CD3 and CD25 labeling profiles of 4^hi, 5^hi, and L-sel^hi cells from day 3 P-Ir thymocytes. Thymocytes pooled from 20 irradiated mice were triple stained with anti-CD3, anti-CD25, and anti-ECM receptor (anti-4 chain, anti-5 chain, or anti-L-selectin) MoAb cocktails, or with irrelevant antibodies (Irrel. Ab). Thymocytes were arbitrarily split into negative/intermediary (R1) or high (R2) staining for ECM receptor expression (histograms) and then analyzed for CD3 and CD25 expression (dot plots).