IL21 and juvenile idiopathic arthritis: Compared to other Treg subsets in oligo JIA SF, this Treg subset adopted a Tph gene expression signature with marked upregulation of CXCL13 in particular, alongside PDCD1, CD40L, IL-21, SH2D1A/SAP and MAF. Previously, we showed that Tregs in oligo JIA SF adopt a Th1-like phenotype while remaining stably committed to the Treg lineage, and identified a small subset of IFNγ expressing Tregs by flow (34).