C57BL/6 thymocytes sequentially were stained with CD4 Biotin, Streptavidin, then 0.2 μg Purified Anti-Streptavidin Antibody[15E6] (Right) and 0.2 μg Mouse IgG1, κ Isotype Control (Left), followed by FITC-conjugated Goat Anti-Mouse IgG Secondary Antibody.