Treg cells are a component of one of the peripheral tolerance mechanisms, which fail in autoimmune diseases such as SLE; therefore, these cells are important in the pathogenesis of the disease.2 However, available data on the number and function of Treg cells in SLE are contradictory, and the definitive role of Treg cells in SLE remains unclear.29 Therefore, we decided to explore, the percentage of Treg cells in patients with active and inactive SLE, and the role played by PRL in the regulatory function of these cells ex vivo. The gene discussed is PRL; the disease is systemic lupus erythematosus.