IL15 and Autoimmunity: Interleukin (IL)-15 is an intriguing cytokine for many reasons—unlike other cytokines, it is mostly trans-presented in a membrane bound form to its target cells, enabling very short-range communication, second, it is produced not just by immune cells, but also by stromal cells, particularly in mucosal tissues, where it can act as a danger signal, and, while it maintains immune cell homeostasis at low levels, at high levels or prolonged up-regulation it causes pathogenesis and autoimmunity [1].