Figure 2. Binding curves of two forms of recombinant E-selectin interacting with (s)PSGL-1.

Adhesion frequency vs. contact duration plots of RBCs coated with sE-selectin at site density of 126 µm⁻² (A) or 46 µm⁻² (B) or E-selectin-Ig at site density of 124 µm⁻² (C) interacting with RBCs coated with sPSGL-1 (square) or PSGL-1 (triangle) at matched densities. Control for nonspecific adhesion was measured using 6 mM EDTA to inhibit binding between sE-selectin and sPSGL-1 (A and B, cross). The different adhesion frequency levels of sE-selectin–PSGL-1 (A) and E-selectin-Ig–sPSGL-1 (C) interactions may result from the differences in how the recombinant proteins were made, how sE-selectin and E-selectin-Ig were coated on RBCs, and how their site densities were measured.