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Y. Lee, C.-R. Yu, X. Liu, C. Egwuagu; Antagonistic Effects of STAT1 and STAT6 on Dendritic Cells (DC): STAT1 Enhances DC Maturation While STAT6 Promotes Production of IL-12 and IL-23. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5199.
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© ARVO (1962-2015); The Authors (2016-present)
We had previously shown that STAT pathways are differentially activated as dendritic cells (DC) differentiate from precursor (pDC) to immature (iDC) and finally to mature DC (mDC). In this study we have investigated the role of STAT1 and STAT6 in DC maturation and regulation of IL-12 family cytokines.
Hematopoietic progenitor cells or pDC (CD5-, B220-, CD11b-, Gr-1-, Ter-119-) from bone marrow of wild type, STAT1-deficient (STAT1-/-), STAT6-deficient (STAT6-/-) or STAT1/STAT6 double knockout (STAT1-/-/STAT6-/-) mice were isolated using lineage cell depletion kit and expanded in teflon culture bags for 9 days in medium containing SCF (100ng/ml), IL-3 (20ng/ml), M-CSF (50ng/ml), GM-CSF (5ng/ml), FLT-3L (25ng/ml). iDC was generated from pDC by culturing for 3 days in GM-CSF (10ng/ml) while mDC was derived by overnight stimulation of iDC with LPS. Phenotype of the cells and analysis of the expression of cytokines and other lymphocyte effector molecules was analyzed by qRT-PCR, ELISA, and FACS.
We show here that in comparison to wild-type DC, STAT6-/- DC express increased levels of CD86, CCR7 and MHC class II molecules while STAT1-/- DC express decreased amounts of CCR7, MHC class II and CD40 proteins that are associated with DC maturation. We further show that STAT6 is required for IL-12 and IL-23 expression in mDC while STAT1 antagonizes their expression. However, expression of IL-12 and IL-23 is also inhibited in STAT1-/-/STAT6-/- DC, suggesting that upregulation of these genes is mediated primarily through STAT6. Analysis of STAT1-/-, STAT6-/- and STAT1-/-/STAT6-/- DC reveal that induction of IL-10 and IL-27 expression is mediated primarily through STAT1 while their expression is negatively regulated by STAT6.
Taken together these results suggest that while STAT1 is required for DC maturation and necessary for secretion of the anti-inflammatory cytokines IL-10 and IL-27 by mDC, STAT6 exerts negative regulatory constraints on DC maturation and promotes production of pro-inflammatory cytokines (IL-12 and IL-23). Understanding how activation and cross-talk between STAT1 and STAT6 signaling pathways are differentially activated or repressed at different stages of maturation may provide unique insights for development of more effective DC vaccines. In addition, therapeutic targeting of these signal-transducing proteins may be exploited to modulate DC activities.
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