CD4 and systemic lupus erythematosus: Both cells exhibit the same CD4+CD25hiCD127low/−FoxP3+ phenotype.16,17 Treg cells exert an inhibitory effect on CD4+CD25−CD127+ conventional or effector T (Teff) cells.18 A numerical defect in Treg cells has been observed in autoimmune pathologies such as thyroiditis19 and diabetes,20 whereas in SLE, decreased21–26 as well as normal27–30 Treg cell numbers have been reported.