Comparison of tethering and rolling of eosinophils and neutrophils through selectins and P-selectin glycoprotein ligand-1.

We compared the abilities of selectins and the selectin ligand, P-selectin glycoprotein ligand-1 (PSGL-1), to support tethering and rolling of eosinophils and neutrophils under physiologic flow conditions. Eosinophils and neutrophils accumulated on P-selectin at similar site densities and rolled at similar velocities, but fewer eosinophils than neutrophils accumulated at any P-selectin density. Compared with neutrophils, few eosinophils accumulated on E-selectin except at high densities, and those cells that did accumulate rolled faster than neutrophils. Examination of the mechanisms for accumulation revealed that eosinophils and neutrophils formed similar numbers of primary tethers to P-selectin, whereas eosinophils formed fewer primary tethers to E-selectin than did neutrophils. Compared with neutrophils, adherent eosinophils also supported fewer leukocyte-leukocyte interactions, resulting in diminished secondary tethers to either P- or E-selectin. Studies with mAbs to L-selectin and PSGL-1 demonstrated that neither cell type used L-selectin to form primary tethers to P- or E-selectin. Both eosinophils and neutrophils used the NH2 terminus of PSGL-1 to form primary tethers to P-selectin, but not to E-selectin. Both cell types used L-selectin and PSGL-1 to promote leukocyte-leukocyte interactions and secondary tethers to P- or E-selectin. However, eosinophils developed significantly fewer secondary interactions, probably because they express less L-selectin than do neutrophils.