[Regulatory T-cells in systemic lupus erythematosus. IL-2 is decisive for loss of tolerance]

Systemic lupus erythematosus (SLE) results from loss of immunological tolerance. Regulatory T‑cells (Treg) are major gatekeepers of peripheral tolerance by suppression of autoreactive lymphocytes. Defects in Treg function are therefore possible pathogenetic mechanisms of SLE. Despite this fact published work about numbers and functions of Tregs in SLE are contradictory and the definitive role of Treg in SLE remains unclear. In this review we summarize the current literature about Treg subtypes and the phenotypic markers in human SLE. We also discuss data from mouse models and ex vivo experiments, which provide indications for possible mechanisms that contribute to loss of tolerance. We also discuss the role of interleukin 2 (IL-2), which is decisive for the function of Treg and has been used therapeutically in preliminary trials in human SLE. The identification of novel Treg markers and the development of novel therapeutic approaches, which restore the balance between Treg and autoreactive T‑cells are future goals for research in SLE.