Figure 6. The mechanosensitive component of persistence for neutrophils migrating on Fn-coated substrates toward fMLP is dependent on β₂ integrins.

Human primary neutrophils migrating on Fn-coated gels of 10 kPa or 100 kPa stiffness toward a fMLP point source were treated with β₂-blocking antibody and tracked over a 30-min period (Supplemental Videos 3 and 4). (A) The MSD of neutrophil migration paths is plotted as a function of time between steps. (Inset) The average MSD at a 150-s time interval for each condition. Blocking β₂ integrins significantly decreased MSD and RMS speed on Fn-coated gels of 10 kPa and 100 kPa. (B) For each cell, index DI(Δt) was fit to an exponential DI fit function, yielding mean values of T_d that represent the time interval at which migration transitions from random to directed. Blocking β₂ integrins increased T_d on 100 kPa Fn-coated gels. β₂-Integrin-blocked cells migrating on Fn-coated gels have a T_d equivalent to untreated cells migrating on Col-coated gels. (C) The fit of DI(Δt) was also used to generate values for DI_< and DI_>. These data are plotted as the directionality transition. Blocking β₂ integrins significantly changes DI_< and alters the directionality transition profile to one indistinguishable from untreated cells on Col-coated gels. (D) Cells migrating on Fn-coated gels after β₂-integrin blocking have significantly lower CIs that are statistically equivalent to those of cells migrating on Col-coated gels. The average CI for neutrophils migrating on Fn- and Col-coated gels toward a fMLP point source is shown as a Box and Whisker Plot, showing mean and quartile data. Error bars represent sem. *P < 0.05 untreated versus β₂-integrin block on Fn.