Comparison of root mean square gel deformation and traction stress exerted by neutrophils on substrates of different stiffness. (A) The root mean square value of the displacements of the fiducial markers embedded in the gel under the area of the cell is plotted as a function of time. There is no statistical difference between gels of different stiffness. (B) The root mean square stress applied by the neutrophil on the gel in the area occupied by the cell is plotted as a function of time for each stiffness. Cell outlines for calculations were determined from DIC images. Error bars represent SEM.