CD4 and systemic lupus erythematosus: Independently, co-culture with our CD4+CD25+CD127low UCB-Tregs significantly decreased IFN-γ secretion by the pathogenic lupus cells in vitro and multiple injections of CD4+CD25+CD127low UCB-Tregs in SLE xenografts decreased circulating IFN-γ levels with a corresponding improvement in kidney function.