Plasticity of Naturally Occurring Regulatory T Cells in Allergic Airway Disease Is Modulated by the Transcriptional Activity of .

The impact of naturally occurring regulatory T cells (nTregs) on the suppression or induction of lung allergic responses in mice depends on the nuclear environment and the production of the pro-inflammatory cytokine interleukin 6 (IL-6). These activities were shown to be different in nTregs derived from wild-type (WT) and CD8-deficient mice (CD8), with increased IL-6 levels in nTregs from CD8 mice in comparison to WT nTregs. Thus, identification of the molecular mechanisms regulating IL-6 production is critical to understanding the phenotypic plasticity of nTregs. Electrophoretic mobility shift assays (EMSA) were performed to determine transcription factor binding to four promoter loci using nuclear extracts from nTregs of WT and CD8 mice. Increased transcription factor binding for each of the loci was identified in CD8 compared to WT nTregs. The impact of transcription factor binding and a novel short tandem repeat (STR) on promoter activity was analyzed by luciferase reporter assays. The promoter regions closer to the transcription start site (TSS) were more relevant to the regulation of depending on NF-κB, c-Fos, and SP and USF family members. Two promoter loci were most critical for the inducibility by lipopolysaccharide (LPS) and tumor necrosis factor α (TNFα). A novel STR of variable length in the promoter was identified with diverging prevalence in nTregs from WT or CD8 mice. The predominant GT repeat in CD8 nTregs revealed the highest luciferase activity. These novel regulatory mechanisms controlling the transcriptional regulation of the promoter are proposed to contribute to nTregs plasticity and may be central to disease pathogenesis.