Because CD4+CD25low/−Foxp3+ T cells are derived from CD4+CD25highFoxp3+ T cells in SLE patients, we could obtain the high purity of inducible CD4+CD25+Foxp3+ T cells in vitro that helps us study the origin of CD4+CD25–Foxp3+ T cells. The gene discussed is CD4; the disease is systemic lupus erythematosus.