CD69 expression and FSC profiles of viable CD4⁺ SP thymocytes after culture of TCR transgenic thymocytes alone or with BALB.D2 thymic or splenic DC for 24, 36, and 60 hours. The cells were triple stained with tricolor-conjugated anti-CD4, FITC-conjugated anti-CD8, and biotin-conjugated anti-CD69 followed by streptavidin-PE. The percentage of CD69⁺ CD4⁺ SP cells and the percentage of CD4⁺ SP blasts (cells with FSC < 100) are shown. The experiment shown is representative of a series of three experiments with similar results.