammatory dendritic cells [5,6]. Since the pathogenesis of MS is not completely understood and current medications have various side effects, a great deal of effort has been devoted to understanding the pathological mechanisms of MS and finding new therapeutic approaches for this disease.