CD4 and systemic lupus erythematosus: The addition of CD4+CD25+CD127low UCB-Tregs to the proliferating SLE-PBMCs significantly decreased the secreted IL-6 levels to 213 ± 3 pg/ml at 3 days (p < 0.0001) and 273 ± 5 pg/ml at 7 days (p < 0.0001, Figure 2E).