Forced overexpression of either of the two common human Foxp3 isoforms can induce regulatory T cells from CD4⁺CD25^– cells

Abstract

The forkhead/winged helix transcription factor (Foxp3) is expressed as two different isoforms in humans: the full-length isoform (Foxp3FL) and an alternative-splicing product lacking the exon 2 (Foxp3DE2). We here studied the cellular distribution of Foxp3 isoforms by quantitative PCR and evaluated the functional outcome of retroviral transduction of Foxp3FL and Foxp3DE2 genes into CD4 + CD25 -cells. In PBMC, both isoforms were preferentially expressed in CD4 + CD25 hi cells. In single-cell-sorted and expanded Treg, both Foxp3 isoforms were expressed simultaneously but without a fixed ratio. Forced expression of Foxp3FL or Foxp3DE2 genes in CD4 + CD25 -T cells induced bona fide Treg that not only displayed Treg phenotype but also were anergic and mediated significant suppressive activity against CD3-activated CD4 + CD25 -cells. GFP -nontransduced cells or cells transduced with an empty vector showed no Treg phenotype, anergy or suppressive activities. In conclusion, our results reveal that both Foxp3 isoforms possess similar capacities to induce Treg; however, unnaturally high expression levels are required to convey Treg functions to CD4 + CD25 -cells. As both Foxp3 isoforms appear to be expressed in an independent fashion, studies aiming at quantification of Treg in peripheral blood or in tissue samples can benefit from determination of total Foxp3 levels rather than one of the isoforms.

Curcumin inhibits suppressive capacity of naturally occurring CD4+CD25+ regulatory T cells in mice in vitro

“…[24,25]. On the other hand, transduction of Foxp3 can induce the expression of CD25, CTLA-4, and GITR, and it exerted suppressive activity in vitro [7,26]. Hence, Foxp3 expression was also detected in our study.…”

Stimulation of α7 Nicotinic Acetylcholine Receptor by Nicotine Increases Suppressive Capacity of Naturally Occurring CD4+CD25+Regulatory T Cells in Mice In Vitro

“…The absence of FOXP3 in patients with immune dysregulation, polyendocrinopathy, enteropathy, X-linked syndrome (IPEX) or scurfy mutation results in a lack of functional Tregs (Bennett et al, 2001). Overexpression of FOXP3 in conventional T cells leads the cells to become a Treg phenotype with suppressive activity, leading to a state of immune deficiency (Aarts-Riemens et al, 2008). In fact, changes in Foxp3 expression on CD4 ϩ CD25 ϩ Tregs were also …”

Forkhead box P3: The Peacekeeper of the Immune System

“…Studies in humans confirmed that FOXP3 is expressed by tTreg cells and crucially controls their function and maintenance [7], as also demonstrated by the observation that high and stable expression of FOXP3 in human Teff cells leads to the acquisition of Treg phenotype and functions [14,15].…”