Normal human peripheral blood cells untreated (orange histogram), treated with Anti-Human CD3 and CD28 Functional Grade Purifieds (Product # 16-0037-81 and Product # 16-0289-81) (purple histogram), or treated with Anti-Human CD3 and CD28 Functional Grade Purifieds and Etopside (green histogram) were stained intracellularly with Anti-Human/Mouse phospho-ATM (S1981) eFluor® 660 using the Intracellular Fixation & Permeabilization Buffer Set (Product # 88-8824-00) and protocol. Cells in the lymphocyte gate were used for analysis.