Figure 4.

Apoptosis is largely associated with DP thymocytes. (A) Thymocytes were isolated and treated with annexin V-FITC, anti-CD4-PE and anti-CD8-Cy. Total thymocytes were first analyzed by flow cytometry for annexin V binding. The lower and upper right quadrants indicate early and late apoptotic cells, respectively. (B) Thymocytes highly labeled by annexin V (early and late apoptotic cells) were separated further by flow cytometry on the basis of anti-CD4 and anti-CD8 labeling. (C) The rate of apoptosis in cultured ROR^−/− thymocytes is greatly increased. Thymocytes were cultured in RPMI medium 1640 plus 10% FBS in the presence (Dex.) or absence (NA) of 0.1 μM dexamethasone. At the indicated times, samples were removed and analyzed for annexin V binding by flow cytometry as in A. The percentage of annexin V^low cells (% viability) was calculated and plotted as a function of time in culture.