Differential effects of glycolipid biosynthesis inhibition and PMA activation on recognition of E- and P-selectins by primary human neutrophils. (Left) Inhibiting GSL biosynthesis inhibits E-selectin but not P-selectin adhesion. Neutrophils were isolated from peripheral venous blood and maintained in culture in medium containing granulocyte colony-stimulating factor.³⁹  After 24 hours, the glycosphingolipid biosynthesis inhibitor P4 was added (5 μM). After an additional 24 hours, cells were harvested, washed, labeled with ⁵¹Cr, and tested for adhesion to immobilized recombinant human P-selectin and E-selectin under static conditions as described.^16,17  Cell adhesion is expressed relative to that of control cells cultured in the absence of P4. Data are from 3 (P-selectin) or 4 (E-selectin) independent experiments. (Right) Activation of human neutrophils with phorbol ester inhibits P-selectin but not E-selectin adhesion. Freshly prepared peripheral blood neutrophils were treated for 10 minutes with PMA (1.6 μM), then were perfused at 1 dyne/cm² over monolayers of CHO-E or CHO-P cells as indicated. Tethering is expressed relative to that of control cells incubated in the absence of PMA. Data are from 3 independent experiments with SEM shown. Statistical comparisons are by Student t test.