VCAM-1⁺ICAM-1⁺stromal cells provide Notch ligands within the fetal liver. CD45^– stromal cells from E12 fetal liver were subdivided into subsets on the basis of expression of EpCAM1, ICAM-1, and VCAM-1. (A) EpCAM1 expression in CD45^–ICAM-1^–VCAM-1^– cells; (B) ICAM-1 and VCAM-1 expression in CD45^–EpCAM1^– cells. Percentages shown are of the CD45^– population. Such populations were sorted by MoFlo and analyzed for expression of Notch ligands by PCR (C-F). Note that expression of DL1 and DL4 by ICAM-1⁺VCAM-1⁺ fetal liver stromal cells (□) is similar to that of thymic epithelial cells (▪). ▦ indicates CD45^–VCAM1^–ICAM1^–EpCAM1⁺ fetal liver cells. Similar data were produced from 3 separate experiments, and are expressed as mean ± SEM.