E-/L-selectin binding. (A) E-/L-selectin–IgG fusion protein binding to HL-60 cells was measured at t = 38 hours after protocols identical to Figure 2I through L, in the absence of prior neuraminidase treatment. In vehicle control runs, selectin binding was blocked by 80% to 100% on addition of 3mM sLe^X analog (TBC1269), 5mM ethylenediaminetetraacetic acid, or 30 μg/mL antiselectin Ab (either EP5C7 against E-selectin or DREG56 against L-selectin). Culturing cells in the presence of 50μM 4F-GalNAc reduced E-/L-selectin binding by more than 70%. (B) Le^X, sLe^X expression and AAL lectin (binds α1,3/4/6-linked fucose antigen) binding were measured at 38 hours. 4F-GalNAc reduced Le^X expression and AAL lectin binding. Data are mean ± SEM (N ≥ 3 experiments). *P < .05 with respect to vehicle control with no blocking reagent.