Three-day coculture increased the percentages of CD4+CD25+CD127low Treg cells and decreased those of CD19+ B cells, CD56+ NK cells, and CD14+ monocytes in UCB-Tregs, SLE-PBMCs, and UCB-Treg:SLE-PBMC, respectively. The gene discussed is CD19; the disease is systemic lupus erythematosus.