Helios expression in CD4+Foxp3− T cells

Abstract

Abstract The transcription factor Helios is expressed in the majority of Foxp3+ Treg cells, where it is necessary for the maintenance of self-tolerance. Mice with a Foxp3-specific deficiency in Helios develop systemic immune activation with increased T follicular helper (Tfh) and T helper 1 (Th1) effector responses. Notably, mice with a CD4-specific deletion of Helios do not exhibit autoimmunity, pointing to an additional role for Helios in CD4+ T cells. In fact, Helios is expressed in a minor population of conventional CD4+ T cells and its expression is upregulated upon activation of CD4+ T cells, yet the role of Helios in these cells remains unknown. We generated TCR Tg mice with a CD4-specific Helios deletion and have shown that Helios deficient naive CD4+ T cells are fully able to differentiate into Th1, Th2 and Tfh effector cells in vivo. Helios deficient CD4+T cells show no defect in expansion or the production of cytokines. However, Helios deficiency increased the propensity of naive T cells to differentiate into antigen-specific pTregs under inflammatory as well as tolerizing conditions and attenuated the induction of a memory response. To further characterize CD4+Foxp3−Helios+ cells, Next-generation sequencing (NGS) analysis was performed. This analysis has yielded evidence for a heterogenous population that is comprised of Tfh, Tmem, iNKT and a population of cells that have Treg-like features. In vitro activation assays and qPCR have validated differentially expressed cytokines between Helios+ and Helios− CD4+ T cell populations, in agreement with the NGS data. Together, these findings suggest that Helios may play a role in stabilizing effector function.