Plasticity of Naturally Occurring Regulatory T Cells in Allergic Airway Disease Is Modulated by the Transcriptional Activity of <i>Il-6</i>

• Main Authors: Morgan MacBeth, Anthony Joetham, Erwin W. Gelfand, Michaela Schedel
• Format: Article
• Language: English
• Published: MDPI AG 2021-04-01
• Series: International Journal of Molecular Sciences
• Subjects: IL-6; naturally occurring T regulatory cells (nTregs); plasticity; transcriptional regulation; transcription factor binding
• Online Access: https://www.mdpi.com/1422-0067/22/9/4582
• ISSN: 1661-6596; 1422-0067

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 <i>Il-6</i> promoter loci using nuclear extracts from nTregs of WT and CD8^−/− mice. Increased transcription factor binding for each of the <i>Il-6</i> loci was identified in CD8^−/− compared to WT nTregs. The impact of transcription factor binding and a novel short tandem repeat (STR) on <i>Il-6</i> promoter activity was analyzed by luciferase reporter assays. The <i>Il-6</i> promoter regions closer to the transcription start site (TSS) were more relevant to the regulation of <i>Il-6</i> depending on NF-κB, c-Fos, and SP and USF family members. Two <i>Il-6</i> 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 <i>Il-6</i> 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 <i>Il-6</i> promoter are proposed to contribute to nTregs plasticity and may be central to disease pathogenesis.