IL21 and Autoimmunity: Meanwhile, this cell subset, having the capacity to produce potent proinflammatory cytokines including IL-17a (IL-17), IL-17F, IL-21, and IL-22, is likely to play an important role in autoimmunity [6, 7], while CD4+CD25+Foxp3+regulatory T cells (Treg) cells expressing forkhead/winged helix transcription factor (Foxp3) are capable of modulating the function of effector T cells, maintaining immunological homeostasis, and preventing autoimmunity [8, 9].