CD8A and type 1 diabetes mellitus: However, they do express ICOSL and CD122 (the IL‐2 receptor β chain, which also forms part of the IL‐15 receptor).224 The mechanisms involved in their differentiation are not fully understood, although Helios‐dependent STAT5 activation has been shown to be important to enable their survival and prevent terminal differentiation.256 Whether similar CXCR5+ CD8+ Treg cells contribute to regulation of GC responses in humans remains unclear, although HLA‐E‐restricted CD8+ Treg cells have been suggested to be involved in the control of type 1 diabetes in humans.257