Expression of adhesion molecules on nonmigrating and transmigrated progenitor cells. While L-selectin was positive on most of the nonmigrating CD34⁺ cells, the expression was markedly reduced after transmigration. No difference in the expression of VLA-4 and LFA-1 was observed when nonmigrating and transmigrated progenitors were compared. Progenitor cells were positive for both VLA-4 and LFA-1. While VLA-4 was positive at a high level, the fluorescence intensity of LFA-1 was only low.