L-selectin–mediated lymphocyte adherence to PSGL-1–deficient KG1a cells.

KG1a cells were sorted by FACS into populations (separated at arrows, upper panel) representing high-level PSGL-1 expression (“high”) and low-level PSGL-1 expression (“low”), as shown in lower panel. Adherence assays were performed on cells from both populations. L-selectin ligand activity was equivalently high in both cell populations (see text for details).