Staining of 3-day Anti-Human CD3 and Anti-Human CD28 Functional Grade Purified (Product # 16-0039-81 and Product # 16-0289-81)-stimulated normal human peripheral blood cells with Mouse IgG1 K Isotype Control eFluor® 450 (Product # 48-4714-82) (blue histogram) or Anti-Human CD357 (AITR/GITR) eFluor® 450 (purple histogram). Total viable cells, as determined by Fixable Viability Dye eFluor® 780 (Product # 65-0865-14), were used for analysis.