Measurements from a LEUKOCYTE that ROLLED and ADHERED to PSELECTIN and VCAM1 after activation by GROA CHEMOKINE. Smith et al.  observed that when the flow chamber surface is coated with P-selectin and VCAM-1 co-immobilized with GRO-α chemokines, monocyte arrest occurred within a few seconds. The data graphed is from an in silico experiment that simulated that protocol and is for an individual LEUKOCYTE that transitioned from ROLLING to FIRM ADHESION (Table 5, part III). (A) Dark line: total number of BONDS formed within the CONTACT ZONE between LEUKOCYTE MEMBRANE and SURFACE. Light gray line: number of high affinity VLA4-VCAM1 BONDS formed: these results show that ADHESION is mediated primarily by the high affinity VLA4-VCAM1 BONDS. (B) DISTANCE-TIME plot and (C) VELOCITY-TIME plot: they show that the LEUKOCYTE rolled for less than a few simulated seconds before firmly adhering to the SURFACE, consistent with leukocyte adhesions observed in vitro. (D) For the same experiment, the number of low affinity VLA4-VCAM1 BONDS and PSELECTIN-PSGL1 BONDS are small and so are plotted here at a smaller scale. Dotted trace: number of low affinity VLA4-VCAM1 BONDS. Lower solid gray trace: number of BONDS formed between PSELECTIN and PSGL1. The black trace is a separate plot of the total number of BONDS formed at each time in the rear row of this CONTACT ZONE; these data show that for the ISWBC, the LOW AFFINITY VLA4/VCAM1 AND PSELECTIN/PSGL1 BONDS play only a minor role in supporting ADHESION. Arrows indicate when a LEUKOCYTE MEMBRANE SPREADING event occurred.