Abstract 709: The Kruppel-like Factor 10 (KLF10) Induces a T regulatory Phenotype and Suppresses Inflammatory Markers
Background: Recent studies have shown a critical role for CD4+ CD25+ T regulatory cells for inhibiting the progression of atherosclerosis in mice, an effect dependent in part on TGF-beta signaling. However, the molecular mechanisms underlying the acquisition of a T regulatory phenotype remain poorly understood. Herein, we identify a member of the Kruppel-like family of transcription factors (KLF10) as TGF-b responsive and a novel regulator of T regulatory cells.
Methods and Results: Magnetic microbead separation was performed to isolate CD4+ CD25-and CD4+CD25+ fractions from mice (purity > 95%). Using Real-Time PCR, we identified that among a panel of KLFs, KLF10 mRNA was robustly expressed (~6-fold) in naive CD4+CD25+ T regulatory cells in comparison to CD4+CD25− cells. Because TGF-b1 induces CD4+CD25+ T regulatory cells from CD4+CD25− precursors, we examined the kinetics of KLF10 mRNA in CD4+CD25− cells in response to TGF-b1 (10 ng/ml) at 1, 6, and 24 hrs. KLF10 mRNA was markedly induced in CD4+CD25- by ~23-fold at 1 hr, ~27-fold at 6 hr, and ~7.5 fold at 24 hrs of TGF-b1 treatment. Remarkably, TGF-b1 induced the expression pattern of the T regulatory marker, Foxp3, in an analogous pattern as KLF10. TGF-b1 also induced expression of KLF10 after 1 hr in the Jurkat T cell line. Retroviral overexpression of KLF10 alone in Jurkat cells conferred the cell surface characteristics of a T regulatory cell (CD25, GITR, CD45, and intracellular Foxp3). In addition, KLF10 nearly abolished cell surface expression of CD1a, an important protein involved in antigen-presentation and activation of T-cells. Functionally, KLF10 overexpressing cells blocked the elaboration of a variety of cytokines/chemokines after stimulation with PMA (20 ng/ml)/ionomycin (3.5 ug/ml) for 6 hrs including IFN-g, IL-2, IL-1b, TNF-a, CD40L, RANTES, MIP-1a, and MIP-1b as measured by ELISA. Finally, reporter gene experiments show that KLF10 can inhibit constitutively active NFAT, a potent transcriptional activator in T cells.
Conclusions: KLF10 is the first member of this family to be identified as a critical regulator of T regulatory cells. These studies may allow for novel therapeutic strategies for treatment of chronic inflammatory states such as atherosclerosis.