Human memory FOXP3+ Treg secrete IL-17 <i>ex-vivo</i> and constitutively express the TH17 lineage specific transcription factor RORγt (33.14)

Abstract

Abstract Recent studies have suggested a close relationship between CD4+FOXP3+ regulatory T cells (Treg) and pro-inflammatory IL-17-producing T helper cells (TH17) expressing the lineage-specific transcription factor RORγt. We report here the unexpected finding that human memory Treg secrete IL-17 ex-vivo and constitutively express RORγt. IL-17 secreting Treg share some phenotypic and functional features with conventional TH17 cells, expressing high levels of CCR4 and CCR6 and low levels of CXCR3. However, at variance with conventional TH17 cells, they express low levels of CD161 and mostly fail to co-secrete IL-22 and TNF-α ex-vivo. Ex-vivo secretion of IL-17 and constitutive expression of RORγt by human memory Treg suggest that, beside their well known suppressive functions, these cells likely play additional yet un-described pro-inflammatory functions.</jats:p