We are analyzing the regulation of cytokine and chemokine gene expression in lymphoid cells. We have chosen IFN-gamma gene expression as a model system for analysis of the control of gene expression in T cells and NK cells. We are continuing to dissect the regions of the human IFN-g genomic DNA to determine which regions enhance/repress gene transcription in response to extracellular signals. In particular, we are utilizing NK cell lines to elucidate the mechanisms, both transcriptional and post-transcriptional, by which interleukins 2,4,12,13,15,18 or activation of LY49 activating receptors (murine models) induce or inhibit IFN-g gene expression. Overall, our data indicate that multiple DNA binding protein family members interact with the human IFN-g genomic DNA and that control of IFN-g gene expression involves 5' and intronic transcriptional control regions as well as DNA methylation and mRNA stability/nuclear localization. We are now investigating the role of STAT, NFkB and T-bet proteins in regulating IFN-g expression. We are also characterizing the biochemical pathways involved in the synergistic induction of IFN-g gene expression in response to IL-2 + IL-12, IL-2 + IL-18 and antibodies to the LY49 activating receptors + cytokines by both microarray and proteomic approaches. In another aspect of CMIS research, we have utilized IFN-g KO mice to identify a novel NK cell population that produces IL-13 and IL-5 in response to IL-2 and IL-18. This cytokine expression profile suggests that this NK population may play a role in influencing humoral immunity. Ongoing studies are focused on characterizing the biochemical/molecular signaling pathways utilized by these cells, determining their function in vivo and defining the molecular pathways involved in the IL-2 and IL-18 induction of the IL-13 gene. In a new aspect of our work, we have been investigating the role of the peroxisome proliferator-activated receptor-gamma in regulating NK gene expression. We have observed that the natural ligand for this receptor, 15d-PGJ2 and synthetic ligands such as ciglitazone, alter NK gene expression by both receptor dependent and independant pathways.
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