Expression of 4 and 5 integrin chains, and L-selectin on day 17 fetal thymocytes. Thymocytes pooled from 15 17-day fetuses were triple stained with anti-CD8, anti-CD25, and anti-ECM receptor (anti-4 chain, anti-5 chain, or anti-L-selectin) MoAb cocktails, or with irrelevant antibodies (Irrel. Ab).