Review Article

[Retracted] A Role for PPAR 𝛾 in the Regulation of Cytokines in Immune Cells and Cancer

Figure 2

PPAR regulation of cytokine-mediated immunoregulatory circuit between monocytes/macrophages and T lymphocytes. T helper (Th) lymphocytes can be traditionally divided into two functional subsets consisting of Th1 and Th2 cells on the basis of the immunoregulatory cytokines that these T cells produce. Thp cells are the pluripotent precursors of Th1 and Th2 cells. IL-4 is principally produced by helper T cells of theTh2 phenotype. IL-4 can induce the upregulation of expression of the enzyme 12/15 lipoxygenase in monocytes/macrophages, providing a potential PPAR-specific ligands 13-HODE. The mediator secreted by monocytes can be taken up by neighboring Thp or Th1 cells and activate PPAR in these cells. Since NFAT and NF-κB bind to the promoter region of the IL-2 gene and are needed to activate IL-2 transcription in T cells, the ligand-dependent binding of PPAR to NFAT and NF-κB correlates the dissociation of NFAT and NF-κB from IL-2 promoter, thus inhibiting gene expression of IL-2 in Thp or Th1 cells.
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