E-selectin binds sLe^xon L-selectin and inhibition with Rivipansel. Isolated human PMNs were treated with IgG, anti-PSGL-1 antibody (KPL-1), anti-L-selectin (DREG56), the combination, or anti-β₂-integrin (IB4) antibody and perfused over (A) E/I or (B) P/I substrate in a microfluidic chamber at 2 dynes/cm². PMN rolling (#P < .05; ##P < .001) and arrest ($P < .01) significance compared with IgG control, subtracting background adhesion. Values depicted are mean ± SEM for n = 3 separate experiments. L-selectin and PSGL-1 were immunoprecipitated from isolated human PMNs with recombinant E-selectin or P-selectin treated with vehicle, or in the presence of Rivipansel (100 μM), or GSnP-6 (120 μM). Western blot protein content of (C) E-selectin-IgG pulldown and quantitation of the ratio of (D) L-selectin (∼69 kDa) or (E) PSGL-1 (∼120 kDa + ∼210 kDa) to untreated immunoprecipitation of total protein. (F) P-selectin pulldown of (G) L-selectin and (H) PSGL-1 relative to total protein pulldown. Relative density of L-selectin and PSGL-1, respectively, was compared between mean ± SEM, as depicted (n = 3 separate experiments). *P < .05; **P < .01; ***P < .001.