Glycolipid ligands for selectins support leukocyte tethering and rolling under physiologic flow conditions

Selectin interactions with glycolipids have been examined previously under static conditions, whereas physiologic interactions mediated by selectins take place under flow. We find that under physiologic flow conditions, sialyl Lewis(x) (sLe(x)) glycolipid and sialyl Lewisa (sLe(a)) neoglycolipid support tethering and rolling adhesions of Chinese hamster ovary (CHO) cells expressing E-selectin and lymphoid and myeloid cells expressing L-selectin. These selectin-mediated adhesions persist at the highest shear stresses that occur in postcapillary venules in vivo and occur at lower site densities than found for sLe(x) on neutrophils. The interactions are Ca(2+)-dependent and can be specifically and completely blocked with anti-selectin mAbs. Asialo nonfucosylated glycolipids are inactive, and sulfatide supports weak tethering, but not rolling, of L-selectin-expressing cells. Rolling velocities and resistance to detachment are related to the glycolipid site density and fall within the range measured for neutrophil and myeloid cell rolling on substrates containing purified selectins. These observations are the first indication that glycolipids can interact with selectins in physiologic flow conditions, and can contribute to rolling adhesions.