Eosinophil Tethering to Interleukin - 4 – Activated Endothelial Cells Requires Both P - Selectin and Vascular Cell Adhesion Molecule

We examined the mechanisms used by eosinophils to tether and accumulate on interleukin-4 (IL-4)–stimulated human umbilical vein endothelial cells (HUVECs) under flow conditions. As previously reported, HUVECs treated for 24 hours with 20 ng/mL IL-4 had increased expression of P-selectin and vascular cell adhesion molecule-1 (VCAM-1) but not E-selectin. We found that eosinophils tethered and rolled on IL-4–stimulated HUVECs at physiologic shear stresses. Eosinophil rolling was quickly followed by firm adhesion. Treatment with either an anti–P-selectin monoclonal antibody (MoAb) or an anti–VCAM-1 MoAb decreased both eosinophil tethering and accumulation at 2 dyn/cm2. VCAM-1 interacts with a4-integrins expressed on eosinophils. We found that an anti–a4-integrin MoAb also blocked eosinophil tethering and accumulation at 2 dyn/cm2. None of these MoAbs alone had an impact on eosinophil accumulation at lower shear stresses, but when either an anti–VCAM-1 or an anti–a4-integrin MoAb was used in combination with an anti–P-selectin MoAb, all eosinophil tethering and accumulation on IL-4–stimulated HUVECs were blocked. This was true at both high and low shear stresses. These data show that both P-selectin and VCAM-1 are required to tether eosinophils at high shear stresses, but at low shear stresses these adhesion proteins can act independently to recruit eosinophils to IL-4–stimulated HUVECs. r 1998 by The American Society of Hematology.