Fig 1.
Diagram of neutrophil with pseudopod under shear flow interacting with the endothelium.
The neutrophil is represented by a spherical body and a Gaussian-shaped pseudopodial extension, and the endothelium is represented as a semi-infinite wall. PSGL-1 is constitutively expressed on the neutrophil’s surface and binds to P-selectin on the inflamed endothelium. Neither the PSGL-1 nor the P-selectin affect hydrodynamics.
Table 1.
Values of bond formation kinetic parameters.
Table 2.
Values of bond dissociation kinetic parameters.
Fig 2.
Comparison of side view trajectories of hydrodynamic and MAD simulations run under the same conditions.
The shear rate is 1000 s-1 and the initial height is 0.5 μm. (A) and (B) are side views of the trajectories for hydrodynamic and P-selectin/PSGL-1 adhesion-enabled simulations, respectively. The asterisks in (B) indicate when bonds exist between the neutrophil and the endothelium, during which time the neutrophil is tethering.
Fig 3.
Comparison of hydrodynamic and adhesion-enabled simulations run under the same conditions.
The shear rate is 1000 s-1, the dimensionless length is 1.9, and the initial height is 0.5 μm. The centroid heights for hydrodynamic and adhesion-enabled simulations are graphed versus time (A). The displacement perpendicular to the flow direction for both simulations is graphed versus time (B).
Fig 4.
Effect of shear rate on adhesion interactions.
(A) Characterization of adhesion behavior, (B) tether lifetime, (C) tether rolling distance, (D) centroid displacement perpendicular to flow, and (E) cumulative frequency distribution for varying shear rates. Ten runs were performed for each condition. *p<0.01, and the mean and standard error are shown.
Fig 5.
Effect of bond formation rate on adhesive interactions.
(A) Characterization of adhesion behavior, (B) tether lifetime, (C) tether rolling distance, (D) centroid displacement perpendicular to flow, and (E) cumulative frequency distribution for varying bond formation rates. Ten runs were performed for each condition. *p<0.01, and the mean and standard error are shown.
Fig 6.
Effect of receptor number on adhesive interactions.
(A) Characterization of adhesion behavior, (B) tether lifetime, (C) tether rolling distance, (D) centroid displacement perpendicular to flow, and (E) cumulative frequency distribution for varying receptor numbers relative to the experimentally-determined value. Ten runs were performed for each condition. *p<0.01, and the mean and standard error are shown.
Fig 7.
Relative contact time for collisions where bonds did and did not occur.
Relative contact time for collisions where (A) no bonds formed and (B) adhesion events occurred, pooled from the collisions of >60 initial angles. Red indicates the longest contact time, and blue is the shortest contact time.
Fig 8.
Contact time and contact area for collisions where bonds did and did not occur.
Contact time (A), contact area (B), and time integral contact area (C) graphs for collisions where no bonds formed and where adhesion events occurred. *p<0.01.
Fig 9.
In vivo example of neutrophil tethering in a blood perfused cremaster muscle venule.
The circled neutrophil is observed to tether to the endothelium from t = 0.06 s until t = 0.42 s, after which it detaches and rejoins the blood flow. The images were acquired using fluorescent confocal microscopy.
Fig 10.
Time-lapse images of a rolling neutrophil in a blood perfused postcapillary venule.
A representative neutrophil tethers to the endothelium at t = 0.13 s and detaches by t = 1.37 s to rejoin the blood flow.
Fig 11.
In vivo sequence depicting a representative, Ly6G labeled neutrophil with a long pseudopod.
It detaches, moves downstream with the pseudopod flipping around, and reattaches via the existing pseudopod.
Fig 12.
Time-lapse images show a representative, activated neutrophil as it slowly rolls along the vascular wall.
The rolling neutrophil (t = 0 s) is observed to slow down through an extension of a pseudopod attached to the vascular endothelium (t = 9.8 s). It continues rolling by disconnecting the pseudopod to rejoin the flow (t = 17.6 s), reattaches to the endothelium using the same pseudopod (t = 18 s), and finally disconnects the pseudopod (t = 19.4), rapidly retracting it into the cell body and continues to roll along the endothelium (t = 19.6 s).