The assembly of the multichannel microfluidic devices used in this study and the coating of coverslips with recombinant human P-selectin-Fc, ICAM-1-Fc, and IL-8 has been described previously.3 (link),12 (link),19 Briefly, coverslips were coated with P-selectin-Fc (2 μg/ml), ICAM1-Fc (10 μg/ml), and IL-8 (5 μg/ml) for 2 h and then blocked for 1 h with casein (1%) at room temperature (RT). After coating, coverslips were sealed to polydimethylsiloxane chips by magnetic clamps to create flow chamber channels ~29 μm high and ~300 μm across. By modulating the pressure between the inlet well and the outlet reservoir, a wall shear stress of 2 or 6 dyn/cm2 was applied. HL-60 cells (5 × 106 cells/ml) were perfused in the microfluidic device over a substrate of recombinant human P-selectin-Fc, recombinant human ICAM-1-Fc with or without IL-8. The rolling and arrest of cells were recorded by an IX71 inverted research microscope (Olympus America Inc, Cypress, CA, USA) with a 10× NA 0.3 air objective. The number of rolling and arrested cells were counted in 5 channels per group. The rolling duration and rolling distance were acquired from the images by analyzing 15 cells started rolling to arrest.