P - Selectin , L - Selectin , and a 4 lntegrin Have Distinct Roles in Eosinophil Tethering and Arrest on Vascular Endothelial Cells

The adhesive interactions of eosinophils with purified E-, P-, and L-selectins; vascular cell adhesion molecule-1 molecule; and HUVEC were examined in shear flow. Compared with neutrophils, eosinophils showed markedly less binding to E-selectin, but significantly stronger avidity for P-selectin. Both cell types showed a similar level of tethering and rolling on L-selectin. Eosinophils tethered and arrested abruptly on vascular cell adhesion molecule-1. However, some of the tethers were detached within several seconds; this was prevented by stimulation with eotaxin. Eosinophils also showed immediate arrest on HUVEC stimulated with 100 U/ml TNF-a for 6 h. Treatment with L-selectin mAb decreased eosinophil accumulation on the HUVEC by abrogating secondary tethers through interactions between flowing and attached eosinophils. mAb to P-selectin but not to E-selectin strongly inhibited primary tethers and accumulation of eosinophils. mAb to the integrin a4 subunit inhibited arrest, induced rolling or detachment of tethered eosinophils, and resulted in partial reduction of eosinophil accumulation. mAb to the integrin p2 subunit had only a slight effect, whereas treatment with mAb to the integrin a4 and p2 subunits together abolished rolling interactions as well as arrest, and thus almost totally inhibited eosinophil accumulation. Our data indicate that P-selectin, but not E-selectin, is directly involved in eosinophil tethering on inflammatory endothelium while L-selectin mainly mediates intereosinophil interaction. VLA-4 has a crucial role in eosinophil arrest, and arrest is enhanced by exposure to chemoattractants. The Journal of Immunology, 1997, 159: 3929-3939.