Regulatory T (Treg) cells exhibit substantial phenotypic and functional plasticity. Hiroshi Takayanagi and his colleagues report that in autoimmune arthritis, a subset of Treg cells can lose Foxp3 expression and convert into TH17 cells. This conversion is mediated by synovial fibroblast-derived IL-6, and in vivo, these cells are osteoclastogenic and exacerbate arthritis. These findings suggest that a proportion of pathogenic TH17 cells in autoimmune disease may be derived from Treg cells.
- Noriko Komatsu
- Kazuo Okamoto
- Hiroshi Takayanagi