FOXP3 and systemic lupus erythematosus: In this paper, we review the following: (1) Foxp3+ T cell plasticity, particularly under inflammatory conditions, (2) the effect of suppressors of cytokine signaling 1 (SOCS1) deficiency on Foxp3+ T cell plasticity, and (3) the effect of Foxp3+ T cell plasticity on the possible pathogenesis of autoimmunity, such as systemic lupus erythematosus (SLE).