To determine if daclizumab remains bound to residual TRegs in TMZ treated patients with GBM, TRegs were isolated both before and after saline or daclizumab administration and identical samples were separately stained for the frequency of CD4+CD25+Foxp3+ TRegs with an anti-CD25 antibody that recognizes the Tac epitope (competing with daclizumab, clone 2A3) and one that does not (non-competing, clone MA251). The gene discussed is FOXP3; the disease is glioblastoma.